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In buildings where it is impractical to keep temperatures above freezing, automatic sprinkler systems can be equipped with an FM Approved dry pipe valve. The sprinkler piping contains air under pressure, instead of water. When a sprinkler operates, air escapes, the dry pipe valve trips, and water is admitted automatically to the system Dry pipe systems should be installed in accordance with FM Global Loss Prevention Data Sheet 2-8N, Installation of Sprinkler Systems. Additionally, if their use is intended for refrigerated storage, FM Global Loss Prevention Data Sheet 8-29 should be referred to. System calculations regarding required system air capacity should be performed if only one air pressure maintenance device is contemplated for several sprinkler systems.

Dry pipe valves are designed so that a moderate amount of air pressure will hold back a much greater water pressure. In the differential type, the air pressure holds the water clapper closed either by means of a difference in areas on which the water and air pressures act, or by a combination of this principal with a lever action. In the mechanical type, a clapper on the water seat is held closed by a system of levers which are controlled by a relatively small air clapper.

A suitable alarm is connected to the dry pipe valve so that a warning is given when the valve operates. This may be a mechanical alarm that operates by a hydraulic motor, or a hydraulic pressure switch that closes an electric circuit to operate a bell, horn, or remote signaling system. Unless otherwise noted in the listing, these dry pipe valves have 175 psi (1205 kPa) rated working pressure.

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Before ordering a fire pump, consult FM Approvals regarding size, type of driver, suction supplies and location. Proposals for fire pump installations, including plans showing location and piping connections, should be sent to FM Global for review before the order is placed. Give the manufacturer complete data, including rated capacity, net head and suction head. Contracts for pump installations or changes should be let subsequent to acceptance of plans and subject to satisfactory field tests by FM Global.

The pump manufacturer or his authorized representative is responsible for furnishing a complete unit consisting of pump, driver and necessary accessories, all according to FM Global's standards.

Satisfactory performance in an operating test after installation should be guaranteed. A new fire pump installation is not acceptable until FM Global has witnessed a satisfactory field acceptance test. This will include a test of endurance of the pump and reliability of the power supply.

Exact horsepower requirements for each pump must be determined by a shop test on the specific pump. Approximate horsepower requirements at rated pump conditions are as follows:
Rated Capacity,
gal/min (dm3 /min) Rated Net Head,
psi (kPa) Approximate Power Required,
hp (kW)
(1895) 100
(690) 50-60
(2840) 100
(690) 60-75
(3785) 100
(690) 75-100
(5680) 100
(690) 100-125
(7570) 100
(690) 125-150
(9465) 100
(690) 150-200

In the listings on the following page, rated net head represents the amount of pressure boost obtainable from a pump of a given type and impeller size when operating at rated speed.

The rated net head range indicates that impellers of various diameters are obtainable for the given type of pump.

Although not recommended for installations where suction is normally taken under lift, FM Approved pumps have been tested for proper operation under negative suction conditions up to 15 ft (5 m) at 150% of rated capacity.