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Maintenance and Servicing
The piston/cylinder assembly is the most critical and sensitive part of the
deadweight tester. To maintain accuracy, the piston must always slide
freely in the cylinder, and the hydraulic fluid must remain clean.
The Figures on the following pages detail the components of each assembly, together
with the relevant part numbers. Where "Spec" appears as a part number, this indicates
that this particular component varies with the specification of the deadweight tester, and
is usually associated with other components in an assembly for replacement purposes.
PCU Assembly - 10 mm Nominal Diameter
Piston Disassembly
1. Hold the weight carrier (1), and lift the piston to its full extent. Tap the carrier
sharply down onto the cylinder (2) to release the tapered fit between the piston and
carrier. Remove the weight carrier.
2. Unscrew the PCU assembly from the instrument; use the dowel hole if the cylinder
is tight.
3. Carefully withdraw the piston from the cylinder.
4. If required, lift support ring (4) from around o-ring (3), the o-ring can now be
withdrawn from the piston.
Piston Cleaning
5. 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.
6. 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.
7. After removal from the solvent, using a NEW tissue, repeat the cleaning procedure in
step 5.
Maintenance and Servicing
Note
W Caution
Chapter 6
6-1
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