A-10
Section 3
Model 199 Differential Pressure Unit (DPU)
5. Install a suitable pulsation dampening device upstream of the DPU.
Where severe pulsation is present, the accuracy of the flow measurement
will be affected.
6. Mount the DPU on a solid support to minimize vibration. Tighten all
points, using a suitable compound; leaks in piping can cause measure-
ment errors.
7. Install a valve manifold connecting the DPU and the source of differen-
tial pressure to facilitate operation and checking of the DPU.
8. Locate all shutoff valves and bypass valves to be readily accessible from
the front of the instrument. Locate block valves at the source of differen-
tial pressure.
Flow Applications
Assure that the DPU high-pressure housing is connected to the upstream tap
of the primary device.
IMPORTANT: To prevent overheating the DPU during blowdown, monitor the tempera-
ture by placing hands on the pipe between the DPU and the manifold
pipe containing the vent valves.
Liquid Level Applications
The process media may be used as a reference leg seal fluid if it will condense
in the reference leg under all conditions.
If the process or process media characteristics are such that the above condi-
tions cannot be met, a special reference leg seal fluid is required. The special
seal fluid must not be volatile and must not be miscible with the process
media. Also, the difference in the densities of the special seal fluid and the
process media will require compensation in calculating the differential pres-
sure range of the DPU.
WARNING: Explosion Hazard—Organic compounds, oil, grease, dirt, or
scale of any kind cannot be tolerated in an oxygen installation.
