NE Fire Sprinkler key terms

A heat-actuated device that discharges water over a designed area when its temperature-sensitive element operates, and that opens individually so only sprinklers near the fire flow water.

The minimum water flow rate, in gallons per minute per square foot, that must be delivered over the design area for the hazard classification being protected.

The assumed worst-case floor area, measured horizontally, over which sprinkler discharge is calculated; it is not the same as the total floor area of the building.

The hydraulically most demanding area of sprinkler operation, where pressure losses from friction and elevation are greatest relative to available supply.

A pressure-and-flow analysis proving the water supply can deliver the required density to the most demanding sprinklers while leaving adequate residual pressure at the base of the riser.

The extra pressure or flow reserved above the calculated system demand so that the supply still satisfies the design when pipes age, valves open, or conditions change.

A graph of available pressure versus flow at a point in the water system, derived from a flow test and used to judge whether the supply meets the sprinkler demand.

A field measurement of static and residual pressure at two known flow rates, used to construct the water supply curve for hydraulic design.

The pressure remaining at a gauge while water is flowing, as opposed to static pressure measured with no flow; it reflects friction losses in the supply main.

The pressure measured at a point when no water is moving, representing only elevation head and the pressure maintained in the supply main.

The categorization of occupancy contents and combustibility, such as light, ordinary, or extra hazard, that determines design density, spacing, and other sprinkler rules.

An occupancy where combustibility is low to moderate and stockpiles do not exceed about twelve feet in height, requiring moderate design densities and protection.

The nominal temperature at which a sprinkler's heat-responsive element is designed to operate, selected to be above expected ceiling temperatures but low enough for prompt action.

The fusible link, glass bulb, or solder component that fails at its rated temperature to release the sprinkler's cap and allow water to discharge.

A discharge coefficient relating sprinkler flow to pressure through the orifice, so that flow equals the K-factor times the square root of pressure.

The opening in a sprinkler through which water passes; its size, expressed through the K-factor, governs flow at a given pressure.

The maximum permitted distance between sprinklers on a branch line and between branch lines, set by hazard and ceiling construction to ensure overlapping coverage.

The floor area protected by one sprinkler, calculated from spacing dimensions and limited by the maximum area allowed for the hazard classification.

The smaller pipe that carries sprinklers along a run and feeds into a cross main; its size and the number of heads it serves affect hydraulic performance.

The larger pipe that supplies branch lines in a tree or gridded arrangement and connects back to the riser or feed main.

The vertical supply pipe that carries water from the source or main up to the sprinkler piping, usually fitted with a control valve, check valve, and alarm connections.

The complete vertical arrangement at the system supply point, including control valve, check valve, pressure gauge, drain, flow switch, and alarm test connections.

A valve that opens on water flow to the sprinklers and simultaneously transmits an alarm, often through a retard chamber or pressure switch.

A device that detects movement of water in the piping and sends an alarm or supervisory signal, commonly used on wet systems and dry pipe systems.

A sprinkler system with water under pressure in the piping at all times, so that a sprinkler operates immediately on fusion of its thermal element.

A system holding air or nitrogen under pressure in the piping, with water admitted only after a sprinkler opens and the resulting pressure drop trips the dry pipe valve.

A differential or latched valve that keeps water out of the dry piping until air pressure drops, then opens to admit water and trip the alarm.

A system where detection must operate before water fills the piping, providing an extra safeguard against accidental discharge in areas where water damage is costly.

A system with open sprinklers or nozzles and a deluge valve that opens on detection, discharging water from all heads at once over the protected area.

A valve held closed by pressure or a latch and released by the detection system, admitting water to open nozzles or sprinklers in a deluge or preaction arrangement.

A device that speeds the drop of air pressure in a dry system, shortening the time between sprinkler operation and water arrival at the fire.

The interval between a sprinkler opening in a dry system and water reaching that sprinkler, limited by code because fire growth continues during the delay.

An exterior pipe fitting where the fire department can pump water into the sprinkler or standpipe system to supplement the supply during a fire.

A one-way valve that permits flow in the intended direction only, preventing backflow and keeping water from draining out through the supply connection.

A valve and pipe connection at the low point of the system used to drain the piping and to conduct the main drain flow test that verifies supply adequacy.

A test connection at the end of the most remote branch line that simulates a single sprinkler opening to verify alarm and flow switch operation.

The decorative plate that covers the gap between a sprinkler and the ceiling or wall surface, which must not obstruct the spray pattern.

The metal plate or vane at the sprinkler outlet that shapes the water discharge into a designed spray pattern for the intended installation orientation.

A sprinkler designed to hang below the pipe with its deflector facing down, producing an umbrella-shaped spray for protection beneath a ceiling.

A sprinkler mounted above the pipe with its deflector facing up, used where the spray must be thrown upward or where piping is exposed.