A technical guide to the engineering features that define IHI-SULLAIR oil-free centrifugal compressors — from titanium impellers to anti-surge control — and the spare parts that keep them running.
IHI-SULLAIR centrifugal air compressors are widely used in industrial plants worldwide, covering a flow range of approximately 10 to 850 Nm³/min and discharge pressures from 2.0 to 50 bar. The product family comprises six series — TX, TRA, TRE, TRX, TA and NK — each optimized for different pressure, flow and power requirements. This guide explains the key engineering features shared across these series and identifies the spare parts that matter most for maintenance and overhauls.
As an independent supplier of alternative spare parts for centrifugal compressors, Turbomax supports IHI-SULLAIR compressor users with replacement impellers, bearings, seals, diffusers, coolers and overhaul service kits. Understanding the machine's design helps you plan maintenance, order the right parts and minimize downtime.
| Series | Stages | Discharge Pressure | Flow Range | Motor Power | Rotor Speed |
| TX | 2-stage | 4-9 bar | 10-75 m³/min | 65-420 kW | 70,000-110,000 rpm |
| TRA | 3-stage (or 2-stage) | 5-9 bar (3-stage) / 2-4 bar (2-stage) | 42-80 m³/min | 224-500 kW | — |
| TRE | 2-4 stage | 2-16 bar (0.2-1.6 MPa) | 65-200 m³/min | 400-1,100 kW | 30,000-53,000 rpm |
| TRX | 2-4 stage | 2-13 bar (0.2-1.3 MPa) | 200-360 m³/min | 900-2,100 kW | 30,000-48,000 rpm |
| TA (custom) | 1-4 stage | 2-20 bar (0.2-2.0 MPa) | 40-750 m³/min | 250-3,000 kW | 21,400-32,000 rpm |
| NK (custom) | 1-4 stage | 24-50 bar (2.4-5.0 MPa) | 210-850 Nm³/min | 1,000-4,100 kW | 16,000-23,000 rpm |
The impeller is the heart of a centrifugal compressor. IHI-SULLAIR machines use titanium alloy impellers forged and then machined on 5-axis CNC equipment. Compared to 17-4PH stainless steel impellers, titanium offers significant advantages:
The impeller design uses a three-dimensional flow backward-curved profile with a unique guide groove pattern that minimizes air turbulence. Each impeller undergoes 115% overspeed testing and multiple dynamic and static balance tests, with a design life of over 30 years.
For replacement impellers, see: Centrifugal compressor impeller spare parts.
Labyrinth seals are used for both air and oil sealing. Key design points:
Labyrinth seal edges wear with every start-stop cycle, making air seals and oil seals among the most frequently replaced spare parts on these machines.
The horizontally split gearbox is a signature maintainability feature. By removing the upper casing, maintenance personnel have direct access to gears, bearings and seals without full disassembly. Inspection of the sealing system, bearings and gears takes only about 2.5 hours — roughly one-seventh of the time required for a vertically split gearbox.
The gearbox and cooler cavity are integrally cast, providing greater rigidity, shorter connecting piping, more compact structure, reduced vibration and noise, minimal pressure drop and fewer leak points.
The high-speed shaft uses five-pad tilting pad sliding bearings that carry only radial load — axial thrust is handled separately. Features include:
The intercooler and aftercooler use a drawer-type design with water inside the tubes and air outside:
After 8-10 years, fouled cooler tubes raise impeller inlet temperature, shrink surge margin and increase power consumption. Replacement cooler bundles are among the most requested spare parts. See: Intercooler & aftercooler spare parts.
The inlet guide vane (IGV) regulates air flow at part load while maintaining high efficiency. Compared to an inlet butterfly valve, the IGV saves up to 9% power at maximum turndown. The IGV works together with the blow-off valve (BOV) to provide a wide operating range from full-load to no-load.
The diffuser is integrally machined from aluminum alloy with a copper-plated surface for corrosion protection. Its unique guide groove design, matched to the titanium impeller, effectively avoids air turbulence and improves stage efficiency.
The volute (scroll) inner surface receives a high-strength corrosion-resistant coating (nickel-chromium plating) that maintains clearance consistency over time. This prevents the efficiency drop caused by volute corrosion and enlarged clearances after years of service.
Gears are manufactured to AGMA Q13 (DIN 5) precision grade — the highest quality level. This ensures high reliability, high mechanical efficiency and low noise.
The control system is built on a Siemens S7-300 PLC with a 5.7-inch LCD touchscreen. Key functions include:
Anti-surge protection is critical: without it, a compressor operating too close to the surge line can suffer violent vibration and impeller damage. The IGV modulates flow while the BOV (blow-off valve) vents excess air, maintaining a safe margin from the surge limit at all times.
The compressor package is highly integrated, including the inlet filter, inlet expansion joint, IGV, compression stages, intercoolers, aftercooler, blow-off valve, silencer, check valve, gearbox, main motor, oil tank, oil coolers and oil filters — all pre-piped and pre-wired. This reduces installation time and cost compared to traditional field-assembled units.
Based on the design features above, the following spare parts should be planned for overhauls:
Turbomax assembles complete overhaul service kits per machine serial number, so all required parts arrive together and nothing delays the shutdown. Critical parts like impellers and bearings are manufactured to order with short lead times; fast-moving consumables are usually in stock.
For model-specific parts lists:
IHI-SULLAIR centrifugal air compressors cover a flow range of approximately 10 to 850 Nm³/min and discharge pressure from 2.0 to 50 bar (0.2 to 5.0 MPa), depending on the series. The standard TX, TRA, TRE and TRX series handle plant air up to 16 bar, while the TA and NK custom series extend to 20 bar and 50 bar respectively.
IHI-SULLAIR uses titanium alloy impellers machined by 5-axis CNC. Titanium has a density of 4.4 g/cm³ (about half that of stainless steel), a tensile strength of 161 kg/mm² (1.5 times that of 17-4PH stainless steel), and allows a maximum tip speed of 530 m/s. This results in lower mechanical losses, higher aerodynamic efficiency and a design life of over 30 years.
A horizontally split gearbox allows maintenance personnel to access gears, bearings and seals by removing the upper casing, without disassembling the entire machine. Inspection of seals, bearings and gears takes only about 2.5 hours — roughly one-seventh of the time required for a vertically split gearbox.
The most frequently replaced spare parts are labyrinth air seals and oil seals (edges wear with every start-stop cycle), five-pad tilting pad bearings, titanium impellers (fouling and erosion), intercooler and aftercooler bundles (fouling), gears and filter elements. These are typically replaced together as an overhaul service kit.
Yes. Turbomax supplies alternative spare parts for the full IHI-SULLAIR centrifugal compressor range including TX, TRA, TRE, TRX, TA and NK series. Parts include titanium impellers, bearings, labyrinth seals, diffusers, coolers and overhaul service kits. Send the part number or machine serial number and we will confirm price and delivery.
Email a photo of the machine nameplate to turbomax@126.com or WhatsApp +86 13814834140. We will identify your model, return the matching spare parts list with quotation, and assemble the overhaul kit for your shutdown date.