Sprinkler systems are an important part of an end user’s overall fire protection program. Not only are these systems often required by the local authority having jurisdiction (AHJ), but when they are used, fire code and most AHJs require that they be connected to a building’s fire alarm system — when there’s one in place.
There are often questions on the part of fire alarm technicians concerning the effectiveness of sprinkler systems in contrast to automatic smoke detectors. From this perspective it’s understandable why fire technicians often become confused when sprinklers are required and automatic smoke detection is not.
This month, we’ll take a closer look at the various types of sprinkler systems on the market. We’ll also look at how they work and what fire alarm companies are required to do so they are code compliant. We’ll look at code references within NFPA 72, National Fire Alarm Code, 2007 Edition; and NFPA 13, Installation of Sprinkler Systems, 2007 Edition. Both code documents are developed and published by the National Fire Protection Association (NFPA). Sprinklers Vs. Smoke Detection
Automatic smoke detectors provide early warning of a fire in an early incipient stage. There is no denying that smoke detectors are critical to saving lives in certain situations. Sprinkler systems, on the other hand, have the task of putting out the fire. In fact, in some cases, a fast-acting sprinkler head may actually detect a fast, raging fire faster than its electronic counterparts.
This dualistic approach to fire protection is actually in the best interest of the client. In fact, when sprinkler and fire alarm companies partner, they actually can create new business for each other. Even when an official partnership is not in place, when both companies act as a team, they provide better protection for their mutual clients.
“The solution to the fire problem lies in the continuous application of three tried and true interventions in synergy. The interventions being education, early warning and early suppression,” says Jim Dalton, director of Public Fire Protection with the National Fire Sprinkler Association (NFSA) of Warrenton, Va. “Synergy means that the sum of the parts will be stronger and more effective then any one applied independently.”
Sprinkler System Basics
There are four basic types of sprinkler systems on the market today, in addition to a number of variations. The four basic systems include wet, dry, deluge and preaction. Understanding what each one does and how they do it is integral to the task of detection and notification. This is true whether we consider local evacuation or remote monitoring with the ultimate goal of fire department dispatch.
General definitions for all four and a few variations can be found in Chapter 3, Section 3.4, NFPA 13, 2007. Complete descriptions are also available in Chapter 7 of the same codebook.
Here is a brief description of each one:
1. A wet pipe system uses closed sprinkler heads with full water pressure applied throughout the sprinkler system. Activation is on a head-by-head basis, which means that water is released only when a sprinkler head(s) detects a high temperature. The intent of all sprinkler systems is to knock down the fire as quickly as possible.
2. In a dry-pipe sprinkler system, water is prevented from filling the pipes until a fire is detected by one or more sprinkler heads. This is accomplished by filling the pipes with air. To do this an air compressor is used along with a special clapper valve inside the main sprinkler riser. When one or more heads detect a temperature that exceeds their rating, the head will open up, thus releasing the air inside the piping. This allows the clapper valve inside the riser to open so water can flow into the pipes. Water is then released, but only by those sprinkler heads that have been activated.
3. In a deluge sprinkler system the sprinkler heads are open at all times in anticipation of a fire. Detection is accomplished using external automatic detectors, such as heat or smoke detectors. When a fire is detected, a deluge water valve is opened, allowing water to fill the pipes. In this case water is expelled by every sprinkler head in the system. This is because in a deluge system all the sprinkler heads are always in an open position.
4. A preaction sprinkler system is similar to a deluge system in that a deluge valve is used. Where they differ, however, is the sprinkler heads in a preaction system are closed in their natural state. A deluge valve holds the water back just like a deluge system, preventing the pipes from filling with water until detection occurs. When detection occurs, the deluge valve opens, thus allowing water to fill the pipes.
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