Compressor process high outlet temperature. 2

[Liftingengineer]

I have been asked by one of our process engineers to examine the effects of running our compressors with higher outlet temperatures. These are reciprocating compressors flowing propylene at ≈ 270. The outlet temperature is above our traditional limit. Being green at this and not know the exact question I should be asking, What factors do I need to consider when reviewing the effects of the high temperature on the compressor?

I've got a PHD is Broscience

 

[racookpe1978]

I'm glad you decided to ask the questions, but you need to start back at the "lessons learned" and "basic engineering practice" of YOUR company's experience that "forced" the previous decision to require a cooler compressor head.

That is, "Why do we require a temperature limit of 115 degrees? Why not 150 degrees? 175 degrees? 200 degrees? 250 degrees? 400 degrees? "

What fails at 150 degrees over long periods of time? Coolant breakdown? Seals? Gaskets? Bolt strength? Bolt stretch? Material in the head? The cylinder? The piston? The bottom of the piston or cylinder get too hot and warp?

Get an IR camera or IR thermometer and go LOOK AT a running compressor head under POOR cooling conditions (hot environment, bad fan, dirty heat exchanger). Find out where it IS "adequately hot" now and where it is at a "limiting"condition of "too hot".

Be ready to find out that the limit was set in in the 1950's and never re-checked by IR instruments and that you can indeed run much hotter. Be ready to find out that every machine you now build has never been checked or measured accurately and that every one of runs too hot during the summer in a closed building in Texas or LA or OK.

 

[rostanlin]

Greetings,
I am not clear about the question, are you talking about °F or C°? multi-stages? is there any downstream process? lubricated or non-lubricated application? Branch? Compressor model? I recommend to you to check it out the specification on the operation and maintenance manual to know the alarms operation limits... The outlet temperature on a reciprocating compressor will mainly affect the discharge valves if the material of its are not appropiate according to the outlet temperatures(Peek? Teflon? etc...). Besides, high temperature could make the oil film thinner, etc... more information is neeed?

 

[dcasto]

A better question to ask is how can you increase the outlet temperature of a reciprocating compressor with a purity product and there is no change in pressures? Ok, higher suction temperatures, which means lower capacities.

Lesson learned? You can't change a temperature without changing other parameters that now add more things to look at.

Today we have better elastomers than in the past. The 270 F was most likely set by limits on rings and valves.

 

[Liftingengineer]

Sorry I have been traveling, thanks all for the help.

racookepe- I believe they chose those limits from looking at historical data on where the temperature has historically run. Those limits were not engineered, and that is what they are looking for me to do. Thanks for the list of possible failure modes, and I will look into an IR camera.

Rostanlin - I was talking degrees F. I didn't find any good information on outlet temperature from the operation manual when I checked.

Dcasto- We are currently running at the higher temperatures without any known problems. I will check on the valve and ring limits.

I've got a PHD is Broscience

 

[rostanlin]

Ok, what compressor do you have? If you want to know what temperature should be at the outlet temperature to compare with your actually outlet temperature, try to simulate using a compressor performance software like Ariel performance (Ariel Compressor), D-R Size (Dresser-Rand), Compass (Cameron, Superior Compressor) and so on. Most of these performance software are available and free on the compressor websites. If your compressor model does not have an own performance software try to do a simulation on PRO/II or hysys to estimate temperatures.