Leakage at the packing of a reciprocating compressor
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It has been observed that during the operation of the reciprocating compressors (two-stage) used in our facility, the process gases (methanol, NO, CO2, CO) leak into the water system of the separate compressors; this results in CO alarms in the water, as well as an acidic pH level of the water. The water outlets of the water station lead to the jacket and cylinder head of the primary and secondary cylinders, as well as the packing in both stages, for a total of 6 circuits. Through experiments, by feeding water to the filler through two separate paths and draining it separately, it was found that the water at the water treatment station was normal (no problems for two weeks). When analyzing the reasons earlier, our maintenance staff said that the process gas leaked from the packing and was discharged directly along the shaft. We also applied a pressure of 0.6 MPa to the packing (with an operating pressure of 0.25 MPa), and there were no issues – no leakage occurred. I hope an expert can analyze it.
Based on your description, could it be that there is a leakage point between the upstream stuffing boxes, causing the leaking gas to enter the water along that leakage point? The reason why the leaked gas did not escape along the piston rod is that the end seal has excellent sealing performance. For your reference only!
In my opinion, the leakage is occurring in the seasoning section; the isolation between the filler’s water jacket and the intermediate shaft cavity should be achieved through multiple O-rings. It is doubtful whether these O-rings provide consistent sealing performance both during operation and when the system is at rest. Additionally, pressurizing the filler’s water circuit does not guarantee that process gas will not leak in during operation, as O-rings can sometimes only provide one-way sealing. I suggest trying to replace the sealing O-rings, using fluororubber as the material at least.