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Case
Gate valves are one of the most critical isolation devices in industrial piping systems, widely used in oil & gas, chemical, power, and water treatment industries. However, gate valve leakage not only leads to media waste and environmental pollution but may also cause serious safety incidents.
Industry data shows that about 35% of gate valve failures are caused by leakage. So, what are the main reasons for gate valve leakage? How can you quickly diagnose and fix the issue? This article will analyze the top 5 leakage causes and provide professional solutions to help extend valve service life and reduce maintenance costs.
The valve seat is the core sealing component of a gate valve and is subject to long-term erosion from media flow, particle abrasion, and chemical corrosion. Common types of wear include:
* Mechanical wear: Solid particles (e.g., sand, welding slag) scratch the sealing surface.
* Corrosive wear: Acidic/alkaline media (e.g., H₂S, Cl⁻) erode metal seats.
* Thermal deformation: High temperatures (>300°C) cause soft sealing materials to degrade.
| Working Condition | Recommended Seat Material | Advantages |
| Room-temperature water | EPDM rubber | Cost-effective, good elasticity |
| High-temperature steam (≤425°C) | Stainless steel + graphite gasket | Heat-resistant, anti-creep |
| Corrosive media | Hastelloy C276 | Acid/alkali resistance, anti-pitting |
* Use 13Cr stainless steel disc + Stellite 6 overlay for 3-5x longer service life.
* Suitable for high-pressure (Class 1500+) and particle-laden media.
* Continuous seepage around the stem (water droplets or steam jets).
* Sudden increase in operating torque (over-tightened packing).
* Asbestos packing: Prone to hardening and cracking (phased out).
* PTFE packing: Not heat-resistant (>200°C failure).
| Type | Temp. Range | Features | Standard |
| Flexible graphite packing | -200~600°C | Self-lubricating, corrosion-resistant | ISO 15848 |
| Bellows seal | -50~400°C | Zero leakage, maintenance-free | API 624 |
| Carbon fiber braided packing | ≤800°C | Ultra-high strength, thermal shock resistance | EN 13625 |
* Use cross-layered compression to avoid stress concentration.
* Tighten packing gland bolts diagonally (torque ≤50 N·m).
* Pipe misalignment: Forced flange bolting causing valve body distortion.
* Welding heat impact: Residual stress in the seat area due to lack of annealing.
Pre-installation Checks
* Verify flow direction markings (double-disc valves are bidirectional).
* Clean pipeline interiors (avoid welding slag entering the valve cavity).
Alignment Calibration
* Use laser alignment tools to ensure pipe offset <0.1mm/m.
Pressure Testing
* Seal test: 1.1x design pressure, hold for 5 minutes (ASME B16.34).
A. Valve Body Cracks
* Cause: Freeze-thaw (water systems), water hammer.
* Solution: Use low-temperature carbon steel (LCC) or add electric tracing.
B. Disc Jamming
* Symptom: Handwheel won’t turn.
* Fix: Inject valve cleaner (e.g., WD-40) or disassemble for descaling.
For critical pipelines (e.g., refineries, LNG terminals), consider IoT-enabled gate valves:
* Real-time monitoring: Vibration sensors detect early leakage signs.
* Predictive maintenance: AI analyzes valve cycles to preemptively replace worn parts.
Temporary fixes (e.g., tightening the packing gland) are possible, but permanent repairs require shutdown and seal replacement.
Bubble test: Inject gas into the low-pressure side of a closed valve and monitor pressure drop rate.
Food-grade graphite complies with FDA 21 CFR 177.2600 standards.
As an API-certified valve manufacturer, we offer:
* Leakage analysis: Spectrometry + 3D scanning for fault localization.
* Long-term sealing solutions: Bellows-seal gate valves (<50ppm leakage rate).
* Resilient seats (EPDM/NBR) suit water systems (<80°C)
* Metal seats (SS316/Stellite) for high-temp (>200°C) or abrasive media
* Standard graphite: 3-5 years
* Bellows seals: 10+ years (API 624 compliant)
* Warning signs: >50ppm fugitive emissions
Not recommended - causes:
* Seat erosion (especially soft seats)
* Vibration-induced stem damage
* Use globe/control valves instead
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