High inlet pressure at the first stage of the reciprocating compressor

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Our factory has two reciprocating compressors of the DW-4/15.7-51.3 type made by Sichuan Jinxing, one in use and one as a spare. The compressor features two-stage compression. The first two units had the same operating conditions and were functioning normally. Once after the engine was started, it was found that for the same flow rate, the inlet pressure at the first stage of compressor B was 1.54 Mpa (the normal value being 1.40 Mpa), while the inlet pressure at the second stage was slightly lower. In October, the facility was under maintenance; components such as gas valves, packing, and piston rings were replaced. The valve that returns from the secondary outlet to the primary level has been checked, and there are no leakage issues. The problem remains unsolved. May I ask what exactly is the problem? This is the primary intake pressure curve after the compressor starts up, which I copied from my computer.