1) material of valve body, valve cap, flange, should be selected according to conditions of use and manufacturing requirements, and shall comply with GB, 12229 GB, 12228 GB and 12230 GB 3077.
2) bolts, stud material available A5, 25, 35, 30 crmoa and 40 MNVB, etc., should be selected according to working pressure and temperature, and shall comply with the provisions of GB 700, GB and 699 GB 3077.
3) nut materials available A3, 20, 30, 35, 45, 3030 crmoa and 40 MNVB etc., should be selected according to working pressure and temperature, and shall comply with the provisions of GB 700, GB and 699 GB 3077.
4) shall not be used for precision casting nominal pressure valve of PN > 10.0 MPa.
5) the graphite material should be paid attention to the following situations might occur:
A. carbon steel is higher than 425 ℃;
B. carbon molybdenum steel is higher than 470 ℃;
C. chrome molybdenum steel (including chromium below 0.6%) is higher than 525 ℃.
6) of the following situations should be paid attention to the possibility of peroxide reaction (scale) :
A. higher than 565 ℃ or more Cr 1-0.5, 1.25 Cr - 0.5 Mo Mo steel steel, 2 Cr Mo - 1 and 3 Cr Mo steel - 1 steel;
B. about higher than 595 ℃ above 5 cr - 0.5 Mo steel.
