CHECK VALVES - SWING, TILTING DISC & PISTON - API594/API6D/BS1868/B16.34
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
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1.4 POST-INSTALLATION PROCEDURES
After installation, the line should be cleaned by flushing to remove any foreign material. When caustics
are to be used to flush the line, additional flushing with clean water is required. The valve should be
opened and closed after installation to ensure proper operating function.
With the line pressurised, check the valve end connections, body to bonnet/cover joints and external
plugs for leaks.
2 . 0 O P E R A T I O N
Refer to Appendix A, Table C, D, E, F to ensure the Cv is as required and there is enough cracking pressure
to open to disc.
The check valve operation is automatic and requires no assistance. When the flow exerts sufficient
pressure against the disc to overcome the disc’s weight, the disc allows the flow to continue through the
piping system. As pressure decreases, the disc lowers until it’s own weight forces it to seat. This prevents
the possibility of a reversal in the flow. Piston and ball check valves should not be used in applications
where rusting or rust particles are present or anticipated. Swing check valves are more tolerant for
applications of this nature.
Metal seated check valves (piston, lift, tilt and swing) are not zero leak devices and will “seep” in service.
This type of valve should always be backed up with an isolation valve (either gate or ball valve). Check
valves are designed to prevent reverse flow. Leakage rates for check valves with metal-to-metal seats
are dependant on the amount of back pressure and the viscosity of the flowing medium. Soft seat check
valves can offer improved leak tightness provided there is sufficient back pressure. However, soft seat
check valves should not be used in gas or low back pressure liquid applications if zero leakage is desired.
3 . 0 M A I N T E N A N C E
No periodic maintenance is necessary unless special external accessories are fitted.
4 . 0 R E P A I R S
Proper safety equipment and apparel should be worn when preparing to service a valve. Observe the
following general warnings:
