Inter-stage overpressure in reciprocating compressors
Thread Content
Dear sea friends, I need your help! Our company’s PSA (Pressure Swing Adsorption) units are equipped with 3 purge gas compressors, model: 4M20-133/32, and overpressure occurs between stages during operation. The specific situation is as follows: The compressors are regulated automatically by four-way and one-way self-regulating valves. When the four-way valves are completely closed and the one-way valves are set at around 45% (with slight variations among the 3 compressors), all three compressors exhibit exhaust pressures that exceed the design values in three different stages. Stage 1 is lubricated with a small amount of oil, while stages 2, 3, and 4 are lubricated without oil. Previously, oil was applied to all four stages; now, only stage 1 uses a small amount of oil, while the remaining stages are lubricated without oil. Additionally, there is a small amount of adsorbent dust in the gas (a legacy from the past). The measures taken have included checking and replacing the piston rings and support rings in each section; the valve seats were suspected to be leaking or blocked, so they were also replaced all, but overpressure still occurs in three sections. I would appreciate it if everyone could help analyze the reasons and provide valuable suggestions for improvement. Thank you!
It could be due to increased leaks after the modification. Leakage increases under oil-free operating conditions. Of course, there could also be other reasons. Try to filter the gas as much as possible. It has oil and dust, so it gets greasy very easily! !
It would be best to describe the structural type of the compressor! !
During operation of the compressor, the outlet pressure at the third stage remains abnormally high, which affects the stable operation of the unit. It is necessary to disassemble and inspect the rotor of the high-pressure cylinder, as well as the gas seals and sealing rings between the third and fourth stages of the compressor, or to check whether the pressure and parameters of the compressor’s buffer tank are normal. .
All three units are exhibiting this issue. I think it’s not a problem with the equipment; instead, the cause should be sought in the manufacturing process. It’s necessary to check whether the pressure at the compressor inlet matches the design value, and whether the back pressure at the compressor outlet also meets the design specifications. Additionally, it’s important to examine the composition of the gas being produced to see if there are any changes in its molecular weight. The design parameters can be compared with the current operating conditions, and various factors should be analyzed one by one to identify the root cause.
It’s too general; more specific information on the structural format and cylinder diameter is needed to come up with a solution