Valves are devices used in fluid systems to control the direction, pressure and flow of fluids. During the construction process, the quality of valve installation directly affects the normal operation in the future. Therefore, it is necessary for construction units and production units to attach great importance to this issue. 

Technical requirements for valve installation

1. Directionality. The valve body of most valves has a marking. The direction indicated by the arrow is the direction in which the gas flows forward. Special attention must be paid; the valve must not be installed in the reverse direction. Because there are various valves that require the gas to flow in a single direction, such as safety valves, pressure reducing valves, check valves, throttle valves, etc. For globe valves, in order to facilitate opening and maintenance, the gas is required to flow from bottom to top through the valve seat. However, for gate valves and ball valves, there is no restriction on the direction of flow. 

2. Installation location. Considering the long-term operation and maintenance of the valve, it is necessary to ensure that the location is as convenient as possible for operation and maintenance. At the same time, attention should also be paid to the aesthetics of the appearance during assembly. 

The direction of the valve handle can be vertically upward, or tilted to a certain angle or placed horizontally, but the handwheel must not be downward to avoid face-up operation; for floor-mounted valves, the handwheel is preferably at chest height for easy opening and closing; for slab gate valves, they cannot be used underground to prevent the valve stem from being corroded. 

Some valves have specific installation requirements. For instance, pressure reducing valves must be installed upright on a horizontal pipeline without any inclination. Lift check valves require the valve disc to be vertical; swing check valves need the pivot shaft to be horizontal. In summary, the installation position of the valve should be determined based on its principle; otherwise, the valve will not function effectively or may even fail to work at all. 

3. Installation of the stop valve. Check the specifications and model, verify for any damage, remove the caps at the threaded ends and the excessive grease and debris inside the threads, and test the sealing performance of the stop valve. When installing the gas stop valve, it is necessary to pay attention to using appropriate force. Select different-sized pipe wrenches or wrenches according to the size of the stop valve for installation. 

4. When installing the threaded valves, the valve manufacturer should ensure that the threads are intact and undamaged. If a wrench can be used, use the wrench; do not use a pipe wrench to avoid damaging the appearance of the valve body. 

5. For the installation of flanged valves, it is essential to ensure that the two flange surfaces are parallel to each other and on the same axis. When tightening the bolts, they should be done in a cross pattern to ensure uniform force distribution on the valve end face. 

6. Valves that are connected by flanges and threads should be installed in the closed position. When welding valves to the pipeline, the bottom of the weld seam should be welded using argon welding to ensure internal cleanliness. During welding, the valve should not be closed to prevent deformation due to heat. 

7. Generally, the valve is directly connected to the bellows expansion joint. Therefore, the pipes on both sides should be cut off according to the dimensions of the valve and the bellows expansion joint, as well as the flange and the gasket, to leave an installation space. 

8. During the hoisting of the valve, the rope must not be tied to the first wheel or the valve stem to prevent damage. It should be lifted and placed gently, and no collision should occur. When placed on the support piers, they should be leveled and stabilized at the required height. The valve must have a firm support pier or bracket to hold it, and it is not allowed for the valve to hang freely and generate stress.