Fire Protection Products

Pre-Action fire sprinklers

Woodward & Co.

Pre-Action fire sprinklers

A ‘Pre-action’ system is a dry pipe system with a pre-action valve – an actuated valve that requires a trigger to operate it. The most common trigger is smoke detection, but there are other forms such as heat detecting cable, linear heat detectors and UV detectors.

They can be set up as single or double ‘knock’ systems. In a single knock system, operation is triggered when a smoke detector senses smoke. It will send a signal to the pre-action panel which releases the water through the valve and down-stream into the empty dry pipe work. As the sprinkler heads are sealed there will be no water discharged even though the pipe is now filled with water. This means that if the smoke detector is accidentally activated, no water is discharged. However, once the sprinkler head which has been affected by the heat activates, then the water is free to be released over the fire.

There are various set up types for pre-action systems and they are often used in sensitive areas where water is required for firefighting, but the risk of accidental discharge is a major consideration.

Typical uses for pre-action systems are libraries, museums, over certain types of machinery or electronic equipment rooms where gas suppression is not practical.