Ch 10 Enhanced Survey Programme j1r56
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Chapter 10 THE ENHANCED HULL SURVEY SYSTEM
Introduction In view of the recent large number of losses of bulk carriers and the pollution caused by accidents to tankers, IMO has raised concern over the issue. A proposal to phase out vessels over 17 years of age has been resisted by ship owners, on the grounds that age is not the sole criteria that determine the condition of a vessel, especially if it is well maintained. An alternative response to the problem of an aging world fleet has been enhanced (more meticulous and stringent) hull surveys. This contains unified requirements to be adopted by all classification societies, while surveying tankers and bulk carriers. This contains unified requirements to the adopted by all classification societies, while surveying tankers and bulk carriers. The rules apply, regardless of size, to self-propelled oil tankers, product tankers and dry bulk cargo vessels including ore carriers and combination carriers. The features of the enhanced survey program are: 1.
Survey Planning.
2.
Document file on board.
3.
Improved procedures for thickness measurement.
4.
Harmonisation between dry-dock and renewal surveys.
5.
Extended Intermediate surveys.
6.
Possible annual examination of tanks/spaces.
7.
Phase-out of continuous Hull survey (CHS) arrangements. The basic feature of the enhanced survey is extensive examination of the hull. A ‘Close-up Examination’ is one where details of structural components are within the inspection range of the surveyor i.e. normally within reach of hand. 105
‘Overall Survey’ is intended to report on the overall condition of the tank/hold/hull structure and determine the extent of additional close-up surveys. Planning of Survey It is expected that proper planning and co-operation between the owner and the Classification society will improve the quality of the survey. Cleaning, descaling and rigging proper means of access must carry out proper preparation. Planning of the survey is done by two methods: 1.
Mandatory Minimum Survey program. This program is worked out for a ship, taking into the mandatory minimum requirements for Overall examination, close-up survey and thickness measurement that have been prescribed by the Classification society. Preparation to be carried out for the survey, such as access, cleaning/descaling, lighting, gas freeing and survey equipment are also described.
2.
Survey based on Survey Planning Document The survey-planning document identifies critical structural features, its operational features and its damage/repair history. It stipulates the location, extent and means of close-up examination of the areas. Where a proper survey planning document is established for a ship, a provision exists for reduced examination of low risk areas, during the renewal survey, provided the condition of the vessel is good after inspection of the high risk areas. Initially the survey of these risk based areas may be less than the general survey, especially when the ship is new, but if deficiencies are found in these risk areas after the ship has spent some years in service, the extent of this survey may be more than the general or mandatory survey. The planning documents contain:
Main particulars of the ship.
Plan of tanks/holds with information on their use, cathodic protection and condition of coating.
Corrosion risk nomination for close-up examination. 106
Structures and sections nominated for thickness measurements.
List of acceptable corrosion allowance for different structures. Risk nomination is an assessment and evaluation of the risk of deterioration of Structures. It takes into :
Design features such as use of high tensile steel.
Local details such as local stresses and local stress concentrations.
History of the ship with regard to corrosion, buckling, cracking, repairs carried out to and spare parts used on that particular ship as well as sister ships.
Information on the use of tanks and condition of the paint and cathodic protection on different ships from the office.
Document File The document file is to provide those concerned with complete information about the structural condition of the vessel. It serves as the basis for the survey and includes a)
Survey Report file containing
Hull survey reports
Hull summary.
Thickness measurement reports.
Survey planning document.
b)
ing Documentation
Structural plans.
Cargo and ballast history.
Repair history.
Inspection and reports of ships’ personnel.
Use of IG plant.
Each part of the document file will be contained in a binder. The four parts of the survey Report file will each have a continuously updated index showing: 107
The Document file number.
Survey type (Annual, Intermediate, renewal, damage, Repair).
Date of survey.
Cross-references between survey reports and thickness measurement report.
A new binder is to be provided for each 5-year period. Old files are to be kept on board, for the lifetime of the ship, regardless of change in management or ownership. The document file will always be examined prior to structural surveys. They are to be readily available for reference to the vessel’s history and condition. Corrosion and Coating Criteria have been established to assess corrosion and to grade the condition of coating. Substantial corrosion has been defined as an extent of corrosion, where the wastage is in excess of 75 % of allowable corrosion margins, but within acceptable limits. The laying down of criteria implies that although mild corrosion can be detected visually, extensive and deep corrosion will have to be quantitatively evaluated by thickness measurements. These values will then be compared with a list of minimum thickness for the different structures of the vessel as prepared by the Classification society.
a
b c
d
0.25c 0.75c
a: Dimension when new. b: Acceptable minimum thickness c: Acceptable maximum margin. d: Substantial corrosion. The condition of coating is defined as 108
Good: if there is only minor spot rusting. Fair: If there is local breakdown of the coating at edges of stiffeners and weld connections and or light rusting over 20 % or so of the area under consideration. Poor If there is coating breakdown in general over 20 % or more area on hard scales over 10 % area. If the coating condition is found good, the classification society may reduce the extent of close-up measurement and thickness measurement but if the coating is poor, the tank may be subjected to annual inspection Typical structural defects and their locations (Bulk carrier) 1.
Cracking of hatch covers.
2.
Cracking of hatch coamings.
3.
Plate buckling of cross deck strips and stiffening structure.
4.
Cracking at fore and aft extremities of topside tank structure.
5.
Corrosion within topside tanks and double skin.
6.
Grab and bulldozer damage the main frame/lower bracket.
7.
Cracking at main frame bracket toes.
8. 9. 10.
Both general and localised corrosion of main ship’s side frames and brackets. Cracking at the connection of the inner bottom and hopper plating. Grab damage to the tank top plating, hopper and lower stool plating.
Where to look and what to look for 1. 2.
Side shell plating – Cracks, leaks and distortion. Connection of side shell frame and end brackets to shell plating and hopper side tank plating – Cracks, corrosion, wastage, deformation and detached frames or brackets.
109
3.
Connection of side shell frames and end brackets to shell plating and topside tank plating- Cracks, corrosion, wastage, deformation and detached frames or brackets.
4.
Connection of side shell frames and end brackets to shell plating and topside tank plating – Cracks, corrosion, wastage, deformation and detached frames or brackets.
5.
Slant plate at junction of lower stool and corrugated bulkhead – Cracks, corrosion, wastage, leaks.
6.
Connecting trunk between tanks, where fitted, - Cracks, corrosion, wastage and leaks. See figures below
3
BUCKING
1 2
CRACKING
CORROSION
5 CRACKING
7
6
4 CRACKING
MECHANICAL DAMAGE
10 CRACKING
CORROSION
8
9
110
6 4 6
2
1
3
111
Introduction In view of the recent large number of losses of bulk carriers and the pollution caused by accidents to tankers, IMO has raised concern over the issue. A proposal to phase out vessels over 17 years of age has been resisted by ship owners, on the grounds that age is not the sole criteria that determine the condition of a vessel, especially if it is well maintained. An alternative response to the problem of an aging world fleet has been enhanced (more meticulous and stringent) hull surveys. This contains unified requirements to be adopted by all classification societies, while surveying tankers and bulk carriers. This contains unified requirements to the adopted by all classification societies, while surveying tankers and bulk carriers. The rules apply, regardless of size, to self-propelled oil tankers, product tankers and dry bulk cargo vessels including ore carriers and combination carriers. The features of the enhanced survey program are: 1.
Survey Planning.
2.
Document file on board.
3.
Improved procedures for thickness measurement.
4.
Harmonisation between dry-dock and renewal surveys.
5.
Extended Intermediate surveys.
6.
Possible annual examination of tanks/spaces.
7.
Phase-out of continuous Hull survey (CHS) arrangements. The basic feature of the enhanced survey is extensive examination of the hull. A ‘Close-up Examination’ is one where details of structural components are within the inspection range of the surveyor i.e. normally within reach of hand. 105
‘Overall Survey’ is intended to report on the overall condition of the tank/hold/hull structure and determine the extent of additional close-up surveys. Planning of Survey It is expected that proper planning and co-operation between the owner and the Classification society will improve the quality of the survey. Cleaning, descaling and rigging proper means of access must carry out proper preparation. Planning of the survey is done by two methods: 1.
Mandatory Minimum Survey program. This program is worked out for a ship, taking into the mandatory minimum requirements for Overall examination, close-up survey and thickness measurement that have been prescribed by the Classification society. Preparation to be carried out for the survey, such as access, cleaning/descaling, lighting, gas freeing and survey equipment are also described.
2.
Survey based on Survey Planning Document The survey-planning document identifies critical structural features, its operational features and its damage/repair history. It stipulates the location, extent and means of close-up examination of the areas. Where a proper survey planning document is established for a ship, a provision exists for reduced examination of low risk areas, during the renewal survey, provided the condition of the vessel is good after inspection of the high risk areas. Initially the survey of these risk based areas may be less than the general survey, especially when the ship is new, but if deficiencies are found in these risk areas after the ship has spent some years in service, the extent of this survey may be more than the general or mandatory survey. The planning documents contain:
Main particulars of the ship.
Plan of tanks/holds with information on their use, cathodic protection and condition of coating.
Corrosion risk nomination for close-up examination. 106
Structures and sections nominated for thickness measurements.
List of acceptable corrosion allowance for different structures. Risk nomination is an assessment and evaluation of the risk of deterioration of Structures. It takes into :
Design features such as use of high tensile steel.
Local details such as local stresses and local stress concentrations.
History of the ship with regard to corrosion, buckling, cracking, repairs carried out to and spare parts used on that particular ship as well as sister ships.
Information on the use of tanks and condition of the paint and cathodic protection on different ships from the office.
Document File The document file is to provide those concerned with complete information about the structural condition of the vessel. It serves as the basis for the survey and includes a)
Survey Report file containing
Hull survey reports
Hull summary.
Thickness measurement reports.
Survey planning document.
b)
ing Documentation
Structural plans.
Cargo and ballast history.
Repair history.
Inspection and reports of ships’ personnel.
Use of IG plant.
Each part of the document file will be contained in a binder. The four parts of the survey Report file will each have a continuously updated index showing: 107
The Document file number.
Survey type (Annual, Intermediate, renewal, damage, Repair).
Date of survey.
Cross-references between survey reports and thickness measurement report.
A new binder is to be provided for each 5-year period. Old files are to be kept on board, for the lifetime of the ship, regardless of change in management or ownership. The document file will always be examined prior to structural surveys. They are to be readily available for reference to the vessel’s history and condition. Corrosion and Coating Criteria have been established to assess corrosion and to grade the condition of coating. Substantial corrosion has been defined as an extent of corrosion, where the wastage is in excess of 75 % of allowable corrosion margins, but within acceptable limits. The laying down of criteria implies that although mild corrosion can be detected visually, extensive and deep corrosion will have to be quantitatively evaluated by thickness measurements. These values will then be compared with a list of minimum thickness for the different structures of the vessel as prepared by the Classification society.
a
b c
d
0.25c 0.75c
a: Dimension when new. b: Acceptable minimum thickness c: Acceptable maximum margin. d: Substantial corrosion. The condition of coating is defined as 108
Good: if there is only minor spot rusting. Fair: If there is local breakdown of the coating at edges of stiffeners and weld connections and or light rusting over 20 % or so of the area under consideration. Poor If there is coating breakdown in general over 20 % or more area on hard scales over 10 % area. If the coating condition is found good, the classification society may reduce the extent of close-up measurement and thickness measurement but if the coating is poor, the tank may be subjected to annual inspection Typical structural defects and their locations (Bulk carrier) 1.
Cracking of hatch covers.
2.
Cracking of hatch coamings.
3.
Plate buckling of cross deck strips and stiffening structure.
4.
Cracking at fore and aft extremities of topside tank structure.
5.
Corrosion within topside tanks and double skin.
6.
Grab and bulldozer damage the main frame/lower bracket.
7.
Cracking at main frame bracket toes.
8. 9. 10.
Both general and localised corrosion of main ship’s side frames and brackets. Cracking at the connection of the inner bottom and hopper plating. Grab damage to the tank top plating, hopper and lower stool plating.
Where to look and what to look for 1. 2.
Side shell plating – Cracks, leaks and distortion. Connection of side shell frame and end brackets to shell plating and hopper side tank plating – Cracks, corrosion, wastage, deformation and detached frames or brackets.
109
3.
Connection of side shell frames and end brackets to shell plating and topside tank plating- Cracks, corrosion, wastage, deformation and detached frames or brackets.
4.
Connection of side shell frames and end brackets to shell plating and topside tank plating – Cracks, corrosion, wastage, deformation and detached frames or brackets.
5.
Slant plate at junction of lower stool and corrugated bulkhead – Cracks, corrosion, wastage, leaks.
6.
Connecting trunk between tanks, where fitted, - Cracks, corrosion, wastage and leaks. See figures below
3
BUCKING
1 2
CRACKING
CORROSION
5 CRACKING
7
6
4 CRACKING
MECHANICAL DAMAGE
10 CRACKING
CORROSION
8
9
110
6 4 6
2
1
3
111
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