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PCU Assembly - 5 mm Nominal Diameter
Piston Disassembly
1. Lift off the weight carrier assembly (1 & 2), and unscrew the piston nut (5). Use the
dowel hole if the nut is tight. Remove the piston/cylinder assembly.
2. Loosen set screw (3) in piston cap (4), and gently pull the piston cap from the piston.
DO NOT PULL IN SUCH A WAY THAT THE PISTON CAN BEND. The
piston and cylinder assembly (6 & 7) can now be removed from the piston nut.
3. Gently withdraw the piston (6) from the cylinder (7).
Piston Cleaning
4. Use "non-fluffing", non-abrasive, lint-free tissue or absorbent cloth. Hold the piston
by the larger "head" end, and rub the tissue back and forth along its length.
5. To remove all traces of contamination (especially important with Water Operated
Testers), the piston can be cleaned in a suitable solvent.
O-ring seals (where fitted) are Nitrile rubber, and should not be
immersed in solvents, as they will become damaged. They
should be wiped carefully with a new tissue.
6. After removal from the solvent, using a NEW tissue, repeat the cleaning procedure in
step 5.
7. Place piston carefully on a NEW tissue where it will not be damaged while the
cylinder is cleaned.
Never touch the working surface of a clean piston with bare
fingers — the natural oil in your skin can cause the piston and
cylinder to stick.
8. Wipe excess fluid from the outside surfaces of the cylinder (6).
9. Roll a NEW tissue into a tapered rod of appropriate size. Force the tissue through the
cylinder bore whilst rotating. Ensure that the tissue is a tight fit inside the bore so that
dirt and contamination is removed.
10. Repeat step 9, using a NEW tissue, but from the opposite end of the cylinder.
11. Immerse the cylinder in a suitable, clean solvent, see note in step 5 above.
12. After removal from the solvent, using a NEW tissue, repeat the cleaning procedure in
steps 9 and 10.
Piston Re-Assembly
13. Holding the piston by the larger "head" end, dip the other end into a container of
clean operating fluid, and transfer to the bore in the underside of the cylinder. Allow
the fluid to run through the bore. Repeat this 2 or 3 times to ensure a good film of
clean operating fluid exists in the cylinder bore.
14. Carefully introduce the piston into the underside of the cylinder, and push gently
through.
15. NEVER FORCE THE PISTON INTO ITS CYLINDER OR DAMAGE WILL
RESULT. If resistance is felt, introduce more fluid. If resistance continues, re-clean
piston, cylinder or both. If, after repeated cleaning, the piston still will not slide freely
within the cylinder, then permanent damage may have occurred. In which case, the
parts should be returned to the factory for evaluation or replacement.
W Caution
W Caution
Maintenance and Servicing
Maintenance and Servicing
6
6-7
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