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Model 199 Differential Pressure Unit (DPU) Section 1
Section 1—Introduction
General
The Barton
®
Model 199 Differential Pressure Unit (DPU) (see Figure 1.1) is
a mechanical device which accurately measures differential pressure relative
to a gas or liquid owing through a process system, or to the level of a liquid
contained in a process vessel.
Figure 1.1—Model 199 DPU unit
For process ow measurements, the DPU is connected across a primary de-
vice (a venturi, an orice plate or a ow tube) located in the process system.
For liquid level measurements, the DPU may be connected in a variety of
ways to measure the difference in pressure caused by variations in the level of
the liquid in the process vessel.
Product Description
The Model 199 DPU is a dual bellows assembly enclosed within pressure
housings. The dual bellows assembly consists of two opposing internally con-
nected liquid-lled bellows, a center plate, range springs, overrange valves,
and a torque tube assembly.
The pressure housings are connected by pipe or tubing to the primary device
located in the system piping. Variations in differential pressure within the
pressure housings cause the bellows to expand or contract in a linear direction
towards the side having the lowest pressure.
The linear movement of the bellows is converted into angular rotation when
transmitted to the torque tube shaft by the drive arm and this mechanical
motion actuates the mechanism of the process monitoring instrument. The
process monitoring instrument that is connected to the torque tube assem-
bly may be an indicator, a switch, a transmitter, a recorder, or other process
control device.
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