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14
23. While the cell is heating up to the desired temperature, open the inlet ball
valve and apply the amount of pressure indicated in the “Recommended
Minimum Back Pressure” table.
Recommended Minimum Back Pressure
Test Temperature
Vapor Pressure
Minimum Back Pressure
°F
°C
PSI
kPa
PSI
kPa
212
100
14.7
101
100
690
250
121
30
207
100
690
300
149
67
462
100
690
350
177
135
932
160
1,104
400*
204
247
1,704
275
1,898
450*
232
422
2,912
450
3,105
500*
260
680
4,692
700
4,830
*For tests above 400°F, use Teflon o-rings.
While the cell is heating, the pressure inside will rise due to the thermal
expansion. Use the pump to release hydraulic oil and prevent over-
pressurization. Maintain the pressure on the fluid until the desired tem-
perature is stabilized, as indicated by the thermometer. Use the hydraulic
pump’s pressure release valve to regulate and maintain the pressure.
The heating time of the sample should
never exceed one hour.
When working with heated pressurized vessels, always wear protec
-
tive safety glasses.
Excessive pressure puts stress on four main areas of the cell:
1. End cap bending - may be observed either by eye or by measure-
ment
2. End cap compression - may be observed as deformed or bent
threads
3. Cylinder shear - elevated areas along the end of the cell bodies
4. Cylinder stress - stress cracking or severe pitting will appear on
the cell body
