CHAPTER 8 FIRE PROTECTION SYSTEMS

This chapter describes the operation, testing, and maintenance of fire protection systems for buildings and other structures. Fire protection systems include automatic sprinkler systems, standpipe and hose systems, foam extinguishing systems, gaseous extinguishing systems, and chemical extinguishing systems. Fire alarm and detection equipment are discussed, showing the relationship between the mechanical and electrical components of these systems.

Because of the large number of manufacturers and models of fire protection systems, the Utilitiesman cannot be expected to acquire a detailed knowledge of all installation and maintenance considerations involved with this equipment. The principles presented in this chapter apply on a general basis for any given device or system you may encounter in the field. Refer to the manufacturer's manuals, job specifications, the National Fire Protection Association Codes, and local codes for in-depth information regarding specific types of equipment.

AUTOMATIC SPRINKLER SYSTEM CHARACTERISTICS

Automatic sprinkler systems automatically distribute water upon a fire in sufficient quantity to either extinguish the fire or prevent its spread. All sprinkler systems have three bassic components. They are (1) a water supply, (2) a piping network to carry the water, and (3) sprinklers that distribute the water. This section discusses the three major categories of sprinkler systems with their related controlling devices, fittings, and the sprinklers that may be chosen for installation into these systems.

TYPES OF SPRINKLER SYSTEMS

There are several types of sprinkler systems. The most common ones are the wet pipe, the dry pipe (that uses the differential dry pipe valve, the low-differential dry pipe valve, or the mechanical or latched-clapper dry pipe valve), the water deluge, the pre-action, and the combined systems.

Wet Pipe System

The wet pipe sprinkler system is the most common type. This system has automatic sprinklers attached to a piping network with piping under pressure at all times. The sprinklers are actuated by the heat of a fire. A wet pipe system is generally used when there is no danger of the water in the pipes freezing or when there are no special conditions that require a special purpose sprinkler system.

The wet pipe sprinkler system may have an alarm check valve (figs. 8-1 and 8-2). This device is used to maintain a constant pressure on the system piping network above the valve. When there is a fire, the flowing water causes the clapper assembly inside the alarm check valve to open. This permits a portion of the water to flow through a port in the valve that is connected to an alarm device. To prevent false alarms, you can place a retard chamber in the piping between the alarm check valve and the alarm device.

  Dry Pipe System heated enclosure because pressurized water is at the underside of the valve. A small amount of water, called priming water, is also inside the dry contain either air or nitrogen under pressure. Dry pipe valve itself to ensure a tight seal of the clapper and to keep the rubber gaskets pliable. The valve is usually made so that a moderate air pressure holds back a much greater water pressure. There are several types of dry pipe valves.

In a dry pipe system, the pipes normally pipe systems are used in areas where the water in the pipes is subject to freezing. A dry pipe valve acts as a control between the water supply and the air under pressure in the piping network. The dry pipe valve must be in a 

Figure 8-1.-Alarm check valve.

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