Pipeline Hydraulics Design Basis Engineering Essay

It includes the pipe and flow features of the transported fluid under specified operating conditions as established in the design footing.

Speed

The grapevine has to be laid for the distance of 770km between Portland and Montreal, the fluid in the pipe is Light Crude Oil.

Speed of flow in a grapevine is the mean speed based on the pipe diameter and liquid flow rate. Its choice is first measure in the scheming process of our undertaking. The flow speed can hold both advantages and drawbacks. High speeds can do turbulency, and the contact of the fluid on the walls of the pipe which will do harm to the pipes and finally gnaw away the pipe, while low speed on the other manus can do the deposition of particulates in the line and cleanliness of the fluid will be compromised. Therefore, to avoid these problemsliquid lines are usually sized to keep a speed sufficient to maintain the solid atoms from lodging and besides to forestall the eroding of the pipe. Under these considerations the recommended speed is in the scope of 3ft/s to 8ft/s.

From this selected scope of speed we have to choose a individual speed. The speed we have selected for our line is 5ft/s. This is the intermediate speed from the recommended scope and all the farther computations will be done on this speed.

Velocity Selection

The scope as mentioned above is taken every bit 3ft/s to 5ft/s. The following measure is to choose a individual speed from this scope. We have selected 5ft/s for our line. The ground for this speed choice is the tradeoff between pipe diameter and figure of pump Stationss. Harmonizing to continuity equation if we increase the speed, the corresponding diameter will cut down but the force per unit area loss will increase due to which a higher figure of pump Stationss are required. Similarly if we decrease the speed, the figure of pump Stationss will cut down but the diameter will increase for a given flow rate. Since the grapevine is laid over a long distance, the grapevine cost holds the major portion of the capital investing hence increasing the diameter will adversely impact the economic sciences of grapevine. This tradeoff is seeable in the computations shown in appendix A.

The other ground for taking this speed is that if the flow rate fluctuates in the hereafter for any ground the diameter selected from this intermediate speed will be able to suit those fluctuations without impacting our system.

Diameter Calculation

Calculation of the diameter is the nucleus of the hydraulic designing.The diameter selected should be able to back up the emphasiss on the pipe, the capacity of the fluid and minimise the force per unit area losingss.

Under given flow rate and false speeds, we can cipher the pipe diameter utilizing continuity equation:

V=Q/A

Volt: Flow speed

Q: Volume flow rate

A: Cross sectional country

The flow rate is given as 109,000bbl/day or 7.1ft^3/s. The diameters are calculated at 3, 4, 5ft/s speeds and the several diameters are 20.83 '' , 18.04 '' and 16.14 '' .

Choice of Diameter

As mentioned above 5ft/s is selected as the recommended speed and the corresponding internal diameter ( ID ) is 16.14in.

Nominal Pipe Size

For the internal diameter later we have to cipher the nominal pipe size. To cipher the nominal diameter we refer to the `` Pipe Data '' provided for the Carbon Steel. From the tabular array shown in appendix B, it is found out that attendant nominal pipe size will be 18in.

Features of Flow

Different flow belongingss are calculated to find the government of flow, losingss in the pipes.

The nature of the flow can be laminal or turbulent.There are two types of the losingss. Major losingss include the losingss due to clash in consecutive pipes and minor losingss due to decompression sicknesss, valves, tees.

To cipher these we will be covering with Reynolds figure ( for nature of flow ) , Moody diagram ( for clash factor ) and head loss computations.

Losingss

As the fluid flows through the pipe there is clash at the pipe wall and unstable interface in the consecutive parts of the pipe due to interference between the fluid and the walls of the pipe. This clash consequences in consequences in the loss of energy in the lineat the disbursal of liquid force per unit area and the losingss are known as the major losingss.

Pipe systems consist of constituents in add-on to consecutive pipes. These include decompression sicknesss, valves, tees etc and add farther to the losingss in the line. These losingss are termed as minor losses.Experimental information is used to cipher these losingss as the theoretical anticipation is complex.

Major Losingss

The force per unit area bead due to clash in a grapevine depends on the flow rate, pipe diameter, pipe raggedness, liquid specific gravitation, and viscousness. In add-on, the frictional force per unit area bead depends on the Reynolds figure ( and therefore the flow government ) . Therefore, the fluid in the grapevine will undergo force per unit area losingss as it runs in the line and cut down the operating force per unit area. This loss needs to be recovered and to keep the force per unit area pumps are installed at specific locations harmonizing to the demand ( pumps are discussed in Chapter in front ) . These force per unit area losingss are calculated by utilizing the Darcy-Weisbach expression

a?†P = degree Fahrenheit ( L/D ) ( V^2/2 ) I?

Where,

f=Darcy clash factor, dimensionless, normally a figure between 0.008 and 0.10

L=Pipe length, foot

D=Pipe internal diameter, foot

The force per unit area loss for speed of 5ft/s comes out to be 9625.15psi. All the relevant computations are shown in appendix A.

Minor Losingss

Real grapevine systems largely consist of more than consecutive pipes. The extra constituents ( valves, tees and decompression sicknesss ) add to the overall loss of the system. These are termed as minor losingss. In instance of really long pipes, these losingss are normally undistinguished incomparison to theA unstable clash in the length considered. But in caseA of short pipes, these minor losingss may really be major losingss such as inA suction pipe of a pumpwith strainer and pes valves.These losingss represent extra energy dissipation in the flow, normally caused by secondary flows induced by curvature or recirculation.

Minor loss in diverging flow is much larger than thatA in meeting flow. Minor lossesgenerally increase with an addition in the geometric deformation of the flow. Thoughminor losingss are normally confined to a veryA short length of way, the effects mayA notdisappear for a considerable distance downstream. ItA is undistinguished in instance ofA laminar flow.

The force per unit area bead through valves and adjustments is generallyexpressed in footings of the liquid kinetic energy V2/2g multiplied by a head loss coefficient K. Comparing this with the Darcy-Weisbach equation for caput loss in a pipe, we can see the undermentioned analogy. For a consecutive pipe, the caput loss H is V2/2g multiplied by the factor ( fL/D ) . Therefore, the caput loss coefficient for a consecutive pipe is fL/D.

Therefore, the force per unit area bead in a valve or adjustment is calculated as follows:

h=K ( V^2 ) /2g

Where,

h=Head loss due to valve or suiting, foot

K=Head loss coefficient for the valve or adjustment, dimensionless

V=Velocity of liquid through valve or adjustment, ft/s

g=Acceleration due to gravitation, 32.2 ft/s2 in English units

The caput loss coefficient K is, for a given flow geometry, considered practically changeless at high Reynolds figure. K increases with pipe raggedness and with lower Reynolds Numberss. In general the value of K is determined chiefly by the flow geometry or by the form of the pressureloss device.

Minor loss is by and large expressed in one ofA the two ways

In footings of minor loss factor K.

In footings length, tantamount to aA certain length of consecutive pipe, usuallyexpressed in footings of figure of pipe diameter.

The minor losingss for our system are calculated and consequence in a really low value and can easy be neglected.

Reynolds Number

Flow in a liquid grapevine may be smooth, laminar flow, besides known as syrupy or streamline flow. In this type of flow the liquid flows in beds or laminations without doing Eddies or turbulency. But as the speed increases the flow alterations from laminar to turbulent with Eddies and turbulencies. The of import parametric quantity used in sorting the type of flow in the pipe is called Reynolds Number.

Reynolds figure gives us the ratio of inertial forces to syrupy forces and is used to find the nature of flow utilizing the recommended speed and the internal diameter. Reynolds figure is given by

Re = I?VD/Aµ

Flow through pipes is classified into three chief flow governments and depending upon the Reynolds figure, flow through pipes will fall in one of the undermentioned three flow governments.

1. Laminar flow: R & lt ; 2000

2. Critical flow: R & gt ; 2000 and R & lt ; 4000

3. Disruptive flow: R & gt ; 4000

Friction Factor

Friction Factor is a dimensionless figure required to cipher the force per unit area losingss in the pipe. Trials have shown that degree Fahrenheit is dependent upon Reynolds figure and comparative raggedness of the pipe. Relative raggedness is ratio of absolute pipe wall raggedness Iµ to the pipe diameter D.

For laminar flow, with Reynolds figure R & lt ; 2000, the Darcy clash factor degree Fahrenheit is calculated from the simple relationship

f=64/R

For laminar flow the clash factor depends merely on the Reynolds figure and is independent of the internal status of the pipe. Therefore, irrespective of whether the pipe is smooth or unsmooth, the clash factor for laminar flow is a figure that varies reciprocally with the Reynolds figure.

For turbulent flow, when the Reynolds figure R & gt ; 4000, the clash factor degree Fahrenheit depends non merely on R but besides on the internal raggedness of the pipe. As the pipe raggedness additions, so does the clash factor. Therefore, smooth pipes have a smaller clash factor compared with unsmooth pipes. More significantly, clash factor depends on the comparative raggedness ( Iµ/D ) instead than the absolute pipe raggedness Iµ .

In the disruptive part it can be calculated utilizing either the Colebrook-White equation or the Moody Diagram.

Colebrook-White Equation

The Colebrook equation is an inexplicit equation that combines experimental consequences of surveies of turbulent flow in smooth and unsmooth pipe The Colebrook equation is given as:

1/a?sf = -2log ( ( Iµ/3.7D ) + ( 2.51/Rea?sf ) )

But the turbulent flow part ( R & gt ; 4000 ) consists of three separate parts:

Turbulent flow in smooth pipes

Turbulent flow in to the full unsmooth pipes

Passage flow between smooth and unsmooth pipes

For disruptive flow in smooth pipes, pipe raggedness has a negligible consequence on the clash factor. Therefore, the clash factor in this part depends merely on the Reynolds figure as follows:

1/a?sf = -2log ( 2.51/Rea?sf )

For disruptive flow in to the full unsmooth pipes, the clash factor degree Fahrenheit appears to be less dependent on the Reynolds figure as the latter additions in magnitude. It depends merely on the pipe raggedness and diameter. It can be calculated from the undermentioned equation:

1/a?sf = -2log ( ( Iµ/3.7D )

For the passage part between turbulent flow in smooth pipes and turbulent flow in to the full unsmooth pipes, the clash factor degree Fahrenheit is calculated utilizing the Colebrook-White equation given above:

1/a?sf = -2log ( ( Iµ/3.7D ) + ( 2.51/Rea?sf ) )

Moody Diagram

The Colebrook equation is an inexplicit equation and requires test and mistake method to cipher f.To provide the easiness for ciphering f scientists and research workers developed a graphical method known as Moody diagram.The Moody chart or Moody diagramis a graph that relates the clash factor, Reynolds figure and comparative raggedness for to the full developed flow in a round pipe.In the diagram clash factor is plotted poetries Reynolds figure. The curves are plotted utilizing the experimental information. The Moody diagram represents the complete clash factor map for laminar and all disruptive parts of pipe flows.

To utilize the Moody diagram for finding the clash factor degree Fahrenheit we foremost calculate the Reynolds figure R for the flow. Following, we find the location on the horizontal axis of Reynolds figure for the value of R and pull a perpendicular line that intersects with the appropriate comparative raggedness ( e/D ) curve. From this point of intersection on the ( e/D ) curve, we read the value of the clash factor degree Fahrenheit on the perpendicular axis on the left.

Other Pressure Drop Relations

Hazen-Williams Equation

The Hazen-Williams equation is normally used in the design of waterdistribution lines and in the computation of frictional force per unit area bead inrefined crude oil merchandises such as gasolene and Diesel. This methodinvolves the usage of the Hazen-Williams C-factor alternatively of pipe roughnessor liquid viscousness. The force per unit area bead computation utilizing the Hazen-Williams equation takes into history flow rate, pipe diameter, and specificgravity as follows:

h=4.73L ( Q/C ) 1.852/D4.87

Where,

h=Head loss due to clash, foot

L=Pipe length, foot

D=Pipe internal diameter, foot

Q=Flow rate, ft3/s

C=Hazen-Williams coefficient or C-factor, dimensionless

In customary grapevine units, the Hazen-Williams equation can berewritten as follows in English units:

Q=0.1482 ( C ) ( D ) 2.63 ( Pm/Sg ) 0.54

Where,

Q=Flow rate, bbl/day

D=Pipe internal diameter, in.

Pm=Frictional force per unit area bead, psi/mile

Sg=Liquid specific gravitation

Another signifier of Hazen-Williams equation, when the flow rate is in gal/ min and caput loss is measured in pess of liquid per thousand pess of pipe is as follows:

GPM=6.7547A-10-3 ( C ) ( D ) 2.63 ( HL ) 0.54

Where,

GPM=Flow rate, gal/min

HL=Friction loss, foot of liquid per 1000 foot of pipe

In SI units, the Hazen-Williams equation is as follows:

Q=9.0379A-10-8 ( C ) ( D ) 2.63 ( Pkm/Sg ) 0.54

Where,

Q=Flow rate, m3/hr

D=Pipe internal diameter, millimeter

Pkm=Frictional force per unit area bead, kPa/km

Sg=Liquid specific gravitation

Shell-MIT Equation

The Shell-MIT equation, sometimes called the MIT equation, is used in the computation of force per unit area bead in heavy petroleum oil and heated liquid grapevines. Using this method, a modified Reynolds figure Rm iscalculated foremost from the Reynolds figure as follows:

R=92.24 ( Q ) / ( DI? )

Rm=R/ ( 7742 )

Where,

R=Reynolds figure, dimensionless

Rm=Modified Reynolds figure, dimensionless

Q=Flow rate, bbl/day

D=Pipe internal diameter, in.

I?=Kinematic viscousness, Central Time

Than depending on the flow ( laminal or turbulent ) , the clash factor is calculated from one of the undermentioned equations:

f=0.00207/Rm ( laminal flow )

f=0.0018+0.00662 ( 1/Rm ) 0.355 ( disruptive flow )

Finally, the force per unit area bead due to clash is calculated utilizing theequation

Pm=0.241 ( f SgQ2 ) /D5

Where,

Pm=Frictional force per unit area bead, psi/mile

f=Friction factor, dimensionless

Sg=Liquid specific gravitation

Q=Flow rate, bbl/day

D=Pipe internal diameter, in.

In SI units the MIT equation is expressed as follows:

Pm=6.2191A-1010 ( f SgQ2 ) /D5

Where,

Pm=Frictional force per unit area bead, kPa/km

f=Friction factor, dimensionless

Sg=Liquid specific gravitation

Q=Flow rate, m3/hr

D=Pipe internal diameter, millimeter

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