Hp Rating Variance

[zdas04]

I'm doing some compression work on skids that include two different Ford engines.

The first one is a Compressco "Gas Jack" that started with a Ford 460 cu in V-8 and had one bank of cylinders converted to gas compression. When I Google "Ford 460" I get around 360 hp. Compressco calls their engine 23 hp. There is just too much difference between half of 500 hp and 23 hp.

Another skid is driven by a Ford 302 which Wikipedia calls a 220 hp engine. On the skid it is called 29 hp.

Is there a major (factor of 10) difference between the way hp is measured for vehicles and the way it is measured for industrial engines?

David

 

[catserveng]

Engines are usually rated for power available at the flywheel under "standard conditions" for air temp, fuel, altitude, etc. Compression packages are using some cylinders to do work or absorb power, not make it, and the hp rating is usually an indication of how much power is available at the flywheel or front pulley to power accessories.

Hope that helps,

 

[zdas04]

One thing makes sense--the published ratings are for gasoline and the compressors are configured as naturally aspirated natural gas engines. That cuts the available hp about in half so now I only have a factor of 5 to account for.

Thanks

David

 

[MikeHalloran]

As gasoline road vehicle engines, those normally develop peak torque between 3000 and 4500 rpm. I'll bet they're governed to less than 2000 rpm as industrial engines, in the interest of durability.

Additionally, I wonder if they're being rated with some pneumatic equivalent of "hydraulic horsepower", i.e. output pressure x flow x some constant.







Mike Halloran
Pembroke Pines, FL, USA

 

[zdas04]

Mike,
Yes, both engines are regulated to 1800 rpm. I don't have hp vs. rpm curves for these engines, but I'm betting that cutting the rpm that much would pretty much account for the missing hp.

When I've asked Cat about how they rate an engine for a compressor they always describe a process much like the auto makers use so I don't think it is related to gas hp developed across the compressor.

Thanks

David

 

[pipehead]

I've run some of the gas jac curves and I can see about 55 HP maximum, add in coolers and such and you can get to 65 hp for compressor. If you ratio a cat engine it would make 85 hp from the same ci displacement. so, its in the same area if you consider that the ford isn't optimized like a cat engine is on CR, valve cams ect....