What are the causes of seal failure？

Seal (Seal Kit) failure is usually not caused by a single factor, but by a combination of multiple issues. Based on practical applications in hydraulic systems and construction machinery (such as pumps and travel motors), the common causes are as follows:

1. Installation Issues (Most Common)

• Improper installation: scratches, twisting, or deformation during assembly
• Incorrect size: seal too large or too small
• Poor groove design: excessive clearance or insufficient compression
• Wrong installation direction (especially for lip seals)

 Characteristic: Leakage occurs shortly after installation

2. Pressure Factors

• Excessive pressure: exceeds seal capacity, causing extrusion or rupture
• Pressure spikes (shock pressure): repeated impact leads to fatigue damage
• Abnormal back pressure: causes seal lip deformation

 Common in hydraulic pumps and valve systems

3. Temperature Effects

• High temperature: material hardens, ages, and loses elasticity
• Low temperature: material becomes brittle and loses sealing performance
• Rapid temperature changes: accelerate fatigue

 Common in high-load hydraulic systems

4. Fluid (Oil) Issues

• Incompatible oil: not suitable for seal material (e.g., NBR with certain additives)
• Contaminated oil: particles cause wear
• Water or air contamination: leads to corrosion or cavitation

 Common in markets where oil quality varies

5. Mechanical Wear

• Worn moving parts: rough shaft or cylinder surface
• Misalignment or eccentric load: uneven stress on seals
• High-speed operation: causes overheating and wear

 Common in travel motors and hydraulic cylinders

6. Material Aging

• Natural aging over time
• Oxidation or UV exposure
• Poor material quality

Symptoms: hardening, cracking, loss of elasticity

7. Insufficient Lubrication

• No lubrication during installation
• Inadequate lubrication during operation

Leads to dry friction → rapid wear

8. Environmental Factors

• Dust and sand ingress (common in construction environments)
• Corrosive environments (chemicals, salt air)
• External shock or vibration

Tips:

1. When a sealing ring twists or deforms due to compression, it is usually necessary to check the assembly process, groove chamfering, mating surface angles, and the sealing ring’s compression ratio.

2. When wear marks, scratches, or detachment appear on the sealing ring surface, attention should be paid to the surface treatment process, groove roughness, the presence of metal wear debris, and the presence of oil or foreign matter in the system.

3. When cracks, carbonization, or discoloration appear on the sealing ring surface, it is important to check if the ambient temperature is normal.

4. When a sealing ring expands, blisteres, or shrinks, it is important to check if the sealing medium is abnormal and the medium resistance of the sealing ring. When numerous micro-cracks appear on the sealing ring surface, the material, hardness, and performance of the sealing ring should be comprehensively tested to determine if the material is aging.

5. When a sealing ring cracks or breaks, the first step is usually to locate the source of the crack or breakage, determine the nature of the fracture, and examine the fracture morphology, focusing on whether there are defects or damage in the source area and surrounding areas. Then, a comprehensive analysis and verification of the sealing ring’s stress, environmental factors, and material properties should be conducted to identify the cause of failure.