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P3100 & P3200 Series
Users Manual
PCU Assembly - 5 mm
Plug the test station to prevent leakage, and open the reservoir valve. Remove the weight
carrier assembly (1 & 2). Hold the piston cap (4), and lift gently up and down, the piston
should slide freely within its cylinder. If any resistance greater than fluid drag or a
"gritty" sensation is detected, then the PCU must be removed and cleaned. (See
Chapter 6, PCU Assembly - 5 mm Nominal Diameter.)
Pressurize the system with 1 large weight so that the piston is rotating and floating
correctly. If the piston does not rotate freely, it must be removed and cleaned. (See
Chapter 6, PCU Assembly - 5 mm Nominal Diameter.)
High PCU Fall-Rate
The piston will always fall slowly due to a small leak between the piston and cylinder.
This fall rate will never be so fast that a stable reading cannot be made.
1. If the system has been pressurized quickly, then sufficient time must be allowed for
2. If PCU has just been re-fitted after cleaning:
1. Reservoir valve may be leaking. Observe fluid level, it will rise slowly if the valve is
2. Rambler seal may be leaking. Check lead screw in screw pump for "wetness" when
System Will Not Prime
1. Check reservoir valve is closed.
2. Check for sufficient fluid in reservoir.
3. Check for damaged/missing/dirty O-ring on test station.
4. Check that the face of the DUT is contacting the O-ring, and that the surface is not
7-2
the instrument to thermally stabilize. Continue re-floating the piston until the fall rate
stabilizes; this should take no longer than one minute.
Air pockets can be introduced when re-fitting a PCU. This will cause the piston to
fall faster while the air bleeds between the piston and cylinder.
Continue to re-float the piston until the fall rate slows down. If the piston continues
to fall quickly, then check for fluid leakage around the base of the PCU assembly.
Check for loose/damaged/dirty seal under the PCU, tighten, clean or replace as
necessary. (See Chapter 6, PCU Assembly - 10 mm Nominal Diameter, PCU
Assembly - 2 and 3 mm Nominal Diameter, and PCU Assembly - 5 mm Nominal
Diameter.)
leaking. This indicates that the valve seat may be damaged or dirty, or the o-ring
below the valve vent may be damaged. It should be disassembled, cleaned and
inspected, then retested or replaced as necessary. (See Chapter 6, Reservoir
Assembly.)
extended, the screw thread should be greased, not running with operating fluid. If
lead screw is "wet", then replace rambler seal and anti-extrusion ring. (See Chapter 6,
Screw Pump Assembly.)
scored or dented.
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