3
C. 3-3/4-inch Dia. Bellows w/Kickoff* Spring (Cont.)
11. Apply 100 percent negative pressure to the high-pressure side of the DPU
and repeat the clearance check and adjustment of step 9
.
12. Apply 100 percent positive pressure to the high-pressure side of the DPU
and repeat the clearance check and adjustment of step 9
.
13. Release all pressure from the instrument and replace the low-pressure hous-
ing. Use new gaskets.
14. Replace the housing bolts. Use the torque values listed in Tables 4-2
through 4-4. Refer to Housing Bolt WARNING, para. 4-2, page 13
.
4-6. Setting Bellows Travel
The travel of the DPU bellows must be adjusted if one of the following occurs.
1. The range spring assembly is removed without following the procedure.
2. Broken range springs are replaced.
3. The indicator pointer has excessive overtravel.
4. The indicator pointer has excessive undertravel.
To set the bellows travel requires that the DPU be attached to the actuated
instrument and connected to a test pressure source. The procedure for this
adjustment is presented in the manual of the actuated instrument
.
4-7. Bellows Unit Assembly (BUA) Replacement (See Figure 2-1)
WARNING
(High-pressure Gas Installations
with pressures greater than 200 psig)
HIGH-PRESSURE GAS HAZARD ON DISASSEMBLY OF THE DPU.
TO PREVENT POSSIBLE SEVERE PERSONAL INJURY, DEATH,
OR SUBSTANTIAL PROPERTY DAMAGE DUE TO THE RELEASE
OF INTERNAL PRESSURE, PERFORM THE PRESSURE CHECK
PROCEDURE IN PARA. 4-2, Step A BEFORE REMOVING THE
DPU HOUSING BOLTS.
NOTICE
If accumulation of solids or semi-solids is extensive, remove the housings
carefully to prevent damaging the bellows.
WARNING
(Housing Bolts)
DO NOT REUSE HOUSING BOLTS. IF BOLTS ARE
DISTURBED, REPLACE WITH NEW BOLTS, PER TABLE 4-2
(STANDARD) or TABLES 4-3/4-4 (NACE).
REUSE OF HOUSING BOLTS, ESPECIALLY IN CRITICAL
APPLICATIONS LIKE HYDROGEN SULFIDE AND SALT WATER
EXPOSURES, CAN RESULT IN SEVERE INJURY, DEATH
OR SUBSTANTIAL PROPERTY DAMAGE DUE TO BOLT
FAILURE.
22
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