Fire - Armstrong - Fire Pumps 58m6a
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Chapter 1: Introduction: Fire Pump Codes and Standards Before discussing the details of fire pump design, codes, and operation, it is important to realize the purpose of a fire pump. A fire pump by itself is not a fire protection item. The pump merely provides the flow capacity and pressure required to operate fixtures in a fire protection system. These fixtures are typically automatic sprinkler heads or standpipe systems (generally supplying hose valves located outside the building or in hose cabinets). The purpose of these fixtures is to protect lives and property against death, injury, and damage resulting from fires. This reality bears with it a responsibility for every person involved in the process from selling, to manufacturing, to installing a fire pump. With this in mind, let us discuss the most important document with respect to the installation of fire pumps - the National Fire Protection Association’s (NFPA) Pamphlet 20.
NFPA20: Standard for the Installation of Centrifugal Fire Pumps Since the inception of the National Fire Protection Association’s (NFPA) Committee on Fire Pumps in 1899, the world of water based fire protection has come a long way. Technological advancements, new industry standards and better awareness of the dynamics of fire itself have made the regulation of fire pump installations of paramount importance. In order to guarantee reliable fire protection and that sprinkler and standpipe systems have water in an emergency, the NFPA publishes a code book Pamphlet 20 - every three years to keep up with the changing industry. Throughout the hundred years of existence, and through all the changes in the industry, though, the basic principles and philosophy of the organization have remained unchanged. Virtually every line of the pamphlet exists to guarantee that a fire pump starts in an emergency and does not shut down. A fire pump is a fire protection item. In the event of a fire, the pump should run to its own destruction, if necessary, to ensure the water required to put out the fire is supplied. With the creation of the NFPA’s fire pump committee also came a requirement for regulation of fire protection equipment, and also the requirement for ruling bodies to assess the codes and make decisions based on individual installations. For this reason, three major regulatory levels exist in fire pump regulation. It is my intention to briefly discuss them. The National Fire Protection Association (NFPA) The NFPA acts much like a legislative body. Every six months, of the committee on fire pumps meet to discuss changes and additions to the fire pump code as published in the pamphlet NFPA20. Every three years, the outcomes of the discussions and meetings are used to update the code book. The NFPA has no real authority in the actual fire protection world in of enforcing the rules - its job is simply to make them and to make general recommendations.
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The Authority Having Jurisdiction (AHJ) The AHJ acts as the judicial body, and is defined in NFPA as “the organization, office, or individual responsible for approving equipment, an installation, or procedure”. The AHJ could be the Fire Marshall or an insurance underwriter who takes into the codes (NFPA20) and any local requirements, to judge whether or not a fire pump installation is acceptable. Often the codes themselves read “where acceptable to the authority having jurisdiction”. This simply means that the codes are a guideline, and the local authority always has the power to judge whether an NFPA requirement is acceptable, whether an NFPA requirement is insufficient, or whether an NFPA requirement can in fact be waived for any particular case.
The Listing Authorities (ULC, UL, FM, LPC) Listing authorities carry more of an executive responsibility in the fire protection world. NFPA20 often states that an item “shall be listed”. This simply means that a nationally recognized testing laboratory must test, approve, and publish their acceptance of equipment to be used for fire protection service. In general, these bodies work to keep a record of approved equipment, and to ensure that manufacturers of equipment maintain the level of quality of the originally tested and listed items. It is extremely important to that the AHJ will generally have requirements of which listings will be required. For example, though a ULC listed piece of equipment satisfies NFPA20, the AHJ may require a UL or FM listing. Because the individual listing authorities often have their own requirements, these listing can in fact make two pieces of equipment for the same application completely different both in construction and cost.
Fire Pump Systems A fire pump system consists of all the components between the supply connection to the building connection required to operate a fire pump safely and effectively. These components can be broken down into the following items: (a) Fire pump. The fire pump increases the pressure of supply water at a certain flow rate to a pressure sufficient to operate fire protection fixtures. (b) Fire pump driver. The fire pump driver is typically an electric motor or diesel engine used to supply the power to operate the fire pump. (c) Valves and fittings. The valves and fittings provide control of the higher pressure discharge from the fire pump. These components allow for fire pump testing, protection of the fire protection system from overpressure or under pressure conditions, and servicing of the components of the system. (d) Fire pump controller. The fire pump controller is responsible for starting the fire pump under whatever adverse conditions may occur during an emergency.
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The controller is also responsible for communicating emergency conditions to the operator of the pump or to the appropriate building emergency control system. (e) Pressure maintenance (jockey) pump and controller. The jockey pump and controller ensure that the fire protection system is filled with water and pressurized in readiness for an emergency situation.
LEGEND 1. FIRE PUMP 2. FIRE PUMP CONTROLLER 3. GATE VALVE 4. BUTTERFLY VALVE 5. CHECK VALVE 6. GAUGES 7. CASING RELIEF VALVE 8. EXCENTRIC REDUCER (IF APPLICABLE) 9. CONCENTRIC INCREASER (IF APPLICABLE) 10. SENSING LINE NFPA 20 11. TEST TEE
Together, these components work to ensure the fire protection system is ready and able to deal with an emergency. It is for this reason that no non-operator initiated obstruction should prevent the fire pump from starting and continuing to run when started. For this reason, the only times a fire pump is allowed to stop automatically are during a test or, in the case of a diesel driven fire pump, if the diesel engine goes into an over speed, over pressurization condition. If the fire pump starts for any reason other than a test, the operator must physically go to the pump room and press the stop button on the fire pump controller. Fire pumps can be started either manually or automatically. Manual starts can be initiated from a remote location, or in the pump room itself. Automatic starting is initiated when the pressure in the fire protection system (as measured by a pressure switch) falls below a predetermined, preset value.
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Chapter 2: Fire Pumps Pumps in General The purpose of a pump is to take a certain volume of water at a certain pressure and to increase the pressure of that water. To this end, the performance of a pump can be described by two variables - the flow through the pump (often referred to as capacity), and the pressure the pump is capable of adding at the given flow rate. In practice, these two variables can be plotted to produce what is called a pump curve. The pump curve is like a fingerprint. Provided the pump is operated at the same speed, it will always generate the same pump curve.
120 100 80
Pressure 60
(in PSI) 40 20 0 0
250 500 750 1000 1250 1500 1750 2000 2250 2500 2750
Capacity (in GPM) Figure 1: A typical pump curve. For any given flow rate through the pump, the pressure boost it will provide is fixed.
The pump itself consists of a hollow casing with an inlet (referred to as the pump suction) and an outlet (referred to as the pump discharge). Within the casing, a rotating shaft assembly with a vaned impeller is spun within the casing to produce the desired pressure increase. The diameter of the impeller can be changed, or “trimmed” to produce a different characteristic pump curve.
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By itself, the pump is useless. The pump shaft must be coupled to a driver of some sort to spin the impeller within the casing to produce pressure. Generally, the driver used is an electric motor, diesel engine, or steam turbine. The most common types of fire pumps are driven by electric motors or diesel engines.
Figure 2: Cross sectional view of a vertical in-line pump. The following parts are shown: (1) Pump suction. (2) Pump discharge. (3) Impeller. (4) Pump seal. (5) Pump-motor shaft coupling. (6) Motor.
Mechanical vs. Packing Seals Because the shaft must protrude from the casing in order to be coupled to a driver, the pump must have at least one seal to prevent water from leaking through the shaft/casing mating surface. Pumps can have two types of seals - mechanical or packing.
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Mechanical seals are constructed of two precisely machined surfaces which are pressed together and generally lubricated by the product being pumped. Mechanical seals allow less leakage, but are more likely to fail catastrophically (i.e. to crack or break). Packing seals are constructed of a gland in which a compressible material (packing) is wrapped around the shaft. The gland can be tightened to compress the packing against the shaft/casing mating surface, preventing leakage. In reality, any seal must allow some leakage to remain effective. A packing seal allows more leakage, but is less subject to catastrophic failure. It is for this reason that NFPA20, the fire pump code book, requires that all fire pumps be of the packing seal type.
Pump Types There are many type of pumps. Only four types of pumps are allowed for use in fire protection service. We will discuss three of them at length. a) Split-case pumps. Split-case pumps are described as such because the pump casing consists of two halves split on a plane parallel to the shaft. A split-case pump has two seals, one on the driver end, where the shaft is coupled to the driver, and one at the opposite end where the shaft is ed. Split case pumps are of the “double suction” type.
Figure 3: Horizontal split-case pump.
b) End-suction pumps. End-suction pumps are constructed so that the pump suction is aligned with the shaft. The pump discharge is perpendicular to the shaft. End-suction pumps have only one seal at the driven end of the pump casing. End-suction pumps are of the “single suction” type. Figure 4: End-suction pump.
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c) In-line pumps. The pump suction and discharge of an in-line pump are aligned and perpendicular to the shaft. In-line pumps also employ only one seal at the driver end of the pump casing. One design and maintenance advantage of the vertical in-line pump is that it requires no pump bearings. In-line pumps are of the “single suction” type and are limited to a maximum capacity of 750GPM by NFPA20.
Figure 5: Vertical in-line pump.
One important note in pump design is that end-suction and split-case pumps must be mounted on a base, isolated from the building by some sort of vibration absorbing structure, and re-aligned whenever they are moved or serviced. In-line pumps can be mounted vertically, eliminating the need for vibration isolation, and are self-aligning. In addition, the vertical in-line pump requires less floor space in a pump room due to the fact that the motor is mounted above the pump (vertically), not on the floor (horizontally). Fire Pumps The NFPA’s Pamphlet 20 states the following: Chapter 3
Horizontal and In-Line Pumps
3-1.1 Types. Horizontal pumps shall be of the split-case, end-suction, or in-line design. 3-1.2 Application. The horizontal split-case pump in horizontal or vertical position, and end-suction and in-line pumps shall not be used where a static suction lift is involved. 3-2
Factory and Field Performance
3-2.1 Characteristics. Pumps shall furnish not less than 150 percent of rated capacity at not less than 65 percent of total rated head. Shutoff head shall not exceed 140 percent of rated head for any type of pump.
The above three points are perhaps the key design and performance requirements for fire pumps. Of note, the definitions of allowable pump types mentions “Horizontal pumps shall...”. In practice, vertical pumps are also acceptable allowing vertical in-line (Armstrong) and vertical split-case pumps to be used in fire protection.
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The concept of suction lift should be briefly addressed here. Suction lift is simply 2 defined as the static pressure at the pump suction minus the dynamic pressure (ρv /2g). Simply put, the pressure of the water entering the pump should not reach the vapour pressure of water. This condition leads to micro-vapour bubble formation at the pump suction, known as cavitation. This condition leads to the rapid deterioration of the pump casing and eventual failure of the pump. Suction lift is typically checked for in application by ensuring that the minimum suction pressure available does not exceed the net positive suction head (NPSH) of the pump. The NPSH of a pump is usually shown on the pump curve, and if not, is available upon request from the fire pump manufacturer.
Formula: where
Suction Lift = Pgauge + ρv2/2g Pgauge = pressure as read by a gauge at the suction inlet ρ = density of water v = velocity of water at suction inlet g = gravitational constant
If this number is negative, a suction lift exists. This is an unacceptable condition for fire pump operation.
The final point is the golden rule of fire pump design, which is illustrated in Figure 6. This rule creates a performance envelope for fire pumps, the most critical feature of which is the 150% rated flow at 65% rated head. The closer a fire pump can be designed to this point, the lower the BHP of the pump will be, and the smaller the driver (electric motor or diesel engine) will be. Fire pump manufacturers design pumps around this rule to maximize the pump’s competitiveness on the market.
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120
Rated
100
Capacity Pressure 80 (in PSI)
Pump BHP Curve
60 40 20 0 0
250
500
750 1000 1250 1500 1750 2000 2250 2500 2750
Capacity (in GPM) Figure 6: Fire pump curve with indication of the rated capacity: 1500GPM @ 95PSI. The lower curve is the BHP of the pump. The maximum BHP will determine our driver selection.
Maintenance and Service The NFPA codes also allow for the serviceability of a fire pump. For this reason, end suction pumps must employ a flexible type coupling designed specifically to allow the impeller and driver side seal assemblies to be removed without disturbing the piping, and without pulling the motor or diesel engine. Vertical in-line pumps are exempt from this rule, and may be close coupled to the motor. The flexible coupling for horizontal pumps is required to isolate vibration caused by the base mounted design. Vertical inline pumps are also exempt from the alignment requirements listed in A-3-5 of NFPA20.
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Chapter 3: Fire Pump Drivers Electric Motors Electric motors are one type of driver allowed by the NFPA codes. In general, electric installations must be supplied with a reliable source of power resistant to damage resulting in exposure to fires and other potential hazards. Electric motor driven fire pumps are often supplied with power from alternate sources such as an on-site generator or a secondary utility line. NFPA20 states the following regarding motor sizing: 6-4.2 Current Limits. 6-4.2.1 The motor capacity in horsepower shall be such that the maximum motor current in any phase under any condition of pump load and voltage unbalance shall not exceed the motor-rated full-load current multiplied by the service factor. The maximum service factor at which a motor can be used is 1.15.
This statement literally means that the motor must be sized to be “non-overloading” across the range of the pump curve; however, the service factor of the motor can be and should be used. What this amounts to is that the maximum pump BHP should be equal to or less than the motor rated HP multiplied by 1.15.
Formula:
Maximum Pump BHP <= Motor HP x 1.15
Example:
A VIL (vertical in-line) pump is sized for 400GPM @ 90PSI. The pump BHP is 45. What motor should be used?
Answer:
45HP/1.15 = 39.13 A 40HP motor is required.
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The NFPA’s Pamphlet 20 also states the following with respect to electric motors:
6-4
Motors
6-4.1 General. 6-4.1.1 All motors shall be specifically listed for fire pump service. (This requirement shall be effective January 1, 1998.) 6-4.1.2 All motors shall comply with NEMA Standard MG-1 and shall be marked as complying with NEMA Design B standards.
In practice, the former of the above points is not in effect. Underwriters Laboratories has only recently created a new listing for fire pump motors. Some, but not all, of the North American electric motor manufacturers have applied for this listing. Until at least one of these manufacturers can offer a workable line of approved motors, it is unlikely that compliance with the code will become an industry standard. Presently, a NEMA B labeled motor is accepted by AHJ’s across North America for use in fire pump installations.
Diesel Engines Diesel engines are becoming more common as drivers for fire pumps. The diesel engine is usually a higher first cost as well as higher maintenance item; however, engines circumvent the problem of supplying an electric motor driven fire pump with a reliable source of electricity. Because of the requirement for maintenance, and the greater likelihood of a diesel engine’s failure to start, the NFPA codes are much more strict and specific with respect to diesel engines than they are for electric motors.
Figure 7: Diesel engine for fire protection service.
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Perhaps the most important of all is the derating of diesel engines for temperature and altitude. The codes state that an engine’s BHP must be derated 3% for every 1000 feet o o over 300 feet (above sea level) and 1% for every 10 F over 77 F.
Example: A diesel engine rated at 73HP is being installed at 2037 feet (above sea level) elevation and expected to operate at a maximum ambient temperature of 89oF. Calculate the real engine BHP as per NFPA20. Answer: Deration for elevation 3% x (2037 - 300)/1000 = 5.21% Deration for temperature 1% x (89 - 77)/10 = 1.20% Total deration = 5.21% + 1.20% = 6.41% Real Diesel Engine BHP BHP = 73 - 6.41% x 73 = 68.3HP
The other important point to when sizing a diesel engine is that the engine rated speed must match the pump rated speed to within 4%. If the rated pump and diesel speeds do not exactly match, it is always wise to consult the manufacturer before quoting a job. If the diesel rated speed is lower than the pump rated speed, the pump may not be able to generate the desired pressure. Diesel engines must start reliably from a cold condition to immediately operate at the design speed. For this reason, control, maintenance and operation must be closely monitored. Diesel engines must be equipped with the following items: (a) Governor. The governor must be capable of regulating the engine speed within 10% of the rated speed across the entire flow range of the pump curve. (b) Overspeed Shutdown Device. Overspeed is the only condition upon which a diesel engine must automatically shut down. This is due to the fact that a runaway diesel engine could cause a dangerous overpressurization of the fire pump and sprinkler system. The engine overspeed shutdown device must activate if the engine operating speed is 20% higher than the rated speed of the engine. This is equivalent to a 44% overpressure condition for the fire pump. (c) Instrumentation. All engines must be equipped with an instrument with gauges for oil pressure, engine speed (tachometer), and engine coolant temperature.
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(d) Manual Cranking Device. All engines must be equipped with two manual cranks, one for each of the two batteries supplied for starting the diesel engine. (e) Heat exchanger. A water to coolant heat exchanger must be provided for all diesel engines. The cooling water is supplied from the pump discharge, after which the cooling water should be piped to a drain. Recirculation of the cooling water can be done where acceptable to the AHJ; however, this practice is not generally accepted. (f) Engine jacket water heater. Because diesel engines must be started cold and immediately operate at the rated speed without idling, an electrically operated engine jacket water heater must be supplied to maintain the engine o coolant temperature at no less than 120 F. This item is generally supplied by the engine manufacturer for operation on either 120V/1/60 or 230V/1/60 power. It is important to that most diesel engines are shipped without coolant or oil. The engine jacket water heater will typically burn out in about 5 seconds if operated dry. The coolant mix should be determined from the diesel engine operation and installation manual. (g) Two starters. Every diesel engine must be capable of being started using one of the two provided batteries. Provisions for manual cranking of the diesel engine must be provided on the fire pump controller and on the diesel engine itself.
The above items must supplied by the engine manufacturer in order for the engine to be listed. The following items must be supplied by the fire pump manufacturer: (a) Cooling water line. A cooling water line of appropriate size must be supplied from the discharge of the pump (before the pump discharge shutoff valve) and connected to the engine heat exchanger cooling water line.
(b) Exhaust connection and silencer. A seamless or welded, insulated flexible connector must the diesel exhaust outlet with the fire pump installation exhaust pipe. A silencer must be connected in the exhaust pipe. Figure 8: Flexible, connection.
insulated
exhaust
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Figure 9: Silencer.
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(c) Dual batteries. Two sets of batteries must be supplied for starting the diesel engine. These batteries must be capable of charging completely in 24 hours from a no-charge condition. The charger for these batteries is supplied in the fire pump controller. Batteries are typically 12V or 24V (2 x 12V) depending on the type of diesel engine being supplied. Figure 10: Batteries with cables and rack.
(d) Diesel fuel tank. A listed fuel tank must be supplied with fill vent, flame arrester, and piping must be supplied. No shutoff valve may be placed in the fuel return line. The tank must be sized to equal at least one US gallon per HP plus 10%. The diesel tank level should be maintained above a half.
Figure 11: Fuel tank with required fittings.
Example: Size a tank for a diesel engine with a BHP of 170. Answer: Tank size = 170 x 1.1 = 187 US Gallons All diesel engine driven fire pumps must be subjected to a weekly test during which the engine is run for not less than 30 minutes.
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Chapter 4: Valves & Fittings The NFPA’s Pamphlet 20 states the following: 3-3
Fittings
3-3.1 Where necessary, the following fittings for the pump shall be provided by the pump manufacturer or an authorized representative: (a) Automatic air release, (b) Circulation relief valve, and (c) Pressure gauges. 3-3.2 Where necessary, the following fittings shall be provided: (a) (b) (c) (d)
Eccentric tapered reducer at suction inlet, Hose valve manifold with hose valves, Flow measuring device, and Relief valve and discharge cone.
It is important to note that these requirements are open to some interpretation, and do not apply to all fire pump types. The first three listed items generally referred to as “minimum fittings”.
Automatic Air Release A listed (ULC, UL, or FM) automatic air release must be mounted on top of the pump casing to ensure the pump is free from air during operation. Due to specific design conditions, top centerline discharge end suction pumps and vertical in-line pumps are exempt from this requirement. It must be noted that the authority having jurisdiction may require that the air release be supplied even though it is not required by NFPA. The air release must be sized ½ inch.
Figure 12: Automatic Air Release Valve.
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Circulation (Casing) Relief Valve A listed (ULC, UL, or FM) circulation or casing relief valve must be mounted on the pump discharge. This requirement can be ignored on diesel fire pump systems, the reason being, a larger main relief valve will be installed from a tee in the discharge line. The purpose of the valve is to prevent over-pressurization and overheating of the system during fire pump operation at low flow conditions. This valve must be sized ¾ inch for fire pumps up to 2500GPM. The valve should be set to discharge below the pump shutoff head at the minimum suction pressure. Figure 13: Circulation (Casing) Relief Valve.
Rule of thumb: The circulation relief valve should be set to below the following condition: Minimum Suction Pressure + Boost Pressure This will ensure that the valve discharges some water at low flow conditions.
The circulation relief valve should be piped to a drain to ensure the sufficient flow of water to protect the pump from overheating. Overheating can quickly damage the pump seal. The valve should not be piped back to the suction side of the pump.
Pressure Gauges Pressure gauges sized at least 3½ inch must be provided - one for the suction side, one for the discharge side. The gauges must be connected using ¼ inch gauge valves. The gauges must meet the following requirements: (a) Suction gauge: must have a range two times the maximum suction pressure and not less than 100PSI. (b) Discharge gauge: must have a range at least twice the rated working pressure of the pump and not less than 200PSI.
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The following fittings will be supplied in specific cases. In general, they are not supplied unless requested specifically by the sprinkler contractor. It is common that the contractor will choose to supply these fittings themselves. Eccentric Tapered Reducer If the pump suction inlet is smaller than the line size, an eccentric tapered reducer must be supplied. The reducer must be mounted such that the non-tapered side of the reducer is flush with the top of the pump suction. This serves to prevent air entrainment on the suction side of the pump. Hose Valve Manifold with Hose Valves Hose valves are supplied as a means of flow testing the fire pump and to provide an external source of water for the fire department to connect to in an emergency. The hose valve manifold is connected to a test tee on the discharge side of the pump through the wall so that the hose valves themselves are outside of the building. The manifold size as well as the number of hose valves are indicated in the table below reproduced from NFPA20.
Figure 15: Hose valve with cap and chain.
Figure 16: Hose valve manifold (header).
Flow Measuring Devices A listed (ULC, UL, or FM) flow meter , where required, must be provided capable of reading up to 175% the rated capacity of the pump. Sizing of the meter must be as per the table below. Listed flow meters are generally available in either the annular or Venturi type. The Venturi type are marginally more costly, but are easier to install properly. The annular type can be mis-aligned in installation, resulting in incorrect flow readings. A suggested piping schematic for installation of a flow meter in a fire pump system is given in NFPA Pamphlet 20 appendix A-2-14.1.2(b).
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Relief Valve and Discharge Cone On systems in which the pump discharge pressure at a no-flow condition exceeds the pressure rating of the fire protection system, a listed (ULC, UL, or FM) main relief valve must be installed. This valve must be the pilot operated or spring loaded type.
Rule of Thumb: If the maximum expected suction pressure + the pump rated head x 1.4 is greater than the rating of any fittings in the pump or sprinkler system, a main relief valve should be installed.
Generally, any diesel system should be supplied with a main relief valve. The reason for this is that a diesel engine may run up to 20% faster than the rated speed. In this “overspeed” condition, the pump discharge pressure increases by 44%. This large increase in discharge pressure makes main relief valve installation a standard practice on diesel systems. Installation of a main relief valve negates the requirement for a circulation (casing) relief valve. Sizing of the relief valve are indicated in the table at the end of the chapter. Figure 17: Main relief valve with open discharge cone (waste cone)..
Example: A diesel fire pump system is sized for a minimum suction pressure of 20PSI (maximum suction pressure of 40PSI). The pump rating is for 1000GPM @ 80PSI (shutoff head of 100PSI). The maximum working pressure of the installation is 175 PSI. Should a main relief valve be installed? Answer: As a rule, any diesel system should have a main relief valve. Let’s calculate if it’s necessary anyway. At engine overspeed of 20% at shutoff Pressure = 40PSI (max. suction pressure) + 100PSI x 1.44 = 184PSI A main relief valve should be installed.
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A main relief valve also requires a discharge “enclosed” cone. These device is simply increaser switch should be installed to discharge to atmospheric pressure into a drain. This ensures that the valve has sufficient differential pressure to relieve the appropriate pressure. A sight glass must be provided so that flow in the pipe is visible. The main relief valve should not be piped back to the suction side of the pump. Other Valves and Fittings The following additional valves and fittings must be installed, but not necessarily supplied by the fire pump manufacturer: (a) A listed (ULC, UL, or FM) OS&Y gate valve on the pump suction. A butterfly valve is not acceptable. (b) A listed (ULC, UL, or FM) check valve on the pump discharge. (c) A listed (ULC, UL, or FM) butterfly valve on the downstream side of the discharge check valve. All isolation valves must be either sealed or locked in the open position, or must be supplied with a supervisory switch for remote indication of the valves’ condition (open or closed). All valves and fittings must be rated to at least the maximum working pressure of the system, and not less than the rating of the fire protection system. The suggested piping material is steel with welded, flanged, V-grooved, or threaded connections.
Fire Pump Rating GPM (L/s)
Suction Size (in.)
Discharge Size (in.)
Relief Valve Size (in.)
25 (95) 50 (189) 100 (379) 150 (568) 200 (757)
1 1½ 2 2½ 3
1 1¼ 2 2½ 3
250 (946) 300 (1136) 400 (1514) 450 (1703) 500 (1892)
3½ 4 4 5 5
750 (2839) 1000 (3785) 1250 (4731) 1500 (5677) 2000 (7570) 2500 (9462) 3000 (11,355)
Flow Meter Size (in.)
¾ 1¼ 1½ 2 2
Relief Valve Discharge (in.) 1 1½ 2 2½ 2½
3 4 4 5 5
2 2½ 3 3 3
6 8 8 8 10
6 6 8 8 10
10 12
10 12
Hose Valve Manifold Size (in.)
1¼ 2 2½ 3 3
Number & Size of Hose Valves 1 - 1½ “ 1 - 1½ “ 1 - 2½ “ 1 - 2½ “ 1 - 2½ “
2½ 3½ 5 5 5
3½ 3½ 4 4 5
1 - 2½ “ 2 - 2½ “ 2 - 2½ “ 2 - 2½ “ 2 - 2½ “
3 3 4 4 4
4 4 6 6 6
6 8 8 8 10
5 6 6 8 8
3 - 2½ “ 4 - 2½ “ 6 - 2½ “ 6 - 2½ “ 6 - 2½ “
6 6 8 8 8
6 8
10 12
8 8
8 - 2½ “ 12 - 2½ “
10 10
Reprinted from NFPA20: Table 20-2: Summary of Fire Pump Data.
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1 1½ 2½ 2½ 2½
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Chapter 5: Pressure (Jockey) Maintenance Pumps Because sprinkler and standpipe systems need water to operate, water pressure must be maintained in the these systems. As stated in NFPA20: 2-19.5 The primary or standby fire pump shall not be used as a pressure maintenance pump.
Since a fire pump cannot be used to maintain the pressure in a sprinkler or standpipe system, a separate jockey pump must be used for this purpose. It is important to note that since a jockey pump and jockey pump controller are not technically pieces of fire protection equipment (they are not used in an emergency situation), jockey pumps and controllers need not be listed for fire protection service. With respect to the sizing and selection of jockey pumps the following is of note: 2-19.1 Pressure maintenance pumps shall have rated capacities not less than any normal leakage rate. They shall have discharge pressure sufficient to maintain the desired fire protection system pressure. Though it is not explicitly stated here, the jockey pump should not be sized to provide more flow than the normal leakage rate plus the flow rate of one fire protection fixture (one sprinkler head). Should one sprinkler head open, the jockey should not be capable of supplying the flow demand - the fire pump should start. As for jockey pump pressure, it is generally accepted that the jockey be sized for 10PSI higher than the rated head of the fire pump. The fittings required for a jockey pump are as follows: (a) Suction and discharge butterfly or gate valves. (b) Discharge check valve. (c) Relief valve. The relief valve is only required if the maximum suction pressure plus the shutoff head of the jockey pump exceed the working pressure of the fire protection system. (d) Pressure gauges. Pressure gauges for the jockey pump are not required by NFPA20, but are sometimes required by the AHJ.
Jockey Pump Controllers Jockey controllers also need not be listed for fire protection service. Jockey controllers typically consist of a disconnect switch, motor overload protector, motor starter, and a pressure switch. In addition, these controllers are often equipped with a minimum run timer to prevent cycling of the jockey pump. The minimum run timer is only acceptable if the maximum suction pressure plus the shutoff head of the jockey pump do not exceed the maximum working pressure of the fire protection system.
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In of installation, the most important factor appears in the electric fire pump controller section of NFPA20: 7-3.4.4 A fire pump controller shall not be used as a junction box to supply other equipment. Electrical supply conductors for pressure maintenance (jockey or make-up) pump(s) shall not be connected to the fire pump controller.
This simply means that, though, the jockey pump controller is often bolted to the fire pump controller, the electrical contractor must bring a separate power supply line to wire the jockey controller.
Jockey Pump Operation
psi
System gradually looses pressure
Stop Point Jockey Pump shuts off
110 100 95 90 boost Jockey pump starts
Fire Pump starts
50 Time period Figure 18: Jockey pump operating sequence. The jockey maintains the system pressure until the demand exceeds the jockey’s capacity to keep up. The fire pump then starts.
Jockey pump operation is illustrated in Figure 18. In the example, the fire pump is rated at 100PSI. As mentioned before, the jockey pump should be sized to provide 110PSI at the rated capacity (typically 5 to 10 GPM). When the system pressure falls to 95PSI, the jockey pump starts to make up for the leakage in the system, repressurizing the system. If the jockey pump is sized properly, and one sprinkler head opens, the jockey pump is unable to maintain pressure. When the system pressure drops to 90PSI, the fire pump starts.
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Chapter 6: Fire Pump Controllers Controller Types As discussed before, a fire pump may have different types of drives. It may be driven by an electric motor (powered by the building electric supply, an on-site generator, or another auxiliary supply) or by an approved diesel engine. Electric and diesel engine driven fire pumps require a controller to start and stop the fire pump in an emergency or for testing purposes. It is important to know the basic differences between the corresponding electric or diesel controller.
The Pressure Sensing Line All fire pump systems are equipped with a pressure sensing line. The line is piped into a pressure switch in the controller. The pressure switch initiates an automatic start of the fire pump if the pressure falls below a pre-determined value. The codes themselves are quite clear regarding the construction of the line. The guidelines for the pressure switch itself are also given. 7-5.2.1 Water Pressure Control. There shall be provided a pressure-actuated switch having independent high and low-calibrated adjustments in the controller circuit. There shall be no pressure snubber or restrictive orifice employed within the pressure switch. This switch shall be responsive to water pressure in the fire protection system. The pressure sensing element of the switch shall be capable of withstanding a momentary surge pressure of 400 psi (27.6 bars) without losing its accuracy. Suitable provision shall be made for relieving pressure to the pressure-actuated switch to allow testing of the operation of the controller and the pumping unit. [See Figures A-7-5.2.1(a) and (b).] (a) For all pump installations (including jockey pumps) each controller shall have its own individual pressure sensing line. (b) The pressure sensing line connection for each pump (including jockey pumps) shall be made between that pump’s discharge check valve and discharge control valve. This line shall be corrosion-resistant metallic pipe or tube, and the fittings (brass, copper, or series 300 stainless steel) shall be of ½ inch (12.7mm) nominal size. There shall be two check valves installed in the pressure sensing line at least 5 feet (1.5m) apart with a 3/32 inch (2.4mm) hole drilled in the clapper to serve as dampening. [See Figures A-7-5.2.1(a) and (b) for clarification.]
The pressure sensing line is typically piped in with ½ inch copper tube. The check valve arrangement must be noted in particular if the controller is piped and wired on site, since no matter how close the controller is located to the pump, there must be at least 5 feet of pipe between the two check valves.
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Electric Controllers Electric controllers must be supplied with at least one reliable source of power. This source may be the building supply power, an on-site emergency power generator, or some auxiliary supply. The voltage of the supply must match the controller voltage and the motor voltage. Because of the importance of a reliable source of power in an emergency situation, fire pumps are often supplied with two sources of power. The primary source is usually the building electric supply; the secondary source being a generator. The transfer of power to the secondary source in the case of primary failure is handled by a transfer switch. A transfer switch may be required by the authority having jurisdiction, and it is therefore essential that this requirement be identified before ordering any fire pump system. that the customer ordering the pump may not be aware of the local requirements for fire protection systems. It is important to note regarding installation that all current carrying components of an electric fire pump controller must be located at least 12 inches above the floor, and housed in a NEMA2 or higher enclosure. If the controller is to be floor mounted, it must be ordered with mounting feet from the controller manufacturer.
The requirements for electric controllers can be separated into two main categories: a) Limited Service Controllers: For systems using a motor less than on equal to 30 HP, a Limited Service Controller may be used if permitted by the authority having jurisdiction. Certain requirements for full service s may be ignored or replaced. Please note that limited service controller requirements are discussed at the end of this chapter. b) Full Service Controllers: Larger fire pumps or where the authority having jurisdiction requires one, a full service controller must be used. With the exception of the section on limited service controllers, this chapter covers full service controller requirements.
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Classification of Electric Controllers Electric controllers are identified based on four basic criteria: a) Motor Horsepower This value must be provided to the controller manufacturer. b) Installation Voltage The installation voltage and horsepower of the motor enables a calculation of the full load current draw of the motor. Wiring sizes and component clearances inside the controller are specified by UL and FM based on the current these components will carry. Example: Consider two full service fire pump controllers using 40 hp motors. In one installation, the voltage is 208V. In the other it is 460V. The 208V controller will require larger wire diameters and higher current ratings for the components. This will consequently increase the price of the controller.
c) Withstand Rating (Interrupt Capacity). Withstand Rating or Interrupting Capacity is the amount of current a controller can bear over a short period of time without sustaining damage. This is a measure of the controller’s performance in the event of a short circuit. The interrupting capacity is outlined by the controller manufacturer based on the full load amperage of the motor. Base controller models are offered with the minimum required withstand rating. Be aware that higher ratings may be required by the customer or the authority having jurisdiction, and that these requests must be forwarded to the controller manufacturer. Higher interrupt capacities are offered at a which can be in the thousands of dollars. d) Starting Method. Upon start-up of a fire pump, the electric motor must be brought from rest up to full speed in a short period of time. This causes the motor to draw up to 600% of its full load amperage rating. In some applications, the power supply may be able to comfortably meet this high in-rush current demand. An “Across-the-Line” or full voltage starter can be used in this application. All Limited Service controllers are of the across the line starting type. Where the power supply cannot meet this in-rush current demand, reduced voltage starting must be used. The most common methods of reduced voltage starting are primary resistor, auto transformer, wyedelta, and part winding starting. Because a large part of knowing fire pump controllers is understanding reduced voltage starting, the different methods warrant a section of their own.
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Reduced Voltage Starting A fire pump controller is allowed to start a motor while limiting the current drawn by the motor. The stipulation is that the starting period cannot exceed ten seconds. Because of the “looseness” of this requirement, a number of different methods of reduced voltage starting can be used. The reason for reduced voltage starting is that an electric motor, when started by bringing a set of ors together, can draw in excess of ten times the full load amperage of the motor (NFPA20 specifies this as six times, however, newer, higher efficiency motors can draw as much as 20 times). For smaller motors, this may not present a problem. For a larger motor, the amperage draw can be higher than the utility line can . For example, a 100HP motor at 208 volts has a full load amp rating of about 275 amps. When starting across the line, this motor can draw upwards of 2000 amps! The unusual thing about reduced voltage starting is that, in general, the voltage is not reduced at all. In fact, the voltage is usually increased. This is just an oddity of industry naming practices. a) Primary resistor. Primary resistor starting takes advantage of the voltage equation to reduce the amperage drawn by the motor. Since V=IR, if the voltage is held constant and the resistance of the circuit is increased, the current (amps) will decrease. A primary resistor controller places an extra resistance in the circuit during starting to reduced the starting amp draw of the motor. Primary resistor starting can be used on a standard across the line motor.
600
e
% of Full 420 Load 390 Current
d a
252 200 100
b c f
Full speed Figure 19: Starting “in-rush” currents for various methods of starting. Starting methods are indicated as follows: (a) Primary resistor. (b) Autotransformer. (c) Wye-delta. (d) Part Winding. (e) Across the line. (f) Motor full load amps.
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b) Autotransformer. An autotransformer is a special transformer capable of changing its output voltage when supplied with constant voltage power. Autotransformer starting takes advantage of the power equation, P=IV, to reduce the amp draw of the motor during starting. If the power is held constant, a higher voltage will require a lower current. The autotransformer starts by supplying the motor with a high voltage, gradually reducing it to the line voltage. Autotransformer starting requires only a standard across the line motor also. c) Wye-Delta. Wye delta starting requires a special motor. The reason for this is that the wyedelta controller must be wired to two different windings on the motor. The motor has a high voltage winding and a low voltage winding. The controller starts the motor on a special set of start ors wired to the high voltage winding of the motor. After the ten second start period, a “shunt trip” circuit in the controller switches to a second set of run ors wired to the lower voltage winding. Additionally, there are two types of wye-delta starting - open transition and closed transition. Open transition starting has a delay between the time the start or opens and the run or closes during the shunt trip. Closed transition starting allows the run or to close before the start or is opened. The difference is critical. A wye-delta closed transition controller can cost thousands of dollars more than an open transition one. d) Part winding. Part winding starting requires a special motor also. The part winding motor is capable of being started on half of its windings. This effectively reduces the horsepower of the motor. The controller has a run and a start set of ors similar to the wye-delta controller. The start or is wired to part of the motor winding. Once again, a shunt trip circuit engages the run or, bringing the motor to it’s full power. Required Components and Features Every full service controller must meet the requirements as given in NFPA20 Chapter 7. The following section briefly outlines and describes these required components. Those requirements which differ for limited service controllers are given in the section to follow. a) Voltage Surge Arrester. A voltage surge arrester is required for each phase of the incoming power lead. This device protects the motors from high voltage surges such as those caused by lightning. The arrester is located between the power source and all other control circuitry. b) Isolating Switch. An externally operable isolation switch is required to ensure power is disconnected from the controller for servicing. The switch is interlocked with the circuit breaker so that the switch cannot be operated while the circuit breaker is closed.
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c) Motor Protector Circuit Breaker (Disconnecting Means). An externally operable circuit breaker is required for protection of the motor from instantaneous operation of the fire pump when the isolation switch is engaged. d) Locked Rotor Overcurrent Protection. The locked rotor protector must be set to trip at between 8 and 20 seconds of exposure to a locked rotor condition (600% the full load amps of the motor). e) Motor ors. Motor ors must be rated for the motor horsepower. f)
Power Available Visible Indicator.
g) Phase Reversal Visible Indicator. Should the phase of the incoming power reverse, the controller must be capable of indicating this condition using a pilot light or lamp on the controller enclosure and energize alarm . h) Manual start handle. The controller must have a manual start handle allowing the operator to mechanically engage the fire pump should the controller fail to automatically start the fire pump. i) Testing means. The controller must have provisions so that the fire pump can be tested. This is often done by providing a deluge valve in the pressure sensing line. When the valve is opened (typically by a manually operated remote switch), the pressure switch automatically starts the fire pump simulating an actual emergency condition.
Figure 20: Electric controller layout.
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Vertical In Line Fire Pump
UL & FM Listed
PARTS LIST
PACKING SEAL
ITEM NUMBER
DESCRIPTION
401 *402 *406 407 409 411 424 *427 428 429 432 434 435 *436 *437 438
SHAFT-MOTOR SHAFT SLEEVE PACKING LANTERN RING GLAND WATER SLINGER WEARING RING-CASING KEY IMPELLER IMPELLER CASING SPACER WEARING RING-SPACER WASHER-IMPELLER BOLT-IMPELLER GASKET-CASING MOTOR
MATERIAL # 304 S.S. TEFLON BRONZE RUBBER CAST BRONZE STEEL CAST BRONZE CAST IRON CAST IRON CAST BRONZE #303 S.S. #303 S.S. RUBBER
* RECOMMENDED SPARES
7
TYPICAL FIRE PUMP & CONTROLLER ARRANGEMENT HORIZONTAL SPLIT CASE - ELECTRIC DRIVEN BUTTERFLY VALVE
BUTTERFLY VALVE
HOSE VALVE WITH CAP AND CHAIN
BUTTERFLY VALVE
FLOW METER
TEE
BACK TO FIRE PUMP SUPPLY BALL DRIP VALVE
OUTSIDE HEADER OUTSIDE WALL
AIR RELEASE VALVE
SUCTION GATE VALVE
GAUGE
GAUGE
BUTTERFLY VALVE
CASING RELIEF VALVE
TO
FROM WATER SUPPLY
SYSTEM REDUCER
INCREASER
PUMP
JOCKEY PUMP
CHECK VALVE
TEST TEE
CHECK VALVE
ELBOW
ELBOW GATE VALVE
GATE VALVE FIRE PUMP CONTROL
JOCKEY PUMP CONTROL
This drawing is a suggested arrangement and is issued for information purposes only.
SENSING LINE
FILE NO: ISSUE DATE: SUPERSEDES: DATE:
F43.169 April 1, 1996 New New
File:\systems\firepump\f_43_169.pm5
PRE START-UP / POST START-UP CHECK LIST CENTRIFUGAL PUMPS START-UP DATE: PUMP SIZE
ORDER No.: MIN. SUCT.PRESS.
SERIAL No.:
FLOW
HEAD VOLT________ PHASE _____ Hz_____
CHECK THE FOLLOWING AT PRESTART-UP 1. STORAGE
OK
REMARKS / CORRECTIVE ACTIONS
equipment for improper storage or mishandling.
2. INSTALLATION Compare electrical supply to one indicated on motor nameplate. Compare current rating of overload relays and fuses in controller against full load current value on motor nameplate.
3. ALIGNMENT the alignment of driver to pump. (Horizontal Pumps Only) suction and discharge for pipe strain. Do the flanges meet squarely?
Indicate alignment reading ___________________
4. ROTATION Manually turn coupling to assure free rotation of pump and motor.
5. SYSTEM Insure system is free of foreign matter which could damage the pump. Responsible parties present when equipment is energized.
6. DIESEL DRIVEN FIRE PUMP ONLY Engine coolant filled to the proper level? Engine oil filled to proper level? Fuel line from the tank connected to engine (supply and return)? Fuel tank filled with proper diesel fuel? Silencer properly connected to engine and outside? Engine controller wiring connected to engine junction box? Is engine jacket water heater connected to AC power? Batteries charged (MIN.24 HRS PRIOR TO START-UP) and connected to engine?
CHECK THE FOLLOWING AT POST START-UP 6. VIBRATION
OK
REMARKS / CORRECTIVE ACTIONS
Upon the occurrence of excessive vibration or noise, was equipment immediately shut down?
7. FLOW Has flow been established? Take gauge and amperage readings (if motor driven) ? Packing been adjusted to a slight leakage? If pumps are equipped with mechanical seals, has the establishment of a clear source of water to lubricate the seals been made? Is the lubricating seal water pressure a constant 10 to 15 PSI above the discharge of the pump?
8. READINGS Flow, pressure and amperage readings taken immediately after correction of all problems and restart.
CUSTOMER’S REPRESENTATIVE(S) WITNESSING TESTS:
ARMSTRONG PUMP DIV., REPRESENTATIVE CONDUCTING TESTS:
WITNESS _________________________________________
WITNESS ____________________________________________
DATE: ____________________________________________
DATE: _______________________________________________
10
TROUBLESHOOTING CAUSES
REMEDY PUMP WILL NOT START
Faulty electrical circuit
Stuffing box too tight or packing improperly installed Impeller locked Excess bearing friction due to wear and dirt
• Make sure both circuit breaker and disconnect switch are in the “ON” position • If the circuit breaker trips when the pump tries to start check horsepower and voltage specified on the schematic and wiring diagram inside the starter door with the pump motor nameplate • Ensure that the pressure switch is working properly and is responding to changes in pressure • Loosen gland swing bolts and remove stuffing box gland halves; replace packing • Remove obstruction • Remove bearings and clean, lubricate, or replace as necessary
PUMP IS NOISY OR VIBRATES Stuffing box too tight or packing improperly installed Impeller obstructed Excess bearing friction due to wear and dirt Foundation not rigid
• Loosen gland swing bolts and remove stuffing box gland halves; replace packing • Pressures fall off rapidly when an attempt is made to draw a large amount of water, remove obstruction from impeller • Remove bearings and clean, lubricate, or replace as necessary • Tighten foundation bolts or replace foundation if necessary
NO WATER DISCHARGE Air pocket or air leakage in suction line Suction connection obstructed Impeller obstructed Pump not primed
• Uncover suction pipe and locate and re-arrange • Examine suction intake, screen, and suction pipe and remove obstruction • Pressures fall off rapidly when an attempt is made to draw a large amount of water, remove obstruction from impeller • First warning is a change in pitch of the sound of the driver; shut down the pump
DISCHARGE PRESSURE TOO LOW Air leakage in suction line Suction connection obstructed Stuffing box too tight or packing improperly installed Water seal or pipe to seal obstructed or air leak into pump through stuffing boxes
Impeller obstructed Speed too low
Wrong direction of rotation
Rated motor voltage different from line voltage i.e., 220 or 440 volt motor on 208 or 416 volt line
8
• Uncover suction pipe and locate and re-arrange • Examine suction intake, screen, and suction pipe and remove obstruction • Loosen gland swing bolts and remove stuffing box gland halves; replace packing • Loosen gland swing bolt and remove stuffing box gland halves along with the water-seal ring and packing. • Clean the water age to and in the water seal-ring. Replace water seal-ring, packing gland and packing in accordance with manufacturer’s instructions • Pressures fall off rapidly when an attempt is made to draw a large amount of water, remove obstruction from impeller • Check that rated motor speed corresponds to rated speed of pump, voltage is correct, and starting equipment is operating properly • With polyphase electric motor drive two wires must be reversed; where two sources of electrical current are available, the direction of rotation produced by each should be checked • Obtain motor of correct rated voltage or larger size motor
TROUBLESHOOTING CAUSES
REMEDY PUMP WILL NOT STOP • Is the pressure switch inside the starter properly piped up to the water system? (system side) • Is the stop valve in the piping to the pressure switch open? • Check that pressure switch is working properly by disconnecting one of the pressure switch leads to simulate open position • Ensure that pressure switch connection lines have been flushed to clear dirt in piping • Make sure that pressure switch set point is correct according to suction and working pressure • Change manual start handle to automatic • Remove jumper if applicable • pressure switch setting compared to system pressure
* Faulty electrical circuit
Run period timer defective Pressure too low
* Note: Refer to control manufactures installation instructions for other controller related problems.
WARRANTY
Armstrong Darling pumps are guaranteed against defective workmanship and material for a period of twelve months from date of shipment. Should the Armstrong Darling pump fail within the warranty period, our responsibility is limited to the repair or replacement of defective parts provided such are returned to our Plant, transportation prepaid. We do not accept liability
for damage or break-down from causes beyond our control, or the result of reasonable wear nor for repair made, or date attempted to be made without prior sanction, nor for any consequential damage resulting from the failure of a pump. The customer will assume all labor charges incurred in our making the replacement of adjustment of the part.
PLEASE NOTE THAT THERE IS NO GUARANTEE ON MECHANICAL SHAFT SEALS
9
Chapter 1: Introduction: Fire Pump Codes and Standards Before discussing the details of fire pump design, codes, and operation, it is important to realize the purpose of a fire pump. A fire pump by itself is not a fire protection item. The pump merely provides the flow capacity and pressure required to operate fixtures in a fire protection system. These fixtures are typically automatic sprinkler heads or standpipe systems (generally supplying hose valves located outside the building or in hose cabinets). The purpose of these fixtures is to protect lives and property against death, injury, and damage resulting from fires. This reality bears with it a responsibility for every person involved in the process from selling, to manufacturing, to installing a fire pump. With this in mind, let us discuss the most important document with respect to the installation of fire pumps - the National Fire Protection Association’s (NFPA) Pamphlet 20.
NFPA20: Standard for the Installation of Centrifugal Fire Pumps Since the inception of the National Fire Protection Association’s (NFPA) Committee on Fire Pumps in 1899, the world of water based fire protection has come a long way. Technological advancements, new industry standards and better awareness of the dynamics of fire itself have made the regulation of fire pump installations of paramount importance. In order to guarantee reliable fire protection and that sprinkler and standpipe systems have water in an emergency, the NFPA publishes a code book Pamphlet 20 - every three years to keep up with the changing industry. Throughout the hundred years of existence, and through all the changes in the industry, though, the basic principles and philosophy of the organization have remained unchanged. Virtually every line of the pamphlet exists to guarantee that a fire pump starts in an emergency and does not shut down. A fire pump is a fire protection item. In the event of a fire, the pump should run to its own destruction, if necessary, to ensure the water required to put out the fire is supplied. With the creation of the NFPA’s fire pump committee also came a requirement for regulation of fire protection equipment, and also the requirement for ruling bodies to assess the codes and make decisions based on individual installations. For this reason, three major regulatory levels exist in fire pump regulation. It is my intention to briefly discuss them. The National Fire Protection Association (NFPA) The NFPA acts much like a legislative body. Every six months, of the committee on fire pumps meet to discuss changes and additions to the fire pump code as published in the pamphlet NFPA20. Every three years, the outcomes of the discussions and meetings are used to update the code book. The NFPA has no real authority in the actual fire protection world in of enforcing the rules - its job is simply to make them and to make general recommendations.
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The Authority Having Jurisdiction (AHJ) The AHJ acts as the judicial body, and is defined in NFPA as “the organization, office, or individual responsible for approving equipment, an installation, or procedure”. The AHJ could be the Fire Marshall or an insurance underwriter who takes into the codes (NFPA20) and any local requirements, to judge whether or not a fire pump installation is acceptable. Often the codes themselves read “where acceptable to the authority having jurisdiction”. This simply means that the codes are a guideline, and the local authority always has the power to judge whether an NFPA requirement is acceptable, whether an NFPA requirement is insufficient, or whether an NFPA requirement can in fact be waived for any particular case.
The Listing Authorities (ULC, UL, FM, LPC) Listing authorities carry more of an executive responsibility in the fire protection world. NFPA20 often states that an item “shall be listed”. This simply means that a nationally recognized testing laboratory must test, approve, and publish their acceptance of equipment to be used for fire protection service. In general, these bodies work to keep a record of approved equipment, and to ensure that manufacturers of equipment maintain the level of quality of the originally tested and listed items. It is extremely important to that the AHJ will generally have requirements of which listings will be required. For example, though a ULC listed piece of equipment satisfies NFPA20, the AHJ may require a UL or FM listing. Because the individual listing authorities often have their own requirements, these listing can in fact make two pieces of equipment for the same application completely different both in construction and cost.
Fire Pump Systems A fire pump system consists of all the components between the supply connection to the building connection required to operate a fire pump safely and effectively. These components can be broken down into the following items: (a) Fire pump. The fire pump increases the pressure of supply water at a certain flow rate to a pressure sufficient to operate fire protection fixtures. (b) Fire pump driver. The fire pump driver is typically an electric motor or diesel engine used to supply the power to operate the fire pump. (c) Valves and fittings. The valves and fittings provide control of the higher pressure discharge from the fire pump. These components allow for fire pump testing, protection of the fire protection system from overpressure or under pressure conditions, and servicing of the components of the system. (d) Fire pump controller. The fire pump controller is responsible for starting the fire pump under whatever adverse conditions may occur during an emergency.
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The controller is also responsible for communicating emergency conditions to the operator of the pump or to the appropriate building emergency control system. (e) Pressure maintenance (jockey) pump and controller. The jockey pump and controller ensure that the fire protection system is filled with water and pressurized in readiness for an emergency situation.
LEGEND 1. FIRE PUMP 2. FIRE PUMP CONTROLLER 3. GATE VALVE 4. BUTTERFLY VALVE 5. CHECK VALVE 6. GAUGES 7. CASING RELIEF VALVE 8. EXCENTRIC REDUCER (IF APPLICABLE) 9. CONCENTRIC INCREASER (IF APPLICABLE) 10. SENSING LINE NFPA 20 11. TEST TEE
Together, these components work to ensure the fire protection system is ready and able to deal with an emergency. It is for this reason that no non-operator initiated obstruction should prevent the fire pump from starting and continuing to run when started. For this reason, the only times a fire pump is allowed to stop automatically are during a test or, in the case of a diesel driven fire pump, if the diesel engine goes into an over speed, over pressurization condition. If the fire pump starts for any reason other than a test, the operator must physically go to the pump room and press the stop button on the fire pump controller. Fire pumps can be started either manually or automatically. Manual starts can be initiated from a remote location, or in the pump room itself. Automatic starting is initiated when the pressure in the fire protection system (as measured by a pressure switch) falls below a predetermined, preset value.
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Chapter 2: Fire Pumps Pumps in General The purpose of a pump is to take a certain volume of water at a certain pressure and to increase the pressure of that water. To this end, the performance of a pump can be described by two variables - the flow through the pump (often referred to as capacity), and the pressure the pump is capable of adding at the given flow rate. In practice, these two variables can be plotted to produce what is called a pump curve. The pump curve is like a fingerprint. Provided the pump is operated at the same speed, it will always generate the same pump curve.
120 100 80
Pressure 60
(in PSI) 40 20 0 0
250 500 750 1000 1250 1500 1750 2000 2250 2500 2750
Capacity (in GPM) Figure 1: A typical pump curve. For any given flow rate through the pump, the pressure boost it will provide is fixed.
The pump itself consists of a hollow casing with an inlet (referred to as the pump suction) and an outlet (referred to as the pump discharge). Within the casing, a rotating shaft assembly with a vaned impeller is spun within the casing to produce the desired pressure increase. The diameter of the impeller can be changed, or “trimmed” to produce a different characteristic pump curve.
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By itself, the pump is useless. The pump shaft must be coupled to a driver of some sort to spin the impeller within the casing to produce pressure. Generally, the driver used is an electric motor, diesel engine, or steam turbine. The most common types of fire pumps are driven by electric motors or diesel engines.
Figure 2: Cross sectional view of a vertical in-line pump. The following parts are shown: (1) Pump suction. (2) Pump discharge. (3) Impeller. (4) Pump seal. (5) Pump-motor shaft coupling. (6) Motor.
Mechanical vs. Packing Seals Because the shaft must protrude from the casing in order to be coupled to a driver, the pump must have at least one seal to prevent water from leaking through the shaft/casing mating surface. Pumps can have two types of seals - mechanical or packing.
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Mechanical seals are constructed of two precisely machined surfaces which are pressed together and generally lubricated by the product being pumped. Mechanical seals allow less leakage, but are more likely to fail catastrophically (i.e. to crack or break). Packing seals are constructed of a gland in which a compressible material (packing) is wrapped around the shaft. The gland can be tightened to compress the packing against the shaft/casing mating surface, preventing leakage. In reality, any seal must allow some leakage to remain effective. A packing seal allows more leakage, but is less subject to catastrophic failure. It is for this reason that NFPA20, the fire pump code book, requires that all fire pumps be of the packing seal type.
Pump Types There are many type of pumps. Only four types of pumps are allowed for use in fire protection service. We will discuss three of them at length. a) Split-case pumps. Split-case pumps are described as such because the pump casing consists of two halves split on a plane parallel to the shaft. A split-case pump has two seals, one on the driver end, where the shaft is coupled to the driver, and one at the opposite end where the shaft is ed. Split case pumps are of the “double suction” type.
Figure 3: Horizontal split-case pump.
b) End-suction pumps. End-suction pumps are constructed so that the pump suction is aligned with the shaft. The pump discharge is perpendicular to the shaft. End-suction pumps have only one seal at the driven end of the pump casing. End-suction pumps are of the “single suction” type. Figure 4: End-suction pump.
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c) In-line pumps. The pump suction and discharge of an in-line pump are aligned and perpendicular to the shaft. In-line pumps also employ only one seal at the driver end of the pump casing. One design and maintenance advantage of the vertical in-line pump is that it requires no pump bearings. In-line pumps are of the “single suction” type and are limited to a maximum capacity of 750GPM by NFPA20.
Figure 5: Vertical in-line pump.
One important note in pump design is that end-suction and split-case pumps must be mounted on a base, isolated from the building by some sort of vibration absorbing structure, and re-aligned whenever they are moved or serviced. In-line pumps can be mounted vertically, eliminating the need for vibration isolation, and are self-aligning. In addition, the vertical in-line pump requires less floor space in a pump room due to the fact that the motor is mounted above the pump (vertically), not on the floor (horizontally). Fire Pumps The NFPA’s Pamphlet 20 states the following: Chapter 3
Horizontal and In-Line Pumps
3-1.1 Types. Horizontal pumps shall be of the split-case, end-suction, or in-line design. 3-1.2 Application. The horizontal split-case pump in horizontal or vertical position, and end-suction and in-line pumps shall not be used where a static suction lift is involved. 3-2
Factory and Field Performance
3-2.1 Characteristics. Pumps shall furnish not less than 150 percent of rated capacity at not less than 65 percent of total rated head. Shutoff head shall not exceed 140 percent of rated head for any type of pump.
The above three points are perhaps the key design and performance requirements for fire pumps. Of note, the definitions of allowable pump types mentions “Horizontal pumps shall...”. In practice, vertical pumps are also acceptable allowing vertical in-line (Armstrong) and vertical split-case pumps to be used in fire protection.
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The concept of suction lift should be briefly addressed here. Suction lift is simply 2 defined as the static pressure at the pump suction minus the dynamic pressure (ρv /2g). Simply put, the pressure of the water entering the pump should not reach the vapour pressure of water. This condition leads to micro-vapour bubble formation at the pump suction, known as cavitation. This condition leads to the rapid deterioration of the pump casing and eventual failure of the pump. Suction lift is typically checked for in application by ensuring that the minimum suction pressure available does not exceed the net positive suction head (NPSH) of the pump. The NPSH of a pump is usually shown on the pump curve, and if not, is available upon request from the fire pump manufacturer.
Formula: where
Suction Lift = Pgauge + ρv2/2g Pgauge = pressure as read by a gauge at the suction inlet ρ = density of water v = velocity of water at suction inlet g = gravitational constant
If this number is negative, a suction lift exists. This is an unacceptable condition for fire pump operation.
The final point is the golden rule of fire pump design, which is illustrated in Figure 6. This rule creates a performance envelope for fire pumps, the most critical feature of which is the 150% rated flow at 65% rated head. The closer a fire pump can be designed to this point, the lower the BHP of the pump will be, and the smaller the driver (electric motor or diesel engine) will be. Fire pump manufacturers design pumps around this rule to maximize the pump’s competitiveness on the market.
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120
Rated
100
Capacity Pressure 80 (in PSI)
Pump BHP Curve
60 40 20 0 0
250
500
750 1000 1250 1500 1750 2000 2250 2500 2750
Capacity (in GPM) Figure 6: Fire pump curve with indication of the rated capacity: 1500GPM @ 95PSI. The lower curve is the BHP of the pump. The maximum BHP will determine our driver selection.
Maintenance and Service The NFPA codes also allow for the serviceability of a fire pump. For this reason, end suction pumps must employ a flexible type coupling designed specifically to allow the impeller and driver side seal assemblies to be removed without disturbing the piping, and without pulling the motor or diesel engine. Vertical in-line pumps are exempt from this rule, and may be close coupled to the motor. The flexible coupling for horizontal pumps is required to isolate vibration caused by the base mounted design. Vertical inline pumps are also exempt from the alignment requirements listed in A-3-5 of NFPA20.
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Chapter 3: Fire Pump Drivers Electric Motors Electric motors are one type of driver allowed by the NFPA codes. In general, electric installations must be supplied with a reliable source of power resistant to damage resulting in exposure to fires and other potential hazards. Electric motor driven fire pumps are often supplied with power from alternate sources such as an on-site generator or a secondary utility line. NFPA20 states the following regarding motor sizing: 6-4.2 Current Limits. 6-4.2.1 The motor capacity in horsepower shall be such that the maximum motor current in any phase under any condition of pump load and voltage unbalance shall not exceed the motor-rated full-load current multiplied by the service factor. The maximum service factor at which a motor can be used is 1.15.
This statement literally means that the motor must be sized to be “non-overloading” across the range of the pump curve; however, the service factor of the motor can be and should be used. What this amounts to is that the maximum pump BHP should be equal to or less than the motor rated HP multiplied by 1.15.
Formula:
Maximum Pump BHP <= Motor HP x 1.15
Example:
A VIL (vertical in-line) pump is sized for 400GPM @ 90PSI. The pump BHP is 45. What motor should be used?
Answer:
45HP/1.15 = 39.13 A 40HP motor is required.
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The NFPA’s Pamphlet 20 also states the following with respect to electric motors:
6-4
Motors
6-4.1 General. 6-4.1.1 All motors shall be specifically listed for fire pump service. (This requirement shall be effective January 1, 1998.) 6-4.1.2 All motors shall comply with NEMA Standard MG-1 and shall be marked as complying with NEMA Design B standards.
In practice, the former of the above points is not in effect. Underwriters Laboratories has only recently created a new listing for fire pump motors. Some, but not all, of the North American electric motor manufacturers have applied for this listing. Until at least one of these manufacturers can offer a workable line of approved motors, it is unlikely that compliance with the code will become an industry standard. Presently, a NEMA B labeled motor is accepted by AHJ’s across North America for use in fire pump installations.
Diesel Engines Diesel engines are becoming more common as drivers for fire pumps. The diesel engine is usually a higher first cost as well as higher maintenance item; however, engines circumvent the problem of supplying an electric motor driven fire pump with a reliable source of electricity. Because of the requirement for maintenance, and the greater likelihood of a diesel engine’s failure to start, the NFPA codes are much more strict and specific with respect to diesel engines than they are for electric motors.
Figure 7: Diesel engine for fire protection service.
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Perhaps the most important of all is the derating of diesel engines for temperature and altitude. The codes state that an engine’s BHP must be derated 3% for every 1000 feet o o over 300 feet (above sea level) and 1% for every 10 F over 77 F.
Example: A diesel engine rated at 73HP is being installed at 2037 feet (above sea level) elevation and expected to operate at a maximum ambient temperature of 89oF. Calculate the real engine BHP as per NFPA20. Answer: Deration for elevation 3% x (2037 - 300)/1000 = 5.21% Deration for temperature 1% x (89 - 77)/10 = 1.20% Total deration = 5.21% + 1.20% = 6.41% Real Diesel Engine BHP BHP = 73 - 6.41% x 73 = 68.3HP
The other important point to when sizing a diesel engine is that the engine rated speed must match the pump rated speed to within 4%. If the rated pump and diesel speeds do not exactly match, it is always wise to consult the manufacturer before quoting a job. If the diesel rated speed is lower than the pump rated speed, the pump may not be able to generate the desired pressure. Diesel engines must start reliably from a cold condition to immediately operate at the design speed. For this reason, control, maintenance and operation must be closely monitored. Diesel engines must be equipped with the following items: (a) Governor. The governor must be capable of regulating the engine speed within 10% of the rated speed across the entire flow range of the pump curve. (b) Overspeed Shutdown Device. Overspeed is the only condition upon which a diesel engine must automatically shut down. This is due to the fact that a runaway diesel engine could cause a dangerous overpressurization of the fire pump and sprinkler system. The engine overspeed shutdown device must activate if the engine operating speed is 20% higher than the rated speed of the engine. This is equivalent to a 44% overpressure condition for the fire pump. (c) Instrumentation. All engines must be equipped with an instrument with gauges for oil pressure, engine speed (tachometer), and engine coolant temperature.
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(d) Manual Cranking Device. All engines must be equipped with two manual cranks, one for each of the two batteries supplied for starting the diesel engine. (e) Heat exchanger. A water to coolant heat exchanger must be provided for all diesel engines. The cooling water is supplied from the pump discharge, after which the cooling water should be piped to a drain. Recirculation of the cooling water can be done where acceptable to the AHJ; however, this practice is not generally accepted. (f) Engine jacket water heater. Because diesel engines must be started cold and immediately operate at the rated speed without idling, an electrically operated engine jacket water heater must be supplied to maintain the engine o coolant temperature at no less than 120 F. This item is generally supplied by the engine manufacturer for operation on either 120V/1/60 or 230V/1/60 power. It is important to that most diesel engines are shipped without coolant or oil. The engine jacket water heater will typically burn out in about 5 seconds if operated dry. The coolant mix should be determined from the diesel engine operation and installation manual. (g) Two starters. Every diesel engine must be capable of being started using one of the two provided batteries. Provisions for manual cranking of the diesel engine must be provided on the fire pump controller and on the diesel engine itself.
The above items must supplied by the engine manufacturer in order for the engine to be listed. The following items must be supplied by the fire pump manufacturer: (a) Cooling water line. A cooling water line of appropriate size must be supplied from the discharge of the pump (before the pump discharge shutoff valve) and connected to the engine heat exchanger cooling water line.
(b) Exhaust connection and silencer. A seamless or welded, insulated flexible connector must the diesel exhaust outlet with the fire pump installation exhaust pipe. A silencer must be connected in the exhaust pipe. Figure 8: Flexible, connection.
insulated
exhaust
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Figure 9: Silencer.
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(c) Dual batteries. Two sets of batteries must be supplied for starting the diesel engine. These batteries must be capable of charging completely in 24 hours from a no-charge condition. The charger for these batteries is supplied in the fire pump controller. Batteries are typically 12V or 24V (2 x 12V) depending on the type of diesel engine being supplied. Figure 10: Batteries with cables and rack.
(d) Diesel fuel tank. A listed fuel tank must be supplied with fill vent, flame arrester, and piping must be supplied. No shutoff valve may be placed in the fuel return line. The tank must be sized to equal at least one US gallon per HP plus 10%. The diesel tank level should be maintained above a half.
Figure 11: Fuel tank with required fittings.
Example: Size a tank for a diesel engine with a BHP of 170. Answer: Tank size = 170 x 1.1 = 187 US Gallons All diesel engine driven fire pumps must be subjected to a weekly test during which the engine is run for not less than 30 minutes.
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Chapter 4: Valves & Fittings The NFPA’s Pamphlet 20 states the following: 3-3
Fittings
3-3.1 Where necessary, the following fittings for the pump shall be provided by the pump manufacturer or an authorized representative: (a) Automatic air release, (b) Circulation relief valve, and (c) Pressure gauges. 3-3.2 Where necessary, the following fittings shall be provided: (a) (b) (c) (d)
Eccentric tapered reducer at suction inlet, Hose valve manifold with hose valves, Flow measuring device, and Relief valve and discharge cone.
It is important to note that these requirements are open to some interpretation, and do not apply to all fire pump types. The first three listed items generally referred to as “minimum fittings”.
Automatic Air Release A listed (ULC, UL, or FM) automatic air release must be mounted on top of the pump casing to ensure the pump is free from air during operation. Due to specific design conditions, top centerline discharge end suction pumps and vertical in-line pumps are exempt from this requirement. It must be noted that the authority having jurisdiction may require that the air release be supplied even though it is not required by NFPA. The air release must be sized ½ inch.
Figure 12: Automatic Air Release Valve.
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Circulation (Casing) Relief Valve A listed (ULC, UL, or FM) circulation or casing relief valve must be mounted on the pump discharge. This requirement can be ignored on diesel fire pump systems, the reason being, a larger main relief valve will be installed from a tee in the discharge line. The purpose of the valve is to prevent over-pressurization and overheating of the system during fire pump operation at low flow conditions. This valve must be sized ¾ inch for fire pumps up to 2500GPM. The valve should be set to discharge below the pump shutoff head at the minimum suction pressure. Figure 13: Circulation (Casing) Relief Valve.
Rule of thumb: The circulation relief valve should be set to below the following condition: Minimum Suction Pressure + Boost Pressure This will ensure that the valve discharges some water at low flow conditions.
The circulation relief valve should be piped to a drain to ensure the sufficient flow of water to protect the pump from overheating. Overheating can quickly damage the pump seal. The valve should not be piped back to the suction side of the pump.
Pressure Gauges Pressure gauges sized at least 3½ inch must be provided - one for the suction side, one for the discharge side. The gauges must be connected using ¼ inch gauge valves. The gauges must meet the following requirements: (a) Suction gauge: must have a range two times the maximum suction pressure and not less than 100PSI. (b) Discharge gauge: must have a range at least twice the rated working pressure of the pump and not less than 200PSI.
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The following fittings will be supplied in specific cases. In general, they are not supplied unless requested specifically by the sprinkler contractor. It is common that the contractor will choose to supply these fittings themselves. Eccentric Tapered Reducer If the pump suction inlet is smaller than the line size, an eccentric tapered reducer must be supplied. The reducer must be mounted such that the non-tapered side of the reducer is flush with the top of the pump suction. This serves to prevent air entrainment on the suction side of the pump. Hose Valve Manifold with Hose Valves Hose valves are supplied as a means of flow testing the fire pump and to provide an external source of water for the fire department to connect to in an emergency. The hose valve manifold is connected to a test tee on the discharge side of the pump through the wall so that the hose valves themselves are outside of the building. The manifold size as well as the number of hose valves are indicated in the table below reproduced from NFPA20.
Figure 15: Hose valve with cap and chain.
Figure 16: Hose valve manifold (header).
Flow Measuring Devices A listed (ULC, UL, or FM) flow meter , where required, must be provided capable of reading up to 175% the rated capacity of the pump. Sizing of the meter must be as per the table below. Listed flow meters are generally available in either the annular or Venturi type. The Venturi type are marginally more costly, but are easier to install properly. The annular type can be mis-aligned in installation, resulting in incorrect flow readings. A suggested piping schematic for installation of a flow meter in a fire pump system is given in NFPA Pamphlet 20 appendix A-2-14.1.2(b).
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Relief Valve and Discharge Cone On systems in which the pump discharge pressure at a no-flow condition exceeds the pressure rating of the fire protection system, a listed (ULC, UL, or FM) main relief valve must be installed. This valve must be the pilot operated or spring loaded type.
Rule of Thumb: If the maximum expected suction pressure + the pump rated head x 1.4 is greater than the rating of any fittings in the pump or sprinkler system, a main relief valve should be installed.
Generally, any diesel system should be supplied with a main relief valve. The reason for this is that a diesel engine may run up to 20% faster than the rated speed. In this “overspeed” condition, the pump discharge pressure increases by 44%. This large increase in discharge pressure makes main relief valve installation a standard practice on diesel systems. Installation of a main relief valve negates the requirement for a circulation (casing) relief valve. Sizing of the relief valve are indicated in the table at the end of the chapter. Figure 17: Main relief valve with open discharge cone (waste cone)..
Example: A diesel fire pump system is sized for a minimum suction pressure of 20PSI (maximum suction pressure of 40PSI). The pump rating is for 1000GPM @ 80PSI (shutoff head of 100PSI). The maximum working pressure of the installation is 175 PSI. Should a main relief valve be installed? Answer: As a rule, any diesel system should have a main relief valve. Let’s calculate if it’s necessary anyway. At engine overspeed of 20% at shutoff Pressure = 40PSI (max. suction pressure) + 100PSI x 1.44 = 184PSI A main relief valve should be installed.
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A main relief valve also requires a discharge “enclosed” cone. These device is simply increaser switch should be installed to discharge to atmospheric pressure into a drain. This ensures that the valve has sufficient differential pressure to relieve the appropriate pressure. A sight glass must be provided so that flow in the pipe is visible. The main relief valve should not be piped back to the suction side of the pump. Other Valves and Fittings The following additional valves and fittings must be installed, but not necessarily supplied by the fire pump manufacturer: (a) A listed (ULC, UL, or FM) OS&Y gate valve on the pump suction. A butterfly valve is not acceptable. (b) A listed (ULC, UL, or FM) check valve on the pump discharge. (c) A listed (ULC, UL, or FM) butterfly valve on the downstream side of the discharge check valve. All isolation valves must be either sealed or locked in the open position, or must be supplied with a supervisory switch for remote indication of the valves’ condition (open or closed). All valves and fittings must be rated to at least the maximum working pressure of the system, and not less than the rating of the fire protection system. The suggested piping material is steel with welded, flanged, V-grooved, or threaded connections.
Fire Pump Rating GPM (L/s)
Suction Size (in.)
Discharge Size (in.)
Relief Valve Size (in.)
25 (95) 50 (189) 100 (379) 150 (568) 200 (757)
1 1½ 2 2½ 3
1 1¼ 2 2½ 3
250 (946) 300 (1136) 400 (1514) 450 (1703) 500 (1892)
3½ 4 4 5 5
750 (2839) 1000 (3785) 1250 (4731) 1500 (5677) 2000 (7570) 2500 (9462) 3000 (11,355)
Flow Meter Size (in.)
¾ 1¼ 1½ 2 2
Relief Valve Discharge (in.) 1 1½ 2 2½ 2½
3 4 4 5 5
2 2½ 3 3 3
6 8 8 8 10
6 6 8 8 10
10 12
10 12
Hose Valve Manifold Size (in.)
1¼ 2 2½ 3 3
Number & Size of Hose Valves 1 - 1½ “ 1 - 1½ “ 1 - 2½ “ 1 - 2½ “ 1 - 2½ “
2½ 3½ 5 5 5
3½ 3½ 4 4 5
1 - 2½ “ 2 - 2½ “ 2 - 2½ “ 2 - 2½ “ 2 - 2½ “
3 3 4 4 4
4 4 6 6 6
6 8 8 8 10
5 6 6 8 8
3 - 2½ “ 4 - 2½ “ 6 - 2½ “ 6 - 2½ “ 6 - 2½ “
6 6 8 8 8
6 8
10 12
8 8
8 - 2½ “ 12 - 2½ “
10 10
Reprinted from NFPA20: Table 20-2: Summary of Fire Pump Data.
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1 1½ 2½ 2½ 2½
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Chapter 5: Pressure (Jockey) Maintenance Pumps Because sprinkler and standpipe systems need water to operate, water pressure must be maintained in the these systems. As stated in NFPA20: 2-19.5 The primary or standby fire pump shall not be used as a pressure maintenance pump.
Since a fire pump cannot be used to maintain the pressure in a sprinkler or standpipe system, a separate jockey pump must be used for this purpose. It is important to note that since a jockey pump and jockey pump controller are not technically pieces of fire protection equipment (they are not used in an emergency situation), jockey pumps and controllers need not be listed for fire protection service. With respect to the sizing and selection of jockey pumps the following is of note: 2-19.1 Pressure maintenance pumps shall have rated capacities not less than any normal leakage rate. They shall have discharge pressure sufficient to maintain the desired fire protection system pressure. Though it is not explicitly stated here, the jockey pump should not be sized to provide more flow than the normal leakage rate plus the flow rate of one fire protection fixture (one sprinkler head). Should one sprinkler head open, the jockey should not be capable of supplying the flow demand - the fire pump should start. As for jockey pump pressure, it is generally accepted that the jockey be sized for 10PSI higher than the rated head of the fire pump. The fittings required for a jockey pump are as follows: (a) Suction and discharge butterfly or gate valves. (b) Discharge check valve. (c) Relief valve. The relief valve is only required if the maximum suction pressure plus the shutoff head of the jockey pump exceed the working pressure of the fire protection system. (d) Pressure gauges. Pressure gauges for the jockey pump are not required by NFPA20, but are sometimes required by the AHJ.
Jockey Pump Controllers Jockey controllers also need not be listed for fire protection service. Jockey controllers typically consist of a disconnect switch, motor overload protector, motor starter, and a pressure switch. In addition, these controllers are often equipped with a minimum run timer to prevent cycling of the jockey pump. The minimum run timer is only acceptable if the maximum suction pressure plus the shutoff head of the jockey pump do not exceed the maximum working pressure of the fire protection system.
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In of installation, the most important factor appears in the electric fire pump controller section of NFPA20: 7-3.4.4 A fire pump controller shall not be used as a junction box to supply other equipment. Electrical supply conductors for pressure maintenance (jockey or make-up) pump(s) shall not be connected to the fire pump controller.
This simply means that, though, the jockey pump controller is often bolted to the fire pump controller, the electrical contractor must bring a separate power supply line to wire the jockey controller.
Jockey Pump Operation
psi
System gradually looses pressure
Stop Point Jockey Pump shuts off
110 100 95 90 boost Jockey pump starts
Fire Pump starts
50 Time period Figure 18: Jockey pump operating sequence. The jockey maintains the system pressure until the demand exceeds the jockey’s capacity to keep up. The fire pump then starts.
Jockey pump operation is illustrated in Figure 18. In the example, the fire pump is rated at 100PSI. As mentioned before, the jockey pump should be sized to provide 110PSI at the rated capacity (typically 5 to 10 GPM). When the system pressure falls to 95PSI, the jockey pump starts to make up for the leakage in the system, repressurizing the system. If the jockey pump is sized properly, and one sprinkler head opens, the jockey pump is unable to maintain pressure. When the system pressure drops to 90PSI, the fire pump starts.
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Chapter 6: Fire Pump Controllers Controller Types As discussed before, a fire pump may have different types of drives. It may be driven by an electric motor (powered by the building electric supply, an on-site generator, or another auxiliary supply) or by an approved diesel engine. Electric and diesel engine driven fire pumps require a controller to start and stop the fire pump in an emergency or for testing purposes. It is important to know the basic differences between the corresponding electric or diesel controller.
The Pressure Sensing Line All fire pump systems are equipped with a pressure sensing line. The line is piped into a pressure switch in the controller. The pressure switch initiates an automatic start of the fire pump if the pressure falls below a pre-determined value. The codes themselves are quite clear regarding the construction of the line. The guidelines for the pressure switch itself are also given. 7-5.2.1 Water Pressure Control. There shall be provided a pressure-actuated switch having independent high and low-calibrated adjustments in the controller circuit. There shall be no pressure snubber or restrictive orifice employed within the pressure switch. This switch shall be responsive to water pressure in the fire protection system. The pressure sensing element of the switch shall be capable of withstanding a momentary surge pressure of 400 psi (27.6 bars) without losing its accuracy. Suitable provision shall be made for relieving pressure to the pressure-actuated switch to allow testing of the operation of the controller and the pumping unit. [See Figures A-7-5.2.1(a) and (b).] (a) For all pump installations (including jockey pumps) each controller shall have its own individual pressure sensing line. (b) The pressure sensing line connection for each pump (including jockey pumps) shall be made between that pump’s discharge check valve and discharge control valve. This line shall be corrosion-resistant metallic pipe or tube, and the fittings (brass, copper, or series 300 stainless steel) shall be of ½ inch (12.7mm) nominal size. There shall be two check valves installed in the pressure sensing line at least 5 feet (1.5m) apart with a 3/32 inch (2.4mm) hole drilled in the clapper to serve as dampening. [See Figures A-7-5.2.1(a) and (b) for clarification.]
The pressure sensing line is typically piped in with ½ inch copper tube. The check valve arrangement must be noted in particular if the controller is piped and wired on site, since no matter how close the controller is located to the pump, there must be at least 5 feet of pipe between the two check valves.
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Electric Controllers Electric controllers must be supplied with at least one reliable source of power. This source may be the building supply power, an on-site emergency power generator, or some auxiliary supply. The voltage of the supply must match the controller voltage and the motor voltage. Because of the importance of a reliable source of power in an emergency situation, fire pumps are often supplied with two sources of power. The primary source is usually the building electric supply; the secondary source being a generator. The transfer of power to the secondary source in the case of primary failure is handled by a transfer switch. A transfer switch may be required by the authority having jurisdiction, and it is therefore essential that this requirement be identified before ordering any fire pump system. that the customer ordering the pump may not be aware of the local requirements for fire protection systems. It is important to note regarding installation that all current carrying components of an electric fire pump controller must be located at least 12 inches above the floor, and housed in a NEMA2 or higher enclosure. If the controller is to be floor mounted, it must be ordered with mounting feet from the controller manufacturer.
The requirements for electric controllers can be separated into two main categories: a) Limited Service Controllers: For systems using a motor less than on equal to 30 HP, a Limited Service Controller may be used if permitted by the authority having jurisdiction. Certain requirements for full service s may be ignored or replaced. Please note that limited service controller requirements are discussed at the end of this chapter. b) Full Service Controllers: Larger fire pumps or where the authority having jurisdiction requires one, a full service controller must be used. With the exception of the section on limited service controllers, this chapter covers full service controller requirements.
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Classification of Electric Controllers Electric controllers are identified based on four basic criteria: a) Motor Horsepower This value must be provided to the controller manufacturer. b) Installation Voltage The installation voltage and horsepower of the motor enables a calculation of the full load current draw of the motor. Wiring sizes and component clearances inside the controller are specified by UL and FM based on the current these components will carry. Example: Consider two full service fire pump controllers using 40 hp motors. In one installation, the voltage is 208V. In the other it is 460V. The 208V controller will require larger wire diameters and higher current ratings for the components. This will consequently increase the price of the controller.
c) Withstand Rating (Interrupt Capacity). Withstand Rating or Interrupting Capacity is the amount of current a controller can bear over a short period of time without sustaining damage. This is a measure of the controller’s performance in the event of a short circuit. The interrupting capacity is outlined by the controller manufacturer based on the full load amperage of the motor. Base controller models are offered with the minimum required withstand rating. Be aware that higher ratings may be required by the customer or the authority having jurisdiction, and that these requests must be forwarded to the controller manufacturer. Higher interrupt capacities are offered at a which can be in the thousands of dollars. d) Starting Method. Upon start-up of a fire pump, the electric motor must be brought from rest up to full speed in a short period of time. This causes the motor to draw up to 600% of its full load amperage rating. In some applications, the power supply may be able to comfortably meet this high in-rush current demand. An “Across-the-Line” or full voltage starter can be used in this application. All Limited Service controllers are of the across the line starting type. Where the power supply cannot meet this in-rush current demand, reduced voltage starting must be used. The most common methods of reduced voltage starting are primary resistor, auto transformer, wyedelta, and part winding starting. Because a large part of knowing fire pump controllers is understanding reduced voltage starting, the different methods warrant a section of their own.
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Reduced Voltage Starting A fire pump controller is allowed to start a motor while limiting the current drawn by the motor. The stipulation is that the starting period cannot exceed ten seconds. Because of the “looseness” of this requirement, a number of different methods of reduced voltage starting can be used. The reason for reduced voltage starting is that an electric motor, when started by bringing a set of ors together, can draw in excess of ten times the full load amperage of the motor (NFPA20 specifies this as six times, however, newer, higher efficiency motors can draw as much as 20 times). For smaller motors, this may not present a problem. For a larger motor, the amperage draw can be higher than the utility line can . For example, a 100HP motor at 208 volts has a full load amp rating of about 275 amps. When starting across the line, this motor can draw upwards of 2000 amps! The unusual thing about reduced voltage starting is that, in general, the voltage is not reduced at all. In fact, the voltage is usually increased. This is just an oddity of industry naming practices. a) Primary resistor. Primary resistor starting takes advantage of the voltage equation to reduce the amperage drawn by the motor. Since V=IR, if the voltage is held constant and the resistance of the circuit is increased, the current (amps) will decrease. A primary resistor controller places an extra resistance in the circuit during starting to reduced the starting amp draw of the motor. Primary resistor starting can be used on a standard across the line motor.
600
e
% of Full 420 Load 390 Current
d a
252 200 100
b c f
Full speed Figure 19: Starting “in-rush” currents for various methods of starting. Starting methods are indicated as follows: (a) Primary resistor. (b) Autotransformer. (c) Wye-delta. (d) Part Winding. (e) Across the line. (f) Motor full load amps.
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b) Autotransformer. An autotransformer is a special transformer capable of changing its output voltage when supplied with constant voltage power. Autotransformer starting takes advantage of the power equation, P=IV, to reduce the amp draw of the motor during starting. If the power is held constant, a higher voltage will require a lower current. The autotransformer starts by supplying the motor with a high voltage, gradually reducing it to the line voltage. Autotransformer starting requires only a standard across the line motor also. c) Wye-Delta. Wye delta starting requires a special motor. The reason for this is that the wyedelta controller must be wired to two different windings on the motor. The motor has a high voltage winding and a low voltage winding. The controller starts the motor on a special set of start ors wired to the high voltage winding of the motor. After the ten second start period, a “shunt trip” circuit in the controller switches to a second set of run ors wired to the lower voltage winding. Additionally, there are two types of wye-delta starting - open transition and closed transition. Open transition starting has a delay between the time the start or opens and the run or closes during the shunt trip. Closed transition starting allows the run or to close before the start or is opened. The difference is critical. A wye-delta closed transition controller can cost thousands of dollars more than an open transition one. d) Part winding. Part winding starting requires a special motor also. The part winding motor is capable of being started on half of its windings. This effectively reduces the horsepower of the motor. The controller has a run and a start set of ors similar to the wye-delta controller. The start or is wired to part of the motor winding. Once again, a shunt trip circuit engages the run or, bringing the motor to it’s full power. Required Components and Features Every full service controller must meet the requirements as given in NFPA20 Chapter 7. The following section briefly outlines and describes these required components. Those requirements which differ for limited service controllers are given in the section to follow. a) Voltage Surge Arrester. A voltage surge arrester is required for each phase of the incoming power lead. This device protects the motors from high voltage surges such as those caused by lightning. The arrester is located between the power source and all other control circuitry. b) Isolating Switch. An externally operable isolation switch is required to ensure power is disconnected from the controller for servicing. The switch is interlocked with the circuit breaker so that the switch cannot be operated while the circuit breaker is closed.
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c) Motor Protector Circuit Breaker (Disconnecting Means). An externally operable circuit breaker is required for protection of the motor from instantaneous operation of the fire pump when the isolation switch is engaged. d) Locked Rotor Overcurrent Protection. The locked rotor protector must be set to trip at between 8 and 20 seconds of exposure to a locked rotor condition (600% the full load amps of the motor). e) Motor ors. Motor ors must be rated for the motor horsepower. f)
Power Available Visible Indicator.
g) Phase Reversal Visible Indicator. Should the phase of the incoming power reverse, the controller must be capable of indicating this condition using a pilot light or lamp on the controller enclosure and energize alarm . h) Manual start handle. The controller must have a manual start handle allowing the operator to mechanically engage the fire pump should the controller fail to automatically start the fire pump. i) Testing means. The controller must have provisions so that the fire pump can be tested. This is often done by providing a deluge valve in the pressure sensing line. When the valve is opened (typically by a manually operated remote switch), the pressure switch automatically starts the fire pump simulating an actual emergency condition.
Figure 20: Electric controller layout.
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Vertical In Line Fire Pump
UL & FM Listed
PARTS LIST
PACKING SEAL
ITEM NUMBER
DESCRIPTION
401 *402 *406 407 409 411 424 *427 428 429 432 434 435 *436 *437 438
SHAFT-MOTOR SHAFT SLEEVE PACKING LANTERN RING GLAND WATER SLINGER WEARING RING-CASING KEY IMPELLER IMPELLER CASING SPACER WEARING RING-SPACER WASHER-IMPELLER BOLT-IMPELLER GASKET-CASING MOTOR
MATERIAL # 304 S.S. TEFLON BRONZE RUBBER CAST BRONZE STEEL CAST BRONZE CAST IRON CAST IRON CAST BRONZE #303 S.S. #303 S.S. RUBBER
* RECOMMENDED SPARES
7
TYPICAL FIRE PUMP & CONTROLLER ARRANGEMENT HORIZONTAL SPLIT CASE - ELECTRIC DRIVEN BUTTERFLY VALVE
BUTTERFLY VALVE
HOSE VALVE WITH CAP AND CHAIN
BUTTERFLY VALVE
FLOW METER
TEE
BACK TO FIRE PUMP SUPPLY BALL DRIP VALVE
OUTSIDE HEADER OUTSIDE WALL
AIR RELEASE VALVE
SUCTION GATE VALVE
GAUGE
GAUGE
BUTTERFLY VALVE
CASING RELIEF VALVE
TO
FROM WATER SUPPLY
SYSTEM REDUCER
INCREASER
PUMP
JOCKEY PUMP
CHECK VALVE
TEST TEE
CHECK VALVE
ELBOW
ELBOW GATE VALVE
GATE VALVE FIRE PUMP CONTROL
JOCKEY PUMP CONTROL
This drawing is a suggested arrangement and is issued for information purposes only.
SENSING LINE
FILE NO: ISSUE DATE: SUPERSEDES: DATE:
F43.169 April 1, 1996 New New
File:\systems\firepump\f_43_169.pm5
PRE START-UP / POST START-UP CHECK LIST CENTRIFUGAL PUMPS START-UP DATE: PUMP SIZE
ORDER No.: MIN. SUCT.PRESS.
SERIAL No.:
FLOW
HEAD VOLT________ PHASE _____ Hz_____
CHECK THE FOLLOWING AT PRESTART-UP 1. STORAGE
OK
REMARKS / CORRECTIVE ACTIONS
equipment for improper storage or mishandling.
2. INSTALLATION Compare electrical supply to one indicated on motor nameplate. Compare current rating of overload relays and fuses in controller against full load current value on motor nameplate.
3. ALIGNMENT the alignment of driver to pump. (Horizontal Pumps Only) suction and discharge for pipe strain. Do the flanges meet squarely?
Indicate alignment reading ___________________
4. ROTATION Manually turn coupling to assure free rotation of pump and motor.
5. SYSTEM Insure system is free of foreign matter which could damage the pump. Responsible parties present when equipment is energized.
6. DIESEL DRIVEN FIRE PUMP ONLY Engine coolant filled to the proper level? Engine oil filled to proper level? Fuel line from the tank connected to engine (supply and return)? Fuel tank filled with proper diesel fuel? Silencer properly connected to engine and outside? Engine controller wiring connected to engine junction box? Is engine jacket water heater connected to AC power? Batteries charged (MIN.24 HRS PRIOR TO START-UP) and connected to engine?
CHECK THE FOLLOWING AT POST START-UP 6. VIBRATION
OK
REMARKS / CORRECTIVE ACTIONS
Upon the occurrence of excessive vibration or noise, was equipment immediately shut down?
7. FLOW Has flow been established? Take gauge and amperage readings (if motor driven) ? Packing been adjusted to a slight leakage? If pumps are equipped with mechanical seals, has the establishment of a clear source of water to lubricate the seals been made? Is the lubricating seal water pressure a constant 10 to 15 PSI above the discharge of the pump?
8. READINGS Flow, pressure and amperage readings taken immediately after correction of all problems and restart.
CUSTOMER’S REPRESENTATIVE(S) WITNESSING TESTS:
ARMSTRONG PUMP DIV., REPRESENTATIVE CONDUCTING TESTS:
WITNESS _________________________________________
WITNESS ____________________________________________
DATE: ____________________________________________
DATE: _______________________________________________
10
TROUBLESHOOTING CAUSES
REMEDY PUMP WILL NOT START
Faulty electrical circuit
Stuffing box too tight or packing improperly installed Impeller locked Excess bearing friction due to wear and dirt
• Make sure both circuit breaker and disconnect switch are in the “ON” position • If the circuit breaker trips when the pump tries to start check horsepower and voltage specified on the schematic and wiring diagram inside the starter door with the pump motor nameplate • Ensure that the pressure switch is working properly and is responding to changes in pressure • Loosen gland swing bolts and remove stuffing box gland halves; replace packing • Remove obstruction • Remove bearings and clean, lubricate, or replace as necessary
PUMP IS NOISY OR VIBRATES Stuffing box too tight or packing improperly installed Impeller obstructed Excess bearing friction due to wear and dirt Foundation not rigid
• Loosen gland swing bolts and remove stuffing box gland halves; replace packing • Pressures fall off rapidly when an attempt is made to draw a large amount of water, remove obstruction from impeller • Remove bearings and clean, lubricate, or replace as necessary • Tighten foundation bolts or replace foundation if necessary
NO WATER DISCHARGE Air pocket or air leakage in suction line Suction connection obstructed Impeller obstructed Pump not primed
• Uncover suction pipe and locate and re-arrange • Examine suction intake, screen, and suction pipe and remove obstruction • Pressures fall off rapidly when an attempt is made to draw a large amount of water, remove obstruction from impeller • First warning is a change in pitch of the sound of the driver; shut down the pump
DISCHARGE PRESSURE TOO LOW Air leakage in suction line Suction connection obstructed Stuffing box too tight or packing improperly installed Water seal or pipe to seal obstructed or air leak into pump through stuffing boxes
Impeller obstructed Speed too low
Wrong direction of rotation
Rated motor voltage different from line voltage i.e., 220 or 440 volt motor on 208 or 416 volt line
8
• Uncover suction pipe and locate and re-arrange • Examine suction intake, screen, and suction pipe and remove obstruction • Loosen gland swing bolts and remove stuffing box gland halves; replace packing • Loosen gland swing bolt and remove stuffing box gland halves along with the water-seal ring and packing. • Clean the water age to and in the water seal-ring. Replace water seal-ring, packing gland and packing in accordance with manufacturer’s instructions • Pressures fall off rapidly when an attempt is made to draw a large amount of water, remove obstruction from impeller • Check that rated motor speed corresponds to rated speed of pump, voltage is correct, and starting equipment is operating properly • With polyphase electric motor drive two wires must be reversed; where two sources of electrical current are available, the direction of rotation produced by each should be checked • Obtain motor of correct rated voltage or larger size motor
TROUBLESHOOTING CAUSES
REMEDY PUMP WILL NOT STOP • Is the pressure switch inside the starter properly piped up to the water system? (system side) • Is the stop valve in the piping to the pressure switch open? • Check that pressure switch is working properly by disconnecting one of the pressure switch leads to simulate open position • Ensure that pressure switch connection lines have been flushed to clear dirt in piping • Make sure that pressure switch set point is correct according to suction and working pressure • Change manual start handle to automatic • Remove jumper if applicable • pressure switch setting compared to system pressure
* Faulty electrical circuit
Run period timer defective Pressure too low
* Note: Refer to control manufactures installation instructions for other controller related problems.
WARRANTY
Armstrong Darling pumps are guaranteed against defective workmanship and material for a period of twelve months from date of shipment. Should the Armstrong Darling pump fail within the warranty period, our responsibility is limited to the repair or replacement of defective parts provided such are returned to our Plant, transportation prepaid. We do not accept liability
for damage or break-down from causes beyond our control, or the result of reasonable wear nor for repair made, or date attempted to be made without prior sanction, nor for any consequential damage resulting from the failure of a pump. The customer will assume all labor charges incurred in our making the replacement of adjustment of the part.
PLEASE NOTE THAT THERE IS NO GUARANTEE ON MECHANICAL SHAFT SEALS
9
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