• Thomasen piston compressor
  • 2 throws, 2 stages
  • Medium: Hydrogen
  • Capacity control: HydroCOM

The compressor has a „Free Floating Piston“ system with non-lubricated cylinder (for lifetime optimization of rider rings) and a mini-lube stuffing box seal. This machine combines the Free Floating Piston system with a Hoerbiger HydroCOM flow regulation. Since the initial compressor start, the piston rings of both stages reached only short operation lifetimes of 1,500 hours and with a decreasing tendency:

Lifetimes before replacement of piston rings of the 1st stage

  • 1,850 hrs
  •    707 hrs
  •    891 hrs
  •    801 hrs
  • 1,607 hrs

Lifetimes before replacement of piston rings of the 2nd stage

  • 3,773 hrs
  • 4,006 hrs

Preliminary PROGNOST® data analysis: Detection and location of the problem

pv diagram
pv diagram2
  • Expansion and compression lines of the p-V diagrams of stage 2 HE (head end) and CE (crank end) are different from normal patterns
  • Stage 2 CE side: Breakthrough suction pressure is earlier than expected and Re-expansion and compression lines are steeper than normal
  • Stage 2 HE side: Breakthrough suction pressure is later than expected and Re-expansion line is steeper than normal and compression line is flatter than normal

→ On the CE side: Possible suction valve leaking; possible piston ring leakage

→ In the HE side: Possible piston ring leakage from the CE side


rider ring
Fractured rider ring
Discharge valve with dirt deposit