Glossary of Hydraulics for Fire Protection

8/2/2019 Glossary of Hydraulics for Fire Protection

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Glossary of hydraulics for fire protection

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

B Barometer: An instrument used for the measurement of atmospheric pressure Bar: Is a unit of pressure 1 bar = 10000 pascal (Pa). The bar is used through Europe for

the measurement of pressure in fire sprinkler systems.

Bernoulli's equation: A mathematical expression of the principle of conservation of energy.

Booster pump: A fire pump used to boot the pressure of the existing water supply

Bourdon gauge: The most common device used to measure system pressures.

C Centrifugal pump: Modern industrial fire pumps are centrifugal pumps. Pressure is

added to the water by the centrifugal force created by a rotating wheel (impeller) or therotating vanes of a turbine.

Certified shop test valve: Before a pump is shipped by the manufacturer, it will betested in the shop. The results of this test will be plotted on graph paper.

Circulation relief valve: A small relief valve that opens up and provides enough waterflow into and out of the pump to prevent the pump from overheating when it is operatingat churn against a closed system.

Complex loop: A piping system that is sometimes called a "grid" and is characterised byone or more of the following: more than one inflow point, more than one outflow point,and/ or more than two paths between inflow and outflow points.

Controller: The electric control panel used to switch pump on and off and to control itsoperation.
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D Darcy -Weisbach: Technique used to establish the pressure lost to friction in a piping

system.

Differential manometer: A device whose primary application is to reflect thedifferences in pressures between two points in a system.

F Flow hydrant: The hydrant from which the water is discharged during a hydrant flow

test.

Flow test: Tests conducted to establish the capabilities of water supply systems andreferred to as flow tests because they involve flowing fire hydrants. The objective of aflow test is to establish quantity ( gallons per minute) and pressures available at a specificlocation on a particular water supply system.

Fluid: Any substance that can flow; a substance which has definite mass and volume atconstant temperature and pressure, but no definite shape; and with the inability to sustainshear stresses.

Fluid mechanics: In the general terms of physics, force is that which causes motion.

G Gridded piping system: See complex loop

H Hardy cross method: An interactive technique used for solving the complicated

problems involving gridded water supply systems.

Hazen-Williams formula: An empirical formula for calculating friction loss in watersystems that is the fire protection industry standard. To comply with the most nationally
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recognised standards, the Hazen-Williams formula must be used.

Head: Pressure expressed in units of feet of water.

Horizontal split -case pump: A centrifugal pump with the impeller shaft installed

horizontally and often referred to as a split-case pump. This is because the case in whichthe shaft and impeller rotates is split in the middle and can be separated exposing theshaft, bearings and impeller.

Hydraulics: The branch of fluid mechanics dealing with the mechanical properties of liquids (in the text water) and the application of these properties in engineering.

Hydrokinetics: A branch of hydraulics having to do with liquids (water) in motion,particularly in relation to forces created by or applied to the liquid in motion.

Hydrostatics: A branch of hydraulics dealing with the properties of liquids (water) at

rest, particularly in relation to pressures resulting from or applied to the static liquid.

J Jockey pump: A jockey pump is a small capacity, high pressure pump used to maintain

constant pressures on the fire protection system. A jockey pump is often used to preventthe main pump from starting unnecessarily.

K Kinematic viscosity: The kinematic viscosity of a fluid is the ration of its absolute

viscosity (lb sec/ft 2) to its mass density (lb sec 2 /ft 4).

Kinetic energy: The energy which a body possesses because of its motion.

L Laminar flow: A fluid is in the state of laminar flow if its Reynolds number is 2,100 or

less; laminar flow is related to very low liquid velocities.

Liquid: A fluid having a definite volume, unlike gases, which will expand to fill the


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vessel containing it.

M Moody diagram: A Diagram used with the Darcy-Weisbach friction loss computation

technique to relate the Reynolds number, pipe size, and roughness to a friction factor.

N Net pressure: The net pressure is the pressure added to the system by the pump.

O Orifice plate meter: An orifice plate meter is a device used for measuring water flow

and is similar in principle to a Venturi meter. The change of water velocity isaccomplished by using a plate with an orifice that is smaller than the diameter of the pipein which it is placed.

P Pascal's law: Principle 1, known as Pascal's law, points out that pressure acts in all

directions and not simply downward. Pascal : The SI unit for pressure is the pascal (Pa) which is equal to one Newton per

square meter (N/m 2). For fire protection this measurement of pressure is small so the unitBar or kPa is used in most part of the world.

Piezometer tube: This device uses the heights of liquid columns to illustrate thepressures existing in hydraulic systems.

Pitot tube: Common device used to measure velocity pressure and thus fluid velocity.The pitot tube consists of a small diameter tube, usually about one-sixteenth inch ininternal diameter which is connected to a pressure gauge.


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Potential energy: Stored energy which has the ability to perform work once released.

Pressure: is the force per unit area (symbol P).

Pressure head: Is a term used in fluid mechanics to represent the internal energy of a

fluid due to the pressure exerted on its container. It may also be called static pressurehead or simply static head.

PSI: In fire protection, pressure is most often dealt within units of pounds per square inch(psi).

R

Relief valve: The relief valve is provided to open up and discharge water to a drainshould the pressure become excessive. This valve is located between the pump and thedischarge check valve and is required with pumps driven by variable speed drivers.

Residual pressure: The pressure at the test hydrant while water is flowing. It representsthe pressure remaining in the system while the test water is flowing.

Reynolds number: is a dimensionless number that state if the flow is in a laminar orturbulent stat (Symbol Re) .

S Simple loop: A loop in which there is exactly one inflow point and one outflow point,

and exactly two paths between the inflow and outflow points.

Specific gravity: The specific gravity (S g) of a substance may be defined generally as theratio of the weight density of the substance to the weight density of another substance,usually water.

Static pressure: The normal pressure existing on a system before the flow hydrant isopened.

T


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Total energy: The total energy (TE) at any point in a system might be defined as thesum of the potential energy and kinetic energy at that point.

Turbulent state: Fluid flow is in the turbulent state higher velocities where there is nodefinite pattern to the direction of the water particles. Turbulent flow is reflected by a

calculated Reynolds number in excess of 2,100.

V Venturi meter: When coupled with a differential manometer, a venture meter may be

used to measure water velocity. The device consists essentially of a piece of pipe inwhich the cross-sectional area has been constricted.

W Water hammer: Stopping any flowing stream too rapidly can cause a phenomenon

called water hammer. Water hammer is a violent increase in pressure which can be largeenough to rupture the piping.

Velocity inpipe

Some fire sprinkler design authorities such as EN 12845 limit the velocity through pipes andvalves in fire sprinkler systems; this is the case with EN 12845 however NFPA and FM do nothave any restriction. The case for limiting velocity is that the Hazen-Williams formula is lessaccurate outside its normal range and equivalent pipe lengths for fittings, which are generallyused, start to lose their validity. Some authorities believe that velocity is self-limiting as pressure

losses increase exponentially as velocities increase, so pipe sizes must be increased to make useof available water supply pressure.

EN 12845 limits velocity to 6 m/s through valves and flow switches and 10 m/s at any otherpoint in the system.

Velocity in pipe can be calculated using the following formula:-
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When:

v = Velocity m/sQ = flow of water in L/mind = internal diameter of pipe in mm

The following table lists the maximum flows in litres per minute which can be obtained throughsteel pipework to EN 10255 specifications for both 6 m/s and 10 m/s.

Maximum flows through pipes for EN 12845 fire sprinkler systems

he Hazen Williams formula for use in fire sprinkler systems

The Hazen Williams formula is an empirical equation and has long been used for calculating thefriction loss in pipework for water based fire sprinkler protection systems. This equation usesthe coefficient C to specify the pipes roughness, which is not based on a function of the


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Reynolds number, as in other pressure loss equations. This however has the disadvantage thatthe equation can only be used when water is flowing within the turbulent' fl ow range. If thesystem is outside the normal pressure and flow range or the system is to use additives, or will besubject to unusual temperature conditions then the Darcy Weisbach equation may be moreappropriate.

The Hazen Williams formula has the advantage of been simple to calculate by using a scientificcalculator where as the Darcy Weisbach equation requires the use f' friction factor and this canonly be calculated by an number of iterations as f' is on both sides of the equation. You can usea Moody diagram to find the value of f' however this is both time consuming and almostcertainly and inaccurate method.

The Hazen William formula has now become adopted through the world as the pressure lossformula to use for the hydraulic design of fire sprinkler systems and in almost all cases the use of the hazen william formula will provide adequate answers. The Hazen William formula can alsobe used for the calculation of water mist systems where the system pressure does not exceed 12

bar (low pressure water mist systems) or the water velocity does not exceed 7.6 m/s and theminimum pipe size is 20mm in the case of intermediate and high pressure water mist systems.

when p = pressure loss in bar per meterQ = flow through the pipe in L/min

C = friction loss coefficientd = internal diameter of the pipe in mm

You can use Canute Hcalc software (hydraulic calculator) to visually explore the relationshipbetween the flow, pipe diameter and the pipe c-factor in the Hazen Williams formula which willgive you a good understanding of the formula. The Hcalc software is free to download and use.

Value of C for use in the Hazen-Williams formula

Listed in the table bellow are typical values for the coefficient C, which can be used in theHazen-Williams formula for different fire sprinkler design standards. The value of C representsthe pipes roughness with higher values of C giving lower friction losses. The values given in thedesign standards allow for degradation of the pipe, for instance new cast iron pipe has a C
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coefficient of 130 and EN 12845 gives the value of 100, this is equivalent to a pipe, which isabout 20 years old.

Bernoullis Theorem

Bernoulli's theorem is a method of expressing the law of conservation of energy to the flow of fluids.

Bernoulli's principle stats that, in the flow of fluid (a liquid or gas), an increase in velocity occurssimultaneously with decrease in pressure. That statement is a simplification of Bernoulli'sequation (below) which plots the situation at any point on a streamline of the fluid flow andapplies the law of conservation of energy to flow. Put another way, the total energy of the flowat any point along a horizontal pipe is equal to the sum of the pressure head, the velocity headand the elevation in the absence of friction. This is a principle of considerable importance to

those concerned with flow in sprinkler pipework.
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When

z = Potential head or elevationp = Pressurev = Velocityg = Acceleration of gravityd = Density of fluidh = Total head

If friction losses are ignored and no energy is added or removed from the pipe the total head h, inthe above equation will be constant for any point in the fluid. However in practice energy willincrease and decrease with the effect of pumps and friction loss and this must be included in the

Bernoulli's equation. All practical formulas for the flow of fluids are derived from theBernoulli's theorem with modifications to account for losses due to friction.

K-Factor formula

When we start any hydraulic calculation for a water based fire protection systems such as firesprinklers, water mist, hose reel and deluge systems the k-factor formula is one formula whichall fire protection engineers must know and understand. It allows us to calculate the dischargeflow from any type of nozzle (fire sprinkler, water mist or a deluge nozzle) for which we have ak-factor. We can also calculate the k-factor for any nozzle if we have not been given one,however you must check with the manufacture that this is acceptable.

The k-factor formula is the start of all hydraulic calculation for fire protection systems for bothmanual and computerized calculations and is also required for the checking of both types.

The discharge from a sprinkler head or nozzle can be calculated from the formula bellow:

q = kp 0.5

when q = flow in L/mink = nozzle discharge coefficient or k-factor for head in Lpm/bar 0.5

p = pressure in bar

This formula can be rewritten to give us:

k = q / p 0.5 and p = ( q / k ) 2

Our Hcalc Hydraulic Calculator will allow you to explore the K Factor formula in more detailand will allow you to calculate the flow, pressure or find the k factor for a nozzle or fire


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sprinkler. You can freely download and use our Hcalc software.

For standard type sprinkler heads the many design standards specify standard k-factors andminimum pressure, which can be used for different Hazard classifications and design densities.For all other types of sprinkler heads the manufactures data sheet should be referred to for the

k-factor and minimum head pressure.

We also use K-factors for many other applications in fire hydraulics such as flow from a firehydrant, wet riser outlet, hose reel or foam monitor. In fact the list is almost endless and this iswhy it is important to be familiar with the above formulas.

Often K-factors are given as an imperial value in gpm/psi this value cannot be entered intoFHC without first converting to its metric equivalent Lpm/bar . To convert gpm/psi to

Lpm/bar we need to multiply by 14.4 (Approximate)

Example: A sprinkler head has a discharge coefficient of 4.2 gpm/psi what is its metricequivalent valve. 4.2 x 14.4 = 60.48 Lpm/bar .

We only need to use K-factors to one decimal place so 60.48 becomes 60.5 Lpm/bar .Hcalc: Free hydraulic calculator for firesprinkler hydraulic calculations

Canute designed this simple hydraulic calculator for use with its FHC training course to teachsome of the fundamental principles of pressure loss calculations and the discard of waterthrough a sprinkler head and other type's nozzles. With this free hydraulic calculator you can

easily change any variable in the Hazen Williams pressure loss equation and see what change ithas made straight away. This is an invaluable free tool for teaching the basics of fire sprinklerhydraulics.
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Every fire protection design will find a use for the free hydraulic calculator, It can be used forteaching the principals of hydraulics in fire protection engineering, checking calculations or forsolving simple hydraulic calculations for fire sprinkler and other types of water based fireprotection systems.

Hazen Williams formula K-factor formula Reynolds Number Scientific calculator

With the free hydraulic calculator you can find the pressure loss in pipework using the HazenWilliams formula which is specified in the NFPA 13 and EN 12845 for fire sprinkler systems.You can very any of the 3 variables, flow, C-factor, pipes internal diameter and the pressureloss will be automatically updated. The free hydraulic calculator will also calculate theReynolds Number and Pipe Velocity .

The second part of the calculator is used to solve the K-factor formula given the flow, K-factoror pressure at a nozzle or fire sprinkler head given the other two factors. By using the slidercontrols to vary any of the variables (flow, K factor, pressure) you can see the effect they haveinstantly.

The third section is a scientific calculation which has a powerful calculation engine and willallow you to solve many complex calculations.

The free hydraulic calculator is free to download and use.
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FHC - Sprinkler Hydraulic Calculation Software for the fire sprinklerIndustry

FHC is a world leader in fire sprinkler hydraulic calculation software

and has hundreds of users in over 40 counties. The software has been successfully used for thedesign of fire sprinkler systems, water-mist, medium and high velocity water spray systems,hydrants and foam/water monitors.

FHC complies with over 12 international standards including LPC , NFPA , FM , BS 5306 part2 and EN 12845 .

With FHC you can build complex hydraulic models simply, with a set of easy to use designtools and you can see the pipe network instantly on the screen.

You can calculate any type of pipework network from simple tree systems to multiple loopedsystems or any other combination. As you create the hydraulic model and connect pipe nodestogether FHC will automatically find any tees and elbows you have create and will add thefitting to the pipe and lookup the equivalent length in its extensive pipe and fitting database.

With FHC's fast calculation algorithm will get your results in seconds allowing you toconcentrate on optimizing the systems for the most economically design.

Pipework pressure losses can be calculated using Hazen-Williams or Darcy-Weisbach equations, making FHC suitable for more demanding systems and high pressure water-mist

calculations.

Two design wizards QUICK-GRID TM and TREE PLANTER are included which will helpyou quickly create a grid system or a terminal end system with minimal information.

FHC will calculate the source pressure and flow requirements or you can balance the system toa fire pump curve, constant pressure pump or to a city water supply.
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Two Installations & one water supply

An example two-installation control valves supplied by one water supply. The first installationis a grid roof sprinkler system designed to give 12.5 mm/min over 260m2, and the secondedinstallation feeds the in-rack sprinkler system. The FHC program calculated this system inunder 1 second.

Within FHC we have specified the required density at roof level and the minimum operationpressure of 2.0 bar for the sprinkler heads within the racks. The FHC program willautomatically balance the water requirements for the two installations and will allow you tooptimised the pipe sizes by making global or selected changes to the pipe sizes. This can helpthe designer reduce pipe sizes and minimize the water flow requirements.Simple Tree Network

This example is of a simple tree pipe network. We used the FHC 'treeplanter' wizard to quickly build the tree network. Then we allowed FHC to automatically sizesthe pipes based on a maximum pipe velocity of 6m/sec which we specified.
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Glossary of Hydraulics for Fire Protection