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4-5. Range Change
Changing the range of the Model 199 DPU requires replacing the bellows unit
assembly with a unit of the desired range (see para. 4-7 Bellows Unit Assembly
(BUA) Replacement).
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.
NOTICE:
The calibration range of the DPU was carefully set at the factory. The
following procedure maintains the original factory bellows travel setting while
the range spring change is performed. This procedure must be strictly followed
while changing the range spring assembly or altering the adjustment.
To replace the range spring assembly with either a new assembly of the same
range or one with a different range value, proceed as follows (this procedure as-
sumes that the DPU is either connected to an indicating instrument or fitted with
a scale and pointer to measure torque tube shaft movement):
A. 2-1/8-inch Dia. Bellows
1. Remove the D PU from service.
2. Remove the pressure housing bolts and the low-pressure housing.
3. With the pointer at zero, remove the spring retainer screw, retainer
springs, and the range spring assembly.
NOTE: The pointer will shift from zero. This is a normal action and the
pointer should not be readjusted at this point.
4. Install the new range spring assembly onto the push rod, and replace
the spring retainer screw.
(Continued on next page)
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