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IHI TX-A Compressor — Surge trip & Repair

An IHI TX-A two-stage centrifugal air compressor surging at 0.7 MPa with final-stage discharge temperature over 60 °C. Turbomax diagnosed the root cause: cavitated inlet scrolls and a leaking intercooler. Replacement parts restored performance close to brand-new condition.

Model	IHI TX-A (IHI-Sullair) — two-stage centrifugal air compressor
Power / Voltage	350 kW · 380 V
Design discharge pressure	0.8 MPa
Customer request	Compressor surges at 0.7 MPa, final stage trips at > 60 °C — find root cause and fix
Service	Turbomax service team — inlet scroll diagnosis + intercooler bundle replacement

Symptoms reported on site

The customer had already tried adjusting the anti-surge setpoints and cleaning the air filter, but every time they pushed the discharge pressure above 0.7 MPa the compressor surged and the final-stage inlet temperature climbed over 60 °C before tripping. The machine was running nowhere near its design point of 0.8 MPa.

Root cause — what we found when we opened it up

After disassembly we measured three things that together explained the surge:

1. 1st and 2nd stage inlet scrolls — heavy cavitation inside the flow passage. The cavitation roughened the metal and increased the effective impeller-to-scroll tip clearance, raising losses at every operating point.
2. Intercooler — leaking and internally fouled. A visual leak had appeared on the water header weeks earlier. More importantly the gas-side passages were partly plugged, creating a much larger pressure drop between stages.
3. The combined effect: bigger intercooler pressure drop means less pressure reaches the 2nd stage, so the 1st stage has to do more work. Rough inlet scrolls waste more power. Both together pulled the machine toward the surge line at a discharge pressure well below design.

What we replaced

We supplied and fitted two pairs of replacement inlet scrolls (1st and 2nd stage, cast iron with the original blade geometry) and one new intercooler tube bundle. Both parts are alternative aftermarket parts designed to the OEM drawing — drop-in fit with original performance.

Photos — before & after

1. 1st-stage inlet scroll — cavitated, then replaced

① Old scroll — cavitation and rust

② New scroll — OEM-equivalent cast iron, machined blade geometry

2. Intercooler bundle — old fouled leaky vs. new clean drop-in

Surge test — before vs. after

After reassembly we ran a full surge point test. The machine now reaches the design operating pressure of 0.8 MPa without surging, and the measured surge line has moved closer to the original commissioning curve.

Surge test	Before repair	After repair
Surge point 1 (Surge2)	0.993 MPa / 719 A	0.945 MPa / 713 A
Surge point 2 (Surge1)	0.790 MPa / 621.9 A	0.780 MPa / 627 A
Design operating pressure	NOT REACHABLE (surged & tripped below 0.7 MPa)	0.8 MPa — reached and stable

The shift of the surge line toward lower pressure at lower flow is actually good news — the repaired machine is more stable than the one that was surging prematurely. The design point 0.8 MPa is now well inside the safe operating window.

Key takeaway

When a centrifugal compressor surges well below its design pressure, don't immediately reach for the anti-surge controller or variable inlet guide vanes. Open the machine and check two parts first: the inlet scrolls (cavitation is silent, gradual, and hugely under-diagnosed) and the intercooler (fouling creates an invisible bottleneck that grows every year). Replacing both is far cheaper than buying a new machine.

IHI TX-A spare parts & overhaul — related pages

IHI TX-A spare parts list Centrifugal compressor intercooler / aftercooler bundles Tilting-pad & journal bearings Previous TX-A major overhaul case