1. Seal failure and leakage
Internal leakage
Improper construction or installation leads to corrosion of the sealing surface, impurities entering the valve seat, or welding spatter damaging the ball and valve seat;
Long-term lack of maintenance causes hardening of the sealing grease, failure of valve seat elasticity or aging of the sealing ring.
External leakage
The sealing gasket at the valve body connection is damaged or the nut is not tightened evenly;
The packing gland bolts are loose or the packing (such as graphite, PTFE) is worn, causing the medium to leak from the valve stem.
2. Operational failure
Valve blocking/difficult rotation
The valve stem and actuator are stuck by foreign objects (such as rust, particulate matter) or insufficient lubrication;
Long-term non-operation causes the valve seat and the ball to stick (common in high temperature or corrosive media scenarios).
Inadequate switching
The actuator limit is inaccurate (such as electric/pneumatic device offset or bolt loosening);
The valve stem block is fouled or the installation angle is deviated, resulting in insufficient rotation angle (an error of 2°~3° can cause leakage).
3. Structural damage and wear
Wear of valve core and sealing surface
Erosion of medium containing hard particles causes scratches on the ball or valve seat sealing surface (especially soft sealing materials);
Frequent switching or high-pressure working conditions accelerate the wear of metal hard seals (such as tungsten carbide).
Channel blockage
Complex flow channel structures (such as T-type and Y-type) are prone to deposit high viscosity or solid-containing media, affecting flow efficiency;
Welding residues or improper cleaning cause foreign matter to get stuck between the valve seat and the ball.
4. Actuator and control abnormalities
Electric/pneumatic actuator failure
Power source abnormality (such as insufficient air pressure, power interruption) or signal transmission error;
Motor overheating or gearbox wear causes the valve to fail to respond to control commands.
Manual operation problems
The handwheel is too tight or the valve stem is bent (due to external impact or improper installation);
Wrong operation (such as forcibly adjusting the flow when it is not fully open/fully closed, resulting in damage to the sealing surface).
5. Adaptability failure of special working conditions
Temperature/pressure abnormality
High temperature (＞300℃) causes deformation of non-heat-resistant materials (such as melting of ordinary PTFE sealing ring);
Overpressure (＞10MPa) causes deformation of forged valve body or crushing of sealing surface.
Media compatibility issues
Corrosive media (such as strong acid) corrodes non-alloy valve body or seals;
Embrittlement of sealing materials (such as NBR rubber) under low temperature conditions causes leakage.
Typical failure phenomena and response examples
Sanitary hot water temperature does not meet the standard: The three-way valve has not switched to hot water mode, and the actuator needs to be checked or foreign objects stuck in the valve core need to be cleaned; Abnormal water temperature of the heating system: The valve core is in a single mode for a long time (such as summer mode), and the motor needs to be reset or replaced; Abnormal valve noise: The linkage parts between the valve stem and the actuator are worn, and lubrication or replacement of worn parts is required.