NICET WBSL Level III flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Design density

The minimum discharge in gpm per square foot applied over the hydraulically most remote area; it is selected from the occupancy hazard table and multiplied by the protected area to get the remote-area demand.

Remote area

The hydraulically most demanding area of sprinkler operation used to compute system demand; it may be reduced for quick-response sprinklers or increased for dry pipe, sloped ceilings, and high-temperature conditions.

Hazen-Williams formula

An empirical friction-loss equation using flow, pipe inside diameter, pipe length, and a roughness coefficient C; it is the standard method for computing friction loss in water-based system layout.

C-factor

The Hazen-Williams roughness coefficient; higher values mean smoother pipe and less friction, so a change in C changes the calculated demand without any change in pipe size.

Equivalent pipe length

The added length of straight pipe that produces the same friction loss as a fitting, valve, or device; it is added to actual pipe length before the friction calculation.

Most remote sprinkler

The sprinkler farthest hydraulically from the supply, not necessarily the farthest physically; it sets the starting pressure and flow for the branch-line calculation.

Minimum sprinkler pressure

The lowest operating pressure permitted at a sprinkler, typically 7 psi for standard spray devices; extended-coverage and special sprinklers require the higher minimum stated in their listing.

K-factor

A discharge coefficient relating flow to pressure by Q = K times the square root of P; it lets the layout convert a required pressure into a flow for each sprinkler.

Branch line balancing

Adjusting assumed flows so that branch lines meeting at a cross main produce equal pressures; for identical orifices, flow varies as the square root of pressure.

Hose allowance

Additional gpm added to the sprinkler demand at specified points to account for fire department hose streams; the amount depends on occupancy and system type.

Pump churn point

The point of zero flow on a fire pump curve, where shutoff head is highest; the curve is plotted from churn through rated flow to maximum flow.

Rated pump point

The flow and head the pump is listed to deliver; the system demand must fall below the pump curve with the required margin at this point and beyond.

Water supply curve

A plot of available pressure versus flow derived from static, residual, and test-flow readings; available pressure at the riser base is read from it at the demand flow.

Static pressure

The pressure reading with no water flowing during a flow test; it establishes the baseline for constructing the supply curve but does not by itself show capacity.

Residual pressure

The pressure remaining at the test hydrant while water flows; together with the flow and static readings it defines the supply curve used in the hydraulic calculation.

Pipe schedule method

A table-based sizing method allowed only for limited wet, light-hazard steel systems within stated size and height limits; outside those limits hydraulic calculation is required.

Occupancy classification

The hazard category assigned to the protected space based on contents and combustibility; it drives density, remote area, sprinkler spacing, and water supply requirements.

Sprinkler coverage area

The floor area protected by one sprinkler, found from spacing along the branch line and between branch lines; it is multiplied by density to get flow per sprinkler.

Maximum spacing

The largest permitted distance between sprinklers and between a sprinkler and a wall or obstruction; it varies with hazard and sprinkler type and must be checked separately from area limits.

Quick-response reduction

A permitted reduction of the remote area when listed quick-response sprinklers are used in qualifying occupancies with adequate ceiling height and no obstructed construction.

Dry pipe increase

An increase applied to the remote area for dry pipe and preaction systems because water delivery is delayed and more sprinklers are expected to operate before the water arrives.

Velocity limit

A practical cap, commonly 20 ft/s, on calculated water velocity in supply and cross-main piping to control friction loss and noise; exceedance triggers review of pipe sizes.

Alarm valve loss

The friction loss through a wet alarm check valve, dry valve, or preaction valve; it is included in the calculation as a pressure loss or equivalent length.

Test and drain

An assembly used to flow-test alarm and waterflow devices and to drain the system; its fittings and piping add friction loss that must be accounted for in the layout.

Hydraulic reference point

The node on the calculation plate from which the supply curve is applied, usually the riser base or the point of connection to the public main.

Safety margin

The required gap between available supply pressure and calculated demand pressure at the reference point, ensuring the system works as installed with some degradation.

Standpipe demand

The flow and residual pressure required at the most remote standpipe outlet for the system class; it is calculated separately and combined with sprinkler demand where both apply.

Seismic bracing spacing

The maximum interval between lateral and longitudinal braces and the clearance required at building separation joints; these layout decisions affect pipe routing before hydraulics are finalized.

Hanger spacing

The maximum support interval for pipe based on diameter and material; hangers and sway bracing must be located so pipe alignment and sprinkler positions remain within tolerance.

Design area shape

The remote area is laid out as a rectangle on the most demanding branch lines, with its long dimension parallel to the branch lines and its length at least 1.2 times the square root of the area.

Density-area curve

A curve allowing reduced density at larger remote areas, or higher density at smaller areas, for a given hazard; it is used when the design area differs from the reference point.

System demand point

The total flow and pressure required at the reference point, including sprinklers, hose allowance, and standpipe demand; it is plotted against the supply and pump curves.

Calculation plate

The summary document showing node flows, pipe sizes, lengths, elevations, and pressures; it must match the plans and identify the hydraulic reference point for review.