Repair Solutions for Roots Pump Bearing Position Wear
Long-term continuous operation of roots pump, liquid ring vacuum pump and roots blower in chemical, mining, pharmaceutical and wastewater treatment industries easily leads to bearing position wear on shaft components. Once bearing wear creates gaps, the unit will generate heavy vibration and abnormal noise, and further damage internal sealing structures, triggering secondary faults such as mechanical seal leakage. Most overseas B2B factories lack mature low-cost repair processes. When shaft wear occurs, they have to purchase brand-new main shafts, which comes with high procurement costs and long delivery cycles, greatly raising the overall operation cost of industrial vacuum equipment. Based on our factory’s years of practical experience in equipment manufacturing and unit overhaul, this article introduces a standardized mold repair process in full detail. We only share operable on-site operations without fabricating overseas service or customized package businesses that we do not provide. The core goal is to help factories shorten downtime and cut spare part expenses.
Multiple Production Losses Caused by Bearing Position Wear
Many factory maintenance teams keep running equipment with minor wear to save short inspection time. However, this practice will trigger a series of long-term losses:
Eccentric gaps formed by worn shafts cause severe vibration during high-speed operation of roots pump, resulting in permanent scratches on impellers and pump chambers, and even scrapping of rotor assemblies in serious cases.
Unbalanced shaft concentricity destroys the airtight environment inside the pump, leading to continuously dropping pumping efficiency, failing to reach the process vacuum standard and reducing production output.
Uneven force on inner and outer bearing rings frequently causes bearing seizure and unexpected production shutdowns, delaying order delivery schedules.
Brand-new original main shafts carry high price tags. For overseas buyers, logistics and customs clearance fees will be added to cross-border purchases, creating heavy spare part expenditure pressure for small and medium-sized factories.
Compared with the traditional method of replacing complete main shafts, the mold composite repair process avoids disassembling large pump components and can be finished on-site, cutting downtime by half. The cost of repair materials is only one-third of a new main shaft. It is a highly cost-effective solution in all types of vacuum pump maintenance. This repair method is compatible with all series of industrial vacuum pump manufactured by our factory, including large-scale units for mine gas extraction and small-sized liquid ring vacuum pump for pharmaceutical processes.
Pre-repair Materials and Workpiece Pretreatment Standards
Full List of Required Tools & Materials
No large professional processing equipment is required for the complete repair process; conventional maintenance workshop tools are sufficient:
Split repair molds matched to the measured shaft diameter, compatible with various sizes of roots pump and blower shafts
Industrial degreaser, 80# / 120# abrasive paper, dust-free wiping cloth
Metal composite repair compound, matching mixing tray and scraper
Release agent, torque wrench, angle grinder and flat file
Mandatory Workpiece Pretreatment Specifications
The adhesion strength of repair compound directly depends on pretreatment quality. Inadequate treatment will cause peeling and re-wear shortly after repair:
Wipe the bearing position repeatedly with degreaser to remove accumulated lubricating oil, corrosion and dust lumps from long-term operation.
Sand the worn area down to bare metal to eliminate oxide rust layers and boost compound adhesion.
Fully air-dry the shaft surface to avoid water or floating dust residue before filling.
Wear depth classification for different solutions: Mold repair works for wear between 0.1mm and 3mm. If wear exceeds 3mm, the repair layer tends to crack under force, so replacement of original main shaft and shaft sleeve assembly is recommended.
Standard 6-Step Mold Repair Process
This set of procedures has been verified by thousands of roots blower and vacuum units in our overhaul workshop. Maintenance technicians can master it after simple training:
Mold Fabrication & Dimension Calibration
Fabricate split molds according to the measured outer diameter of the worn shaft. The inner bore of the mold must strictly match the standard shaft diameter after repair with a tolerance within 0.02mm to prevent bearing assembly failure. Only molds need to be replaced for different models of liquid ring vacuum pump, while the whole process remains applicable.
In-depth Workpiece Pretreatment
Repeat degreasing and sanding procedures twice or more, then air-dry completely. Residual oil stains will cause delamination of repair compound and lead to recurrent wear after short use.
Uniform Compound Mixing
Blend base material and curing agent strictly per the ratio, stir evenly for 3 to 5 minutes until free of lumps and color difference. Control construction time after mixing to avoid premature curing before filling.
Full Surface Coating
Cover the entire worn area completely with compound with slightly extra thickness to compensate for curing shrinkage, without hollow gaps or dead corners.
Mold Clamping & Positioning
Spray a uniform layer of release agent on the inner mold wall, align and fasten the mold on the repaired segment. Excess compound squeezed out during curing does not need manual cleaning and will not affect forming dimensions.
Post-curing Finishing
Do not dismantle the mold or hit the repaired layer with hard tools until fully cured. Polish extra protrusions with a grinder and file, then measure the shaft diameter repeatedly until it meets factory standards before bearing assembly testing.
Post-repair Inspection & Long-term Protection Measures
Two Mandatory Acceptance Tests
Do not install the pump directly after mold removal and polishing. Two inspections must pass to qualify the repair:
Multi-point measurement of shaft diameter, fully compliant with factory drawing tolerance;
Slide standard bearings onto the repaired segment by hand, with smooth rotation and no excessive clearance.
Low-cost Daily Maintenance Tips to Reduce Wear
Most bearing wear stems from insufficient lubrication, intrusion of process moisture and long-term overloading. Standard daily inspections can drastically cut fault frequency:
Refill matched grease on schedule to avoid dry friction, extending the service life of shaft sleeve and bearings fundamentally.
Install dust-proof retaining rings at shaft ends to block process moisture and dust from entering bearing chambers, lowering the chance of mechanical seal leakage.
Forbid long-term operation over rated pressure and speed, which causes eccentric shaft deformation.
Record vibration and abnormal noise data per shift; address minor wear at early stages to prevent fault deterioration.
Universal Applicability for Multiple Equipment Models
This mold repair process is not limited to roots pump bearing wear. All full-series liquid ring vacuum pump and roots blower manufactured by our factory with minor shaft wear can adopt the same operation logic. Only molds need to be replaced based on shaft outer diameter. Factories equipped with multiple types of production lines do not need dedicated repair supplies for each unit, saving workshop procurement costs.
A key reminder before repair: Inspect the complete mechanical seal kit simultaneously. Water seepage at the shaft end is the core cause of bearing rust and wear. If the seal shows leakage, replace fluororubber O-rings as a full set to avoid recurrent shaft wear shortly after repair.
Linked Fault Troubleshooting Points
Bearing position wear is an apparent surface defect. Check two related vulnerable parts before repair to eliminate root causes of repeated failures:
Inspect the whole mechanical seal kit for water seepage and medium corrosion. Impurities in circulating water penetrate through seal gaps and rust the shaft surface continuously.
Disassemble and inspect original bearings. If pitting or excessive clearance exists, replace bearings together with the repaired shaft to avoid rapid re-abrasion.
Conclusion
When roots pump or liquid ring vacuum pump suffers bearing position wear, full main shaft replacement is not the only solution. As a professional vacuum pump manufacturer, our factory has developed mature mold composite repair technology from years of workshop overhaul experience. Conventional maintenance tools are enough for on-site construction, greatly shortening production downtime and lowering annual spare part expenditure for factories. If you have questions about unit maintenance, original shaft sleeve or mechanical seal kit selection, feel free to contact our technical team for free practical guidance.
