AL Fire Sprinkler key terms

A heat-activated device that discharges water over a specific area when its thermal element operates, opening individually while the rest of the system stays closed and pressurized.

The heat-sensitive component of a sprinkler, such as a fusible solder link or a glass bulb, that ruptures at its rated temperature and releases the water seal.

The nominal activation temperature marked on a sprinkler's thermal element, chosen to exceed expected ambient heat while responding quickly to a developing fire.

A number expressing the discharge coefficient of a sprinkler or nozzle, relating flow in gallons per minute to the square root of supply pressure in psi.

The minimum water flow rate, in gallons per minute, that must be applied over each square foot of the design area for a given hazard classification.

The most hydraulically demanding remote group of sprinklers, measured in square feet, assumed to be flowing simultaneously when calculating system demand.

A pressure-and-flow analysis proving that the water supply can deliver the required density to the design area while meeting minimum residual pressure at the most remote sprinkler.

A category assigned to an occupancy based on the amount and combustibility of its contents and expected heat release, which sets density, spacing, and protection requirements.

A classification for occupancies where combustibility is low to moderate and fuel loads are moderate, such as offices, restaurants, and mercantile areas, requiring moderate design densities.

A classification for occupancies with low combustibility and small quantities of combustible contents, such as churches, schools, and hospitals, allowing the lowest design densities.

A classification for occupancies with high amounts of combustibles, flammable liquids, or dusts that produce rapid, intense fires, requiring the highest design densities and flows.

The maximum permitted distance between adjacent sprinklers and between sprinklers and walls, set by hazard classification and ceiling construction to ensure adequate coverage overlap.

The floor area assigned to a single sprinkler, calculated from the spacing between branch lines and between sprinklers on a line, and limited by hazard classification.

A sprinkler with a fast-acting thermal element and high response time index, designed to operate sooner in a fire and often permitting reduced design areas in wet systems.

A sprinkler system in which pipes are always filled with pressurized water, so a sprinkler opens and discharges immediately upon activation, with no delay for water travel.

A sprinkler system where pipes hold pressurized air or nitrogen and water is admitted only when a sprinkler opens and drops the pressure, tripping the dry pipe valve.

A latching valve that separates the air-filled sprinkler piping from the water supply and opens automatically when air pressure drops, allowing water to enter the system.

A system where piping is normally dry and water is admitted only after a fire detection signal, often with a second interlock, protecting areas where accidental discharge is costly.

A system with open sprinklers or nozzles where a single detection event opens a control valve and discharges water from every head simultaneously over the protected area.

A valve held closed by pressure or a mechanical latch that releases on a detection signal, admitting water to open nozzles in a deluge or preaction system.

The vertical section of pipe that connects the water supply main to the overhead sprinkler piping and typically carries the main control valve, check valve, and alarm devices.

A check valve on a wet system riser that opens to allow water flow but closes to hold pressure, and that routes water to a water motor gong or pressure switch when a sprinkler flows.

A mechanical alarm device driven by water flowing through the alarm line of a sprinkler system, producing a loud local sound when a sprinkler or valve operates.

An electrical device installed in sprinkler piping that detects water movement and sends an alarm signal to the fire alarm panel or monitoring service.

A valve at the end of the alarm test line that simulates a sprinkler flow, allowing the alarm devices and water flow to be tested without opening an actual sprinkler.

A valve and drain connection on the riser used to remove water from the system and to conduct a flow test that reveals the condition of the supply and the valve.

A pump, typically centrifugal, that boosts water pressure from a supply to meet sprinkler system demand when the available pressure is insufficient.

The flow, in gallons per minute, at which a fire pump is designed to operate and at which its rated pressure is stated, usually the pump's best efficiency point.

The condition of a fire pump operating at zero flow with its discharge closed, producing its maximum pressure and requiring a bypass or relief arrangement to prevent overheating.

The pressure actually added by a fire pump, equal to discharge pressure minus suction pressure, used when plotting the pump curve against system demand.

The pressure available at the pump inlet from the water supply, which affects the pump's net output and must be subtracted from discharge pressure to find net pump pressure.

The pressure measured in a water supply when no water is flowing, reflecting elevation and the pressure in the source main or tank.

The pressure remaining in a water supply while water is flowing at a measured rate, used with static pressure and flow to estimate the supply's available capacity.

A field test that measures static pressure, residual pressure, and flow rate at hydrants to determine the actual water supply available for sprinkler system design.

The electrical panel that starts and stops a fire pump automatically or manually, monitors power, and provides alarms and transfer between normal and emergency power.

A small jockey pump that keeps sprinkler system pressure above the fire pump start point to prevent the main fire pump from cycling during minor leaks.

The source of water for a sprinkler system, such as a public main, private main, tank, or reservoir, evaluated for its available flow, pressure, and reliability.

An alarm signal indicating an abnormal condition in a system, such as a closed control valve, low air pressure, or low water level, that could impair fire protection.