CHECK VALVES - SWING, TILTING DISC & PISTON - API594/API6D/BS1868/B16.34
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
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• A valve is a pressurised device containing energised fluids and should be handled
with care.
• Valve surface temperature may be dangerously too hot or too cold for skin
contact.
• Upon disassembling, attention should be paid to the possibility of releasing
dangerous and or ignitable fluids.
• Adequate ventilation should be available for service.
4.1 REPAIR INSTRUCTIONS
Due to the relatively low replacement cost of small diameter standard carbon steel valves especially
under 100 NB (4”), it is usually less expensive to replace the complete valve than to have maintenance
personnel effect repairs. Generally, the only viable repairs are replacement of bonnet gasket. However,
see Section 4.2 and 4.3 below for further extraordinary repairs.
Always replace the bonnet gasket whenever a valve is disassembled. Gasket seating surfaces should be
scraped clean (avoid radial marks). Bonnet bolts should be tightened in a diagonal pattern at several
different increasing torque settings in accordance with the recommended torque value (see table
Appendix A, Tables A & B).
4.2 DISASSEMBLY & GASKET REPLACEMENT
Before disassembling:
1. Check that the line is in a complete shut down phase, then remove the valve from pipeline.
2. Pre-order all necessary spare parts and joining gaskets.
3. Put identification markings on valve body, disc and bonnet. This helps to avoid mismatching of parts at
the time of re-assembly.
4. If the bolts and nuts are too tight, apply deep penetrating oil and then unscrew.
Disassembly:
1. Disassemble all cover bolts and nuts.
2. For check valves, lifting lugs are generally provided. Lift up the cover utilising lifting lugs. For smaller
and lower class valves the bonnet should be easy to remove without the aid of a mechanical lifting
device. In both cases gently break the seal with a lever, gradually lifting the bonnet flange at intervals
360° around the bonnet.
3. Clean gasket surface areas, replace gasket and refit bonnet as detailed in 4.1 above.
4. ‘Pressure seal’ valves use a proprietary graphite gasket.
4.3 VALVE INTERNALS DISASSEMBLY INSPECTION AND REPAIR
1. Check that the (where applicable) hinge, nut and pin are in good condition and firmly connected.
Replace damaged parts as necessary.
2. For swing and tilt check valves, remove the pin then lift and remove the disc hinge assembly. If
