Latch assembly for slam-shut valves

Abstract

A slam-shut valve provides overpressure protection in a pipeline in the event of pressure regulator failure. The slam-shut valve is normally held in the open position by a latch assembly. Overpressure or failure of the regulator will automatically trigger operation of the slam-shut valve to close the same and prevent further passage of the gas through the pipeline. The reset assembly must be manually operated to re-engage the latch assembly so as to open the slam-shut valve once it has been triggered closed. The latch assembly coacts with a release assembly having a release shaft which detachably holds a spring latch affixed to a lever pivotally mounted upon the reset shaft of the reset assembly. Subsequent to its release, the spring latch will be re-engaged with the release shaft in order to reopen the slam-shut valve. Dependent upon the position of the release shaft, the spring latch may be required to deflect prior to relatching upon the release shaft. Otherwise, the lever of the reset assembly will reposition the release shaft in the raised position upon the spring latch being re-engaged therewith. In any event, the latch assembly provides for low-friction, binding-free release of the reset assembly promptly to close the slam-shut valve once an overpressure condition triggers operation thereof.