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Safety Pressure and Temperature Considerations
Do not use or recongure this equipment in a manner not specied in this manual.
Pressure
There are two reasons for operating at elevated pressures when performing a
ltration analysis:
1. To test uids at temperatures above the boiling point, the vessel must
be pressurized, which in turn elevates the vapor pressure (boiling point)
so that the uid remains liquid and does not turn to steam.
2. If testing for drilling applications, pressurization will more approximate
down-hole conditions, enabling the technician to match both bottom
hole temperatures and pressures.
For temperatures less than 200°F (93°C) a back pressure receiver is
not required as the ltrate will not reach the boiling point. However when
operating above the boiling point of water, a suitable back pressure
receiver is required, otherwise the test uid will turn to steam and the
test is invalidated. The standard receiver tube supplied with the 175 mL
HTHP Filter Press holds 15 mL of ltrate, so it is very important that the
receiver outlet ball valve is opened after approximately ten seconds of
ltrate collection, as a uid with poor ltration qualities can easily ll the
15 mL receiver tube almost instantaneously. If this happens the ltrate
hopefully will all be ejected from the safety bleeder valve, but if there is too
much uid volume, the liquid may end up inside the regulator rendering
it useless which will require servicing by a knowledgeable technician.
Nitrogen is commonly used as a pressure source. A small Nitrogen cylinder
(#170-37), size 21" × 7" (Optional) provides the pressure source. These
cylinders are shipped empty, but when lled they may be pressurized
to 2,216 psi / 153 Bar. They have a standard CGA-580, Compressed
Gas Association – left handed thread tting connection. CGA 590 right
handed thread ttings are available upon request. A dual Nitrogen
manifold assembly is used and pressurizes both the top and the bottom
or back pressure devices simultaneously or individually as needed.
Temperature
Normally when one experiences a loss of pressure it is not due to a failure
of the metal alloy in the cell, but rather is a failure of the o-ring or elastomer,
which provides the seal. These o-ring may deform or melt under elevated
temperatures usually over 400°F (204°C) causing a pressurization failure of
the cell, which is often sudden and catastrophic. For example, if the valve
stem o-ring suddenly fails, then steam at 400°F and under great pressure
may shoot outward horizontally in one or several directions. A safety
shield should always be used when operating any HTHP Filter Press and
especially when one is going to extreme temperatures and pressures. Above
350°F (176°C) all o-rings must be replaced after each and every test.
