Purifier Room Fire: Causes, Prevention and What to Do

The purifier room is one of the most fire-prone spaces in a ship's engine room. It holds the centrifugal separators that clean heavy fuel oil, diesel oil and lubricating oil, and that oil is pumped, heated and spun at high speed in a small enclosed room, close to hot pipework and electrical equipment.

Why purifier room fires start

A fire needs fuel, oxygen and a source of ignition, and a purifier room usually has all three. The fuel is the oil in the separators and their pipes; the oxygen comes in with the room's ventilation; and the ignition sources are the oil heaters, steam lines, other hot surfaces and electrical equipment such as motors and starters. Oil leaking from a flange, a gauge connection or a separator onto a hot surface can ignite at once.

Why does purifier room oil ignite so easily?

Heavy fuel oil is heated to around 98 degrees Celsius at the purifier inlet so that water and sludge will separate out. Marine fuel oil must have a flashpoint of at least 60 degrees Celsius under SOLAS, so the oil in that compartment is already well above the temperature at which its vapour will light.

A pinhole in a pressurised line makes it worse. The oil leaves as a fine mist, and a mist takes fire from a source that would never light a pool. SOLAS chapter II-2 requires surfaces above 220 degrees Celsius to be shielded for exactly that reason, and oil soaked lagging on an exhaust or a steam line is the ignition source that keeps returning in casualty reports.

How they are prevented

Separators handling heated oil are normally placed in a room of their own. IACS guidance recommends steel boundaries from deck to deck, self-closing steel doors, ventilation that can be shut off separately from the rest of the engine room, fire detection, and a fixed fire-extinguishing system that can be released from outside, with the controls to stop the fans and purifiers close to the release point. Inside the room:

• Spray shields or anti-spray tape on the flanges and joints of oil lines, so a leaking joint drips rather than spraying across the room. SOLAS requires oil fuel lines to be screened or otherwise protected to keep leaks off hot surfaces and other sources of ignition.
• Insulation on hot surfaces, kept intact and free of oil.
• Drip trays under the separators and pumps.
• Quick-closing valves on the outlets of the settling and service tanks and remote stops for the separators and their pumps, operated from outside the room, so the oil supply can be cut without going in.
• A local fixed fire-fighting system over the separators. SOLAS requires a local application system, such as water mist, over purifiers for heated fuel oil in the larger machinery spaces of passenger ships of 500 gross tonnage and above and cargo ships of 2,000 gross tonnage and above built since 2002, in addition to the engine room's main fixed system.
• Good housekeeping, with no oily rags or rubbish left in the room.

First response to a fire

Whoever finds a very small fire raises the alarm and can then tackle it with a portable foam or powder fire extinguisher, keeping their escape route clear. For anything larger:

• Raise the fire alarm and tell the bridge and the chief engineer where the fire is.
• Stop the separators and their feed pumps with the remote stops, and close the quick-closing valves to cut off the oil.
• Stop the ventilation to the room and close its fire dampers and doors.
• Release the local water mist system if one is fitted.
• Send in only a properly equipped team, in fire suits and breathing apparatus with charged hoses, led by the chief engineer under the muster list. Water spray is used to cool and knock the fire down; a solid jet of water must not be aimed at burning oil.
• Cool the boundaries of the room to stop the fire spreading to neighbouring spaces.
• If the fire cannot be controlled, withdraw everyone and prepare to use the fixed fire-fighting system, as described below.

What is usually found broken afterwards

The quick closing valves and the remote stops decide whether a purifier room fire stays small, and they are the items inspections keep finding defective. Linkages seize, operating wires part, and valves are found blocked or wired open because they kept tripping in a seaway.

The drip tray is the other one. If the tray drain to the sludge tank is blocked, the tray fills and oil goes over the coaming instead of away from the hot surfaces. Both can only be proved by operating them.

Before the carbon dioxide goes in

Releasing a fixed carbon dioxide system into a machinery space is a one-shot decision, and the sequence around it matters as much as the release. Account for every person, stop the ventilation fans, shut the skylights and dampers, and close the quick closing valves so no more oil feeds the fire.

After release the space stays shut. Boundary cooling continues, because steel that is still hot will reflash the moment a door is opened and air returns. Re-entry is made with breathing apparatus once the space has been ventilated and tested, and the party goes in ready for the fire to reignite.