Troubleshooting Bearing Clearance Issues in Tungsten Carbide Bushings

Bearing clearance is one of the most important factors in the performance of tungsten carbide bushings.

If the clearance is too tight or too loose, problems such as friction, vibration, heat, noise, or even full pump failure can occur.

This article explains the common causes of clearance problems, how to detect them, and the best ways to fix and prevent them in pumps, compressors, and other rotating equipment.

Why Correct Clearance Matters

Tungsten carbide bushings are used because they provide strength, 경도, and stability under high load. But they can only work correctly when the bearing clearance is within the design range.

1). If clearance is too small

Excessive friction
과열
Risk of seizing
High shaft wear

2). If clearance is too large

Shaft instability
진동
Noise
Premature bushing wear
Poor sealing performance

3). Typical Clearance Ranges

These are general values used in many industrial pumps:

Pump Type	Recommended Clearance	Risk if Below Range	Risk if Above Range
Vertical turbine pump	0.15–0.25 mm	Friction, heat	Vibration, wobble
Centrifugal pump	0.10–0.20 mm	Seizure	Noise, instability
High-speed pump	0.05–0.12 mm	Rapid failure	Seal leakage

Correct clearance ensures smooth rotation, long service life, and reduced maintenance costs.

Common Causes of Incorrect Clearance

When clearance is not correct, the root cause usually comes from one of the following issues.

1). Manufacturing tolerance errors

Bore diameter too small or too large
Shaft size variation
Incorrect roundness

2). Thermal expansion

High temperatures cause the shaft to expand
Bushing expands less because carbide has a different thermal expansion rate
Clearance becomes too small during operation

3). Misalignment

Shaft not centered
Housing not straight
Pump and motor misaligned

4). Wear from dirty or abrasive fluids

Particles entering the bearing can:

Increase clearance
Score the surface
Damage roundness

5). Poor lubrication or dry running

Without proper fluid film, both the shaft and bushing wear faster.

Detecting Clearance Problems Early

Early detection is the best way to avoid serious equipment failure.

1). Key Warning Signs

Sign	Likely Cause	Too Small Clearance	Too Large Clearance
High temperature	Friction or lack of lubrication	Very likely	Rare
진동	Shaft instability	Possible	Very likely
Noise	Rubbing, wobble, or contact	Likely	Likely

2). Other signs include

Shaft contact marks
Uneven wear
Changes in pump efficiency
Frequent shutdown alarms

These symptoms usually appear long before total failure.

How to Measure Bearing Clearance Accurately

To troubleshoot clearance problems, accurate measurements are essential.

1). Tools Commonly Used

Feeler gauge
Bore gauge
마이크로미터
Dial indicator
CMM(좌표측정기)

2). Direct Clearance Measurement Methods

Measure shaft OD and bushing ID: Clearance = ID – OD
Use feeler gauge between shaft and bushing: Works well for large bearings.
Use CMM for precision-grade pumps: Very accurate for high-speed systems.

3). Important Notes

Always measure at room temperature
Measure in multiple directions (X, Y, and angular)
Check for out-of-round errors
Compare to engineering drawing values

Solving Too-Small Clearance Problems

A clearance that is too small causes the most serious damage because it leads to heat and friction.

1). Main Causes

Incorrect machining
열팽창
Installation force distortion
Wrong interference fit

2). Solutions

Re-hone the bushing bore
Increase lubrication flow
Improve shaft cooling
Use a carbide grade with slightly higher thermal expansion
Adjust installation process

3). When to Replace

If the inner wall is scored or heat-damaged, replacement is recommended.

Solving Too-Large Clearance Problems

Large clearance reduces stability and may cause vibration or leakage.

1). Main Causes

Abrasive wear
Long-term operation
Shaft wear
Manufacturing tolerance issues

2). Solutions

Replace worn bushings
Rebuild or hard-coat the shaft
Improve filtration
Use harder carbide grade
Reduce flow turbulence

3). When to Replace

Replace if clearance exceeds the engineering limit or if vibration becomes severe.

Preventing Clearance Problems in the Future

Prevention is always cheaper than repair.

1). Key Prevention Steps

Maintain correct pump alignment
Monitor temperature and vibration
Improve filtration and remove solids
Ensure proper lubrication flow
Use the correct tungsten carbide grade
Avoid sudden start-stop cycles

2). Recommended Maintenance Schedule

Interval	행동	목적	Result
월간 간행물	Check vibration	Detect instability early	Longer bushing life
Quarterly	Check shaft condition	Find wear issues	Lower repair cost
Yearly	Inspect bushing clearance	Maintain performance	Better pump reliability

결론

Bearing clearance problems can cause serious damage to tungsten carbide bushings and the equipment they support.

By understanding the causes, detecting early signs, measuring correctly, and applying the right corrective steps, decision-makers can greatly extend the life of their pumps and reduce downtime.

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