1 Impeller Clearance Adjustment

Pump efficiency is closely related to the clearance between the impeller and the intake side liner.

As slurry pumps operate, wear gradually increases this clearance. When the gap becomes larger, pump efficiency will decrease.

To maintain optimal performance:

• Stop the pump periodically

• Adjust the impeller forward to restore proper clearance

This adjustment can usually be completed within a few minutes and does not require dismantling the pump.

Before restarting the pump, ensure:

• The impeller rotates freely

• Bearing housing clamp bolts are properly tightened

For pumps equipped with a centrifugal shaft seal, moving the impeller forward may increase seal pressure. In certain applications, slightly larger clearance may be required to maintain proper sealing performance.

2 Bearing Lubrication

Bearings play a critical role in the reliability of slurry pumps. A properly assembled and pre-greased bearing assembly can operate for long periods with minimal issues, provided it is protected from contamination.

Maintenance personnel should inspect bearing housings at regular intervals, typically not exceeding 12 months.

During inspection, it is important to evaluate:

• Lubrication frequency

• Lubricant quantity

• Next inspection schedule

Several factors influence lubrication intervals, including:

• Bearing size and rotational speed

• Frequency of pump start and stop cycles

• Ambient and operating temperature

• Environmental contamination

Although slurry pump bearings typically operate at relatively low speeds, over-lubrication can still cause overheating and premature failure.

Therefore, operators should monitor bearings closely during early operation and observe:

• Temperature changes

• Cleanliness of lubrication components

3 Recommended Grease Types

For most slurry pump bearing applications, lithium complex grease is recommended.

Typical grease characteristics include:

• NLGI Grade: 2

• Dropping Point: approximately 280°C

• Worked Penetration: 280

• Base Oil Viscosity: 220 cSt at 40°C

A commonly used lubricant is Mobilgrease® XHP 222, which provides:

• Oxidation resistance

• Rust prevention

• Extreme pressure protection

For higher speed applications or heavy load conditions, synthetic lubricants such as Mobilith® SHC 220 are recommended.

4 Bearing Seal Protection

Modern slurry pumps are equipped with advanced bearing sealing systems to prevent contamination.

These sealing systems may include:

• Lip seals

• Flinger rings

• Piston rings

• Labyrinth grease purge systems

Regular purging of grease in the labyrinth seal helps prevent dust, water, and slurry particles from entering the bearing housing.

Lubrication intervals vary depending on pump operating hours and environmental conditions.

5 Shaft Seal Maintenance

For slurry pumps using gland packing seals, proper sealing water supply is critical.

Operators should:

• Periodically check gland seal water pressure

• Maintain a small amount of clean water leakage along the shaft

This leakage helps cool and lubricate the packing rings.

When gland adjustment can no longer control leakage, all packing rings should be replaced.

6 Grease Lubrication for Centrifugal Seals

Some slurry pumps utilize centrifugal expeller seals that require grease lubrication.

In these systems:

• The expeller ring is equipped with a grease cup

• Grease should be injected at approximately 12-hour intervals

Operators should ensure grease levels remain adequate at all times to maintain proper sealing performance.

Routine maintenance plays a vital role in maximizing slurry pump reliability and performance.

By following proper procedures such as:

• Regular impeller clearance adjustment

• Correct bearing lubrication

• Effective seal maintenance

operators can significantly extend pump service life and reduce maintenance costs.

Implementing these best practices helps ensure that slurry pumps continue to operate efficiently even in demanding industrial environments such as mining, dredging, and mineral processing.