Diesel Engine Runaways – Everything You Need to Know

Although a rare occurrence, diesel engine runaways are a dangerous phenomenon that can occur in high-risk areas often found in the oil and gas industry. They can pose a catastrophic risk to anyone in the nearby vicinity when they occur.

Luckily, due to most of the potential components being electronic these days, the chances of a diesel engine runaway occurring are very low. But still, the best way to avoid one happening is through regular maintenance from a trusted diesel mechanic and checking on your vehicle’s turbine and intake hose every once in a while.

Petrol vs. diesel engines

To properly understand this event, it’s important to know the difference between petrol and diesel engines. In a petrol engine, spark plugs ignite the combination of air and petrol inside the cylinders. In a diesel engine, however, this process is entirely different. Instead, it works by drawing in clean air via its intake into a combustion chamber. Once inside, the air and fuel combination is compressed so much that it creates enough heat to ignite.

The fuel fed into the combustion chamber is controlled by a governor that controls the speed of the engine. The more fuel allowed in by the governor, the faster the engine will run. A diesel engine can only be shut down when the fuel supply is removed or the air supply is cut off.

How a diesel engine runaway occurs

A diesel engine runaway occurs when the engine uses extra fuel, such as a flammable or hydrocarbon vapour, from an unintended source through its air intake system. As the engine begins running off this external fuel source, less diesel fuel will be released by the governor until the extra fuel becomes its only source.

This can then cause the engine to over speed and the valves to move around, causing flames to pass through the manifold. These flames can then ignite once they meet with the external fuel source and cause dangerous fires or explosions.

How to stop it from occurring

A diesel engine runaway can begin in as little as 3 to 12 seconds after fuel begins being sucked into the engine, giving you a very small amount of time to react appropriately. If you are unsure of how to stop it, simply get as far away as you can from the engine as possible and protect yourself.

While most people’s first instinct would be to turn the engine off, unfortunately, this won’t help due to the engine already being running off the flammable vapours it is ingesting. It will not stop the engine from running uncontrollably and the best option is to cut off the air supply instead. This can either be done physically using some sort of cover or with a CO2 fire extinguisher that can be used to smother the engine.

Luckily, there are devices available that can be installed on an engine’s air intake hose that can tell when it’s overspeeding. It then will cut off the air supply immediately, shutting down the diesel engine safely and efficiently.

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