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9
Refurbishment
Refer to the health and safety (see section 2) before starting any refurbishment work.
Never remove or perform maintenance on a valve or flange joint unless the line has
been fully depressurised, drained and where necessary, purged of toxic, explosive,
or flammable media.
DN 15 to 50 control valves are fitted with a matched ball and stem to reduce
hysteresis. If either the ball or stem needs replacing, then both items must be
replaced with another matched pair.
V-flow characterised seats, i.e. 30°V, 60°V etc. must be correctly oriented for proper
function. A location pin on the body and a groove in the seat ensures proper
alignment. On sizes DN 80 and DN 100 post-1996, the seats have a male pip on the
outside diameter that locates in a groove on the body. Ensure that the replacement
seals are of the same design as the originals.
Only valve sizes up to and including DN 100 can be fitted with characterised metal
seats. Above this size, only round port metal seats are available.
All of the following rebuilding instructions refer to valves with metal seats fitted on
one end. If the valve is fitted with metal or Fluorofill seats in both ends, then the
procedure for pre-compression of seat seals is not required and should be ignored.
9.1
Disassembly
a) Remove the valve from the pipeline, ensuring that it is correctly supported.
b) Securely clamp the valve and place it in the open position.
c) Remove the insert using the appropriate four-pin drive adaptor. It may be
necessary to use a heavy mallet on the tommy bar of the insert tool to break
the metal-to-metal seal. For DN 80 valves and above, it is recommended to
use a suitable hydraulic torque drive.
d) Lift the insert squarely out of the body to prevent damage to the sealing face.
e) Remove and discard the first seat and body seal.
f) Close the valve and using a soft drift, tap out the ball.
g) Using a suitable hook, pull out the second seat being careful not to damage
the seat sealing face of the valve body.
h) To dismantle the stem assembly, remove:
Wrench assembly (if fitted)
•
•
Gland nut locking clip
•
Gland nut
•
Belleville washers
•
Gland
i)
Remove the stem through the body. For DN 15 valves, remove the gland
packing and align the stem wrench flats across the valves to facilitate stem
removal. The gland packing and thrust seal can now be removed, taking
care not to damage the sealing faces.
j)
All components not replaced by parts in the repair kit should be thoroughly
cleaned and stored in a clean, secure area.
Worcester V-Flow 51 / 52 Series User Instruction – WCENIM0026-01
Page 9 of 15
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