The Barton Model 224/224C Differential Pressure Unit (DPU) is a mechanical device that measures differential pressure relative to a gas or liquid flowing through a process system, or to the level of a liquid contained in a process vessel. For process flow measurements, the DPU is connected across a primary device (e.g., venturi, orifice plate, or 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.
The Barton Model 224/224C DPU is available in various pressure ratings to measure to specific ranges between 0-30 inches of water column and 0-1000 psi, with safe working pressure (SWP) ratings from 500 to 10,000 psi (224 Non-C limited to 500 to 3,000 psi SWP). See Table 1-1, page 4. The 224C Bellows Unit Assembly (BUA) is produced in three bellows sizes: 1- 5/8 inch, 5/8 inch, and 3/4 inch diameter. The 1-5/8 inch diameter BUA accommodates differential pressures to 55 psi. The range springs of this BUA are contained within the bellows and do not come in contact with the measured liquid. The 3/4 inch BUA accommodates differential pressures up to 400 psi and the 5/8 inch BUA up to 1,000 psi. The range springs of these BUAs are grouped around the outside of the bellows.
The Barton Model 224/224C DPU is a dual bellows assembly enclosed within pressure housings. The dual bellows assembly consists of two opposing internally connected liquid-filled 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 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 assembly may be an indicator, a switch, a transmitter, a recorder, or other process control device.