BS 1868 Standard specifies requirements for cast steel check valves or forged steel check valves with flanged or butt-welding ends of the following types:
a) swing, for vertical or horizontal flow (see Figure 1);
i) piston type, for angle or horizontal flow (see Figure 2);
ii) ball type, for angle or horizontal flow (see Figure 3);
iii) ball type, for vertical flow (see Figure 4);
iv) disk type, for vertical flow (see Figure 5).
The terms “vertical”, “horizontal” and “angle” relate to the axes of the body ends.
When swing check valves are used in vertical lines the flow must be in an upward direction. For the purposes of this standard any line with a slope (upward or downward) of 5° or less is deemed to be horizontal. In the case of angle pattern valves the inlet should be vertical.
4 Pressure classification
This standard applies to valves of the following class designations:
Classes 150, 300, 400, 600, 900, 1500 and 2500.
The numerals in these class designations represent the primary pressure ratings of the valves in pounds force per square inch.
5 Pressure/temperature ratings
The pressure/temperature ratings applicable to valves covered by this standard shall be in accordance with tables PE 1 to PE 12 as listed in BS 1560-2 for the particular shell material specified. There is, however, a temperature restriction on certain trim materials and soft seal ring (see clause 15 and 20.4).
If valves complying with the requirements of 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