The issue of one cycle at a time in reciprocating machines
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Our company currently has three reciprocating compressors of the 4M20 model. The issue we’re facing is that when one inlet valve is closed, the pressure still remains high. The inlet pipeline has a diameter of DN500, while the outlet pipelines have a diameter of DN300; one of the inlet valves connects to a pipeline with a diameter of DN100. As long as 35% of the flow remains when one inlet valve is closed, the pressure at the three outlets exceeds the allowed level. The set pressure for the safety valves at these outlets is 1.55 MPa, and this value is reached when 35% of the flow is blocked. As a result, the operators are reluctant to close those valves any further. Initially, the design called for two compressors in operation with one as a backup, but now all three compressors are in use. If the combined diameter of the outlets from these three compressors isn’t sufficient, then pressure should exceed the limit at all four outlets, rather than just three. Could there be an issue with the exhaust volume of the cylinders? I have cleaned all the inter-stage heat exchangers, and there are no signs of blockages. Please help me figure out what’s going on!
Listen to each of the four inlet valves to check for any leaks
The inlet and outlet valves in those four sections must be leaking air
Has this problem existed since the project started? Did the problem arise recently?
You need to know that in some compressor processes, the flow doesn’t go directly from stage 3 to stage 4; instead, it goes to the static equipment and then back to stage 4. In a normal situation, overpressure occurs at the exit of stage 3, and this is related to the issue of flow from stage 3 to the inlet of stage 4
In principle, it is definitely the gas trapped in the space between outlet 3 and inlet 4 that causes the high pressure at outlet 3. It is recommended that you conduct a thorough inspection of this pipeline, including the four air inlet valves.