Comparision between 2 reciprocating compressor
Comparision between 2 reciprocating compressor
(OP)
Hi all.
I want to know about advantages and disadvantages of these 2 configurations form your approach.
I want to compress 780 m3/h from suction condition of t=65 & p=5bara to discharge pressure of 126bara. Molecular weight is about 32 and i have sour gas to compress.
I want to use LP,MP,HP configuration to overcome increasing discharge temperature. But as a parallel i can use a single reciprocating compressor with 6 throw to meet my condition with a 1 electro motor.
What do you suggest? And why? Consider intercooler's prices.
Thanks
I want to know about advantages and disadvantages of these 2 configurations form your approach.
I want to compress 780 m3/h from suction condition of t=65 & p=5bara to discharge pressure of 126bara. Molecular weight is about 32 and i have sour gas to compress.
I want to use LP,MP,HP configuration to overcome increasing discharge temperature. But as a parallel i can use a single reciprocating compressor with 6 throw to meet my condition with a 1 electro motor.
What do you suggest? And why? Consider intercooler's prices.
Thanks





RE: Comparision between 2 reciprocating compressor
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Comparision between 2 reciprocating compressor
RE: Comparision between 2 reciprocating compressor
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Comparision between 2 reciprocating compressor
RE: Comparision between 2 reciprocating compressor
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Comparision between 2 reciprocating compressor
2) 3 recip compressor in series( LP,MP,HP)
RE: Comparision between 2 reciprocating compressor
1)Is this six throw recip a single stage compressor? a compression ratio of 126/5 in a single stage is not possible?
2) The LP/MP/HP setup implies a three stage compressor with intercoolers?
please clarify
RE: Comparision between 2 reciprocating compressor
1)it depends on your discharge temperature
2)yes
RE: Comparision between 2 reciprocating compressor
I would be reluctant to do this in a single 3 stage machine (regardless of the number of throws). I would probably make the first machine a single stage recip (the gas is just too difficult to ever get a compatible screw oil) and do the rest with a 2-stage recip. The single stage has some reasonable ability to handle variability, and getting the gas up to around 20 bara fixes a lot of low pressure operations problems for the 2-stage skid. Doing 6 ratios in two stages is a cake walk.
As to how many frames you need. I would twin both frames. Design two single stage recips in parallel each able to move 90% of your required flow and discharging into a common header. Then put two 2-stage machines (each able to do 70% of the design conditions) in parallel sucking on that header. By oversizing the first stage you are accounting for all of the unpleasantness of your gas and low pressures, which allows the 2-stage machines to have a chance to work. The compressor guys will tell you that you are wasting available power by doing that, but what are you selling, KPI's or gas?
Putting this into three frames is a waste of money since every skid have a fixed cost component that can be significant (a two stage cooler costs about 120% of the cost of a single stage cooler or 60% of two single stage coolers). Doing it in a single frame forces the aggressive use of suction control to keep all the stages balanced. Two frames is a compromise.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Comparision between 2 reciprocating compressor
I cant truely understand why we should have change our mind to a parallel 90% recip in first compressor and to 70% 2-stage recip after header? Why dont we use 100% recipcompressor
RE: Comparision between 2 reciprocating compressor
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Comparision between 2 reciprocating compressor
I dont want to account hope in design and i also find out behind of every comment of you, a lot of experience is hidden. I ask you because this problem is related to the process guys and i want to know my problem very well from process approach. I understand because of variable behaviour of gas field you dont use a (1+1) 100% recip compressor. I must explain that these compressor are used in a off-gas unit of gas refinery, so we dont face of variable behaviour of gas field. From now on, i want to know you insist on 90% (1+1) recip in first stage and a 2 stage of 70% (1+1) recip?
Then i want to know about unpleasantness of gas for oversizing the compressor. Would i ask you to explain more?
RE: Comparision between 2 reciprocating compressor
I've never worked inside a plant, so I don't know how consistent the off-gas is in real life. If the off-gases have a reasonably consistent composition then I would back off on my safety factors. Probably to no lower than each compressor sized for 60% of full stream because running at a higher load than that in steady state has a long history of high rate of failures.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"