Slam shut-off valve is installed immediately after the filter and prior to the Regulator. It normally remains open, in case the outlet pressure of the regulator exceeds the permissible limits, the slam shut-off valve senses it through the impulse line and immediately shut-off the flow to downstream. When the regulator is repaired the slam shut-off valve is to be opened manually by pilling the knob. Once the flow starts through the slam shut-off valve it remains open till the outlet pressure of the regulator is within limits.
