Why is the valve stem inflexible?

There are a few potential causes of valve stem inflexibility, along with corresponding solutions:

Reason1: Corrosion: Over time, the valve stem may become corroded due to exposure to moisture, chemicals, or other corrosive substances. This can cause stiffness and inflexibility. 

Method: Solutions include regular maintenance, cleaning, and applying protective coatings to prevent corrosion. In extreme cases, the valve stem may need to be replaced.

Reason2: Lack of lubrication: Insufficient lubrication of the valve stem can lead to increased friction, resulting in inflexibility. 

Method: Applying a suitable lubricant can help reduce friction and improve the flexibility of the stem. Using lubricants compatible with the valve material and the fluid or gas being controlled is important.

Reason3: Debris or foreign objects: Accumulation of dirt, debris, or foreign objects in the valve stem can hinder its movement and cause inflexibility. 

Method: Regular cleaning and inspection of the valve can help prevent this issue. If debris is present, it should be removed carefully to avoid damaging the stem or other valve components.

Reason4: Mechanical damage: Physical damage to the valve stem, such as bending, dents, or warping, can result in inflexibility. 

Method: In such cases, the damaged stem should be replaced with a new one to restore proper functionality.

Reason5: Improper installation: Incorrect installation or assembly of the valve stem can cause misalignment or binding, leading to inflexibility. 

Method: Ensuring proper alignment and following the manufacturer's instructions during installation can help prevent this issue.

Reason6: Material fatigue: In some cases, prolonged use or high-stress conditions can lead to material fatigue, causing the valve stem to become inflexible. 

Method: Regular inspection and monitoring of valve components can help identify signs of material fatigue and prompt replacement before failure occurs.

Reason7: Low precision of valve stem and its matching parts, large surface roughness value, too small matching clearance.

Method: Improve the manufacturing and repair quality of the valve stem and its matching parts, and the surface roughness and matching clearance meet the technical requirements.

Reason8: The valve stem, valve stem nut, bracket, gland, packing and other parts are not assembled correctly and are not on the same axis.

Method: The valve stem and its matching parts should be assembled correctly, the gap should be consistent, keep concentric, rotate flexibly, and do not allow the bracket and gland to be skewed.

Reason9: The packing is too tight, locking the valve stem.

Method: The gland packing should be pressed moderately. After pressing the gland, the valve stem should be rotated to test the packing tightness.

Reason10: the valve stem is bent.

Method: Before assembling the valve stem, its quality should be checked, and if the valve stem is found to be bent, correct it in time.

Reason11: The trapezoidal thread on the stem and stem nut is poorly lubricated and full of dirt and dust.

Method: The trapezoidal thread should be cleaned frequently and lubricated. High temperature and dusty environments can be lubricated with a layer of graphite or molybdenum disulfide.

Reason12: valve stem nut loose, trapezoidal thread sliding wire.

Method: Check and repair regularly, lubricate regularly, find that the parts that fasten the valve stem nut such as set screws are loose, and tighten them in time. 

Reason13: The sliding parts of the valve stem nut and the bracket are poorly lubricated and mixed with abrasive particles, resulting in wear, seizure, and rust.

Method: Clean and lubricate regularly, keep the sliding surface clean, the oil path is smooth, and the lubrication is good. Prevent abrasive particles from mixing into the sliding surface to cause scratches and seizures.

Reason14: Poor operation and excessive force cause premature damage and deformation of the valve stem and its matching parts.

Method: Operate the valve correctly, the closing force is moderate, and it is forbidden to abuse the long lever wrench. After the valve is fully opened or fully opened, it should be reversed a little.

Reason15: The connection between the valve stem and the transmission device is loose or damaged.

Method: The connection between the valve stem and the transmission device such as the hand wheel is correct and firm, and the loose phenomenon is found and repaired in time.

Reason16: The valve stem is blocked or stuck by the closing piece.

Method: To operate the valve stem correctly, there should be measures to prevent the closing member from exceeding the top dead center and to prevent the closing member from being closed too tightly. The valve should be reversed a little after it is fully open or fully closed. Normally open or normally closed valve, at least once every half month to avoid rust.

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