Falling Pressures - Micromeritics 1305 Operator's Manual

Model 1305 Multivolume Pycnometer
Perform the checks and tests described in this section before seeking further assis-
tance. Contact your local service representative or the factory when unsuccessful
in resolving the difficulty.
Unstable Pressures

Falling Pressures

Falling temperatures or rising ambient pressure can cause the indicated pressure
to continue to fall beyond the expected transients following filling and expansion.
The effects are usually minor in a comfortable room and under normal ventilation
conditions due to the speed with which sample runs are accomplished.
The most serious cause of falling pressures is a leak. The first leak check should
be that of the sample cap O-ring and the sample chamber surface against which
it seals. Inspect the O-ring to determine whether it is damaged; replace it if neces-
sary. Clean the sealing surfaces and lightly grease the O-ring with vacuum grease.
To isolate system leaks:
1. Place the PREP/TEST valve in the PREP position, the >5/<5 valve in the <5
position, and the >35/<35 valve in the <35 position.
2. Close the VENT valve.
3. Open the FILL valve. Allow the pressure to increase to approximately
19.500 psig, then close the FILL valve.
If the pressure remains stable, no leak exists in the sample chamber and asso-
ciated tubing and components.
4. Place the PREP/TEST valve in the TEST position
If the pressure remains steady, no leaks exist in the V
ated positions.
5. Place the >5/<5 valve in the >5 position; observe the pressure stability.
If the pressure remains steady, no leaks exist in the volumes and tubing be-
tween the >5/<5 and the >35/<35 valves.
6. Place the >35/<35 valve in the >35 position.
If the pressure remains steady, no leak exists in the largest increment of ex-
pansion volume.
Jun 99
TROUBLESHOOTING
Unstable Pressures
volume or associ-
EXP5
4-1