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SECTION 1 - INTRODUCTION
1-1. 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 flowing through a process system, or to the level of a liquid con
tained in a process vessel.
For process flow measurements, the DPU is connected across a primary device
(a venturi, an orifice plate or a flow 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.
1-2. Product Description
The Model 199 DPU is a dual
bellows assembly enclosed within
HP Housing
LP Housing
Connection
Pressure
pressure housings. The dual
bellows assembly consists of two
opposing internally connected liq-
Venting
uid-filled bellows, a center plate,
Connection
range springs, overrange valves,
Torque Tube
and a torque tube assembly.
Shaft
The pressure housings are con-
nected by Pipe or tubing to the
primary device located in the sys-
Mounting
tem piping. Variations in differen-
Bracket
tial 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 mo-
tion actuates the mechanism of the process monitoring instrument.
The process monitoring instrument that is connected to the torque tube as-
sembly may be an indicator, a switch, a transmitter, a recorder, or other process
control device.
1-3. Specifications
Torque Tube Rotation (full scale DP).............8° ±10%
Torque Tube Material..................................Beryllium Copper (BeCu)
Temperature Limits ....................................-40°F/°C to +180°F (+82°C)
Maximum Non-linearity:
0-10" w.c. to 0-400" w.c.
(0-25 mbar to 0-993 mbar) .........................±0.5% of full scale with
appropriate linkage
0-401" w.c. to 0-100 psi
(0-996 mbar to 0-6.9 bar) ...........................±0.75% of full scale with
appropriate linkage
Repeatability ..............................................0.20% of full scale DP
Housing Materials/Ranges ..........................Refer to Table 1-1
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