1. Leakage at the connection between the gate valve and the gate valve

Firstly, it is necessary to check whether the connecting bolts between the gate valve and the gate valve are tightened. If they are not tightened, the sealing gasket ring inside them may not fully integrate with the flange sealing groove surface, which can often lead to leakage. The bolts and nuts should be inspected in sequence, and all bolts should be tightened until the sealing gasket ring is pressed tightly. Secondly, the size and accuracy of the sealing gasket ring and flange sealing groove surface should be checked. If the sealing contact surface size is incorrect or too rough, the sealing gasket ring should be repaired or updated. Furthermore, check whether there are pitting, sand holes, sand holes, or impurities in the contact surface between the sealing gasket ring and the flange sealing groove. If there are such defects, they should be repaired, repaired, or cleaned accordingly.

2. Valve cover leakage

The valve cover leaks, which is mainly manifested in the leakage of the packing seal. Firstly, check whether the sealing element is selected correctly and matches the sealing groove. If there are such problems, replace the sealing ring or repair the sealing groove. Secondly, check if there are any burrs, fractures, twisting or other phenomena on the sealing element, and in this case, replace the sealing element. Once again, check whether the sealing surfaces of each sealing groove are rough or have other defects. If there are defects, eliminate them or update the damaged parts.

There are packing materials in the valve cover or bracket that are sealed by compression. The installation of these packing materials should be checked. If the upper and lower packing materials are found to be installed upside down, they should be removed and reinstalled according to the correct method. Special attention should be paid to the fitting of the packing sealing surface. Furthermore, check whether the accuracy of each contact surface of the sealing element meets the specified requirements.

3. Valve body cavity surface leakage

During the casting process of the valve body, sometimes casting defects such as sand holes and sand holes may appear, which are difficult to detect during machining. Once pressure is applied, hidden casting defects will be exposed. If this situation occurs, it needs to be repaired, repaired, or updated.

4. Leakage at the valve seat and plate

Leakage at the valve seat plate is the most common phenomenon during installation or maintenance of gate valves. Generally, it can be divided into two categories: one is leakage from the sealing surface, and the other is leakage from the root of the sealing ring.

Firstly, the accuracy of the contact sealing surface between the valve seat and the valve plate should be checked. This sealing surface should be ground at least. If the surface accuracy is found to be too rough, it should be removed and ground again. Secondly, check the sealing surface for defects such as pitting, indentation, sand holes, cracks, etc. If this occurs, replace the valve plate or valve seat. For valve seats with pressure springs, the elasticity of the pressure spring should be checked to ensure it meets the requirements. If the elasticity weakens, the pressure spring should be updated. Furthermore, check if the T-shaped connection between the valve plate and the valve stem is too loose, causing the valve plate to tilt during the compression process. In this case, the valve plate should be removed and adjusted to the optimal size.

At the opening of the valve body, it is easy for foreign objects such as welding, iron filings, and impurities to enter during the installation process. Such debris should be cleaned before installation. If the cleaning is forgotten or not thorough, it may cause the valve plate to not close to the expected depth and cause leakage. In this case, the valve body should be removed and cleaned again.

When installing the valve seat, special installation tools should be used and the valve seat should be checked for proper installation. If the thread cannot be tightened to the expected depth, leakage may occur at the valve seat. In this case, special tools should be used to reinstall the valve seat.

5. The handwheel rotation is not flexible

(1) Main reasons. ① The valve stem is bent or twisted. ② Insufficient surface accuracy. ③ Excessive operation may cause thread damage. ④ Lack of lubrication or lubricant failure. ⑤ The valve stem nut is tilted. ⑥ Inaccurate fit tolerance, biting too tightly. ⑦ The outdoor gate valve lacks protection, and the valve stem threads are covered with dust and sand, or corroded by rain, dew, frost, and snow. ⑧ The thread is corroded by the medium (referring to the gate valve with a non rising stem or valve stem nut at the bottom) Improper material selection, such as the valve stem and valve stem nut being of the same material, which can easily bite.

(2) Preventive measures and solutions. ① Strict control should be exercised over the timing of force and not forcefully twist (referring to gate valves that are directly connected to the handwheel and valve stem) Improve processing quality to meet standard requirements Carefully operate, do not use force when closing, and do not reach the top dead center when opening. After reaching the dead center, the handwheel should be turned back one or two turns to make the upper side of the thread close to prevent the medium from pushing the valve stem upwards. ④ Regularly check the lubrication condition and maintain normal lubrication status. ⑤ Align or correct the valve stem nut. ⑥ Correct or update the valve stem nut to meet the standard specifications. ⑦ Regularly clean the dust and sand on the valve stem nut to prevent rust and corrosion. ⑧ Outdoor gate valves should be equipped with valve stem protection sleeves It is better to use copper material for the valve stem nut, and do not use the same material as the valve stem.