This is a highly specific turbomachinery component. When dealing with a centrifugal impeller for a MAN Energy Solutions compressor (e.g., the MAN AIR or RH series, or legacy brands like Sulzer or GHH BORSIG that MAN now supports), there are critical technical and commercial factors.
Here is the breakdown of what you need to know to identify, replace, or procure this part.
1. Critical Identification Data (Find this on your nameplate)
MAN does not make generic impellers. Before ordering, locate the compressor type designation and serial number. Typical MAN centrifugal compressor series include:
RG, RI, RK, RA (integrally geared)
MH (horizontally split)
RB (barrel type)
AIR 16, AIR 18, AIR 26 (direct drive)
2. Impeller Design Features (MAN Specific)
MAN typically uses one of two designs depending on the vintage and application:
Closed Impeller (Shrouded): Most common for high efficiency. These are usually 5-axis milled from a single forging or have a friction-welded shroud.
Open Impeller (Unshrouded): Used in some high-flow or specific gas applications.
Material:
Standard air: High-strength Aluminum alloy (e.g., 7075-T6) – lightweight, but susceptible to erosion/damage.
High pressure/corrosive: 17-4 PH stainless steel or Titanium (Grade 5).
3. Replacement Options
You have three paths, with significant cost and lead time differences:
| Option | Lead Time | Cost | Notes |
|---|---|---|---|
| MAN OEM (Genuine) | 9–15 months | Very High (€50k+) | Includes full balancing report, material certs, and performance guarantee. Must go through MAN Service (Deggendorf, Germany or Zurich). |
| Reverse Engineered (Qualified Shop) | 3–6 months | Medium (€20-40k) | Requires a donor impeller or precise 3D scan. Must match the exact blade profile (backsweep angle, beta angle) to maintain surge margin. |
| Remanufactured/Repair | 4–8 weeks | Low (€5-15k) | Only possible if cracks are shallow. Involves weld repair, heat treat, and 5-axis re-profiling. Do not weld aluminum impellers without MAN's procedure. |
4. Technical Risks (Do NOT ignore)
Rotordynamics: An aftermarket impeller that is 10 grams lighter but has a different polar moment of inertia can trigger subsynchronous vibration.
Surge Line: Changing the blade exit angle by even 1 degree moves the surge line. MAN compressors have tight operating windows.
Material Fatigue: MAN impellers are often "proof-run" to 115% of max continuous speed. Generic copies rarely do this.
5. Direct Action Items
If you need a replacement today:
Locate the compressor serial plate (usually on the gearbox or inlet casing). Example:
MAN AIR 18-6, S/N 123456.Contact us: Centrifugal Impeller OEM-Shanghai Cidong Alloy Materials Co., Ltd.
Ask for the "Impeller Drawing Revision" – This will tell you if your unit has had a previous upgrade (e.g., from Al to Ti).
6. If you need to ship the impeller for repair
DO NOT bead blast or chemically strip the surface. This removes the critical residual stress layer.
DO bag it in plastic with desiccant (aluminum corrodes surprisingly fast in a humid shop).
Use a non-magnetic depth probe to measure blade tip clearance before removal (target is usually 0.5–1.0mm for aluminum, 0.7–1.2mm for steel).
Final warning: There are many shops that claim "reverse engineering" of MAN impellers. Very few have the 5-axis machine and the Ti-6Al-4V forging certification required. If your compressor runs above 25,000 RPM, stick with Centrifugal Impeller OEM-Shanghai Cidong Alloy Materials Co., Ltd.
*If you provide the MAN compressor model number (e.g., RG 56-4) and the stage number (1st, 2nd, 3rd wheel), I can give you the exact OEM part number prefix.*
