Maintenance and Replacement 20
Type T Hydraulic Deadweight Tester Operation Manual
CLEANING
Each M&G piston and cylinder assembly is tested within very close tolerances during manufacture for pressure retention (leak rate), for sensitivity, and for ac-
curacy of calibration. Each assembly is then cleaned, identied by a serial number and stored until shipped.
!
CAUTION: A piston and cylinder assembly is a very closely tted assembly. Clearances between the piston and cylinder are on the order of 5 to 20
millionths of an inch. Such clearances require utmost cleanliness for satisfactory operation.
X
To Clean the Piston and Cylinder Assembly
!
CAUTION: Extremely small particles can cause trouble in this closely tted assembly. Take extreme care to ensure cleanliness.
1
Carefully wipe o any visible dirt or for
eign matter from the protruding part of the piston and slowly withdraw the piston from the cylinder.
!
CAUTION: Do not use force, but be sure all dirt is removed so the piston will slip out easily.
2
The cylinder bore should be wiped with a small, soft
-handled wiper such as a cotton swab to remove all evidence of dirt.
3
Wipe the piston dry and clean with a lint free wiper
, such as a lint free cloth.
4
Rinse the piston and cylinder in a residual free solvent.
5 Wipe the cylinder bore and piston again to remove any dirt.
6 Pick up the piston by the piston cap.
7 Dip it in clean test uid.
8
Carefully insert the piston in the cylinder.
!
CAUTION: Repeat this cleaning procedure if you notice any roughness or grit in the annulus area while re-inserting the piston.
9
The deadweight column in which the piston is t
o be mounted should be drained and ushed with a solvent such as ethyl alcohol, then cleaned, dried, and
relled using clean test uid.
See To Install the Piston and Cylinder Assembly on page 16 to install the piston and cylinder assembly into a column.
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