Principles for selecting pressure-reducing valves for industrial steam pipelines shared by Valve China Manufacturer.
Selection principle of pressure reducing valve for industrial steam pipeline:
1. First of all, according to the working process requirements, the selection of the right type of pressure reducing valve;
Small load and control pressure requirements are not high position can choose a simple structure of direct action pressure reducing valve, for all other situations, pilot pressure reducing valve is the choice, especially harsh working conditions, such as downstream pressure less than 1barg, must choose diaphragm pilot pressure reducing valve.
2. The selection must be based on actual working pressure (primary pressure and secondary pressure) and flow rate.
Any type of control valve can not be too large, pressure relief valve is the same, prefer to choose small can not choose large.
Because the disc is too close to the seat, wet steam flow through the erosion, wire phenomenon. In addition, because any small movement of the disc can lead to large fluctuations in the flow through the valve, it is difficult for the valve to accurately control the pressure, the more unstable the pressure, the more frequent the valve action, the more severe the valve wear, the shorter the life. So the valve selection is too large, not only cost increase, valve China life will be shortened, pressure is not so stable!
3. Diaphragm pilot pressure-reducing valve is recommended for working conditions with secondary pressure lower than 2barg; Diaphragm pilot type pressure reducing valve is recommended for dn15-50 caliber. For DN65 caliber and above, and the secondary pressure is greater than 2barg working conditions, it is recommended to use piston pilot type pressure reducing valve.
4. For the front does not install a soda separator, it is recommended to choose piston pressure reducing valve, because the piston structure is durable, strong water hammer resistance ability; The diaphragm relief valve may break the diaphragm each time it is turned on due to the impact of the huge water hammer.
However, no matter what kind of pressure relief valve is used, once water enters, the pressure relief valve will fail and cannot control the pressure, which must be manually reset and re-adjusted. Of course, if the internal parts are damaged, the parts or valves must be replaced.
5. For the working condition with large pressure difference, two pressure-reducing valves are selected in series to perform secondary pressure reduction. Typical working conditions are boiler thermal deaerator; If the flow rate is too large or the flow rate varies too much, choose two or more pressure-reducing valves in parallel, as described in section 6.5.