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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.