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[Radionise]

Hello all,

You may notice that this topic is actually a spin-out from Gunjan's previous question about the discharge temperature of recips compressor.

How about the discharge temperature from screw compressor, especially oil-injected type?

API 619 covers the discussion on rotary machines but ironically has not put forward any recommended temperature limit for this type of machine, even in their latest 2004 edition (Or may be I may have missed the discussion somewhere).

In any case, please shed some lights.

Thanks

[Art Montemayor]

Radionise:

The Foreword of API Standard 619, Rotary-Type Positive-Displacement Compressors for Petroleum, Petrochemical, and Natural Gas Industries, reads as follows:

“The primary purpose of this standard is to establish minimum requirements. This limitation in scope is one of charter as opposed to interest and concern.”

Therefore, API 619 doesn’t make any attempt to go into any details as to design and operational performance calculations. I disagree with your statement that “API 619 covers the discussion on rotary machines”. However, I agree that it fails to offer any recommended temperature limit for this type of machine.

My experience has been in the utilization of such machines for refrigeration and industrial gas compression – up to discharge pressures of 350 psig. All of these machines have been oil-flooded. I employed Ingersoll-Rand “Axi” models in the 1970’s, but those were more in the blower class and not really compressors. The Axi models handled hydrogen and were not flooded.

I have seen the development of the screw compressor to the present state of application but I have not come across any thermodynamic book or literature that has described the operation on a theoretical or actual basis. All of the operating characteristics of the machines I’ve run have been predicted or dictated by the manufacturer – presumably under captive and arcane know-how or empirical experience. Therefore, such critical design information as discharge temperatures and actual capacities under running conditions have been furnished by the manufacturer and not calculated by methods similar to those used for reciprocating or centrifugal machines. I attribute this vacuum in calculating screw compressor performance to the inherent slippage and other characteristics controlled by the manufacturer (such as internal oil and gas cooling) that have not yet made it into the published public sector.