Cameron Barton 199 - Page 6

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The bellows and center plate are lled with ll liquid via the drive arm hole
plug. An opening through the center plate provides a passageway for the
transfer of ll liquid between the two bellows. This opening also allows the
bellows to be connected internally by a valve stem
.
C. Range Springs
The range of the dual-bellows type DPU is determined by the force required
to move the bellows through their normal range of travel.
The range springs, which are available in various ranges (refer to
Table 1-1), act with the bellows and torque tube to balance the differential
pressure applied to the unit. The number of springs used and their spring
rate depends on the individual differential pressure range requirement
.
Drive Arm
Hole Plug
(DO NOT LOOSEN)
Retainer
Screws
Torque Tube Gland Nut
(DO NOT LOOSEN)
Range
Spring
Assembly
Push
Rod
Torque
Tube
Lock
Shaft
Range
Nu
t
Springs
2-1/8" Bellows Unit Assembly (BUA)
Drive Arm
Hole Plug
Retainer Nut
End Cup
Push Rod
Nut
Range
Shaft
Spring Post
(DO NOT LOOSEN)
Range Spring
Assembly
Spring
Lock
Springs
Torque
Tube
Torque Tube Gland Nut
(DO NOT LOOSEN)
3-3/4" Bellows Unit Assembly (BUA)
Figure 2-2. Bellows Unit Assemblies (BUAs)
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