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Diesel engine damage

Diesel engine damage

Diesel engine damage

(OP)
Hello dear engineers,

Could a diesel engine be damaged severely because of back pressure due to non holding check valve? The diesel engine operates a fire water pump.

RE: Diesel engine damage

Explain to the rest of us, where that check valve is in the system and what it's meant to be stopping the back-flow of.

I can guess, but I don't want to guess.

RE: Diesel engine damage

So you mean the engine runs in reverse without fuel going in?

Won't do it good for sure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Diesel engine damage

(OP)
It’s a fire water system. The check valve in the pump discharge was found passing and reverse flow is allowed. My question is: Could the diesel engine be damaged because of back pressure?

RE: Diesel engine damage

Your question makes little sense.
why is there reverse flow, if there is - where is it coming from?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Diesel engine damage

(OP)
It was weekly diesel fire pump check. While the test was running the electrical fire pump was also running. This is where back pressure came from.

RE: Diesel engine damage

Backpressure won't hurt anything unless there was sufficient reverse flow to drive the pump and engine backwards for a period of time.

RE: Diesel engine damage

(OP)
Thank you all for your responses. Would this back pressure interrupt cooling water circulation towards the engine’s heat exchanger?

RE: Diesel engine damage

Does your engine circulate firefighting water through the heat exchanger? I doubt this to be the case.

RE: Diesel engine damage

(OP)
Yes the heat exchanger takes its feed from pump discharge and circulates back to pump suction.

RE: Diesel engine damage

Still don't understand, was the electric pump running at the same time as the diesel pump?

If yes what back pressure are you talking about?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Diesel engine damage

Well those weekly dead head fire water tests are designed, IMHO, to simply destroy your pump for sure.

Now what it does to the engine I don't know but the cooling water might increase in temperature as it goes around in a loop...

If the other pump was running at the same time, then when you shut off the diesel pump you might get a sudden stop, but basically everyone here is guessing.

Post a diagram of the system nd a timeline and description of the operation and we might, just might, get somewhere.

Even if the NRV was passing, it's difficult to see enough flow to be able to turn the diesel pump in reverse. Normally the water would just flow through the pump.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Diesel engine damage

On the diesel engine driven fire pumps I've worked with, the fire pump discharge water supplies the engine cooling water. That flow also provides the minimum flow required by the fire water pump to prevent it from overheating in a deadhead situation.

RE: Diesel engine damage

What actually failed on the diesel engine? Overheat? Reverse rotation? Reverse rotation can absolutely wreck a diesel if sustained. Will wreck the bearings as there is no oil flow. Same with an overheat, not sure if a fire pump engine has an overheat shutdown, there is a good case for it to run to failure in a fire scenario.

RE: Diesel engine damage

I've actually seen a diesel fire pump that ran until it had sucked-up all the water there was, and the engine kept running. And the fire pump supplied the engine cooling water. Someone had shut it down before it failed. The paint on the engine was blistered and peeling a bit when I got there - about 10 minutes after it was shut down. After things were sorted out, we hit the start button the next day, and it fired-up and ran smoothly. We were amazed...

RE: Diesel engine damage

Most FM approved engine drive fire pumps do use heat exchange cooling using fire water as the raw water source. Also these packages, especially single engine pump systems, have no or minimal engine protection shutdowns, with maybe the exception of overspeed.

Have seen an engine damaged by reverse flow due to a check valve not closing, however was on a high rise building with a lot of head, and the supply water coming from a tank, so it had enough energy to rotate the engine backwards after it shutdown, resulting in damage to crankshaft and camshaft bearing. In those type applications normally you would also see a backstop to prevent reverse rotation.

In several systems I worked on over the years systems that tested regular into a "deadhead" circuit, had a shunt line to flow enough raw water to keep the unit from overheating.

FM1333 is the standard for diesel engines driving fire pumps, and is adopted in many countries.

To the OP, need way more info from you to make any kind of determination about your actual problem.

MikeL.

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