Have you ever seen the Arnold Schwarzenegger movie Kindergarten Cop? In a scene near the end of the movie, a school is being evacuated because of a fire. Although the fire is contained in a small area of the building, the sprinklers throughout the entire building are going off. As someone with quite a bit of sprinkler knowledge, I can tell you that scene is definitely fiction!
A common misconception about sprinklers is that water is discharged from every sprinkler head when the system is activated. However, if this were true, sprinkler systems would only add to the damage, not help prevent it. Each sprinkler head is tripped individually by a heat-sensitive device built into the head. There is a type of sprinkler system called a deluge system in which all sprinkler heads operate at once, but this type of system is quite rare. It is generally found in a building where there is a risk for rapid flame spread.
The sprinkler head is the central nervous system of a sprinkler system. Although there are many different types of sprinkler heads, they all have the following components:
- an outer shell that screws into the pipe called a frame
- a cap which plugs the water hole
- a heat-sensitive device which connects the cap to the deflector
- a deflector that deflects the water to make a cone-shaped spray
The heat-sensitive device is either a glass bulb or a two-part metal link which is fused together. Both types operate in the same way. The liquid in the glass bulb will boil at a given temperature. This causes the glass bulb to break which removes the cap of the sprinkler head, allowing water to flow from the sprinkler pipes to the deflector. The two-part metal link will melt at a given temperature causing the same outcome.
Deflectors can be upright or a pendent. Upright heads are located on the top of the sprinkler pipes and are designed to deflect the water from an upward position to a downward spray. The pendant sprinkler head is located at the bottom of the sprinkler pipe and is designed to deflect the water so it makes a cone-shaped spray to the area below.
The most important component of a sprinkler system is water, of course! Water is fed to the sprinkler system from a public water line or a private source of water. The size of the pipe from these sources varies depending on the amount of water needed for the system to operate. Water is sent into the sprinkler control valve which is the “brain” of the system. The system can be shut on and off from this valve which you’ll typically find in the building’s basement or utility room.
Although there are multiple types of sprinklers systems, they are all either wet or dry systems. With a wet pipe sprinkler system, the pipes are filled with water at all times. The pipes in a dry pipe sprinkler system are filled with compressed air, and the water is kept within the sprinkler control valve. The water is blocked by a clapper which is held down by the compressed air within the sprinkler lines. These systems are equipped with a jockey pump to keep the air at a higher PSI than the water level below to keep the system from tripping.
Although this was just a “sprinkling” of facts about sprinkler systems, I hope it gives you a better understanding of how they work. The more you know, the more effectively you can utilize them in your business. Contact your insurance company’s loss control representative for more information about sprinkler systems.