IHI TX-A Compressor — Major Overhaul After 37,451 Hours
Second major overhaul of an IHI TX-A two-stage centrifugal air compressor at a manufacturing plant in Shenzhen, South China — cavitation repair, bearing & seal replacement, with surge test, clearance and alignment measurement data included. Carried out by Turbomax engineers.
Machine background
This IHI TX-A two-stage centrifugal air compressor was delivered in 2012 and has been running at a manufacturing plant in Shenzhen, South China ever since. In December 2019 it came into our workshop for its second major overhaul, by then with 37,451 running hours, 34,784 loaded hours and 317 starts on the counter.
| Model | IHI TX-A (two-stage centrifugal air compressor) |
| Discharge pressure | 0.69 MPa |
| Shaft power | 290 kW ±4% |
| Compression stages / gas | 2 stages / air |
| Motor | Siemens 290 kW, 380 V, 515 A, 2,988 rpm |
| Running time at overhaul | 37,451 hours (2nd major overhaul) |
Condition found during overhaul
- Inlet scrolls & volutes (1st/2nd stage) — badly rusted; the flow passage between the inlet scrolls and diffusers was heavily cavitated
- 2nd-stage impeller — trailing edge eroded round by cavitation
- Gearbox bearings — 1st/2nd-stage bearing pads heavily carbonized, babbitt surface worn uneven; bull gear bearings replaced
- Coolers — heavy oxidation on the copper tubes; 4 tubes plugged solid, drilled through one by one
- Oil system — oil aged and discolored (yellow), sludge in the tank; oil filter element damaged
- Accessories — air filter element clogged, drain traps rusty, discharge check valve worn
Measured data — surge test, clearances & alignment
Every overhaul we document with numbers, not only photos. Below is the measured data recorded in the overhaul report for this machine.
Surge test — before vs. after overhaul
| Surge test point | Before overhaul | After overhaul |
| Surge point 1 | 0.645 MPa @ 437 A motor current | 0.616 MPa @ 439 A motor current |
| Surge point 2 | 0.794 MPa @ 516 A motor current | 0.704 MPa @ 505 A motor current |
Both surge points were re-verified on site after the overhaul (December 2019) and the anti-surge control settings were confirmed against the measured data.
Rotor & stator clearances (TX-A clearance table)
| Clearance position | Measured |
| High-speed shaft (B) bearing | 0.25 mm |
| Impeller ↔ inlet scroll, 1st stage | 0.36 mm |
| Impeller ↔ inlet scroll, 2nd stage | 0.61 mm |
Coupling alignment (motor ↔ compressor)
- Allowable deviation: 0.2 mm (rim & face)
- Motor shaft is positioned at a different height by design (to allow for thermal growth of the motor bed) — but the shafts must remain parallel to each other
- Final dial-indicator readings after alignment: 0.01 mm / 0.03 mm — well within tolerance
- Vibration probe gap voltage: standard 8.5 ± 1.0 V — re-adjusted to 8.2 V
Photos from the job
1. Inlet scrolls & oil cooler end cover — cavitation grinding & coating
① As found — rusted scrolls, rusty end cover
② After grinding — approx. 1 mm of cavitation removed
③ After protective coating
2. Volutes & 1st-stage bearing pads — grinding & coating
① As found — rusted volutes, carbonized bearing pad
② After grinding & carbon removal
③ After coating
3. Cooling chambers, 2nd-stage cooler & 2nd-stage bearing pads
① As found — heavy rust, heavy carbon
② After grinding
③ After coating / carbon wiped off
4. Cooler covers & shaft journals
① As found — rusty covers, carbon on journals
② After grinding & wiping
③ Coating & 2nd-stage journal
5. Impellers — cleaning & dye penetrant inspection
① Before cleaning
② After cleaning
③ Dye penetrant test in progress
④ PT result — no defects found
6. Bull gear & bearings — replacement
① As found
② Bearing replacement & test
7. Air & oil seals — replaced with new
8. Coolers & oil system
① As found — plugged tubes, aged oil
② After cleaning
9. Air filter & oil mist separator
① As found — clogged element, dusty housing
② New element & clean housing
10. Valves, coupling, gearbox & rotor checks
Full inspection record
The overhaul followed the standard IHI inspection checklist. Every item below was opened up and checked — the work actually carried out on each part is listed here. (Items marked N/A are not fitted on this two-stage machine.)
| Item inspected | Work carried out |
| Air end & gearbox | |
| Bull gear — tooth contact, meshing flank condition | Inspected & cleaned |
| High-speed pinion gear & shaft | Inspected & cleaned |
| Low-speed pinion gear, shaft & bearing | N/A — not fitted |
| Bull gear shaft bearing | Replaced |
| High-speed pinion bearing | Inspected, cleaned & repaired |
| 1st / 2nd stage impellers | Inspected & cleaned (PT: no defects) |
| 1st / 2nd stage scroll casings | Inspected, cleaned & repaired |
| 1st / 2nd stage diffusers | Inspected, cleaned & repaired |
| 1st / 2nd stage air inlet piping | Inspected & cleaned |
| 1st / 2nd stage air seals | Replaced |
| 1st / 2nd stage oil seals | Replaced |
| Coolers | |
| No. 1 / No. 2 intercoolers | Inspected, cleaned & adjusted |
| Oil cooler | Inspected, cleaned & adjusted |
| Aftercooler | N/A — not fitted |
| 1st / 2nd stage drain traps | Inspected, cleaned & repaired |
| Drain trap check valve | Inspected |
| Lubrication system | |
| Oil tank | Inspected & cleaned |
| Vacuum differential gauge | Replaced |
| Oil heater | Inspected |
| Main oil pump | Inspected; coupling element replaced |
| Auxiliary oil pump | Inspected; coupling element replaced |
| Oil filter | Replaced |
| Oil circuit check valve | Replaced |
| Intake air filter | |
| Air filter element | Inspected & replaced |
Alarm & safety function test
| Alarm item | Alarm / trip set point | Result |
| 2nd-stage shaft vibration, upper limit | 27 / 33 | OK |
| Lubrication oil pressure, lower limit | 0.10 / 0.07 MPa | OK |
| Lubrication oil temperature, upper limit | 55 / 60 °C | OK |
| Final-stage intake air temperature, upper limit | 55 / 60 °C | OK |
| Motor trouble signal | — | OK |
| Auxiliary oil pump trouble signal | — | OK |
Scope of work — parts replaced
- Bull gear bearings
- 1st / 2nd stage air seals
- 1st / 2nd stage oil seals
- Air filter element
- Oil filter element
- Oil mist separator
- Cooler gasket kits (1st / 2nd stage)
- Oil cooler gasket kit
- Main oil pump coupling repair kit
- Gearbox repair kit
- Oil piping repair kit (incl. oil check valve)
- Discharge check valve
- Vacuum differential gauge
In addition: repair grinding and protective re-coating of the cavitated inlet scrolls, volutes, cooling chambers and cooler covers; dye penetrant inspection of both impellers (no defects); drilling through all plugged cooler tubes; chemical cleaning of the coolers; oil tank and gearbox cleaning; coupling alignment within 0.2 mm; vibration probe gap voltage re-adjustment to standard; and a full surge re-test after reassembly.
Post-overhaul operation record
| Item | After overhaul |
| Discharge pressure | 0.56–0.57 MPa |
| Motor current | 515 A loaded / 220 A unloaded |
| Inlet air temperature | 21 °C |
| 2nd-stage inlet temperature | 32–33 °C |
| Oil temperature | 38 °C |
| Motor bearing temperature | 50–60 °C |
| Cooling water inlet | 23–24 °C |
The machine was restarted right after the overhaul and all operating parameters were normal.
Root cause & our recommendation
The rust and cavitation on the scrolls and volutes came from years of humid coastal air combined with aging oil, and the plugged cooler tubes from the plant's cooling-water side. For the next overhaul we recommend inspecting the impellers, bearings, inlet scrolls and coolers, and keeping the recommended spares on stock: 1st/2nd-stage bearings, air seals, oil seals, inlet scrolls, air coolers, air filter, oil filter and oil mist separator.
Planning an overhaul or need IHI TX-A spare parts?
Turbomax supplies alternative spare parts and overhaul service kits for the IHI TX-A and other IHI centrifugal compressor series — inlet scrolls, volutes, diffusers, impellers, air seals, oil seals, journal and thrust bearings, bull gear bearings, coolers, air filters, oil filters and oil mist separators — and supports overhaul projects worldwide. Our founder has 10 years of IHI-Sullair field service experience.