DH Instruments ADCS-601 - Disassembling the Module and Cleaning the Piston-Cylinder Assembly; Overview; Disassembling and Reassembling the Module

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ADCS-601™ OPERATION AND MAINTENANCE MANUAL

6.6.3 DISASSEMBLING THE MODULE AND CLEANING THE

PISTON-CYLINDER ASSEMBLY

6.6.3.1 OVERVIEW

The PG7601 piston-cylinder module is a high precision metrological assembly.

The annular gap between the piston and the cylinder is adjusted to be less than

1 micron. In normal operation, the test gas. If the space becomes contaminated,

usually due to foreign matter carried by the pressurized medium, PG7601

performance can be affected. Symptoms of contamination of the space (a dirty

piston-cylinder) include:

• Difficulty rotating piston: The motorized rotation system is unable to start

piston rotation.

• Decay in rotation rate is more rapid than normal: Piston rotation slows

down too quickly, especially at low mass loads.

• Poor sensitivity: Very small mass changes do not have the usual effect.

• Noisy pressure: The pressure defined when the piston is floating is not a

stable as it usually is.

If any of these symptoms are present, they may be caused by a dirty piston-

cylinder. The piston-cylinder module should be disassembled and the piston-

cylinder cleaned.

If symptoms of contamination develop rapidly with operation after cleaning

the piston-cylinder module, there is almost certainly a source of

contamination within the ADCS-601 system. This source must be identified

and eliminated to reduce piston-cylinder cleaning frequency. Very often, the

source of contamination is the test gas supply itself (which contains

humidity or lubricating oil) or it is the return from unclean gas operated

DUTs that are connected to the system.

6.6.3.2 DISASSEMBLING AND REASSEMBLING THE MODULE

The PG7601 piston-cylinder module design affords maximum protection to

the piston-cylinder element assuring that it is protected during routine

piston-cylinder handling. Cleaning the piston-cylinder requires disassembly

of the module and exposure of the piston-cylinder to possible damage.

These risks include damage to the critical working surfaces for all piston-

cylinder sizes and chipping or breaking. Only qualified personnel should

undertake piston-cylinder disassembly and reassembly and the instructions

and recommendations contained in this manual should be followed carefully

throughout the operation.

NEVER touch the lapped surfaces (polished appearance) of the piston or

cylinder with your bare hands. Body oils and acids can permanently etch the

surfaces.