Is the pressure at the first-stage outlet of the cyclic hydrogen compressor high?

Several situations can occur. As you said, if the secondary piston ring is severely worn, the secondary compression ratio cannot be increased; since the system pressure remains constant, the pressure at the primary outlet will rise. The same thing happens if there is a leak in the secondary intake valve.

Is there air leakage from the secondary outlet to the secondary inlet?

The secondary piston rod has dropped, so the secondary compression ratio must have decreased. Since the temperature at the primary stage hasn’t changed, there should be no problem with the exhaust valve; the issue is likely related to the secondary intake valve. Is there anything abnormal with the temperature of the secondary intake valve?

A high outlet pressure at a certain stage of a reciprocating machine is often related to the following reasons: 1. Leakage from the exhaust valve or gasket of the subsequent stage, or problems with the unloader, which leads to an increase in the exhaust pressure of the preceding stage. 2. Leakage occurs due to sticking, wear, or breakage of the piston rings, resulting in insufficient gas discharge ； 3. Leakage from the exhaust valve and gasket at this stage results in loss of power generation. If the owner’s inspection only revealed damage to the secondary piston rings… it is recommended that you check the primary and secondary valves as well, because such a situation would not occur if it were merely a problem with the piston rings. There must be an issue with at least one of the intake or exhaust valves. Moreover, if my guess is correct, the secondary piston rings are so severely damaged that they are almost completely ineffective by now :L