Gate valve common failures and preventive measures

Gate valve common failures and preventive measures: 1. Leakage: Check the sealing surface regularly and replace the sealing gasket in time. 2. Blockage: Keep the valve clean and free of debris to prevent blockage. 3. Corrosion: Use corrosion-resistant materials and coatings to protect the valve from corrosion. 4. Wear: Regularly inspect the valve components for wear and replace them if necessary. 5. Improper operation: Train personnel on the correct operation of gate valves to prevent damage. 6. Overloading: Avoid exceeding the maximum pressure and temperature limits of the valve to prevent overloading.

Gate valve is the main component of the oil production (gas) wellhead device, several gate valve in the use of common failures are as follows.

Gate valve and gate valve joint leakage

First of all, we should check whether the gate valve and gate valve coupling bolts are tightened, such as not tightened, the sealing gasket ring and flange sealing groove surface is not sufficiently combined often lead to leakage. The bolts and nuts should be checked in order, and all the bolts should be tightened until the gasket ring is pressed. Secondly, the size and accuracy of the gasket ring and flange sealing groove surface should be checked. If the sealing contact surface size is not correct or too rough, the gasket ring should be repaired or renewed. Further check the gasket ring and flange sealing groove contact surface whether pitting, sand holes, sand holes or impurities, if there are such defects, it is necessary to carry out the corresponding patch welding, repair or cleanup.

Bonnet leakage

Bonnet leakage, this failure phenomenon is mainly manifested in the packing seal leakage. First of all, check whether the seal is selected correctly, whether with the sealing groove, if there is such a problem to replace the seal or repair the sealing groove. Secondly, check whether the seals have burrs, cracks, twisted and other phenomena, this situation is to replace the seals. Again, check whether the sealing surface of each sealing groove is rough or has other defects, if there are defects, then eliminate the defects or renew the damaged parts.

Check the installation of these fillers inside the packing after compression to seal. If the upper and lower filler installation is found to be reversed, it must be removed and re-installed correctly, paying special attention to the alignment of the filler seals with the sealing surface. Also, verify if the precision of each contact surface of the seal meets the specified requirements.

Valve body cavity decent leakage

Valve body in the casting process, sometimes there will be sand holes, sand holes and other casting defects in the machining process is difficult to be found, once the pressure is applied, the hidden casting defects will be exposed. In this case, it is necessary to patch welding, repair or update.

Valve seat valve plate leakage

Valve seat valve plate leakage, in the installation or repair of gate valve is the most common phenomenon. Generally can be divided into two categories: one is the sealing surface leakage, the other is the sealing ring root leakage.

First of all, you should check the valve seat and valve plate contact sealing surface accuracy, this sealing surface should be at least grinding, such as found that the surface accuracy is too rough, it should be removed to re-grind. Secondly, the sealing surface should be checked to see if there are defects such as pitting, indentation, sand eyes, cracks, etc. If this happens, the valve plate or seat should be replaced. For the valve seat with pressure spring, the elasticity of the pressure spring should be checked to meet the requirements, and if the elasticity is weakened, the pressure spring should be renewed. Furthermore, check whether the valve plate and valve stem T-shaped joint is too loose, resulting in the valve plate in the process of compression of the tilt of the situation, in this case, the valve plate should be removed and adjusted to the optimal size.

Valve body internal open file, in the installation process is easy to enter the welding, iron filings, impurities and other foreign objects, should be cleaned up before installation of such debris. If you forget to clean up or clean up is not complete, it will cause the valve plate to close the expected depth and produce leakage, in this case, the valve body should be removed to clean up.

The valve seat should be installed using a special installation tool, and it should be checked if the valve seat is properly installed. If the threads are screwed in less than the expected depth, there may be a leakage issue with the valve seat, in which case it should be re-installed using the special tool for the valve seat.

Handwheel rotation is not flexible

(1) The main reason. (1) Valve stem bending and twisting. ② surface precision is not enough. ③The operation is too violent to make the thread damage. Lack of lubrication or lubricant failure. ⑤ Stem nut tilt. ⑥ Matching tolerance is not allowed, bite too tight. (7) lack of protection of open-air gate valve, stem threads covered with dust and sand, or rusted by rain, frost and snow. (8) Thread corrosion by the medium (refers to the dark stem gate valve or stem nut in the lower part of the gate valve). ⑨ Improper selection of materials, such as valve stem and stem nut for the same material, easy to bite.

① Strictly control the force proportion, avoid hard twisting (refers to the handwheel and valve stem directly coupled gate valve). ② Enhance processing quality to meet specification requirements. ③ Operate carefully, avoid hard closing, do not open to the upper dead center, when reaching the stop point, invert the handwheel one or two turns to close the upper side of the threads to prevent the medium from impacting the valve stem upwards. ④ Regularly check the lubrication condition and maintain normal lubrication. ⑤ Square or correct the valve stem nut. ⑥ Correct or update the stem nut to meet standard specifications. ⑦ Frequently clean the stem nut from dust and sand to prevent corrosion. ⑧ Add a protective sleeve to the valve stem when opening the gate valve. It is better to use copper material for the valve stem nut, do not use the same material as the valve stem.