Rod Load Tension and Compression
Rod Load Tension and Compression
(OP)
Hello, would anyone be able to explain what are the variables that causes a "rod load tension/compression" to rise on a recip (process) compressor and what can you do to lower it? Thanks in advance.





RE: Rod Load Tension and Compression
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: Rod Load Tension and Compression
Reduce the discharge pressure to lower the rod load.
Independent events are seldomly independent.
RE: Rod Load Tension and Compression
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: Rod Load Tension and Compression
RE: Rod Load Tension and Compression
RE: Rod Load Tension and Compression
RE: Rod Load Tension and Compression
RE: Rod Load Tension and Compression
The "4" is a rule of thumb for maximum compression ratios in a non-cooled conventional cylinder. We use it for design conditions, and it is really conservative. I've seen recips run for years with 5 ratios. I've seen recips fail with 4.2 ratios. When I'm picking a frame for an application I use 4 ratios/stage as my design point. This means that if the discharge pressure divided by the suction pressure is > 4 I'm looking at a 2-stage, > 16 I'm thinking 3 stage, > 64 is probably a 4 stage, etc. It is conservative, but being conservative is a pretty good way to avoid broken.
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: Rod Load Tension and Compression
Now if the piston was 2" diameter you could get a 1500 psi differential.
The easiest way to estimate compressor cylinder sizing is maximum rod load divided by area of the piston, that gives you differential pressure, from there you can get ratios given either suction or discharge pressure. BUT, ratios are a unknown until the very end, not in the beginning.