1. Preparation: Inform the watch/ duty engineer, obtain permission, and prepare a permit-to-work/ risk assessment. Stop the boiler firing and allow it to cool and depressurise.
2. Blow down: Open the bottom blowdown valve (and surface blowdown as required) to discharge sludge and concentrated boiler water to the blowdown tank/ overboard (in accordance with MARPOL/ local regulations - blowdown water must not be discharged overboard in port/ restricted areas). Blow down until the boiler is empty/ drained as required.
3. Isolate: Close and secure the steam, feed water, fuel and air connections; blank off or lock the valves; tag the boiler "not to be fired".
4. Vent and cool: Open the vents/ manhole to allow the boiler to cool and the atmosphere to be safe; ventilate thoroughly.
5. Open up: Remove the manhole covers (top and bottom) and the inspection/ handhole covers to give access to the steam space, water space, tubes, drum and headers.
6. Clean: Remove sludge, scale and deposits from the water side; clean the fire side (tubes, furnace) of soot and deposits.
7. Inspect: Carry out the internal and external inspection (see part c).

During inspection:

• Ensure the boiler is isolated, cooled, vented and gas-free; test the atmosphere before entry (enclosed-space entry permit).
• Use correct PPE and follow the enclosed-space entry procedure (stand-by watch, lifeline, communication).
• Do not enter until the boiler is safe (cool, no pressure, no toxic/ flammable gas).
• Use adequate lighting (approved, low-voltage) and tools.
• Protect the boiler internals from damage.

When boxing up:

• Ensure all personnel are out and all tools/ materials are removed from the boiler.
• Clean and inspect the manhole/ handhole faces and fit new gaskets.
• Refit and torque the manhole covers correctly (in the correct sequence).
• Close all vents, drains and openings.
• Refill the boiler with treated feed water to the correct level.
• Carry out a hydraulic/ steam test as required before returning to service.
• Reconnect the steam, feed, fuel and air connections and remove the blanks/ locks.
• Bring the boiler back on line gradually, checking for leaks and correct operation.

Parts requiring close attention:

• The water side: tubes, tube plates, drum, headers, for corrosion, pitting, scale, cracking and wastage.
• The fire side: tubes, furnace, for soot, corrosion, erosion and cracking.
• The manhole/ handhole faces and gaskets.
• The safety valves, water level controls, and the feed water system.
• The boiler shell/ drum for corrosion, cracking and distortion.

Setting of safety valves:

• The safety valves are set to lift at the correct pressure (the boiler's working pressure, or as per Class requirements - typically set to lift at the working pressure and to reseat at a set blowdown).
• Procedure: With the boiler at operating pressure (or using a test/ gagging arrangement), the safety valve spring/ setting is adjusted so the valve lifts at the set pressure. The valve is tested by raising the boiler pressure (or by a test rig) and observing the lift and reseat. The setting is verified and recorded, and the valve is sealed/ locked to prevent tampering. The safety valve must be set to comply with the classification society requirements (e.g. lift at working pressure, reseat within a set blowdown, and have adequate capacity).