HI Fire Sprinkler key terms

The minimum water flow rate, in gallons per minute, that must be delivered over each square foot of floor area protected by sprinklers, chosen from the occupancy hazard table used for the design.

The hydraulically most demanding portion of the sprinkler system, where pipe friction losses are greatest relative to available pressure, and where flow is assumed concentrated for calculation purposes.

A step-by-step pressure and flow analysis through each pipe segment of the system, summing friction loss, elevation change, and fitting losses to confirm the supply can meet design demand.

An empirical equation relating friction loss in a pipe to flow rate, internal diameter, pipe length, and a roughness coefficient, widely used for fire sprinkler piping calculations.

The internal roughness coefficient used in the Hazen-Williams equation; lower values represent rougher pipe interiors and produce greater friction loss for the same flow.

The amount by which available water supply pressure exceeds calculated system demand at the design flow, ensuring the system still performs if the supply degrades or the calculation was slightly optimistic.

A field test using hydrant or test outlets and pressure gauges to measure static pressure, residual pressure, and flow rate at a site, producing the data used to plot the available water supply curve.

The pressure measured in a water supply system when no water is flowing, reflecting elevation head and any pressurization from pumps or municipal storage.

The pressure remaining in a water supply while a measured quantity of water is flowing from the system, used with flow data to establish the available supply curve.

A semi-logarithmic plot of available water supply, with flow on a logarithmic scale and pressure on a linear scale, drawn as a straight line from flow test results to extrapolate pressure at higher flows.

The categorization of an occupancy by its fuel load, combustibility, and expected heat release, which drives the required design density, sprinkler spacing, and water supply duration.

An occupancy with low fuel load and low combustibility, such as offices, churches, or schools, where relatively small design densities and larger sprinkler protection areas are permitted.

An occupancy with moderate fuel load and combustibility, such as mercantile, parking garages, or light manufacturing, requiring higher design densities than light hazard occupancies.

An occupancy with high fuel load or rapid heat release, such as flammable liquid handling or plastics processing, requiring the highest design densities and often special protection schemes.

A discharge coefficient that describes how much water a sprinkler discharges at a given pressure; higher K-factors deliver more flow and are used for high-challenge or high-ceiling applications.

The relationship Q equals K times the square root of pressure, used to compute flow from a single sprinkler given its K-factor and the pressure at the head.

The maximum permitted distance between adjacent sprinklers on branch lines and between branch lines, set by hazard classification and ceiling construction.

The floor area assigned to one sprinkler, calculated as the product of branch line spacing and sprinkler spacing, which must not exceed the maximum allowed for the hazard.

The required vertical clearance between the sprinkler deflector and the ceiling or roof above it, which allows the spray pattern to develop and hot gases to reach the heat-responsive element.

Any building element, such as a beam, duct, or light fixture, that can block sprinkler spray or delay heat travel to the sprinkler, requiring additional sprinklers or repositioning.

The smaller-diameter pipe on which sprinklers are mounted, typically running perpendicular to the cross main and feeding water to individual heads.

The larger feed pipe that supplies water to multiple branch lines, distributing flow from the riser or feed main across the protected area.

The vertical pipe that carries water from the supply main or fire department connection up through the building to feed the sprinkler system's cross mains.

A valve that allows water to flow in only one direction, preventing backflow from the sprinkler system into the public supply and holding pressure in the system.

A valve on the riser that both controls water flow and, when opened by a sprinkler discharge, activates the water motor gong or alarm device to signal system operation.

A device that detects water movement in the sprinkler piping and sends an alarm signal, often used as an alternative or supplement to a pressure-activated alarm valve.

The alarm signal transmitted to the fire alarm panel or monitoring company when a flow switch or alarm valve detects sustained water movement through the sprinkler system.

An exterior pipe connection with inlets that lets responding fire apparatus pump water into the sprinkler system to supplement the building's supply during a fire.

A device that stops water from reversing from the sprinkler system into the potable water supply, protecting the public supply from contamination while still permitting forward flow.

A scaled drawing showing the layout of sprinklers, piping, valves, and related equipment, submitted for approval before installation and used as the basis for construction.

The formal check of submitted drawings and calculations against code requirements and project specifications, performed before installation to catch errors and omissions.

A drawing updated after installation to show the actual installed configuration of the sprinkler system, including deviations from the approved working plans.

A pressure test in which the piping is filled with water and pressurized above the system's normal working pressure for a specified duration to detect leaks and weak joints.

Passing water through the piping at adequate velocity to remove debris, scale, and construction material before the system is placed in service, preventing blockage of sprinkler heads.

The final series of field tests and inspections, including hydrostatic and flow tests, that verify the completed sprinkler system meets design and code requirements before handover.

A condition in which a sprinkler system or part of it is out of service, whether planned or accidental, requiring notification, fire watch, and restoration procedures to manage risk.

A safety procedure that isolates energy sources and applies locks and tags to prevent accidental startup or release of stored energy during maintenance or repair work.

A space with limited entry and exit, not designed for continuous occupancy, that may contain hazardous atmosphere or engulfment hazards and requires special entry procedures.