KOBELCO VGP31649#01 Rotor ASSY. 3-4 STG
Overview
The KOBELCO VGP31649#01 Rotor ASSY. 3-4 STG is a genuine OEM rotor assembly for the 3rd and 4th compression stages of Kobelco (Kobe Steel) multi-stage compressors. It is supplied as a complete, factory-balanced assembly, so a worn or damaged rotor can be replaced without balancing individual impellers on site. That keeps overhaul time short and returns the compressor to its original performance.
Kobelco compressors are widely installed in refineries, petrochemical complexes, gas processing plants and air separation units across the Middle East. In these continuous-duty services, the later compression stages see the highest pressures and temperatures. The rotor assembly is a critical spare to keep available for planned turnarounds and for emergency repairs.
Technical Specifications
| Parameter | Value |
|---|---|
| Manufacturer | KOBELCO (Kobe Steel) |
| Part Number | VGP31649#01 |
| Product Type | Compressor rotor assembly |
| Stages | 3rd and 4th compression stages (3-4 STG) |
| Supply Condition | Complete, factory-balanced assembly |
| Compatible Equipment | Kobelco multi-stage compressors |
Role of the 3-4 Stage Rotor
In a multi-stage machine, each rotor stage raises gas pressure step by step. The 3-4 stage rotor handles gas that has already been compressed and intercooled by the earlier stages, so its dimensional accuracy directly affects discharge pressure, stage efficiency and running clearances. Wear on the rotor, erosion from process contaminants, or damage after a surge event show up as:
- Rising vibration readings at the high-pressure stage bearings
- A drop in discharge pressure or capacity at a constant driver load
- Higher discharge temperature and specific power consumption
- Seal leakage caused by increased rotor runout
Replacing the assembly with the original KOBELCO VGP31649#01 part restores the designed clearances, balance grade and aerodynamic profile of the stage.
Key Benefits
- Genuine OEM part: built to Kobelco drawings and tolerances for a direct fit with the existing casing, bearings and seals.
- Dynamically balanced: supplied as a balanced assembly, which reduces vibration risk and commissioning time.
- Restored efficiency: correct clearances bring back stage efficiency and lower energy cost per unit of compressed gas.
- Reduced downtime: holding the rotor as a spare turns an unplanned failure into a short, planned exchange.
- Traceability: an original part number ensures documentation and quality records stay consistent for plant audits.
Typical Applications
- Process gas compressors in refineries and petrochemical plants
- Instrument and plant air compressors in oil and gas facilities
- Gas gathering, boosting and processing stations
- Air separation and industrial gas production units
- Power, fertilizer and chemical plants with Kobelco compressor packages
Installation and Maintenance Notes
Rotor replacement should be carried out during a planned outage, following the compressor’s Kobelco maintenance manual. Before installing the new KOBELCO VGP31649#01 Rotor ASSY. 3-4 STG, inspect the bearings, seals and diaphragms, and replace any that are worn. After assembly, check rotor float, radial clearances and alignment with the driver. Record baseline vibration data at start-up so future condition monitoring has a clean reference. Always confirm the part number against your compressor’s serial number and parts list before ordering.
Why Choose Seven Star LLC
Seven Star LLC supplies genuine Kobelco compressor spare parts, including rotor assemblies, to customers in Oman and across the GCC. Our team checks the part number against your equipment data, confirms availability and lead time, and supports the order through to delivery on site. Send us your compressor model, serial number and required quantity for a fast quotation.
Confirming the Part Before You Order
Rotor assemblies are engineered for a specific compressor build, so the same frame size can use different rotors depending on the service conditions it was designed for. A correct match depends on data from your own machine, not just the part description.
- Read the compressor model and serial number from the nameplate on the casing or the package skid.
- Check the part number in the parts list or the rotor drawing supplied with the compressor; the suffix after the # sign identifies the variant and should match exactly.
- Compare with the markings on the removed rotor, if one is available.
- Note any upgrades or modifications made to the machine since delivery, which may have changed the rotor version.
Sending this information with your enquiry allows the part to be confirmed before a long lead-time item is committed.
Receiving, Storage and Handling
A balanced rotor can be damaged by poor handling long before it reaches the casing. Keep it in its shipping crate or on a proper rotor stand, lift it only at the points shown in the maintenance manual and never rest its weight on the impellers or seal areas. For long-term storage, keep the rotor indoors in a dry, temperature-stable store, inspect the preservation coating periodically and rotate it at intervals if the manufacturer recommends it. On receipt, check journals, seal areas and impellers for transport damage before placing it in stock.
After the Overhaul: What to Watch
- High vibration at start-up: check alignment, coupling fit, bearing clearances and soft foot before suspecting the rotor.
- Higher discharge temperature than before: review intercooler performance and seal clearances.
- Axial position alarm: recheck the thrust bearing setting and rotor float.
Compare the start-up readings with the baseline recorded before the overhaul and with the manufacturer’s acceptance limits.
Applications in Oman and the GCC
Multi-stage compressors from Kobelco serve refineries, petrochemical plants, gas processing and industrial gas facilities in Oman, including the industrial hubs around Sohar and Duqm. Hot, dusty air adds to the load on inlet filtration and intercoolers, which can shorten rotor life when filters are not maintained. Many operators hold a spare rotor so a turnaround does not depend on the delivery time of a new part.
Related Products
Kobelco parts and consumables listed here
Three compressor items are listed: the VGP31649#01 rotor assembly for the third and fourth stage, a lubricator assembly and a low level alarm pump assembly. These are machine-specific spares. The fourth item is Kobelco DW-50, a rutile flux-cored welding wire for carbon steel.Ordering Kobelco spare parts: what we need
Compressor spares are identified through the machine, not through a catalog. Send the compressor model and serial number from the nameplate, the Kobelco part number, and the item number and drawing number from the parts list in your manual. A photo of the old part and its markings helps. For Kobelco welding wire, send the trade name, the AWS classification your procedure calls for, the wire diameter, spool weight and quantity. We handle Kobelco compressor parts inquiries from across the GCC and check every part number against the manufacturer documentation.Browse Kobelco products by category: Compressor.
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