Overview Our BARTON 199 differential pressure units (DPUs) serve as actuating units for a wide variety of instruments. All models feature rupture-proof bellows.
Each DPU consists of a bellows unit assembly (BUA) and removable pressure housings. Within the BUA, flexible bellows are secured to a centerplate. In dual-bellows models, the movable bellows are rigidly connected by a dual valve stem that passes through the centerplate. Valve seats, in the centerplate passage, form a seal with the valves. Contacting the valve stem in the centerplate is a drive arm pivoted on the end of a sealed torque tube. The bellows is filled with a clean, noncorrosive, low-freezing point liquid. A range spring assembly provides tension against applied pressures.
In operation, pressure is applied to both sides of the bellows. Any difference in pressure causes the bellows to move until the spring effect (range springs) balances out the force. The linear motion of the bellows (proportional to the DP) is transmitted as a rotary motion through the torque tube. In dual-bellows units, if the bellows are subjected to a DP greater than the unit’s DP rating, a valve closes and traps the fill liquid in the bellows — fully supporting the bellows and preventing rupture. Since opposing valves are used, full protection is provided in either direction.
The BARTON 199N NACE DPU is a 199 DPU specifically designed to meet NACE requirements for HzS service. It can measure DP up to 2000 psi (138 bar) without damage to the unit due to overpressure. For DP up to 15 psi (1 bar), a 3-3/4" diameter bellows is used; above 15 psi (1 bar), a 2 1/8" diameter bellows is used. All other features and functions are the same as the standard M199 DPU.