BS 1873 Standard specifies requirements for cast or forged carbon and alloy steel outside screw and yoke globe valve and globe stop valve and check valves, straight pattern, angle pattern and (oblique) Y pattern, with flanged or butt-welding ends in nominal sizes within the range of 15 mm to 400 mm (1/2 inch to 16 inch) and Classes 150 to 2500. BS 1873 standard can also be used as a general guide where valves of material composition outside the scope of section three of this standard are required as, for example, for use in highly corrosive services or environments or for low temperatures (see clause 37).
BS 1873 standard can be adapted to apply to valves with needle type seats in 15 mm (1/2 inch) an 20 mm (3/4 inch) nominal sizes which will meet all requirements of this standard, except that the valve seat bore is reduced and the needle point may be either integral with or loose on the stem.
4 Pressure classification
This standard applies to valves of the following pressure class designations:
Class 150, Class 300, Class 400, Class 600, Class 900, Class 1500 and Class 2500.
The numerals in these class designations represent the primary service pressure ratings of the valves in pounds-force per square inch.
5 Pressure/temperature ratings
The pressure/temperature ratings applicable to valves specified in this standard shall be in accordance with Tables PE-1 to PE-12 of Appendix A of BS 1560-2:1970 for the particular shell material specified. There is, however, a temperature restriction on soft seals and on certain trim materials (see 18.3 and 30.5).
Where valves in accordance with this standard are to be used at service temperatures below – 30 °C, reference should be made to BS 3351. Service temperature refers to the temperature of the fluid in the line at the valve.
6 Nominal sizes
This standard covers valves of the following nominal sizes:
For each valve class the applicable sizes are shown in Appendix A.
Note (a) These sizes have been retained only for the purpose of replacing existing valves. Their use for new construction in piping systems using BS 1560-2 end flanges should be avoided.