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238 ST 3000 Release 300 and SFC Model STS103 User’s Manual 6/08
B.1 Possible Solutions/Methods, Continued
Sealing liquid method,
continued
Zerex are solutions of ethylene-glycol with some rust inhibitors and
possibly leak sealants added; they may be used in place of pure ethylene-
glycol.
Another sealing liquid, used in many chemical plants, is dibutylphalate an
oily-type liquid with a specific gravity of 1.045 at 70°F (21°C). It has a
boiling point 645°F (340°C) and does not freeze so it can be used down to
about –20°F (–30°C).
Figures B-1 and B-2 show typical piping installations for this method. The
process fluid must be heated above its freezing point. This is frequently
done by lagging in (insulating) the connecting nipple, shut-off valve and
“T” connector with the process piping. Where the process piping itself
requires heating, a steam or electric trace is run around their components
with consideration given to the boiling point of the sealing liquid.
Figure B-1 Piping Installation for Sealing Liquid With Specific Gravity Heavier Than
Process Fluid.
1/2" seamless pipe nipple 6" long
1/2" shut-off valve (thru
port type desirable)
1/2" pipe cross
with 2 pipe plugs
1/2" seamless pipe
(slope at least 1"
per foot downward
1/2" 3-valve
manifold,
standard type
1/2" seamless pipe
(short as possible to
reduce head effect)
Differential
pressure
transmitter
Process pressure
transmitter
1/2" pipe union
or coupling
1/2" pipe cross
with 2 pipe plugs
1/2" shut-off valve (thru
port type desirable)
1/2" seamless pipe nipple 6" long
Continued on next page