The 106-PR-48 and 206-PR-48 series pressure reducing valves with low flow by-pass are based on the 106-PG or 206-PG main valve. In addition, a direct acting pressure reducing valve is piped in parallel, using the main valve back port connections.
The pilot valve senses the downstream pressure through a connection at the main valve outlet. Under flowing conditions, the pilot reacts to small changes in pressure to control the main valve position by modulating the pressure above the diaphragm. The downstream pressure is maintained relatively steady at the pilot set-point.
The by-pass valve is set 5 psi / 0.35 bar higher than the main valve. Under low flow conditions, the main PR valve closes and the by-pass stays open, controlling the pressure at very low flows without seat chatter.
In typical pressure reducing applications, the reduced port Model 206-PR-48 is often the best selection.
For more information on the 106 / 206-PR-48 pressure reducing valve: