3 Basic Piping 52

8/8/2019 3 Basic Piping 52

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Piping Fundamentals

Piping System - What is that?Concept Layout Development

Piping Components & their access requirement.

Straight length requirements.

Orientation of various tapings, components, etc.

Piping Drains & Vents

Material & Sizing

Critical piping system consideration.

Pipe Supports

Let us first Discuss about WHAT IS PIPE!

Pipe

Piping Fundamentals

s a u e w roun cross sec on con orm t e mens ona

requirements of ASME B36.10M &ASME B36.19M and used for

conveying Liquid, Gas or any thing that flows.

Tube.

A hollow product of round or any other cross section having a

continuous eri her . Round tube size ma be s ecified withrespect to any two, but not all three, of the following:-

outside diameter, inside diameter, and wall thickness.

Dimensions and permissible variations (tolerances) are specified

in the appropriate ASTM or ASME specifications.


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In any plant fluids flow throughpipes from one end to other.

Now let us start with a plant where

we see three tanks.

Tank-1 Tank-2 and Tank-3

We have to transfer the content ofTank no. 1 to the other two tanks.

We will need to connect pipes totransfer the fluids from Tank-1 toTank-2 and Tank-3

We have just brought the pipes, now we

need to solve some more problems.Pipes are all straight pieces.

To solve theseproblems we need the

pipe components,which are called

PIPE FITTINGS

We need somebranchconnections

We need some bendconnections


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These are the pipe fittings,

There are various types of fittings for variouspurposes, some common types are -

Elbows/Bends, Tees/Branches,

Reducers/Expanders, Couplings, Olets, etc.

Anyway, the pipes andfittings are in place, but theends are yet to be joined withthe Tank nozzles.

We now have to complete the end

connections.These, in piping term, we call

TERMINAL CONNECTIONS.

So far this is a nice arrangement.

But there is no control over the flow fromTank-1 to other tanks.

We need some arrangement to stop theflow if needed

These are flanged joints

This is a welded joint

To control the flow in a pipe line weneed to fit a special component.

That is called - VALVE


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There are many types of valves, categorized based on theirconstruction and functionality,

Those are - Gate, Globe, Check, Butterfly,

Other than valves another importantline component of pipe line is a

filter, which cleans out derbies fromthe flowing fluid. This is called a

STRAINER

Here we see a more or less functional piping

system, with valves and strainer installed.

Let us now investigate some aspects of pipe

flexibility.

If this tank

nozzleexpands, whenthe tank is hot.

In such case we need to fit a flexiblepipe component at that location,

which is called an EXPANSION

JOINT


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When some fluid is flowing in a pipe we mayalso like know the parameters like, pressure,temperature, flow rate etc. of the fluid.

To know these information we need

to install INSTRUMENTS in thepipeline.

There are various types instruments to measure various

parameters. Also there are specific criteria for installationof various pipe line instruments.

Next we shall lookinto how to

SUPPORT thepipe/and itscomponents.


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Here are some of the pipe supporting arrangements.There can be numerous variants. All depend onpiping designers preference and judgement.

Let us see some OTHER types of supports


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Anchor. Arigidrestraintprovidingsubstantiallyfullfixation,permittingneitherLateralnorrotationaldisplacementofthe

pipe.

We have just completed a pipe line design.We shall rewind and check how it is done in practice.

First the flow scheme is planned,

1) What, 2) From what point, 3) To which point

Pipe sizes are selected, pipe material and pipe wallthickness are selected.

Types of Valves are planned Also the types of instruments required are planned

We represent the whole thing in a drawing which iscalled Piping and Instrumentation Drawing, in shortP&ID. For P&ID generation we use SPP&ID software.


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By this time you have already come to know thatwhile we prepare P&IDs in SPP&ID, we enter all the

pipe lines system information in the drawing.

o e raw ng s an n e gen raw ngwhich under its surface carries all the informationabout a pipe like, Pipe size, Flowing Fluid, etc.

Let us see a P&ID prepared in SPP&ID


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This is screen picture of P&ID made by SPP&IDIf we click on any line it will show the Data embedded.

After the P&ID is ready we start the layout work.

Here we carryout pipe routing / layout in Virtual 3Denvironment.

Plant virtual 3D space.

We call this as piping modeling or physical design.

While development of piping layout we have to

consider the followingPiping from source to destination should be as short as

possible with minimum change in direction.

Should not obstruct any normal passage way.

Also should not impinge any equipment maintenance space.


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Not Preferable

Preferable

While carrying out pipe routing we also need to consider thefollowing:-

Valves, strainers, instruments on the pipe should be easily

accessible.

If needed separate access platforms to be provided to facilitate

these.

Desired location and orientation of valves / instruments and other

pipe components are to be checked and maintained, like some

valves or strainers can only be installed in horizontal position.

Specific requirements for instrument installation to be checked,

like temperature gauge can not be installed in pipe which is less

than 4 inch in size.


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Specific requirements of STRAIGHT LENGTH of pipe forsome components to be maintained, like for flow orifice we

need to provide 15 times diameter straight pipe length atupstream of orifice and 5 times diameter straight at down

stream of orifice.

Example of Straight length requirement for Flow Orifice

For Pipeline which shall carry liquid, we have to make sure that all air

is allowed tovent out of the line when the line is filled with liquid.

To achieve this a Vent connection with Valve is provided at the top point of

the pipeline.

Also arrangement is kept in the

pipeline so that liquid can be

drained out if required.

To achieve this a DRAIN

connection with Valve is provided

at the lowest point of thepipeline

Pipes are also slopped towards

low points.

Let us look into typical Vent and

Drain arrangement in a pipeline

Lowest point pipe line

Drain with valve


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This is a 3D modelof Feed water linealong with pumps

Let us have a look into a piping model done by PDS 3D

and otheraccessories

Piping system calcification Initially a system known as iron pipe size (IPS)

was established to designate the pipe size.

the pipe in inches.

An IPS 6 pipe is one whose inside diameter isapproximately 6 inches (in),

Users started to call the pipe as 2-in, 4-in, 6-in and so on.

At the beginning, each pipe size was produced withone thickness, which later was termed as standard(STD) or standard weight (STD.WT.).


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The outside diameter of the pipe was standardized.

As the industrial requirements demanded the handling ofhigher-pressure fluids, pipes were produced having thicker

walls, which came to be known as extra strong (XS) orextra heavy (XH).

The higher pressure requirements increased further,requiring thicker wall pipes. Accordingly, pipes weremanufactured with double extra strong (XXS) ordouble extra heavy (XXH) walls while the

Standardized outside diameters are unchanged.

With the development ofstronger and corrosion-resistantpiping materials, the need for thinner wall pipe resulted in anew method of specifying pipe size and wall thickness.

The designation known as nominal pipe size (NPS)replaced iron pipe size IPS, and the term

schedule (Sch) used to specify the pipe Nominal wall thickness.

Schedule word re lace the wei ht word with the same means.

Nominal pipe size (NPS) is a dimensionless designator ofpipe size.

It indicates standard pipe size when followed by the specific

size designation number without an inch symbol. For example, NPS 2 indicates a pipe whose outside diameter

is 2.375 in.

See the pipe line specification xls sheet


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Piping standard sizes

Start from 1\8 and increased by 1\8 up to 1.5.

From 1.5 it increased by 0.5 up to 4. From 4 increased by 1 up to 6.

From 6 increased by 2 up to 36.

Pipe classification

The NPS 12 and smaller ( just commercial number ) has outside

diameter greater than the size designator However,

The outside diameterof NPS 14 and largerpipe is the same as

the size designator in inches. For example, NPS 14 pipe has anoutside diameterequal to 14 in. The inside diameter will depend

upon the pipe wall thickness specified by the schedule number.

Pipe Wall Thickness Schedule is expressed in numbers (5, 5S, 10, 10S, 20, 20S, 30, 40,

40S, 60, 80, 80S, 100, 120, 140, 160). A schedule number indicatesthe approximate value of the expression 1000 P/S, where Pis theservice pressure and S is the allowable stress, both expressed in

.

The higher the schedule number, the thicker the pipe is.

The outside diameter of each pipe size is standardized therefore; aparticular nominal pipe size will have a different inside diameterdepending upon the schedule number specified.

Note that the original pipe wall thickness designations ofSTD, XS,

and XXS have been retained however the corres ond to a certainschedule number depending upon the nominal pipe size.

The nominal wall thickness ofNPS 10 and smaller ** schedule 40pipe is same as that of ** STD.WT. Pipe.

Also, NPS 8 and smaller *** schedule 80 pipe has the same wallthickness as *** XS pipe ( extra strong or extra heavy ).


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The allowable pressures were calculated by the formula given in the code for

pressure piping ANSI B31.8-1966 par. 841.1

P

St

D F E T=

2

Where :

P = Design pressure, PSIG

S = Specified minimum yield strength, PSIG

D = Nominal outside diameter (in)

t = Nominal wall thickness, (in)

F = Construction type design factor

E = Longitudinal joint factor, normally a factor of 1.0 is used for seamless.

T = Temperature de-rating factor, for 250 F or less = 1.0

Type A, F = 0.72 For cross country locations include crossing in casings.

Type B, F = 0.6 For fringe areas around cities and towns includes road crossings

without casings and crossings in casing if in type 2 locations.Type C, F = 0.5 For commercial and residential sections.

Type D, F = 0.4 For areas with multistory buildings.

Thepipescheduleisroughlycalculatedas:-

Sch = (1000 x internal operating pressure ) / tensile strength(Tensile strength is the stress at which a material breaks or permanently deforms)

As example the tensile strength of the carbon steel API 5L startfrom 35,000 psi up to 80,000 psi

For a carbon steel with 35,000tensilestrength with an operatingpressure 1000 psi the schedule must equal to[ 1000 x 1000 / 35000 ] = 28.6 so we can use pipe schedule 30.

TheschedulenumbersfollowedbytheletterS are per ASME

. ,steelpipe.

The pipe wall thickness specified by a schedule number followed by theletter S mayormaynotbethesameasthatspecified by a schedulenumber withouttheletterS.


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There are three definitions of tensile strength:

Yield strength

The stress at which material strain changes from elastic

,

permanently.

Ultimate strength

The maximum stress a material can withstand when

subjected to tension, compression or shearing. It is the

- .

Breaking strength

The stress coordinate on the stress-strain curve at thepoint

of rupture.


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Two units are used in measuring the piping size1. The Englishunit

2. SI

( metric ) system

The im ortant note is that all the i in size in metricsystem express the outsidediameter so the size of the12 piping or less are not the same in both unit systembut for the 14 or more pipe diameter the English unitsare equivalent to SI unit.

s examp e t e p pe n un t system s es gneto have outside diameter of 114.3 mm ( equal 4.5 )

The 18pipein SI unit is designed to have outsidediameterof 457.2 mm ( equal 18 )


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Max Allowable Working Pressure

The allowable working pressure is depends up on:-

1. The pipe wall thickness ( expressed as schedule / weight).

2. Material o construct on car on stee , stee , p ast c, .

3. Operating temperature.

The piping schedule is expressed as number varying from 10

to 160 from thin to thick pipe

e p p ng we g s expresse as g , s an ar , ex ra

heavy and double extra heavy ( L,S,XH,XXH)

MAWP = 1.1 : 1.3 From The Design Pressure

Operating pressure mustn't exceeds 90 % from MWAP

Usually the RV setting is the MAWP and the operationis recommended not to be more than 90 % of MAWP.

Iftwo RV,s installed the first one is setting at the MAWP

Thepiping rating must be governed by the pressure-

temperature ratingof the weakestpressure containing item

in the piping

In no case shall themanufacturers rating be exceeded. In

addition, the manufacturer may impose limitations which

must be adhered to.


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Pipe Fittings

-

1. Produce change in geometry

2. Modify flow direction

. r ng p pes oge er

4. Alter pipe diameter

5. Terminate pipe


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A reducer serves the dual purpose :-1. Changing the piping diameter and

2. Handling the expansion, misalignment orvibration problem.

Both concentric and eccentric, are offered mainl from " to 12 Piping systems should be anchored when using concentric reducer. The length of the reduction is usually equal to the average of the

larger and smallerpipe diameters

Concentric or eccentric reducers are used to properly reduce intoand out ofcirculating pumps.

Preferred for Oil services preventing

turbulence avoid emulsion

If installed in gas services must be up ward if

used foroil service as pump suction must be

downward

gas oil


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Gasketa gasket of some softer material is usually inserted between contact faces.

Tightening the bolts causes the gasket material to flow into the minor

machining imperfections, resulting in a fluid-tight seal.

A considerable variety of gasket types are in common use. Soft gaskets, such

as rubber, fiber, graphite, or asbestos.

Resilient material

Compressed by bolts to create seal

Commonly used types Sheet

Spiral wound

Solid metal ring


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Expansion joints are used in pipingsystem to absorb thermal expansion where

the use of expansion loops is undesirable or

impractical. Expansion joints are available

, ,

Slip-type expansionjoints are particularly

suited for lines having straight-line (axial)

movements of large magnitude. Slip joints

cannot tolerate lateral off set or angular

rotation since this would cause binding ,

and possibly leakage due to packing

distortion .Therefore ,the use of properpipe alignment guides is essential.

Expansion joints

Ballexpansion joints (Fig.A2.12b)

consist of a socket and ball with a

sealing mechanism placed between

them. The seals are of rigid materials,

The joints are capable of absorbing

angular and axial rotation ;however,

they cannot accommodate movement

.There-fore ,an offset must be installed in

the line to absorb pipe axial movement.


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Strainers are used in piping systems to protect equipment sensitiveto dirt and other particles that may be carried by the fluid . During

system start-up and flushing, strainers may be placed upstream of

pumps to protect them from construction debris that may have been leftin the pipe. FigureA2.9 is a typical start up conical strainer

Strainers are available in a variety of styles,

including wye and basket. The wye strainer(Fig.A2.10)is generally used up stream of traps,

control valves, and instruments. The wye

strainer resembles a lateral branch

FlangesUsually all the pipes from 2 and larger are connected via flanges

Types of flanges

-

It is not considered to give the high mechanical strength as :-

1. Thread flange

2. Slip on flange

-

It is casted with integrally nozzle neck as

1. Socket weld flange

2. Weld neck flange


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weld neck flangeloose flange slip on or threads

Flat flange

Spiral wound gasket


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lap joint flangeBlind flange

threaded flangeslip on flange

Ring gasket

ring joint flangering joint flange


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Types of Flange Attachment and Facing

Flange Facing TypesFlange Attachment Types

Flat FacedThreaded Flanges

Socket-Welded Flanges

Raised FaceBlind Flanges

Slip-On Flanges

Ring JointLapped Flanges

Weld Neck Flanges


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Contact surface facings

may be plain, grooved for ring joints, seal-welded, Selection of

the type of facing depends to a considerable extent on the natureof the service. However, it is not possible to determine exactly

w c ac ng s ou e use . r or exper ence s usua y re e

on as a guide.

Plain-face joints with rubber gaskets have been found

satisfactory for temperatures up to 220oF (105oC),

a flat metallic gasket) between the grooved surfaces of the mating FF

flanges. FF flanges are normally used on the least arduous of duties,

such as low pressure water piping having Class 125 and Class 250flanges and flanged valves and fittings. In this case the large gasket contact

area spreads the flange loading and reduces flange stresses.

Raised-facejoints with graphite-steel-composition gaskets arecom-monly used for temperatures up to 750oF (400oC).

The RF is ( 1 ) high for Class 150 and Class 300 flanges and 1-in high for all pressure classes, higher than Class 300.

Ring joints are used forhigh temperatures and pressures, and

also forlarger pipe sizes

the gasket load must be checked to ensure that the gasket is not

over compressed.

pressure rating.

The number of holes varying from 4 to 20 or even more.


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Weld-Neck (WN) Flange.

The long, tapered hub provides an important reinforcement of the

flange, increasing its strength and resistance to dishing. WN flangesare typically used on hard duties involving high pressures or

.

Socket-Weld (SW) Flange.

Socket-weld flanges are oftenused on hazardous duties involving

high pressurebut are limited to a nominal pipe size NPS 2

(DN 50) and smaller , the pipe is fillet-welded to the hub of

the SW flange. Radiography is not practical on the fillet

weld; therefore correct fitting and welding is crucial. The

fillet weld may be inspected by surface examination,magnetic particle (MP), or liquid penetrant (PT)

examination methods.

Slip-on Flanges.

Slip-on flanges arepreferred to weld-neck flangesby many

users because of their initial low cost and ease of

installation.

Their calculated strength underinternal pressure is about

two-thirds ( 2/3 ) of that of weld-neck flanges.

They are typically used on low-pressure, low-hazard

services such as fire water, cooling water, and other

services, the slip-on flanges are used onpipe sizes greater

than NPS 21 .


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Blind Flange.

Blind flanges are used toblank off the ends of piping,valves, and pressure vessel openings.

From the standpoint of internal pressure and bolt loading,

blind flanges, particularly in the larger sizes, are the most

highly stressed of all the standard flanges.

However since the maximum stresses in a blind flan e are

bending stresses at the center, they can be safely permitted

to be stressed more than other types of flanges.


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Max. Allowable PressurePressure Class

425 psi150

1100 psi300

Hydrostatic test pressures at 100 F or less

2175 ps600

3250 psi900

5400 psi1500

Contact Vendor2500

Cast and steel valves bear a mark such as 150,300 ,600 , etc. Thesefigures denote the maximum pressure in pounds per square inch (psi)at a certain temperature (usually 800 F) for which an item is suited. Acertain 600 -pound valve may be suited for 600 -pound pressure attemperatures up to 850 F.But if the temperature exceeds that point, say up to 1000 F, the valve isnot recommended for pressures over 170 pounds.


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All the data are stamped on the outer edge of the flange as per the photo


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Sample Problem 1

Flange Rating

piping system to be installed at existing plant.

Determine required flange class.

Pipe Material: Cr 1 , Mo

Design Temperature: 700F

es gn ressure: ps g


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Sample Problem 1 Solution

Determine Material Group Number (Fig. 4.2)Group Number = 1.9

Find allowable design pressure at intersection of design

temperature and Group

Now Check Class 150.

=

Move to next higher class and repeat steps

For Class 300, allowable pressure = 570 psig

Required flange Class: 300

Principles of flow Liquid flow

The main idea of the flow is the difference in pressurebetween the two terminals of the piping.

The pressure drop is the main component in selectingt e pipe size.

The pressure drop will depends up on

1. Flow rate

2. Fluid viscosity

3. Fluid density

. .

Any increase of any factors of the above mentioned will cause

increase of the pressure drop.

See module PE 121 at min 25 horizontal piping

system plus type of valves


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Pressure drop We have two factors could be considered as constant

1. Most of the hydrocarbon liquid have nearly the same viscosity

so it may be considered constant.( 6-10 cp )2. The pipe roughness also may be considered constant.

1. The flow rate ,

As appears from the equation if the flow rateduplicated the pressure drop will increase 4 times, tocontrol the pressure drop we must stabilized the flowrate.

Pressure drop continue The last factor affecting the pressure drop is the fluid density

and usually all the flow calculation are completed for waterflowing then corrected for the fluid density as the relation

The equation isPressure drop with liquid = pressure drop with water x relative density

All the different piping system accessories have an equivalentlength to be used in pressure drop calculations by adding allthe accessories equivalent length to the original pipes length.

Tables are available with all the equivalent straight lengths forall the piping accessories valves , elbows , tee,.


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Common pressure drop equation

Using the above equation is not easy so many developed charts created tomake it easy.

Most of the piping system designed are based on 1 psi /100 ft.

piping system designed based on fluid velocity from 3 to 15 ft / second.

Higher velocity will cause erosion. Lower velocity will precipitate all the suspended solids.

Gravity settling alone gives low

ve oc y or m cro me er rop esettling in oil with 33 API at 110 deg

F , viscosity 6.5 cp the velocity is

0.07 ft / hr

How many hours you needs to separate the water from a tank with 30 ft

height by gravity only


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26..1078.1 dGS

Remember the Settling Equation

Oil droplet will settle at a terminal velocity Vt

ra orce

Vertical gas flow upward

Drag Force

Horizontal gas flow

Oil

droplet

m

tV =

Where

S.G. = difference in sp. gr of the

drop and the gas.

Gravity Force

m ,

= viscosity of the gas, cp


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Usually liquid flow rate is design with a safety factor20%to 50 % over the normal expected flow rate.

we must remember that small size are cheaperbut it leadsto high pressure loss which increase the pumping cost.

For two hase flow it is recommended to desi ned based on10 ft / sec velocity, this to minimize the slugging toseparator.( due to the low velocity , segregation happenedand so two phase flow appear and so slug flow observed)

The rapid change in flow may cause hammering in the linethe hammer my result due

ar s op o pump ng sys em

Opening or closing valves

The velocity may hit the sonic velocity 3000-4000 ft / sec.

This change in velocity may cause surge and so be a sourceof pressure as per the following equation :-


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Water Hammer

The energy necessary to move the water through the piping is supplied by

the pump.If avalve is suddenly closed at the end of the discharge line, the moving

column of water is brought to a stop at the valve.

The kinetic energy contained in the column of water, originally given to

the water by the pump, is still present and must be dissipated.

So Water hammer is a pressure wave, usually resulting from rapid changes

n e ow ra e n a p pe, w c s c arac er ze y e rans orma on o

kinetic energy of moving fluid into pressure.

Typical transients for a water-filled system include rapid valve closure,

pump start / stop , within the circulating water system,

The water hammer phenomenain a piping system also may resultdue to formation of vapor pockets at locations where the

pressures are reduced to or below vapor pressure.

This phenomenon is normally called column separation.

Thesubsequent collapse of these vapor pockets may develop significant

pressure spikes which should be taken into consideration in system

design and analysis.


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Hammer head = a V / g

Table C1.6 gives the water-hammer wave velocity as a function of diameter-

to thickness ratios for different piping materials encountered frequently inwater supply or distribution systems. In this tabulation, a is the wave

velocity in ft/sec (m/sec), D/t is the dimensionless ratio of diameter to

thickness, and E is the modulus of elasticity.

Hammer head = a V / g

Where

a = velocity of pressure wave propagation ft / sec

V = change in velocity ft / sec

g =acceleration of gravity = 32.174 ft / sec2

If a is estimated to be 3000 , a change in velocity from 10 ft / secto zero the pressure head due to hummer effect may be calculated

H = 3000 x ( 10 0 ) / 32.174 = 930 ft

If water gradient used the pressure = 0.433 x 930 = 403 psi

It mentioned that the effect of the hammer is reduced as be away rom e or g n o e surge.

A means of eliminating water hammer is to permit the liquid to surge into a

tank or discharge to atmosphere.

To quickly suppress all the momentum in a long pipe system would require

high-pressure piping, which is very costly.


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Pump type Suction velocity ft / sec Dischargevelocit ft / sec

Pumps typical velocities at both suction and discharge

Reciprocating

Up to 250 rpm 2 6

250 to 330 rpm 1.5 4.5

> 330 r m

Centrifugal pump 2 to 3 6 to 9

Depending upon the material selected, piping design and size iseither in the low or high side of this range, for brass pipe a

velocity between 4 to 15 ft/sec would be recommended, while

forsteel pipe, a velocity of 7 to 10 ft/sec is the recommended

higher velocities are acceptable if materials less at risk to

erosion (e.g., stainless steel) are selected


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Gas flow

Gas flow is very sensitive for both pressure and temperature.

Equation of state is used to indicate this relationship.P V P V

Ts Ta

=

Gas piping design

Most of the gas piping system are design for a pressure drop of1 psi / 100 ft as the liquid piping system design.

Also a charts created to make the pipe selection for gas systemeasy all the charts used based on the same pressure drop 1 Psi /100 ft.

Gas piping system design based on a velocity of 15 to 60 ft/ sec


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The maximum flow rate through the piping system is related

to the sonic velocity 340 m /sec ( 1110 ft / sec ).

Liquid pipes are design for 3 to 15 ft / sec and also gas pipesare design for 15-60 ft / sec.

Both of liquid and gas design system are far away from the

sonic velocity.

Max velocity means severe internal corrosion especially at

the elbows and tee connections , and at any place with the

change in direction of flow.

The sonic velocity may be achieved at high pressure and the

second pipe terminal is opened to the atmosphere.


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The end


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DualRatings

Sometimesapipingsystemmaybesubjectedtofullvacuumconditionsorsubmergedinwater andthusexperienceexternalpressure,inadditiontowithstandingtheinternalpressure oftheflowmedium.Suchpipingsystemsmustberatedforbothinternalandexternalpressures atthegiventemperatures.Inaddition,apipingsystemmayhandlemorethanoneflowmediumduringitsdifferentmodesofoperation.Therefore,suchapipingsystemmaybeassignedadualratingfortwodifferentflowmedia.Forexample,apipingsystemmayhavecondensateflowingthroughitatsomelowertemperature

duringonemodeofoperationwhilevapormayflowthroughitatsomehighertemperatureduringanothermodeofoperation,

itmaybeassignedtwopressureratingsattwodifferent

temperatures.


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The Pipes and Tubes can be compared on the following lines:

Tube Pipe

1. Lower thickness and Lower ductility makes it

higher ductility permits unsuitable to coil. Due to

high differential stress larger bending momentum is

between inside and required for the same radius.

outside of coil. This means larger residual stress.

2. Specified by outside dia- Specified byNominal Bore and

meter and actual thickness thickness b Schedule. .in mm/inch or wire gauges.

3. Uniform thickness means Variation in thickness can

less chance of tube failure cause hot spots and consequent

due to hot spots. failures.


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4. Low roughness factor and Higher roughness factor and

lower pressure drop. high pressure drop.

5. Normally used in heat Normally used in straight length

exchangers & coils for heat for fluid transfer.

transfer.

6. Limitation in sizes. No limitation.

Useful conversion of units:

1 inch 25.4 mm; 1 ft 0.3048 m; 1 ft3 0.02832 m3; tC (tF 32); Note:For calculations for pipes other than Schedule 40, see explanation in Table

B8.14.

Note: For pipe lengths other than 100 ft, the pressure drop is proportional

to the length. Thus, for 50 ft of pipe, the pressure drop is approximately

one-half the value given in the table . for 300 ft, three times the given

value, etc.

Velocity is a function of the cross-sectional flow area; thus, it is constantfor a given flow rate and is independent of pipe length.

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