A-1
Model 224 Differential Pressure Unit
Appendix A
Appendix A—Model 224 DPU
DPU Description
The Barton Model 224 Diff erential Pressure Unit (DPU) is a mechanical
device that measures diff erential pressure relative to a gas or liquid fl owing
through a process system, or to the level of a liquid contained in a process
vessel.
For process fl ow measurements, the DPU is connected across a primary mea-
suring device (e.g., venturi, orifi ce plate, or fl ow tube) located in the process
system.
For liquid level measurements, the DPU may be connected in a variety of
ways.
The Model 224 DPU is a dual bellows assembly enclosed within pressure
housings. The dual bellows assembly consists of two opposing internally con-
nected liquid-fi lled bellows, a center block, range springs, overrange valves,
and a torque tube assembly.
The pressure housings are connected by pipe or tubing to the primary measur-
ing device located in the system piping. Variations in diff erential pressure
within the pressure housings cause the bellows to expand or contract laterally.
The linear movement of the bellows causes the torque tube to rotate, which
actuates the process monitoring instrument.
The process monitoring instrument may be an indicator, a switch, a transmit-
ter, a recorder, or other process control device.
Specifi cations
The Model 224 DPU is available in various pressure ratings to measure to
specifi c ranges between 0-30 inches of water column and 0-1000 psi, with
safe working pressure (SWP) ratings of 500, 1000, 1500, 3000 and 6,000 psi.
See Table A.1, page A-3.
The Model 224 Bellows Unit Assembly (BUA) is available in three bellows
diameters: 1 5/8 inch, 3/4 inch and 5/8 inch (shown in Figure A.1, page A-2).
The BUA with 1 5/8-inch bellows accommodates diff erential pressures to 60
psi. The range springs are contained within the bellows and do not come in
contact with the measured liquid.