A-14
Appendix A
Model 580A Differential Pressure Switch
Table A.2—Bolt Torque Ratings
HOUSING
BOLT
LUBE
(Note 1)
TORQUE
LB-FT
(Note 2)
ROTATION
(Degrees)
(Note 3)
SWP
MATL.
MATL.
SIZE
500
SST
SST
1/4-28 x 2.5
YES
12-14
180
500
CuNi
Monel
1/4-28 x 2.5
YES
9-11
180
1,000
Cu-Ni
Monel
1/4-28 x 2.5
YES
9-11
180
1,500
SST
SST
1/4-28 x 2.5
YES
12-14
180
3,000
SST
SST
3/8-24 x 2.5
YES
35
90
6,000
SST
SST
3/8-24 x 2.5
YES
40
135
Notes:
(1)
Lubricant: Molykote G paste, graphite-base grease, or similar lubricants. Lube first
thread only.
(2)
Torque on bolts is accomplished in 3 or 4 steps. Tighten uniformly.
(3)
Cameron
recommends using a torque wrench whenever installing housing bolts.
Rotation of bolt head is
measured after bolt is "snug" (approx. 1/16 turn past head contact) with approximately 2 ft-lb torque.
Do not exceed this rotation. To tighten bolts without torque wrench, use the following values: 1/4 turn
= 90
º
, 1/2 turn = 180
º
Changing the DPU Range
To change the range of the DPU, replace the BUA with a unit of the desired
range.
Replacing the Bellows Unit Assembly (BUA)
!
WARNING: Review the warnings under
DPU Cleaning and Inspection,
page A-13,
before performing this procedure.
IMPORTANT: Do not loosen the drive arm hole plug
located on the top of the BUA
center block when removing the mounting bracket. If the plug is loos-
ened, the fill fluid in the bellows will be lost and the unit will be inoper
-
able.
1. Disconnect the DPU piping, remove the process monitoring instrument
from service, and remove the mounting bracket from the DPU.
IMPORTANT: See the manual for the process monitoring instrument for particular
components that must be removed to gain access to the DPU mounting
fasteners.
2.
Loosen the drive arm from the process monitoring instrument and
separate it from the torque tube shaft. Do not disconnect the instrument
linkage.
3.
Perform a pressure check of the DPU 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.