OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: 832-320-7300 / Fax: 713-880-9886 / www.ofite.com
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The Permeability Plugging Tester (PPT) is a modification of the standard 500-
mL HTHP Filter press. It may be used in the field or in a laboratory environ-
ment. The instrument is useful for performing filtration tests on plugging ma-
terials without the interference of particles settling on the filter medium during
the heat up process. The PPT is very useful in predicting how a drilling fluid
can form a low permeable filter cake to seal off depleted, under pressured
intervals and help prevent differential sticking. Typical differential pressures
are much higher than those seen in standard HTHP testing
The pressure cell is similar to those seen in standard HTHP filtration testing,
but it is inverted with the filter medium and the back pressure receiver on top
of the assembly. The conventional cell may be operated to 2,000 PSI by us-
ing hardened steel set screws to secure the cell cap. For elevated pressure,
OFITE has designed a special cell with a working pressure of up to 4,000
PSI, pressurized with the conventional hydraulic pump. The cell is pressur-
ized with hydraulic oil and a floating piston separates the oil from the test fluid
within the cell.
The cell is furnished with a threaded cell inlet cap, a floating piston, and a
threaded scribed outlet cap for the ceramic filter disks. The outlet end of the
cell has a ¼" (6.35 mm) deeper recess than a standard cell to allow for the
ceramic disk as a filter medium. The end cap used with the ¼" (6.35 mm)
disk has a scribed concentric pattern rather than the conventional screen.
Filter paper or other thin filter medium may be used with this cap by using
the spacer ring (#170-72) to fill the extra ¼" (6.35 mm) space. Also, an extra
thick end cap with a standard screen backup is furnished to use with thin filter
media - paper or metal.
All of the end caps are designed to accept the standard valve stem. The
inlet, or bottom, valve stem is fitted with a quick-connect for the connection
to the hydraulic pressure manifold. The standard hydraulic pressure mani-
folds are equipped with a 4,000 PSI (27,600 kPa) relief valve. The outlet, or
upper, valve stem assembly consists of a dual valve stem with a ball valve in
the middle, which facilitates the opening and closing of the outlet flow. Power
consumption for the PPT heating jacket is 800 watts.
The 100-mL back pressure receiver is mounted on top of the heating jacket
and upside down, when compared to the normal HTHP filter press configura-
tion. It attaches to the cell outlet valve stem and is secured with the safety
pin (#171-23-1). The fittings on the receiver are reversed with the pressure
inlet on the small end (the upper end). A flare fitting may be provided if it is
desired to use the low-pressure side of a dual manifold on a nitrogen bottle
instead of the standard CO
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cartridges.
Intro
Description
