There are three basic ways of fighting fires. Cooling, to reduce heat; starving to remove fuel and smoldering to cut out air/oxygen. This would depend on several factors, like the materials burning, threat of collateral damage to other equipment and risk of escalation, etc. This is achieved using agents like water, foam, powder, specialized gasses and shut-off valves, etc.

When some metals are rapidly cooled, they become more brittle and are subject to fracture. Brittle failure often does not show the initial cracks on the surface. But on closer inspection, one would find many small vein-like lines. This may make the metal fail in service at a later date. For example, fires involving pipework in high temperature service, carrying flammable gasses are not cooled with water “by default” except as a last resort, where the fire is now uncontrollable and the section of pipe needs to be sacrificed to save the larger process facility and prevent escalation beyond that area.

The preferred way to kill such fires is by starving. The source of fuel (e.g flammable gasses) is simply cut off by closing a valve upstream and the fire gradually recedes as the gas left in the line is burnt out. This ensures that the affected pipe section retains its integrity to the extent that it can be returned to service quickly and reliably. Going the route of quenching with water may see the fire go out quicker, yet, the facility may either suffer a repeat fire due to leaks resulting from pipe fracture caused by cracks not observed and addressed; or if observed,  extended periods of downtime from replacing the whole line.

Sometimes, we do more damage when all we have in our bag is one tool for every problem.

 

SAN

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