Marine Engineering Study Materials

Procedure

Boiler is a pressurized vessel. Incorrect opening procedure could lead to personnel injury as well as equipment damage.

• Change over boiler fuel oil to diesel oil.
• Make sure all diesel engines are stopped or changed over to diesel oil.
• Electric fuel oil heaters can be put in use if fitted on board.
• Shut main steam stop valve and put off feed water pump.
• Carry out scum blow down to remove floating oil, sludge, etc.
• Carry out bottom blow down after scum blow down, otherwise oil carry over may occur.
• Boiler blow down to be carried out in steps to avoid thermal stresses. Excessive stresses may lead to cracking.
• Sudden cooling down and drop in pressure may cause stresses in boiler. So reduction of pressure must be gradual.
• Make sure nobody is standing near ship side blow down valve.
• Gradually reduce boiler pressure in steps, 5bar—–>4.5bar——>4bar and so on. This helps in gradual reduction in boiler temperature also.
• Safety gear to be used by the personnel operating blow down valves.
• When boiler pressure reaches 1bar, open up the vent.
• Now if the ship is loaded and having high draft, it may not be possible to drain boiler water completely. In such case arrangements to be made for transferring remaining boiler water to bilges.
• Once the boiler is fully depressurized, slack top manhole door first, make sure no pressure is inside, support the door with chain block, and slowly remove it and secure.
• Now open bottom manhole door slowly. This procedure is to be followed.
• Now open remaining mud boxes.
• Water washing and inspection of boiler can now be carried out after ventilating sufficiently.