Gas valve selection criteria are as follows :

       1 , the spring pressure at a given level within the outlet pressure between the maximum and minimum values ??can be continuously adjusted , without jamming and abnormal vibration ;

2, for the soft seal valve , within a specified period of time may not have leakage ; For metal seal valve, its leakage should not exceed 0.5% of the maximum flow ;

3, the outlet flow rate change , the direct -acting outlet pressure deviation is not greater than 20% , not more than 10% of the pilot ;

4, the inlet pressure changes, the direct-acting outlet pressure deviation is less than 10% of the pilot less than 5% ;

5 , in general, the pressure reducing valve  before the pressure should be less than 0.5 times ;

6, the valve very wide range of applications , in the steam , compressed air, industrial gas , water, oil, and many other devices and the tube the liquid medium can be used on the road , the medium flows through the valve at the outlet amount of the general with a mass flow or volume flow representation ;

7 , bellows direct-acting pressure reducing valves for low , medium and small caliber steam medium ;

8 , the film direct-acting pressure reducing valves for low-voltage , medium -caliber air, water medium ;

9 , the pilot piston valve , suitable for all kinds of pressure , of various calibres , a variety of temperature steam , air and water medium ,

If using acid-resistant stainless steel, suitable for a variety of corrosive media ;

10 , the pilot valve bellows , suitable for low voltage , medium and small caliber steam, air and other media ;

11 , the pilot valve membrane is suitable for low, medium , small and medium -caliber steam or water and other media ;

12 , relief valve inlet pressure fluctuation should be controlled at a given inlet pressure value of 80% to 105% , if more than this range, decompression early performance suffers ;

13 , usually after the pressure reducing valve valve valve before the pressure should be less than 0.5 times ;

14 , valve springs only every file in a certain outlet pressure range applies beyond the scope should replace the spring ;

15 , in the medium temperature is relatively high occasions , generally used in pilot piston bellows valve or pilot valve ;

16 , the medium is air or water ( liquid ) of the occasion, the general should use direct acting diaphragm type pressure reducing valve or pilot film ;

17 , the medium is steam occasions , should use the pilot or pilot piston bellows valve ;

18 , in order to operate , easy adjustment and maintenance , valve is generally should be installed in horizontal pipelines .