Types of Sprinkler Systems

There are numerous types of sprinkler systems. They can be wet pipe, preaction, dry pipe, deluge or antifreeze. 

There are also areas such as flammable liquids storage areas where recent tests have shown even NFPA sprinkler requirements could be inadequate. This was very obvious when tests were made on flammable and combustible liquids in plastic containers. The best guidance for this type of room can be obtained through the IR information sheets or FM data sheets. 

There are service aisles/floors that are return air plenums. Here a more important decision needs to be made. Are the sprinklers to be located at what would normally be the room ceiling or are they located at the top of the plenum Sprinklering either might leave you with an under-designed 

---

There are four basic types of sprinkler systems wet pipes, dry pipes, pre-action, and deluge. These are described in the following sections. 

What type of sprinkler system does code permit ... 

Four types of sprinkler systems are available wet-pipe, dry-pipe, alternate and pre-action. A wet-pipe system can only be used in premises not subject to frost or ambient temperatures above 70 C. A dry-pipe system is only suitable in premises subject to continuous temperatures below 0 C or above 70 C. An alternate system which enables either wet or dry operation to be selected is suitable in premises subject to freezing during cold weather. Finally a pre-action system, which is a system with a separate heat or smoke detector that allows water into the sprinkler pipework before the first head operates, should only be used where none of the others is suitable. 

Analyze the fire loads and fire controls. Determine if com-partmentation is adequate. Analyze water supplies for adequacy at all locations where there is a need for extinguishing water or emergency showers. Consider the value of sprinkler systems and the type best suited to each location. 

A variety of valves are required on a sprinkler system. There must be a main stop valve which on a wet system must be locked open, conveniently placed and fitted with an approved sign. Downstream of this is an alarm valve which opens when a demand is put on the system and also provides a flow to actuate the alarm. Other valves include a drain valve which allows the system to be drained and tests to be carried out on the system and a test valve which simulates the operation of a sprinkler head and enables the operation of the alarm valve and the alarm to be tested. Dry systems and alternate wet/dry systems require further valves. The principal valves in the control units of various types of sprinkler installation are summarised in Table 25.8. 

There are several different types of foam systems which can either use a traditional sprinkler pipework system employing a proportional-tank mechanical foam insfallation, shown in Figure 4.2.12, in the supply line to... 

The location and spacing of sprinklers depends on the degree of hazard and type of construction. NFPA 13, Installation of Sprinkler Systems, provides detailed design and installation requirements. Table 4.58 provides a summary of spacing requirements for sprinkler installation. 

Regarding fires, water is the primary extinguishing agent, and it should be available in adequate supply and pressure at all of the locations in the plant. The layout for various types of installations and the appropriate recommendations are found in the standards of the National Fire Protection Association. Fire hydrants, hose lines, automatic sprinkler and water spray systems should all be a part of the permanent equipment facilities of the plant. 

If sprinklers are required, or if the sprinkler system is to be modified, such work should only be performed by a company certified to do it. Fire extinguishers are almost always required. The number of them, their placement, and the types needed are matters to be discussed with fiire officials. Extinguishers should be regularly serviced by qualified specialists. 

The fully developed fire is affected by (a) the size and shape of the enclosure, (b) the amount, distribution and type of fuel in the enclosure, (c) the amount, distribution and form of ventilation of the enclosure and (d) the form and type of construction materials comprising the roof (or ceiling), walls and floor of the enclosure. The significance of each phase of an enclosure fire depends on the fire safety system component under consideration. For components such as detectors or sprinklers, the fire development phase will have a great influence on the time at which they activate. The fully developed fire and its decay phase are significant for the integrity of the structural elements. 

Fire detectors—dry-pilot head and pneumatic rate-of-rise heat detectors are the most frequent devices used. A dry pilot head detection systems uses 165°F (74°C) V2-in sprinkler head with air pressure maintained in the piping. When the sprinkler opens the air is released resulting in the sprinkler valve opening. Other types of detectors include ultraviolet, infrared flame detectors, or thermostatic cable heat detection. 

In open process structures or grade level process areas, deluge or water spray nozzles should be of the open type to ensure rapid actuation and to combat the effects of wind. For enclosed structures, closed head sprinkler systems can be used. 

Preplans are similar to floor plans except they will often show features on the outside of the building in addition to the floor plan, although they may have somewhat less detail on the interior of the building. Preplans are frequently made for businesses, churches, and similar types of commercial buildings. These plans are often carried on the trucks for reference by the crews at an incident. A preplan may include information on access roads around the building, connections to sprinkler systems, location of gas or bulk material storage, locations of fire hydrants, information on alarm systems in the building, and other critical information for the crews. 

OS Y Valve A type of outside screw and yoke valve used on piping or in pits connected to sprinkler systems. The position of the stem shows the valve to be eidier open or closed. Osteroporosis a condition in which bones become very fragile. 

Pre-action System A type of automatic sprinkler system in which thennostatic devices are employed to charge the system with water before individual sprinkler heads are fused. 

A wide variety of sensing and initiating devices are available that can detect heat, smoke, radiant energy, and fire gas products. These devices should be selected based upon the type of fire anticipated. Additionally, sprinkler system water flow, activation of other extinguishing systems, and manual fire alarm pull stations can also be used to initiate an alarm signal. 

There are two different types of water sprinkler systems, wet-pipe and dry-pipe. The lines leading to the sprinkler heads are full of water in a wet-pipe system so that water will be discharged immediately from an open sprinkler head, while in a dry-pipe system, the lines are full of air under pressure instead of water. This latter type of unit should be used where the temperature is not maintained above freezing at aU times. Both types of systems include a main control valve which is designed not only to supply water to the sprinkler heads but also to provide a mechanism to cause an alarm to sound. The valves also usually provide a visual indication of whether they are open or closed. Except during maintenance, they should be in the open position. There are a number of design features for these valves which are beyond the scope of this document, except to note that some are intended to avoid false alarms due to surges or variations in the water supply pressure to the system. 

A variation of the dry-pipe system is the deluge system. The sprinkler heads are continuously open and water is prevented from entering the system by a deluge valve. When a fire is detected the valve to the water supply opens and water flows into the system and out of aU the sprinkler heads. This not only wets the immediate area of a small fire, but the entire area to which the fire may spread. This type of system is usually chosen when the contents of the space are unusually hazardous. A variation on this system is the pre-action system in which the sprinkler heads are not open, but when a fire is detected the deluge valve opens and water is supplied to the sprinkler heads. The water entering the system causes an alarm to be sounded. When the heat causes the sprinkler heads to fuse, or open, water is discharged onto the fire. 

---