Double seal titanium plug valve is widely used in chemical industry, marine engineering, environmental protection, pharmaceutical and other fields with its excellent corrosion resistance and reliable sealing structure. However, in long-term operation process, due to the characteristics of media, operating conditions, maintenance level and other factors, there may still be various problems. Understanding common failure modes and their causes can improve the reliability and service life of equipment.
1.Sealing Surface Wear Failure
The sealing surface is the key part of the plug valve to realize the function of closing and sealing. Frequent opening, inclusion of solid particles in the medium, or insufficient lubrication can lead to the sealing surface wear.
Main Manifestations:
Internal leakage after valve closure
Reduced seal specific pressure
Increase operating torque.
Reason:
Frequent long-term open and closing operation
Medium, such as sand and crystals, containing abrasive impurities.
Insufficient abrasion resistance of sealing material;
Preventive measures:
Regularly check the condition of the cover.
Keep it moderately clean.
Select sealing material suitable for operating conditions.
2.Corrosion Failure
Titanium has excellent corrosion resistance, but it can still corrode in some special media or extreme conditions.
Common Corrosion Types
Crevice Corrosion
Occurs in an enclosed space, such as the contact area of a sealed cover and flange connections.
Pit Corrosion
Corrosion pits formed locally in highly concentrated chlorine ion environments.
Electrochemical Corrosion
Galvanic corrosion may occur when titanium comes into contact with other metals.
Main Manifestations
Surface corrosion spots
Local perforation
Decreased sealing performance
Preventive measures
Avoid inappropriate material pairings.
Control of moderate temperature and concentration
Periodic inspection of key components
3. Double structural failure
Double sealing system is generally composed of main seal and auxiliary seal. Fault may occur when sealing element ages or breaks.
Main Manifestations
Increased external leakage
Decreased sealing performance
Pressure test fails
Reasons
Seal ring aging
(a) Long-term high temperature operation;
Chemical media corrosion
Improper installation resulting in deformation.
Preventive measures
Replace seals regularly.
Controlling operating temperature
Choose good media resistance sealing material.
4. Plug Valve Jamming Failure
Plug valves is opened and closed by rotation. If there is a blockage between the plug and the valve body, normal operation will be affected.
Main Manifestations
Switching difficulties
Increases operating torque significantly.
Unable to fully open or close
Reasons
Long-term inactivity
Crystallization and deposition of media
Lack of lubrication
Thermal expansion leads to over-tightening;
Preventive measures
Open and close valves regularly
Maintain a normal lubrication system
Remove scales and sediment
5. Valve Stem Failure
The stem plays a vital role in transferring operating torque and is an important load-bearing component of the valve.
Common Problemss
Stem bending
Stem wear
Valve stem breakage
Reasons
Too much torque operation
Frequent on and off
Corrosion thinning
Eccentric installation
Preventive measures
Avoid coercion.
Periodically inspect valve stem wear
Use design-compliant actuators
6.Packaging seal failure
The stuffing box is responsible for preventing media leakage from the valve stem.
Main Manifestations
valve stem leak
Frequent adjustment of packing caps
Reasons
Aging packaging
Insufficient clamping force
Valve stem surface wear
Preventive measures
Regularly adjust glands
Replace old packaging
Check valve stem surface quality.
