A-7
Model 752 and 752A Differential Pressure Transmitters
Appendix A
Liquid Flow, DPU Below Run
The following steps are recommended for hot or gassy liquids. Periodic in-
spections of piping are recommended.
1. Close both shutoff valves and open both block valves.
2.
Open the bypass valve. Crack the vent valves or loosen the plugs from
the top ports of the DPU pressure housings.
3. Crack and close the shutoff valves alternately until the liquid is free of
bubbles and spills out of both upper DPU body ports.
4. Close the vent valves or tighten the plugs. Close the block valves and
open the shutoff valves.
5.
The pointer should rest at zero (or output will be 4 mA or 10 mA as ap
-
plicable). If it does not and no leaks are detected, the housing and/or pip-
ing are not completely filled with liquid. Repeat steps 1 through 4 until
the output is stable at the lowest value.
6. Slowly open both bl ock valves and close the bypass valve.
7.
For service with hot or gassy liquids, fill both sides of the manifold
through the fill tee, with the liquid to be measured cooled to +200°F
(+93.3°C) or less, and expel gas bubbles from DPU and piping.
8.
Open the vent valve and the bypass valve. Tighten the fill plug when
bubble-free liquid flows.
BLOCK
VALVES
PRIMARY
DEVICE
BYPASS
VALVE
FILL TEE AND
VENT VALVE
FOR HOT OR
GASSY LIQUIDS
SHUT-OFF
VALVES
DPU
Figure A.6—Liquid Flow, DPU Below Run
