Deluge And Preaction Fire Protection Systems

Deluge Fire Protection Systems

Deluge Systems are normally used in special hazard installations where water must be applied to an entire area for protection. The arrangement of deluge system piping is similar to a wet or dry pipe system with two major differences:

  1. Standard sprinkler heads are used, but they are all open. The activating elements have been removed so that when the control valve is opened water will flow from all of the sprinklers simultaneously and deluge the area with water.
  2. The deluge valve is normally closed. The valve is opened by the activation of a separate fire detection system.

Deluge systems are used where large quantities of water are needed quickly to control a fast-developing fire.  Deluge valves can be electrically, pneumatically or hydraulically operated, and often opened by a fire detection system installed in the same area.

Preaction Fire Protection Systems

Pre-action sprinkler systems are similar to a deluge sprinkler systems, except the sprinkler heads are closed. This type system is typically used in areas containing high value equipment or contents and spaces which are highly sensitive to the effects of accidental sprinkler water discharge.

The pre-action valve holds back water from entering the system until it is tripped by a separate electronic detection system. Activation of a heat or smoke detector in that separate system will open the pre-action valve, allowing water to enter the system piping. Because the sprinkler heads are closed, water will not flow from the sprinklers until heat activates the operating element in individual sprinkler heads.  Basically, the automatic opening of the pre-action valve effectively converts the system to a wet pipe sprinkler system.

In a pre-action system the piping is pressurized with air or nitrogen, monitoring of this air pressure provides a means of supervising the system piping. Loss of the supervisory air pressure in the system piping results in a trouble signal at the alarm panel. A prealarm of a possible fire allows time for alternate fire extinguishment prior to a sprinkler discharge. In the event the fire cannot otherwise be extinguished, the preaction sprinkler system will then perform as the primary fire protection system. They are designed for applications such as refrigerated areas that require maximum protection against inadvertent operation of the sprinkler system.

Applications include:

  • Flammable Liquid Handling
  • Storage Areas for Valuable Artifacts
  • Aircraft Hangars
  • High-Hazard Installations Using Water as Extinguishing Agent
  • Computer Rooms
  • Libraries
  • Archives
  • Refrigerated Spaces

Thorpe’s Fire Sprinkler System Services