Precautions to Take When Installing Safety Valve
1. Safety valves in the equipment or pipe should be installed upright. But for safety valves set up in liquid pipes, heat exchangers and containers, when the valve is closed, in occasions where the pressure may increase due to thermal expansion, they can be horizontally installed.
2. The safety valve should be installed as close as possible to the protected equipment or pipe. If the valve can’t be close to the layout, then it is required that the pressure drop of the pipe from the inlet of protected equipment to inlet of the safety valve does not exceed 3% of the constant pressure of the sanitary valve.
3. The safety valve should not be installed at the dead ends of horizontal pipes so that the accumulation of solid or liquid materials at the dead ends can be prevented, so as not to affect the normal operation of the safety valve.
4. The safety valve should be installed in places where it’s easy to maintain and regulate, and there should be enough work space around.
5. For safety valves of large diameter, we need to consider the possibility of lifting after disassembly. If necessary, lifting stem can be used.
6. The inlet pipe of the safety valve should use long radius elbow.
7. The design of the outlet pipe of the safety valve should take into consideration the fact that the back pressure doesn’t exceed certain value of the constant pressure of the valve. For instance, for ordinary spring safety valve, its back pressure does not exceed 10% of the constant pressure of the valve.
8. The outlet pipe of the safety valve that is buried into the closed system should follow the flow direction of the medium and be connected to the top of the pressure relief pipe at a 45-degree slant. This is to prevent the condensate in the general pipe from flowing back into the branch pipe. This can also reduce the back pressure of the safety valve.
9. There can’t be a “bag” at the outlet pipe of the safety valve. When the outlet pipe is long, a certain slope should be set up (except for dry gas system).
10. When the discharge pipe of the safety valve discharges to the atmosphere, its exit can’t be directed towards equipment, platforms, ladders, cables and so on.
11. There should be a “bag-shaped” liquid container inside the discharge pipe of the wet gas pressure relief system. The installation height of the safety valve should be higher than that of the pressure relief system. If the safety valve outlet is lower than the pressure relief general pipe or the discharge pipe needs to be lifted up to be connected to the general pipe, we should set dispensers at low and accessible point.
12. When there’s a shut-off valve on the outlet pipe of the safety valve, single gate plate gate valve should be used. The valve stem should be horizontally installed in order to prevent the valve plate from slipping down when the pin connecting the valve stem and valve plate is corroded or loose. When the safety valve is with a bypass valve, the valve should be sealed.