A-13
Model 580A Differential Pressure Switch
Appendix A
!
WARNING: The unexpected release of internal pressure from a DPU can
result in severe personal injury, death or property damage. Before remov
-
ing DPU housing bolts, perform a pressure check. This is especially im
-
portant if the DPU is installed in a gas application with working pressures
exceeding 200 psig.
DPU Cleaning and Inspection
1. Remove the DPU from service.
2.
Check for internal DPU pressure as follows:
a. Back off all housing bolts 4 turns.
b.
Attempt to move the housing in and out along the bolts
If the housing moves freely, no pressure is present. Servicing or
repair may continue.
If the housing does not move freely, the bellows may be pressurized.
Immediately stop all disassembly, tighten the housing bolts, and
return the unit to the factory or authorized service center for repair.
Tag the unit and specify "Gas in the Bellows."
3.
Carefully remove the pressure housing bolts and pressure housings.
IMPORTANT: If a heavy buildup of solids or semi-solids has accumulated inside the
housing, rapid removal of the housing may damage the bellows convolu-
tions.
4.
Remove the accumulation from between the bellows convolutions and
from the inside of the housings. Use a solvent if possible. Do not use a
hard or sharp instrument to clean between convolutions.
5.
Check for broken range springs and replace as necessary.
6. Replace the housings and the O-rings.
IMPORTANT: It is recommended that new O-rings be used whenever pressure hous-
ings are replaced.
7. Reinstall housing bolts and apply torque as required. See Table A.2 for
appropriate torque values.
