Reducing rpm gas engine under increasing suction pressure recip compre

[weldsv1]

Hi all!
I have problem with Driver – Caterpillar with BHP 810 HP. When the suction pressure is 36 psi, rpm is about max – 1150 -1170, but when the suction pressure starts to increase a bit till 40 – 42 psi, speed starts to reduce and compressor stopped under 50 psi. The discharge pressure doesn’t change. I used Ariel Performance software, and received calc BHP – 512 HP under suction pressure 50 psig. The compressor was designed under suction pressure 60 psig (at this case BHP- 615HP). The output signal from control panel is 100%, and the fuel gas throttle is full opened.
Is this problem can be caused by incorrect adjusted a pressure controller of fuel gas?
Best regards.

 

[pmover]

"Is this problem can be caused by incorrect adjusted a pressure controller of fuel gas?"

if fuel pressure to engine is lower than mfg recommended pressure, then the engine's performance is likely limited or impacted. although i would expect the engine's performance to be impacted regardless of load; unless the fuel pressure is at/above recommended pressure at the lower loads. not only should pressure be at the recommended levels, the pipe should be properly sized to handle the needed capacity (volume) for engine to operate satisfactorily throughout its design range.

double-check the recip comp performance calcs and ensure the data you are using is representative of the actual operating conditions of the compressor.

good luck!
-pmover

 

[zdas04]

I agree that the problem is most likely with either the fuel system pressure or the size of the piping. But that isn't the only possibility.

You need to check the engine intake-manifold pressure at each suction pressure to see if the Cat hp calculates out to a number close to the Ariel required hp. If they are very different (more that you would expect from auxilliary loads) then you could easily have other problems (engine valves, etc) that have little to do with the fuel-system.



David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[quadtracker]

Check condition of fuel gas filter or any pipe strainers in the fuel gas system. Check the all the fuel gas regulator orifice sizes to make sure they are large enough for the needed flow rate. If you need more fuel gas, you may have to pipe in another fuel gas regulator in parallel to the primary Reg. If this engine is a Cat 3512, the fuel gas regulator (secondary) on the engine is sized ok, but the primary regulator upstream may have too small of an orifice. Normally, if its a Fisher model 627 the orifice is usually 1/2" and pressure reduced down to about 40 psig. Get a qualified Field Mechanic out to check out your fuel gas system and check pressures after your primary and secondary (engine manifold)pressure at various loads, he should have all recommended fuel gas pressure info.