A valve that is too tight may be caused by various reasons. Here are some common factors:
Problems with the valve itself
Valve stem deformation: External impact, improper installation or uneven force application for a long time may cause the valve stem to deform, reducing the fit clearance between the valve stem and the stuffing box or other components, generating additional friction, and thus making valve operation difficult.
Sealing parts aging or damage: The sealing parts of valves, such as sealing rings and packing, may age, harden, wear or be damaged after long-term use. Aged or damaged seals will lose their original elasticity and flexibility, increasing the friction between them and the valve stem or valve seat. This results in greater force being required to close the valve and makes it more difficult to open it.
Impurities inside the valve: Impurities, particles, rust, etc. in the pipeline may enter the valve interior and accumulate on the valve seat, valve disc or valve stem and other parts, hindering the normal movement of the valve and increasing the operating resistance of the valve.
Improper valve selection: If the diameter, pressure rating, material, etc. of the valve are not properly selected, it may cause the valve to bear excessive pressure or friction during operation, resulting in operational difficulties. For instance, if the rated pressure of a valve is lower than its actual working pressure, the internal components of the valve will be subjected to excessive pressure, resulting in the valve being tightly closed and difficult to open.
Installation and environmental issues
Improper installation position: If the valve is installed in an unreasonable position, such as in a narrow space or a place that is difficult to operate, it may make it difficult for the operator to apply sufficient force to operate the valve, and it is also not conducive to the normal maintenance and repair of the valve. In addition, the stress in the pipeline may also be transferred to the valve, causing additional resistance to the valve.
Pipe connection issues: If there are deviations, misalignments or excessive stretching during pipe connection, the valve will be subjected to additional external forces after installation, causing uneven force distribution on the internal components of the valve and making valve operation more difficult.
Environmental temperature influence: In a low-temperature environment, the material of the valve may become brittle, and the performance of the sealing parts may also decline, resulting in an increase in the friction of the valve. In high-temperature environments, the components of the valve may experience a reduction in fit clearance due to thermal expansion, making the operation of the valve difficult. For instance, at high temperatures, the gap between the valve stem and the stuffing box becomes smaller, making it prone to jamming.
Operation and maintenance issues
Long-term inoperation: If a valve is not opened or closed for a long time, it may cause the sealing parts to stick to the valve stem or valve seat, or the internal components to rust, making it difficult to open the valve.
Improper maintenance: The lack of regular lubrication, cleaning and other maintenance work will accelerate the wear of the transmission and sealing components of the valve and increase the friction force. In addition, if the components of the valve are not installed properly during the maintenance process, it may also lead to abnormal operation of the valve.
The above are some possible reasons that may cause the valve to be too tight. The specific situation needs to be comprehensively judged based on the actual usage environment, operation history and relevant inspection results of the valve. For different causes, corresponding solutions can be taken, such as repairing or replacing damaged parts, cleaning impurities inside the valve, adjusting the installation position, and strengthening maintenance and care, to ensure the normal operation of the valve.
