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11
Safety
Pressure and Temperature Considerations
Do not use or reconfigure this equipment in a manner not specified in this
manual.
Pressure
There are two reasons for operating at elevated pressures when performing a
filtration analysis.
1. To test fluids at temperatures above the boiling point, the vessel must
be pressurized, which in turn elevates the vapor pressure (boiling
point) so that the fluid 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 filtrate will not reach the boiling point. However when operat
-
ing above the boiling point of water, a suitable Back Pressure Receiver is
required, otherwise the test fluid 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 filtrate, so it is very important that the receiver outlet ball valve is
opened after approximately ten seconds of filtrate collection, as a fluid with
poor filtration qualities can easily fill the 15 mL receiver tube almost instan
-
taneously. If this happens the filtrate hopefully will all be ejected from the
safety bleeder valve, but if there is too much fluid 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 cyl
-
inders are shipped empty, but when filled they may be pressurized to 2,216
psi / 153 Bar. They have a standard CGA-580, Compressed Gas Association
– left handed thread fitting connection. CGA 590 right handed thread fittings
are available upon request. A dual Nitrogen manifold assembly is used and
pressurizes both the top and the bottom or back pressure devices simultane
-
ously 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.
