Sealing surface leakage is one of the most common valve failures in industrial service. When the ball, seat, or stem seal fails, the entire valve may need to be replaced. Whether it is the ball, seat, or stem seal, once the sealing surface is compromised, the entire valve may fail. Understanding the common causes helps in prevention during manufacturing and maintenance.This article briefly analyzes the main causes of sealing surface failure from three dimensions: material, machining, and assembly.
Cause 1: Improper Material Selection
Sealing surface materials must simultaneously meet requirements for corrosion resistance, wear resistance, and temperature resistance. Improper selection is often the primary cause of early failure.
Common issues:
- Using ordinary stainless steel in chloride-containing service, leading to pitting or stress corrosion cracking
- Using soft sealing materials (e.g., PTFE) in media containing solid particles, leading to rapid scoring and leakage
- Using coatings without thermal stability verification at high temperatures, leading to softening or spalling
Prevention:
- Select appropriate sealing surface materials based on service conditions, such as Stellite alloy, tungsten carbide coating, ceramics, etc.
- Conduct targeted validation for special conditions, such as media simulation testing
Cause 2: Insufficient Machining Precision
The roundness, roughness, and concentricity of the sealing surface directly determine sealing performance. Insufficient precision results in leakage even with correct material selection.
Common issues:
- Excessive ball roundness deviation, causing uneven contact and uneven stress on the sealing surface
- Excessive surface roughness (Ra>0.4μm), allowing media to leak through micro-scratches
- Concentricity deviation between stem and ball connection, causing abnormal operating torque and uneven sealing surface wear
Prevention:
- Use precision grinding processes to control ball roundness ≤0.005mm
- Achieve sealing surface roughness Ra≤0.1μm (mirror finish)
- Implement 100% dimensional inspection for critical processes
Cause 3: Improper Assembly and Adjustment
Sealing surfaces may be damaged or fail during assembly or testing, even if they are manufactured correctly.
Common issues:
- Failure to clean sealing surfaces before assembly, causing scratches from metal chips or particles
- Incorrect fastener torque, resulting in uneven preload on sealing surfaces
- Impact damage during installation
Prevention:
- Clean and inspect sealing surfaces before assembly
- Tighten connections to specified torque values
- Assemble in a clean environment to avoid impact
TONGBALL's Quality Control Practices
In response to the above failure causes, TONGBALL has established corresponding control measures in production:
- Material validation: Incoming material spectroscopy, hardness testing, and metallurgical sampling to ensure compliance
- Process control: First-article inspection, patrol inspection, and final inspection as three lines of defense
- Seal testing: Air tightness testing on every product before shipment, high-pressure gas seal leakage rate ≤0.1cc/min
- Cleanliness management: Cleanliness inspection after final cleaning to ensure no oil residue or particles
Conclusion
Sealing surface failure is often the result of multiple factors combined - material, machining, and assembly. TONGBALL reduces sealing surface failure risk at the source through full-process quality control, helping customers lower valve failure rates and maintenance costs.
If your valves frequently experience sealing surface leakage issues, please contact our technical team - we are ready to discuss solutions.
