Single-Interlocked Preaction Systems are commonly used where the sprinkler system piping and/or sprinkler may be subject to damage. The most common applications are in areas where it is important to control accidental water discharge due to a damaged sprinkler or damaged sprinkler piping. Viking’s supervised Single-Interlocked Preaction Systems use a Viking Deluge Valve and a pneumatically pressurized automatic sprinkler system.  The system piping is pneumatically pressurized for supervisory purposes only. This feature serves to prevent undetected leaks.  If the system piping or a sprinkler is damaged, supervisory pressure is reduced and a “low air” alarm is activated. Electrically controlled preaction systems require an electric solenoid valve controlled by an approved release control panel with compatible detection system.  In fire conditions, when the detection system operates, the system control panel energizes the solenoid valve open, causing the deluge valve to open.  The sprinkler system then fills with water.  If any sprinklers have opened, water will flow from the system.  If sprinklers have not opened, water will be in the sprinkler system piping when the sprinkler operates.  A sprinkler head must open before water flows from the system.