A-6
Section 2
Model 199 Differential Pressure Unit (DPU)
The DPU has two bellows. One end of each bellows is sealed. The open end
of each bellows is attached and sealed to a side of the center plate (one bel-
lows on each side) as shown in Figure 2.2.
The bellows and center plate are filled with fill liquid via the drive arm hole
plug. An opening through the center plate provides a passageway for the
transfer of fill liquid between the two bellows. This opening also allows the
bellows to be connected internally by a valve stem.
Drive Arm
Hole Plug
(DO NOT LOOSEN)
Retainer
Screws
Range
Spring
Assembly
Push
Rod
Lock Nut
Range
Springs
Torque
Tube
Shaft
Torque Tube Gland Nut
(DO NOT LOOSEN)
2-1/8" Bellows Unit Assembly (BUA)
Spring Post
Drive Arm
Hole Plug
(DO NOT LOOSEN)
Range Spring
Assembly
Retainer Nut
Spring
End Cup
Push Rod
Lock Nut
Range
Springs
Torque
Tube
Shaft
Torque Tube Gland Nut
(DO NOT LOOSEN)
3-3/4" Bellows Unit Assembly (BUA)
Figure 2.2—Bellows unit assemblies (BUAs)