A-5
Model 224 Differential Pressure Unit Appendix A
For applications requiring special cleaning/precautions, a polyethylene bag
is used to protect the instrument from contamination. Remove this bag only
under conditions of extreme cleanliness.
Mounting
Mount the instrument to a solid support with four 5/16-inch (8 mm) grade
5 or better bolts, and apply 17 ft-lb of torque. To minimize relative motion
of the DPU connections, use a mounting structure that will also support the
interfacing process tubing.
Mounting structures shall be designed to avoid resonance and/or minimize
resulting amplifi cation below 33 Hz. Response spectra at the mounting
surface of the instrument shall not exceed those in the applicable nuclear
qualifi cation report.
Piping
WARNING: High pressure hazard. To prevent personal injury or damage
to equipment, direct all piping away from the operator while connecting
the DPU to system piping.
IMPORTANT: Do not share fi lling or vapor return lines with DPU piping lines.
Observe the following standard practices when installing piping:
• Shorten the distance between the primary measuring device and the DPU
as much as possible. Distances exceeding 100 ft are not recommended.
For distances up to 50 ft, use 1/4-in. pipe or tubing. For runs of 50 to
100 ft, use 1/2-in. pipe or tubing. The recommended limitation does not
apply if an air purge or blow-back system is used.
• Slope all piping at least 1 inch per linear foot to avoid liquid or gas
entrapment.
• If process media exceeding +200ºF (+93.3ºC) must be measured, install
2 ft of uninsulated piping between the DPU and the primary measuring
device for each 100ºF (37.8ºC) in excess of +180ºF (+82.2ºC).
• Assure that the temperature of the DPU never exceeds 180°F (+82.2°C).
When steam tracing is necessary, the steam pressure should not exceed
5 pounds per square inch and insulation should not be used. If pressure
must exceed 5 pounds per square inch, limit the length of tubing around
the DPU to two turns and do not insulate.
• When severe pulsation is present, install a suitable pulsation dampening
device upstream of the DPU.
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