roughness coefficient & piping schedule no22.pptx

7/23/2019 Roughness Coefficient & Piping Schedule No22.pptx

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Roughness Coefficient , Equivalent Length &

Piping Schedule No.

Joon EeoSchool of Chemical Engineering

University of Ulsan

26- NOV -2015


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Commercial pipes comes in many different materials and many different sizes. The

internal roughness of a pipe is an important factor when considering the friction

losses of a fluid moving through the pipe.

For each pipe material either a single pipe roughness value or a range of roughness

values is normally provided by the manufacturer. The roughness value, usually

denoted as e, is used in the calculating the relative roughness of a pipe against the

size of its diameter

Absolute Roughness : The roughness of a pipe is normally specified

in either mm or inches and common values range from .!" mm

for #$C pipes through to %. mm for rough concrete pipes.

The relative roughness of a pipe is its roughness divided by itsinternal diameter or e&', and this value is used in the calculation

of the pipe friction factor, which is then used in the 'arcy()eisbach

e*uation to calculate the friction loss in a pipe for a flowing fluid.

Roughness Coefcient

Roughness Coefcient


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Roughness Coefcient

Roughness Coefcient


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Roughness Coefcient

Roughness Coefcient


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Roughness Coefcient

Roughness Coefcient


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Factors to affect the head loss in pipe

- Viscosity to be handled

- Size of the pipe

- Resistance through various valves and fittings- Roughness of the internal surface of the pipe

- Changes in elevation

- Length of travel of the fluid

Friction Loss

Friction Loss


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Darcy Weisbach !uation"his for#ula recognized that pipe friction is dependent on

condition li$e roughness of pipe internal surface% internal

dia#eter% internal velocity and viscosity&

where ' friction loss% ft or # of li!uid ' friction factor

L ' (ipe length % ft or #D ' (ipe inside dia#eter% ft or #

V ' )verage pipe velocity in ft*sec or #*sec

g ' +ravitational constant ,.&/01 ft*2

,3&4#*2

Friction LossFriction Loss


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, which is 4 times greater than the Fanning Friction actorused with Weisbach equation has now become the standard headloss equation or calculating head loss in pipes where the ow isturbulent

!nitiall" the #arc"$Weisbach equation was difcult appl", since noelectronic calculators were a%ailable and man"calculations had to be carried out b" hand

For laminar ow&Re"nolds 'o below ()))* the roughness has no

e+ect and the riction actor

Friction Loss #arc" Friction FactorFriction Loss #arc" Friction Factor


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For laminar ow&Re"nolds 'o below ()))* the roughness has noe+ect and the riction actor

For turbulent ow&Ra"nolds 'o abo%e 4)))* the riction actor isa+ected b" both the roughness and the Re"nolds 'o and can be

determined rom an equation de%elopment b" CF Coolbroo-&./0/*

= -2

Where R = VD/

/sec

Friction Loss #arc" Friction FactorFriction Loss #arc" Friction Factor


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1ince the Colebroo- equation is nonactorable in &* and thereoredifcult to sol%e, its solution is presented graphicall" on chart

de%eloped b" CF 2ood"

Friction Loss 2ood" ChartFriction Loss 2ood" Chart


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+CA- obtaining complete test data on the pressure drop of every

available size and type of valve and pipe fitting is impossible,

a practical method for e/tending available information is useful.

This techni*ue, 0nown as the e*uivalent(length method for calculating

pressure losses, applies only to single phase, non(compressible, non(flashing li*uids.

3qui%alent Length3qui%alent Length


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1crewed ttings

Flanged ttings



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A pipe run consists of %1 ft of 2 inch diameter straight pipe,

%(34 elbows, 5(wide open gate valves and !( wide open glove valve.

)hat total e*uivalent length of straight pipe is used to calculate head

loss6

olution :

From the table

- traight pipe %1 ft- %(34 elbows : % 7 !! ft 8 %% ft

-5(wide open gate valves : 5 7 5." 8 ". ft

- !( wide open glove valve : !!" ft

Total e*uivalent length : %1 9 %%9 " 9 !!" 8 !3 ft

3qui%alent Length 35ample3qui%alent Length 35ample


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1chedule 'o1chedule 'o

For all pipe sizes the outside diameter ;.'.< remains relativelyconstant. The variations in wall thic0ness affects only the inside

diameter =.'.


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1chedule 'o1chedule 'o

)elded and eamless )rought teel #ipe

To distinguish different weights of pipe, it is common to use the chedule terminology

from

A>=&A? +%@.! )elded and eamless )rought teel #ipe ,

ight wall : CB !, 5,%,2

tandard )eighttd, T', T< : CB @/tra strong/tra Beavy, B, B, < : CB D,!,!5,!2

'ouble /tra trong'ouble /tra Beavy, B,

roughness coefficient & piping schedule no22.pptx

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