Common Failure Causes of Gear Pumps

Common Failure Causes of Gear Pumps

Gear pumps are widely used in hydraulic systems, lubrication systems, and industrial fluid transfer applications due to their simple structure and stable flow characteristics. However, during long-term operation, various faults may occur, most of which are closely related to installation, operating conditions, fluid properties, and component wear.

Insufficient Flow or Pressure Drop

One of the most common issues is insufficient flow output or reduced discharge pressure. This is often caused by excessive internal leakage within the pump.

The main reasons include:

• Excessive wear of gears and side plates, increasing internal clearance

• Low fluid viscosity, which reduces sealing effectiveness

• Suction line leakage or air ingress, leading to unstable volumetric efficiency

• Clogged inlet filter, restricting fluid supply

When internal leakage increases, the pump cannot maintain designed volumetric displacement, resulting in performance degradation.

Abnormal Noise and Vibration

Unusual noise or vibration is a key indicator of mechanical or hydraulic problems. Common causes include:

• Cavitation due to insufficient inlet pressure (low NPSH conditions)

• Air entrainment in the hydraulic oil or process fluid

• Misalignment between pump and motor coupling

• Excessive gear wear or damaged bearings

Cavitation is particularly harmful, as it produces localized shock waves that damage gear surfaces and housing walls over time.

Overheating of Pump Body

Overheating is another frequent failure symptom. It is usually associated with excessive friction or insufficient lubrication.

Typical causes include:

• High-viscosity fluid at low temperature, increasing resistance torque

• Poor lubrication conditions in hydraulic oil systems

• Incorrect system pressure setting causing overload operation

• Internal mechanical friction due to tight clearances or wear debris

Continuous overheating can accelerate seal failure, gear deformation, and oil degradation.

Leakage Problems

External or internal leakage is a common issue in gear pumps. External leakage is usually observed at shaft seals, gaskets, or housing joints.

Main causes include:

• Seal wear or improper installation

• Aging of sealing materials due to temperature or chemical exposure

• Excessive system pressure exceeding design limits

Internal leakage, on the other hand, results from increased clearance between gear teeth and pump casing, which directly reduces efficiency.

Wear and Mechanical Damage

Long-term operation leads to progressive wear of key components, especially gears and bushings.

Wear mechanisms include:

• Abrasive wear caused by solid particles in the fluid

• Adhesive wear due to poor lubrication conditions

• Cavitation erosion on gear surfaces

• Fatigue damage from cyclic loading

If not addressed early, wear can lead to gear tooth damage, reduced efficiency, and eventual pump failure.

Cavitation and Air Entrapment Issues

Cavitation occurs when local pressure drops below vapor pressure, forming vapor bubbles that collapse violently. This is often caused by:

• Restricted suction piping

• Clogged filters or valves

• High rotational speed without sufficient inlet supply

Air entrainment, on the other hand, leads to compressibility effects in hydraulic fluid, resulting in unstable flow and noise.

Improper Installation and Operation

Many gear pump failures are related to installation and operational errors, such as:

• Incorrect shaft alignment

• Reverse rotation during start-up

• Operation beyond rated pressure or speed

• Poor piping design causing flow restriction

These issues often lead to premature wear and unstable hydraulic performance.

Summary

In summary, the common failures of gear pumps are mainly caused by mechanical wear, cavitation, improper installation, lubrication issues, and system design problems. Understanding these failure mechanisms helps improve equipment reliability, extend service life, and reduce maintenance costs.

References

• Hydraulic Institute Standards (HI)

• API Standard 614: Lubrication, Shaft-Sealing, and Control Oil Systems

• Karassik, I.J. Pump Handbook

• Stepanoff, A.J. Centrifugal and Axial Flow Pumps

• Gülich, J.F. Pump Technology and Hydraulic Design Principles