Precautions for Installation of Valves
Valve should not be installed under tension and at least one technically qualified person should be present while the installation is going on. E.g.: Total face to face length of the valve-200mm. Then distance between tow flanges should be 200mm+ 3mm X 2 Gasket+1mm clearance = 207mm max. There are chances of leakage if installed under tension.
If it is observed that the gap in the pipeline where the valve is to be fixed is more then required and the line is rigid, cannot be moved then use of spacer is absolutely necessary.
Valve body should be properly supported so that the torque generated while operating the valve will not damage the pipeline.
Uniform fitting of all flange bolts is essential to get long service form the valves.
Gasket used should be full and flat faced, preferable of rubber which is flexible Avoid use of rigid gasket like PTFE / PVC since they will not provide proper sealing in case of plastic valves, thus sometimes higher pressure may be applied for sealing which could result in the breakage of valve.
Companion flanges between which the valve is to be installed should be flat face only. If raised face flanges are provided, due to more gap between valve flange and companion flange, valve flange may buckle at the time of tightening, sometime end piece may also be pulled apart resulting into leakage of the valve (as shown In fig A-A)
When valve are installed in C.S or M.S. / R.L. piping, care should be taken that the pipeline should be in one axis. If there is any deflection. The whole tension will come on the valve, which may result in breakage / leakage. Secondly valve and pipe are to be fully supported; pipe load should not come on the valve.