CHECK VALVES - SWING, TILTING DISC & PISTON - API594/API6D/BS1868/B16.34
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
9
necessary, remove the spot weld on the disc nut, then remove the disc nut, pin, swing arm and disc in
sequence. Movement should be free and not hindered by any malfunction of the hinge pin. Where disc
travel is not sufficiently smooth, remove plugs or blind flanges and then remove hinge pin. Check
surface for seizure or scraping marks. If marks are deeper than 1.5mm (1/16”), re-machine hinge pin
and reassemble hinge pin and re-assemble. If defect depth is greater than 1.5mm (1/16”), a new hinge
pin is necessary. When reassembling hinge pin, it is recommended that the disc be removed by
loosening the nut. For piston/lift check valves, if there is a spring ensure it is functioning properly and
is sufficiently energised. The spring should hold the disc/ball tightly against the seat no matter what
position the valve is in.
3. When leakage is due to deterioration of seal surfaces caused by corrosion, erosion or foreign
substances, it must be determined whether the disc or seal seat are the cause. Where special soft seat
inserts are supplied, consult APV.
a) Deterioration of disc surfaces:
Swing check valves: - Disassemble disc by removing nut and washer. (Ball/Piston check valves have a
free floating disc). Repair surface by grinding and relapping using a fine grade abrasive paste.
b) Deterioration of seat seal surfaces:
When seal surfaces are damaged and defects are confined to a small area but are not deeper than
0.4mm the seal surface can be relapped. For smaller sizes the recommended method is to use a cast
iron strap with an outside diameter matching the valve’s raceway. If the seat surfaces cannot be
relapped an APV approved repairer will decide if the surface has to be reground/re-machined or
replaced. When defects are deeper than 0.4mm and found on the entire surface, re-metallising or a
new seat is required. For threaded-in seats it is recommended that an anti seizure compound be
used when installing the replacement seat to make threading it in the body easier.
Always be sure that the valve is de-pressurised and isolated prior to performing
any maintenance work. Remove any dangerous fluids from valve before commencing
maintenance.
4.4 BOLTED BONNET SWING/LIFT CHECK VALVE REASSEMBLY
a) Refer to Appendix A, Tables A & B for bolting torques.
b) To assure the valve is sealing properly, perform the required pressure testing per recognised and
applicable design standards.
4.4.1
When re-assembling the valve, inspect and ensure that all components are thoroughly clean before
installing into the valve body. All rust and dirt should be removed with a wire brush or emery cloth. Oil
solids and grease adhered to the valve internals should be removed with approved solvents.
