How to Change Pump Bearings

When to Replace Bearings

Bearings should be replaced proactively based on condition monitoring — not reactively after failure. Replace bearings when you observe:

• High vibration at bearing frequency: Non-drive-end (NDE) or drive-end (DE) bearing frequency peaks in vibration spectrum.
• Temperature rise: Bearing temperature exceeds 80°C or rises more than 15°C above baseline.
• Audible noise: Grinding, rumbling, or clicking sounds from the bearing housing.
• Oil degradation: Oil analysis shows high metal particle count or water contamination.
• Lubricant leakage: Seal failure allows grease or oil to escape, leading to dry running.

Safety and Preparation

1. Isolate and lock out the pump and motor.
2. Close the suction and discharge isolation valves.
3. Open the casing drain valve and drain all liquid.
4. Disconnect the coupling guard and separate the coupling.
5. Mark the orientation of the bearing housing, impeller, and casing with a centre punch or paint marker for reassembly reference.

Step 1: Remove the Motor

1. Remove the coupling guard.
2. Loosen and remove the coupling spacer or coupling halves.
3. Remove the motor holding-down bolts.
4. Slide or lift the motor clear of the pump.
5. If only replacing the drive-end (DE) bearing, you may be able to work without fully removing the motor — but ensure the shaft is accessible.

Step 2: Remove the Bearing Housing

1. Remove the bearing housing end cover bolts.
2. Withdraw the shaft and impeller assembly from the casing — support the shaft to avoid damaging the mechanical seal.
3. Remove the bearing housing from the casing, noting any shims or gaskets.
4. Clean the external surfaces of the bearing housing.

Step 3: Remove the Old Bearings

1. Remove the bearing end cap and any bearing locking devices (locknut, lockwasher, or snap ring).
2. Use a bearing puller to withdraw the bearing from the shaft — always pull on the inner race, never the outer race.
3. If the bearing is tight, heat it with an induction heater to 100–110°C to expand it — never use an open flame.
4. Remove the bearing from the housing if it is a clearance-fit housing — tap it out gently with a soft-faced mallet.
5. Clean the shaft journal and bearing housing bore — remove all old lubricant, rust, and burrs.
6. Inspect the shaft journal for wear, scoring, or fretting. Measure with a micrometer — if out of tolerance, the shaft must be repaired or replaced.

Step 4: Install the New Bearings

1. Verify the new bearing part number matches the old one — same bore, outer diameter, width, and type (ball, roller, angular contact).
2. Clean the new bearing with lint-free cloth — do not wash it in solvent unless the packaging specifies it is not pre-lubricated.
3. Heat the new bearing using an induction heater to 100–110°C. Never exceed 120°C.
4. Slide the heated bearing onto the shaft quickly — it should slide on with hand pressure only.
5. Hold the bearing firmly against the shaft shoulder until it cools and shrinks onto the shaft.
6. If a cold installation is required, use a bearing installation tool that presses on the inner race only — never tap the outer race.
7. Install the bearing locknut or snap ring to secure the bearing axially.

Step 5: Lubricate the Bearings

Correct lubrication is critical. Over-greasing causes overheating; under-greasing causes dry running. Follow the manufacturer's recommendation for grease type and quantity.

• Grease lubrication: Fill the bearing cavity 1/3 to 1/2 full of grease. Do not overfill — excess grease causes churning and overheating. Use a grease gun with a pressure relief fitting to prevent over-greasing.
• Oil lubrication: Fill to the oil level mark on the bearing housing sight glass. Use the correct viscosity oil specified by the pump manufacturer.
• Grease compatibility: If mixing greases, verify compatibility — lithium complex and polyurea greases are often incompatible and will break down.

Step 6: Reassemble the Pump

1. Install the bearing housing back into the pump casing with new gaskets and shims.
2. Reinstall the shaft and impeller assembly, ensuring the mechanical seal is not damaged.
3. Reinstall the bearing end cap and locking devices.
4. Reconnect the coupling and coupling guard.
5. Reinstall the motor and align it to the pump shaft (see 'How to Align a Pump').
6. Remove LOTO and open isolation valves.
7. Start the pump and monitor bearing temperature for the first hour — temperature should stabilise below 70°C.