The 106-EF-8837BX and 206-EF-8837BX excess flow valves are based on the 106-PT and 206-PT Double Chamber main valves. The valve is designed to shut-off tightly when flow exceeds a predetermined amount.
The 625-RPD pilot senses the pressure drop of the valve and closes the valve when the tripping flow is reached. Typical pressure drop at tripping is 5 psi / 0.35 bar.
Tripping flow is adjusted by limiting the valve opening with the X102 Stroke Limiter. 10 psi / 0.7 bar inlet pressure must be maintained at the valve inlet when the valve has tripped to prevent self re-setting. This valve closes fast and from a significant velocity. If the upstream pipe is longer than 2,000 ft /600 m, closing speed control should be included. When tripped (closed), this valve has a continuous exhaust of about 1 GPM / 0.063 L/sec to drain.
For more information on the 106 / 206-EF-8837BX: