WET
This is your run of the mill sprinkler system. It’s great for office buildings, churches, apartments, and ten thousand other applications.
NFPA 13 states that a wet pipe sprinkler system employs “automatic sprinklers attached to a piping system containing water and connected to a water supply so that water discharges immediately from sprinklers opened by heat from a fire.”
DRY
A dry pipe sprinkler system is…well…dry. There is no water in it, that is, at least until there is a fire. In the event of a fire, water is released by a valve to fight the fire. Dry systems are essential for areas exposed to freezing conditions, such as outdoor storage areas, canopies, parking garages and unconditioned attics.
NFPA 13 states that a dry pipe sprinkler system employs “automatic sprinklers that are attached to a piping system containing air or nitrogen under pressure, the release of which (as from the opening of a sprinkler) permits the water pressure to open a valve known as a dry pipe valve, and the water then flows into the piping system and out the opened sprinklers.”
PREACTION
A preaction system is like a dry system, in that there is no water in the pipes until a fire. However, in a preaction system there is added protection against an accidental system trip. Basically, preaction systems are great for museums, data centers or anywhere else where giving something an accidental shower could cost big bucks.
NFPA 13 states that a preaction sprinkler system employs “automatic sprinklers that are attached to a piping system that contains air that might or might not be under pressure, with a supplemental detection system installed in the same areas as the sprinklers.”
DELUGE
The purpose of a deluge system is simple: Get a lot of things wet—fast! On a deluge system all of the sprinkler heads are “open”, which means if the system trips every sprinkler head will be flowing water. This type of system has erroneously stared in more Hollywood movies than Tom Cruise.
NFPA 13 states that a deluge sprinkler system employs “open sprinklers that are attached to a piping system that is connected to a water supply through a valve that is opened by the operation of a detection system installed in the same areas as the sprinklers. When this valve opens, water flows into the piping system and discharges from all sprinklers attached thereto.”
SPECIAL HAZARDS
- Foam
- There are many different types of foam systems and many different types of foam. It all depends on what is being protected, how is it being stored, and how is the foam applied to the fire. Foam is able to smother a fire and/or separate flammable vapors from ignition sources.
- NFPA 11 defines foam as “stable aggregation of small bubbles of lower density than oil or water that exhibits a tenacity for covering horizontal surfaces.”
- Clean Agent
- Clean agent systems use no water. When people talk about a clean agent system they are usually referring to big tanks of gas that, upon a fire, expel large amounts of gas into a room. The deployed gas interrupts the combustion process through heat absorption and chemical interaction. These systems are becoming the norm for data centers or any area where damage from conventional protection (water) cannot be tolerated.
- NFPA 2001 defines clean agents as an “electrically nonconducting, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation.
- Antifreeze
- Antifreeze systems are not common. Their best application is in places where it is cold, like freezers. The advantage to antifreeze systems is that they are a wet pipe system (not dry), but on the down side, they require special design, equipment, and maintenance.
- NFPA 13 states that an antifreeze sprinkler system is a “wet pipe sprinkler system employing automatic sprinklers that are attached to a piping system that contains an antifreeze solution and that are connected to a water supply. The antifreeze solution is discharged, followed by water, immediately upon operation of sprinklers opened by heat from a fire.”
- Rack Storage
- A rack storage sprinkler system refers to sprinkler piping and sprinkler heads installed within storage racks. Not every warehouse storage scenario will require them. There are a lot of issues to consider, but when the potential for a nasty fire is high, a rack storage system could be a must.
- NFPA 13 defines a “rack” as “any combination of vertical, horizontal, and diagonal members that supports stored materials. Shelving in some rack structures use shelves that can be solid, slatted, or open. Racks can be fixed, portable, or movable. Loading can be either manual (using lift trucks, stacker cranes, or hand placement) or automatic (using machine-controlled storage and retrieval systems).”