10.Scavenge fire actions

SCAVENGE FIRE:

The combinations of following three things lead to scavenge fire.

Oxygen -this is available plenty in the scavenge space.
Heat source- this could happen because of blowing by of gases between piston rings and liner or as a result of any rubbing between two surfaces.
Fuel- this can be from un-burnt fuel, carbon or cylinder lubricating oil leaked into the space

Causes of scavenge fire
1.       Excessive wear of the liner.
2.       The piston rings might be worn out or have loose ring grooves.
3.       Broken piston rings or rings seized in the grooves.
4.       Dirty scavenge space.
5.       Poor combustion due to leaking fuel valves or improper timing.
6.       Insufficient or excess cylinder lubrication.

 Indications of scavenge fire

1.       Scavenge temperature will start increasing.

2.       The turbochargers will start surging.

3.       High exhaust temperature.

4.       Loss of engine power and reduction in rpm.

5.       Smoke coming out of the scavenge drains.

6.       The paint blisters will be formed on the scavenge doors due to high temperature but this will occur only in large fires and extreme cases.

7. Black smoke in the funnel due to insufficient air for combustion. 

 Actions to be taken

1. Start reducing the engine rpm and reduce it to slow or dead slow.

2. Increase the cylinder lubrication of the affected unit. Special attention to be given for this as this does not feed the fire. In case of increase of fire do not increase the lubrication.

3. Cut off the fuel for that affected particular unit.

4. Keep scavenges drain closed.

5. Keep monitoring the scavenge and exhaust temperatures and let the fire starve and wait for it to burn itself out.

6. if fire still there, stop the engine immediately and engage turning gear, and keep engine rotating with turning gear.

7. Put the aux. blower in stop mode.

8. Cover the turbocharger suction filter.

9. Extinguish the fire with fixed fighting system for scavenge fire. This may be co2 system or a steam connection for smothering the fire.

10. Once after confirming that the fire is extinguished. The scavenge space is allowed to cool down and later opened for inspection and cleaning of the scavenge space and check for any metal deformation and visible damage.

Safety devices provided for Scavenge fire:

            1. Scavenge high temperature alarm

            2. Scavenge space relief valve

            3. Fixed firefighting equipment(steam)