Water flow test

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A water flow test, also known as a hydrant flow test, [1] is a way to measure the water supply available at a building site, usually for the purposes of installing a water based fire protection system (fire sprinkler system).

Contents

The most common test involves measuring the flow of water flowing out of a municipal fire hydrant (measured in gallons per minute) while recording how much the water pressure has dropped (from no water flow to test flow). When the results are collected carefully, formulas can be applied to figure the varying pressure(s) that will be available when different amounts of water flow are used from the same source. A process to perform a water flow test is explained in the model fire codes as published by NFPA (National Fire Protection Association).

If a water supply source is considered weak compared to what is required by the sprinkler system design hydraulic calculation, the water pressure can be boosted by means of a fire pump.

General testing procedure

A set of three water pressure measurements are recorded from two hydrants. One hydrant is known as the residual hydrant or test hydrant and is located on or near the water main where a new water connection is desired. From this test hydrant, a static pressure and a residual pressure will be measured. The other hydrant, known as the flow hydrant, is usually the nearest hydrant away from the test hydrant. The flow hydrant is fitted with a diffuser device containing a pitot tube that measures stagnation pressure in the middle of the stream while the hydrant is flowing. First, a static pressure gauge is attached to the test hydrant and the static water pressure is measured at the test hydrant. Second, the flow hydrant opened to allow water to flow in a fully open condition. Simultaneously the pitot tube pressure is recorded from the flow hydrant while the residual pressure is measured from the test hydrant. These three pressures, the static pressure, the stagnation pressure, and the residual pressure, along with a specified design pressure of 20psi taken from the American Water Works Association (AWWA) or the NFPA are input into the Hazen-Williams formula to calculate the available flow for fire protection.

The residual flow formula

where: [2]

The Hazen-Williams formula for flow testing

where: [2]

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Fire hydrant Connection point by which firefighters can tap into a water supply

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Airspeed

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Blower door

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This is a glossary of firefighting equipment.

Pitot-static system

A pitot-static system is a system of pressure-sensitive instruments that is most often used in aviation to determine an aircraft's airspeed, Mach number, altitude, and altitude trend. A pitot-static system generally consists of a pitot tube, a static port, and the pitot-static instruments. Other instruments that might be connected are air data computers, flight data recorders, altitude encoders, cabin pressurization controllers, and various airspeed switches. Errors in pitot-static system readings can be extremely dangerous as the information obtained from the pitot static system, such as altitude, is potentially safety-critical. Several commercial airline disasters have been traced to a failure of the pitot-static system.

Garden hose

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In fluid dynamics, stagnation pressure is the static pressure at a stagnation point in a fluid flow. At a stagnation point the fluid velocity is zero. In an incompressible flow, stagnation pressure is equal to the sum of the free-stream static pressure and the free-stream dynamic pressure.

The Hazen–Williams equation is an empirical relationship which relates the flow of water in a pipe with the physical properties of the pipe and the pressure drop caused by friction. It is used in the design of water pipe systems such as fire sprinkler systems, water supply networks, and irrigation systems. It is named after Allen Hazen and Gardner Stewart Williams.

Fire pump

A fire pump is a part of a fire sprinkler system's water supply and powered by electric, diesel or steam. The pump intake is either connected to the public underground water supply piping, or a static water source. The pump provides water flow at a higher pressure to the sprinkler system risers and hose standpipes. A fire pump is tested and listed for its use specifically for fire service by a third-party testing and listing agency, such as UL or FM Global. The main code that governs fire pump installations in North America is the National Fire Protection Association's NFPA 20 Standard for the Installation of Stationary Fire Pumps for Fire Protection.

Air flow bench

An air flow bench is a device used for testing the internal aerodynamic qualities of an engine component and is related to the more familiar wind tunnel.

Wildland fire engine

A wildland fire engine is a fire engine specifically designed to assist in fighting wildfires by transporting firefighters to the scene and providing them with access to the fire, along with water or other equipment. Most commonly used by the United States Forest Service, there are multiple types of wildfire apparatus which are used in different scenarios. According to the National Fire Protection Association, if the apparatus will be used primarily for outdoor and wildland responses, then it is to be considered a wildland fire apparatus and must conform to NFPA 1906.

Hard suction hose

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Any design project for a water transport or distribution network requires hydraulic calculations to determination the need for hydraulic supply (Qh) at one or several consumption points and the water pressure needed to maintain the required flow.

San Francisco Fire Department Auxiliary Water Supply System

The Auxiliary Water Supply System is a high pressure water supply network built for the city of San Francisco in response to the failure of the existing emergency water system during the 1906 earthquake. It was originally proposed by San Francisco Fire Department chief engineer Dennis T. Sullivan in 1903, with construction beginning in 1909 and finishing in 1913. The system is made up of a collection of water reservoirs, pump stations, cisterns, suction connections and fireboats. While the system can use both fresh or salt water, it is preferential to not use salt water, as it commonly causes galvanic corrosion in fire equipment.

Liverpool Hydraulic Power Company

Liverpool's Hydraulic Power Company were the operators of a public hydraulic power network supplying energy across the city of Liverpool, England, via a system of high-pressure water pipes from two pumping stations. The system was the third public system to be built in England, opening in 1888. It expanded rapidly, but gradually declined as electric power become more readily available. The pumping station was converted to electric operation in 1960, but the system was turned off in 1971. One of the pump sets was salvaged and presented to the Liverpool Museum.

References

  1. Cooper, James; Parsons, Frank; Walski, Tom (April 6, 2016). "Webinar: Hydrant Flow Testing: Purpose, Process, and Experiences" (PDF). www.awwa.org. Retrieved October 12, 2019.
  2. 1 2 McCulloch, Paul (December 2011). "How to Conduct a Fire Hydrant Flow Test" (PDF). www.aspe.org. Retrieved October 12, 2019.