The operation of single interlock systems are similar to dry systems except that these systems require a “preceding” fire detection event, typically the activation of a heat or smoke detector, takes place prior to the “action” of water introduction into the system’s piping by opening the pre-action valve, which is a mechanically latched valve (i.e., similar to a deluge valve) Key Points: Nominal Size : 50, 80, 100, 150 & 200 NB Maximum Working Pressure : 250 PSI Data Sheets: Single Interlock Preaction System