Boiler Operation And Safety Precaution 48591s

Principles

of Operation Main Components Safe Operation

PRINCIPLES OF OPERATION

USE OF BOILERS ON BOARD 

In ships using diesel engines as main propulsion, the auxiliary boilers fitted onboard are normally used for air conditioning and heating purposes such as fuel oil heating, fuel tanks heating, lubricating oil sump tank heating, purifiers heater, domestic hot water system etc.

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Steam turbine driven cargo pumps and boiler feed pumps are also commonly used on board tankers.

Cochran Boiler

Cochran Boiler The

boiler onboard our vessel is a horizontal smoke tube COCHRAN type vertical boiler, which employs forced draft oil burning, and is capable of generating saturated steam of 7bar with a production rate of 2t/hr. The

boiler construction is vertical steel type, having fire hole and hemi-spherical and tubular combustion chambers at the lower portion.

Cochran Boiler 

Combustion gas enters the smoke chamber from the combustion chamber, and escapes into the chimney from the smoke box after ing through a group of stacks.

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The boiler shell is divided into a water drum at its central portion and a steam drum at its upper portion, and calories are transmitted to the boiler from the combustion chamber, rear tube plates, and a group of stacks, all of which are heated by combustion gas.

COMPONENTS OF BOILER

Burners

Steam Drum & Boiler Tubes   

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The Steam drum provides the space for the separation of steam and water mixture. In smoke tube boilers the water mixture is at the bottom of the drum and the steam is at the top of the drum. The steam from the steam drum is supplied to the necessary services by means of a Main Steam Stop Valve. Smoke from the boiler furnace es through the smoke chamber and enters through the smoke tubes of the boiler and escapes through the smoke box to the chimney. Water to be vaporized lies outside these tubes. These tubes are approx. 64mm diameter welded to the flat tube plates.

Safety Valve

Safety Valve 



The function of a safety valve is to prevent excessive pressure from building up in a steam boiler. It prevents boiler pressure from rising above a certain predetermined pressure by opening to allow excess steam to escape into the atmosphere when that point is reached, thus guarding the boiler against possible explosion. The SOLAS regulation says that there should be minimum two safety valves on a boiler.

Level Condenser

Low water level cut-off switch

Water Level Gauge

Water Level Gauge 

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At least two water level indicators must be fitted to each boiler . In practice the usual arrangement consists of two direct reading water level gauges mounted on steam drum and a remote reading indicator placed at a convenient control position. Gauge glasses are fitted to determined the water level in the boiler. Onboard we have Igema type gauge glass.

Main Steam Stop Valve

Main Steam Stop Valve 

This is mounted on the top of the boiler and enables the steam from boiler to be supplied to various heating devices.

Scum Valve

Scum Valve They are mounted on steam drum having an internal fitting in the form of shallow pan situated just below the normal water level with which any oil or scum which is floating on surface of water can be removed.  These valves discharge into the bottom blow down line to overboard discharge valve. 

Soot blower

Soot Blower 



In order to maintain the gas side heating surfaces of a boiler in a clean condition and so as to prevent an undue build up of deposits which can lead to corrosion or uptake fires, soot blowers are fitted. They may be operated by steam or compressed air.

Air Vent

Air Vent  They

are fitted on the top of the boiler to release air when filling the boiler or when initially raising steam.

Feed Check Valve

Feed Check Valve 

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These are fitted to give final control over the entry of feed water into the boiler. They must be screw down non return valve so that in the event of loss of feed pressure the boiler water can not blow back into the feed line. Main and auxiliary feed checks are fitted .

Bottom Blow Valve

Blow down valve 

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They are fitted to the water drum to enable water to be blown from boiler when the boiler is shut down. They can also be used to lower the density by blowing down the settled salts.

Boiler Feed Water Regulator

Boiler Feed Water Regulator 

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Automatic feed water regulator are fitted in the feed line prior to main check line. It is fitted to maintain the flow of water into the boiler and maintain the water level at its desired value during all load conditions.

Forced Draft Fan

PRIMARY SECONDRY

Forced Draft Fan 

Both the fans are driven by a single by-axial motor. Priming air from the priming fan is mixed with oil particles at an early phase of combustion and the secondary air from the secondary fan shares a substantial percentage of combustion air.

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The dampers of both the fans are coupled with spill control valve in the fuel line so that an appropriate air fuel mixture can be obtained through out the combustion.

Manhole Door

Manhole Door  Internal

access to the boiler is provided by the manhole door in the top of the shell for cleaning and inspection.  Hand holes in the lower section of the shell provide access to the lower part of the water space for cleaning and inspection.

Cascade Tank

Observation Tank

Control

Level Transmitter with Pressure Regulator

Manifold Valve

Diaphragm Valve

Valve positioner

KY-Z Type Strainer

Reducer

Burner Assembly

MAGNET VALVE

SOLENOID VALVE

SPILLCONTROL VALVE

PEG CAM

AIR FUEL RATIO CONTROL

Main Burner

FO Strainer

FO Pump

FO Heater

Heater Relief Valve

Pressure Transmitters

SAFE OPERATION

Safety Precautions

Safety Precautions

Safety Precautions

Safety Precautions

Safety Precautions

Safety Precautions

Safety Valves 

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At least two safety valves have to be fitted to the boiler as per SOLAS regulation. BLOWDOWN : The pressure drop below the lifting pressure for a safety valve is set at 5% by regulation although it is more normal to set valve at 3% to prevent excessive loss of steam. For boilers with a superheater it is important that the superheater valve not only lifts first but closes last.

Safety valve setting 

Must be set with the surveyor present except when on the waste heat unit. A chief engineer with three years experience may then set the safety valve but must submit information to surveyor for issue of certificate. Superheated steam safety valves should be set as close to operating temperature as possible as expansion can alter the relationships between valve trim and guide/nozzle rings which can effect the correct operation of the valve.        

Two safety valves- each set independently Each safety valve must release entire steam flow in pressure accumulation test Surveyor uses specially checked gauge One valve gagged valve initially set to approximately the correct position then steam pressure increased to set pressure adjust valve to lift raise and lower pressure to check fit locks to both valves on completion

Safety valve setting 

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Easing gear to be checked free before setting valves. Steam should not be released as this can damage seat. Adjustment by compression nut on top spring plate Compression spring over nut-no movement Cap with cotter –prevent unauthorized person Easing gear for manual operation

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