A-4
Appendix A
Model 752 and 752A Differential Pressure Transmitters
Gas Flow, Hydrates Present
The following steps are recommended for applications in which hydrates
or heavy solids are present, and piping and shutoff valves are not less than
1/2-inch in diameter. Bypass the manifold above to isolate the meter from
connecting piping. Drip pots prevent plugging.
1.
Open the bypass valve(s) and close the vent valve.
2.
Open both shutoff valves and one block valve to pressurize the DPU,
then close the block valve.
3. Close one bypass valve and check the system for leaks. If output travels
upscale, check for low-pressure piping leaks. If output travels down-
scale, check for high-pressure piping leaks.
4. Repair piping if necessary and repeat steps 1 through 3 until output
remains stable at zero.
5. Close the bypass valves. If two bypass valves are used, open the vent
valve.
6. Drain the drip pots of hydrates at regular intervals.
BLOCK
VALVES
PRIMARY DEVICE
DRIP POTS
STATIC PRESSURE
CONNECTION
(USE ONLY ONE)
BYPASS
VALVES
VENT
VALVE
SHUT-OFF
VALVES
DPU
Figure A.3—Gas Flow, Hydrates Present