The Barton Model 199 Differential Pressure Unit (DPU) 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 contained in a process vessel. For process flow measurements, the DPU of the Barton model 199 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.
The Barton Model 199 DPU is a dual bellows assembly enclosed within 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 connected 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 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.