Answer EKG Question 14
Q14.
As second engineer onboard a tanker, describe the procedure for
presenting a Main Boiler for survey by a classification society.
Answer: Need for Boiler Survey:-
Flag State and Classification society regulations require that marine boilers be surveyed at specified intervals. Class Machinery status reports give details of past inspections of the boilers on board a ship and the due date range for the next inspection. Boilers are surveyed to meet the Class requirements during installation and commissioning. Subsequently, surveys are conducted at specified intervals to ensure that they continue to be fit for duty.
At the time of survey internal inspection and external examination are carried out. Regular internal and external examination during such survey constitute the preventive maintenance schedule the boiler goes through for a safe working condition.
Frequency of Surveys:-
Water tube main propulsion boilers are surveyed at 2 yearly intervals. All other boilers including exhaust gas boilers are surveyed at 2 yearly intervals until they are 8 years old and then surveyed annually. For auxiliary boilers of water tube type, the classification may allow the 2-year incidence to continue even often the expiry of 8 years period.
Scope of Surveys:- A complete boiler survey allows us to check out if any build-up of deposits has taken place, and deformations or wastage of plate work, piping or any of the various parts, which may compromise the safe working order of the unit. The survey should include finding reasons for any anomalies found and should also ensure that any repair carried out does not affect the safe working order of the boiler. A complete survey means full internal and external examination of all parts of the boiler and accessories such as super heaters, economiser, air-heater and all mountings. The examination may lead the surveyor to require hydraulic testing of pressure parts or thickness gauging of plate or tubes that appear to be wasted and eventually assign a lower working pressure. The collision chocks, seating stools and rolling stays are also to be checked for good working condition.
Shutting down a boiler for inspection or repair:
(a) Read and follow maker's instruction manuals and company procedures. All personnel involved should wear PPE i,e. helmet, safety shoes, hand gloves, etc.
(b) Issue work permits mentioning the nature of work, scheduled work time and persons involved. Inform the chief engineer, duty officer and post necessary notices. Soot blow the boiler and change the boiler control from automatic to manual.
(c) Stop the boiler firing, shut off the fuel and feed systems. Purge the boiler for three to five minutes.
(d) Switch off the main power and turn off the air circuit breakers for the combustion control panel, the forced draught fan, the fuel oil pump and the boiler feed water pump dose the main and auxiliary steam-stop valves.
(e) Let the boiler steam pressure drop to 1 bar. Open the air vent to avoid vacuum formation and allow the boiler to cool down. Open the blow-down to empty the boiler drum.
(f) Ensure boiler is drained and is sufficiently before opening up.
(g) Loosen the nuts on the top manhole doors and gently knock the door into ensuring there is no residual steam pressure. Open the top doors first, and then the bottom doors.
(h) Open the furnace door taking necessary precaution. Thoroughly ventilate the boiler for 12 to 24 hours. Personnel should not enter boiler, furnace or flue until the unit has cooled sufficiently.
(i) Ensure all connections to drum are either blanked off, removed or valves locked in dosed position with posted notices.
The survey is not complete until the boiler has been examined under steam and the following items dealt with:
(a) Pressure gauge checked against a test gauge.
(b) Testing of water level indicators and protective devices.
(c) Safety valves adjusted under steam to blow off at the required pressures;
(d) The oil fuel burning system examined.
(e) Testing of remote control gear for oil fuel shut off valves.
Arrangement before Survey
(a) Boiler must be sufficiently cleaned and dried to make a thorough examination possible. Sludge deposits continue to be the prime cause of non-operation of internal controls and overheating of furnace in vertical boilers. Boilers should be manually wire-brushed to clean the internal surfaces.
In case of difficulty in manual cleaning, a chemical cleaning with hydro-chloric- acid plus an inhibitor to prevent acid attacking the metal without affecting removal of deposits is the best procedure.
For oil contamination, alkali boil-out using tri-sodium phosphate solution (which produces a detergent action) is essential prior to acid cleaning.
A thorough water flushing must be carried out after acid cleaning to avoid acid concentrating in crevices and captive spaces.
(b) All internals which may interfere with the inspection has to be removal.
(c) Wherever adequate visual examination is not possible, surveyor may have to resort to drilling, ultrasonic or hydraulic testing.
(d) All manhole doors and other doors must be opened for a reasonable time previous to survey for ventilation.
(e) If another boiler is under steam arrangement of locking bar and other security devices must be in position preventing the admission of steam or hot water to the boiler under survey, The smoke trunking (separating device), exhaust-gas shut-offs etc. must also be in position and in proper working condition.
(f) Ship's staff or repairer's staff should stand by the manhole in case of emergency and to note any repairs required.
1. Fuel oil burner put off, pump stopped and fuel oil line shut and isolated.
2. Air supply to the furnace shut after purging.
3. Main aux steam stop valve kept shut and hand wheel removed.
4. 3/4th gauge glass water taken to the boiler for proper scum blow, then all feed check valves kept shut and hand wheel removed.
5. Allow boiler pressure to fall about 4-5 bar naturally or by easing gear.
6. Boiler ship side blow down cock is to be opened, then boiler to be scum blown so that oily grease can bot adhere to the internal surfaces. After scum blow down, valve to shut, then bottom blow down valve to be open slowly and boiler to be blow down completely, Initially open the valve fully for 3-4 seconds so that sudden surge of water carried the sludge with it. Repeat 3-4 times, then close bottom blow down valve and then ship side blow down cocks.
7. The vent cock is to be open at a pressure of one bar in order to fully release the pressure and destroy the vacuum, otherwise a serious accident may occur while opening the manhole door.
8. The top manhole door is to be knocked first otherwise if bottom door is opened first, there is a danger of being met with a rush of scalding vapour when the top door is knocked in, the person may meet serious accident, the top manhole door is to be tied with a rope, the dog nut are to be slackened and the door joints broken, person should stand well clear off the door. After removing nuts and dogs, the door to be removed.
9. After knocking the top door the bottom manhole door to be opened in a similar manner. when doing so the person should stand well clear in case there is any hot water present inside.
10. The boiler is allowed to cool down and ventilated by natural circulation of the air and it is ready for cleaning next day. No naked light is allowed near the boiler until it is ventilated due to danger of explosive gas in the boiler.
11. Periodical Surveys of boilers and other pressure vessels to carried out as required by the Rules and the safety devices to tested. External visual examination. External examination of boilers including test of safety & protective devices and test of safety valve using it's relieving gear. For exhaust gas economizers, review of engine log book to verify that Chief Engineer has tested the safety valves at sea within the window period of Annual Survey.
Flag State and Classification society regulations require that marine boilers be surveyed at specified intervals. Class Machinery status reports give details of past inspections of the boilers on board a ship and the due date range for the next inspection. Boilers are surveyed to meet the Class requirements during installation and commissioning. Subsequently, surveys are conducted at specified intervals to ensure that they continue to be fit for duty.
At the time of survey internal inspection and external examination are carried out. Regular internal and external examination during such survey constitute the preventive maintenance schedule the boiler goes through for a safe working condition.
Frequency of Surveys:-
Water tube main propulsion boilers are surveyed at 2 yearly intervals. All other boilers including exhaust gas boilers are surveyed at 2 yearly intervals until they are 8 years old and then surveyed annually. For auxiliary boilers of water tube type, the classification may allow the 2-year incidence to continue even often the expiry of 8 years period.
Scope of Surveys:- A complete boiler survey allows us to check out if any build-up of deposits has taken place, and deformations or wastage of plate work, piping or any of the various parts, which may compromise the safe working order of the unit. The survey should include finding reasons for any anomalies found and should also ensure that any repair carried out does not affect the safe working order of the boiler. A complete survey means full internal and external examination of all parts of the boiler and accessories such as super heaters, economiser, air-heater and all mountings. The examination may lead the surveyor to require hydraulic testing of pressure parts or thickness gauging of plate or tubes that appear to be wasted and eventually assign a lower working pressure. The collision chocks, seating stools and rolling stays are also to be checked for good working condition.
Shutting down a boiler for inspection or repair:
(a) Read and follow maker's instruction manuals and company procedures. All personnel involved should wear PPE i,e. helmet, safety shoes, hand gloves, etc.
(b) Issue work permits mentioning the nature of work, scheduled work time and persons involved. Inform the chief engineer, duty officer and post necessary notices. Soot blow the boiler and change the boiler control from automatic to manual.
(c) Stop the boiler firing, shut off the fuel and feed systems. Purge the boiler for three to five minutes.
(d) Switch off the main power and turn off the air circuit breakers for the combustion control panel, the forced draught fan, the fuel oil pump and the boiler feed water pump dose the main and auxiliary steam-stop valves.
(e) Let the boiler steam pressure drop to 1 bar. Open the air vent to avoid vacuum formation and allow the boiler to cool down. Open the blow-down to empty the boiler drum.
(f) Ensure boiler is drained and is sufficiently before opening up.
(g) Loosen the nuts on the top manhole doors and gently knock the door into ensuring there is no residual steam pressure. Open the top doors first, and then the bottom doors.
(h) Open the furnace door taking necessary precaution. Thoroughly ventilate the boiler for 12 to 24 hours. Personnel should not enter boiler, furnace or flue until the unit has cooled sufficiently.
(i) Ensure all connections to drum are either blanked off, removed or valves locked in dosed position with posted notices.
The survey is not complete until the boiler has been examined under steam and the following items dealt with:
(a) Pressure gauge checked against a test gauge.
(b) Testing of water level indicators and protective devices.
(c) Safety valves adjusted under steam to blow off at the required pressures;
(d) The oil fuel burning system examined.
(e) Testing of remote control gear for oil fuel shut off valves.
Arrangement before Survey
(a) Boiler must be sufficiently cleaned and dried to make a thorough examination possible. Sludge deposits continue to be the prime cause of non-operation of internal controls and overheating of furnace in vertical boilers. Boilers should be manually wire-brushed to clean the internal surfaces.
In case of difficulty in manual cleaning, a chemical cleaning with hydro-chloric- acid plus an inhibitor to prevent acid attacking the metal without affecting removal of deposits is the best procedure.
For oil contamination, alkali boil-out using tri-sodium phosphate solution (which produces a detergent action) is essential prior to acid cleaning.
A thorough water flushing must be carried out after acid cleaning to avoid acid concentrating in crevices and captive spaces.
(b) All internals which may interfere with the inspection has to be removal.
(c) Wherever adequate visual examination is not possible, surveyor may have to resort to drilling, ultrasonic or hydraulic testing.
(d) All manhole doors and other doors must be opened for a reasonable time previous to survey for ventilation.
(e) If another boiler is under steam arrangement of locking bar and other security devices must be in position preventing the admission of steam or hot water to the boiler under survey, The smoke trunking (separating device), exhaust-gas shut-offs etc. must also be in position and in proper working condition.
(f) Ship's staff or repairer's staff should stand by the manhole in case of emergency and to note any repairs required.
1. Fuel oil burner put off, pump stopped and fuel oil line shut and isolated.
2. Air supply to the furnace shut after purging.
3. Main aux steam stop valve kept shut and hand wheel removed.
4. 3/4th gauge glass water taken to the boiler for proper scum blow, then all feed check valves kept shut and hand wheel removed.
5. Allow boiler pressure to fall about 4-5 bar naturally or by easing gear.
6. Boiler ship side blow down cock is to be opened, then boiler to be scum blown so that oily grease can bot adhere to the internal surfaces. After scum blow down, valve to shut, then bottom blow down valve to be open slowly and boiler to be blow down completely, Initially open the valve fully for 3-4 seconds so that sudden surge of water carried the sludge with it. Repeat 3-4 times, then close bottom blow down valve and then ship side blow down cocks.
7. The vent cock is to be open at a pressure of one bar in order to fully release the pressure and destroy the vacuum, otherwise a serious accident may occur while opening the manhole door.
8. The top manhole door is to be knocked first otherwise if bottom door is opened first, there is a danger of being met with a rush of scalding vapour when the top door is knocked in, the person may meet serious accident, the top manhole door is to be tied with a rope, the dog nut are to be slackened and the door joints broken, person should stand well clear off the door. After removing nuts and dogs, the door to be removed.
9. After knocking the top door the bottom manhole door to be opened in a similar manner. when doing so the person should stand well clear in case there is any hot water present inside.
10. The boiler is allowed to cool down and ventilated by natural circulation of the air and it is ready for cleaning next day. No naked light is allowed near the boiler until it is ventilated due to danger of explosive gas in the boiler.
11. Periodical Surveys of boilers and other pressure vessels to carried out as required by the Rules and the safety devices to tested. External visual examination. External examination of boilers including test of safety & protective devices and test of safety valve using it's relieving gear. For exhaust gas economizers, review of engine log book to verify that Chief Engineer has tested the safety valves at sea within the window period of Annual Survey.
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