Gas in engine sump

Question

Gas in engine sump

SuperMan11 (Mining)

(OP)

10 Jun 19 22:04

Hi all,

I have a Waukesha VHP natural gas engine (low pressure GSI-D setup) where I am getting natural gas into the crankcase (a routine gas leak test saw a gas atmosphere coming out of the dipsticks and the engine level controller breather). First thought was that we had too great of a vacuum in the engine crankcase (drawing unburnt fuel gas into the crankcase), so we adjusted this to a positive pressure - gas still in the system. The next thought was that the common crankcase oil line between the compressor (driven equipment) and the engine may have been allowing some natural gas to migrate, but this was debunked.

Has anyone seen this before? Our major gas engine compressor package contractor has never seen this before. Any help would be appreciated to solve this potentially unsafe event.

Cheers

Lou Scannon (Automotive) · Answer 1 · 2019-06-10 22:17:33

Maybe your final stage pressure regulator has a leaky diaphragm and the reference line is passing gas to the intake system.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

TugboatEng (Marine/Ocean) · Answer 2 · 2019-06-11 06:20:57

I find the majority source of blow-by into the crankcase of heavy duty engines is through the valve guides. I'm not familiar with gas engines. Is there any fuel in the intake air?

CWB1 (Mechanical) · Answer 3 · 2019-06-11 15:25:22

Does this engine spend significant time shutdown? If so, ensure the gas shutoff valve is functional. I've seen instances of bad shutoffs allowing engines to fill with gas overnight.

michaelwoodcoc (Automotive) · Answer 4 · 2019-06-11 20:21:31

Far off possibility. How's co pression amd leak down? Is it pirt fuel injection or kindof a tgrottle body type? How close is any crankcase cent to the point of the fuel entering the intake?

On a carbed engine with poor valve timing for exanple the air flow in the intake tract will reverse and push fuel up amd into a good carb diaphragm. I've never seen valves ir valve timing bad enough to push it all the way to a crankcase vent but i suppose it's remotely possible.

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Gas in engine sump