Water Transport Modelling

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POLITECNICO DI TORINO

WATER AND OILPIPELINES SIZING

Master of Science: Petroleum Engineering

Course: Oil and Gas Transportation

Prof. Coordinator: Student:

Guido Sassi Frincu Iuliana Aurora

S196092

2014



#

TABLE OF CONTENTS

INTRODUCTION……………….……………….……………….……………….……………….…3

I.

WATER PIPELINE……………….……………….……………….…………………… 4

I.1. Geometry and elevation……………….……………….……………….……………5

I.2. Water properties……………….……………….……………….……………….….. 5

I.3. Water pipeline sizing……………….……………….……………….……………….6

I.4. Water pipeline pressure profile……….……………….………………….………… 8

I.5. Pumps and valves……….……………….………………….……………….……… 9

I.6. Other considerations……….……………….………………….……………….… ..15

II. OIL PIPELINE……….……………….………………….……………….……….……..16

II.1. Oil properties……….……………….………………….……………….…………..16

II.2. Oil pipeline sizing……….……………….………………….……………….……..16

II.3. Other considerations……….……………….………………….…………….….…..23

III.

CONCLUSIONS……….……………….…………….……………….………….....……24

Bibliography



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INTRODUCTION

Transport or transportation is the movement of people, animals and good from one location to

another. Modes of transport include air, rail, road, water, cable, pipeline and space. Transport is

important because it enables trade between people, which is essential for the development of

civilizations.[1]

Pipeline transport sends goods through a pipe; most commonly liquid and gases are sent. Short-

distance systems exist for sewage, slurry water and beer while long-distance networks are used for

petroleum and natural gas.

A water pipeline will pump water from a large source and transfer it across a great distance to

areas in need. Water pipelines are large in diameter and the purpose is to pump without causing

erosion.[2]

Figure 1. Water pipeline

Friction loss is the loss of energy or “head” that occurs in pipe flow due to viscous effects

generated by the surface of the pipe. Friction loss is considered as a “major loss” and it is not to be

confused with “minor loss” which includes energy lost due to obstructions.

This energy drop is dependent on the wall shear stress between the fluid and pipe surface. The shear

stress of a flow is also dependent on whether the flow is turbulent or laminar. For turbulent flow, the

pressure drop is dependent on the roughness of the surface, while in laminar flow the roughness effects

are negligible. This is due to the fact that in turbulent flow, a thin viscous layer is formed near the pipe

surface, which causes a loss in energy, while in laminar flow the viscous layer is non-existent. [3]

In the present report will be calculated all parameters for dimensioning in the first row a water

pipeline, then an oil pipeline. Flow type, pressure profile and different parameters influecing the

pressure profile will be presented.



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I. WATER PIPELINE

The case study is done on a waterworks pipeline which has to serve a city of 100,122

inhabitants. The pipeline is coming from a natural source situated in mountains, serving the citysituated at the basis of the mountain.

Figure 1. Water pipeline pathway

Considering an average consumption of 24 m3/year/inhabitant, we will a need a water supply

structure able to provide a water flow of:

QH2O

= 0,0762 m3/s

Also, we will consider a flow variation of 4 m3/year/inhabitant, so we have to chose a proper

diameter for the pipeline which will transport the water without any problem regarding the flow

variation issues.



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I.1. Geometry and elevation

We will consider the distance from the delivery point and the city to supply of 130,9 km.

Figure 2. Altrimetry Profile

I.2. Water Properties

We assume a constant temperature along the pipeline, which is not subject to seasonal changes.

Also, we consider constant properties even with the temperature variations.

Table 1. Water properties

Propriety Value Unit

Temperature 21 !

Density 1000 Kg/m

Viscosity 0,0015 Pa.s

Vapor pressure 0,0087 bar

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I.3. Water pipeline sizing

We will assume liquid velocities from 0.5 to 2 m/s with a spacing of 0.25 m/s. Then, according

to the velocity interval assumed, we can calculate the diameter using following formula:

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After calculating pipe diameter, we can choose from standards the commercial size of the

diameter. Also, maximum allowable pressure can be calculated using data provided by the

standardization table of commercial steel pipes.

Table 2. Diameter calculation

If friction is neglected and no energy is added or given, the total head H is constant for any

point in the pipeline. But in the real systems, flow is creating always energy losses due to friction. The

energy losses can be measured with two gauges along the pipeline.

After choosing the commercial size of the steel pipes, we can recalculate the velocities and

choose the diameters which give us a velocity in our considered range, regarding the flow variations.

We will choose the last four diameters, keeping into account that one diameter is the same.

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Table 3. Velocity calculation

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We must determine the type of flow we have in the pipeline and also the relative roughness.

Re=!·v·D

µ

For laminar flow regime Re < 2000, friction factor can be calculated, but for turbulent regime

with Re>4000 are used experimentally obtained results.

The relative roughness is the absolute

roughness of the pipe compared with the diameter.

The pipes are manufactured from steel, which has an

absolute roughness of ! = 50 µm. Internal absolute

pipe roughness is actually independent of the size

diameters. So pipes with smaller diameter will have ahigher relative roughness, while the pipes with bigger

diameter of the same material will have a lower

relative roughness. On Moody Diagram friction factor

is expressed in function of value of Reynolds number

and relative roughness. Because relative friction is a

function of diameter, we can observe that Reynolds

number will reduce while the diameter and the

friction number will increase.

Figure 3. Moody Diagram

The minimum pressure inside the pipe will be consider equal with the atmospheric pressure in

order to avoid cavitation due to the bubble gas formed at vapour pressure. For calculating the

maximum allowable operating pressure inside the pipeline, I will consider a design factor equal to 0.7:

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I.4. Water pipeline pressure profile

The first set of calculation is done in a system without pump or valves.

If we use Bernoulli’s equation, assuming incompressible fluid, adiabatic conditions, we can calculate

the pressure drop inside the pipeline.

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As I said before, the pressure drop due to friction in the pipeline can be determines with

Fanning equation.

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The pressure profile equation without pump or valve is as follows;

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The pressure profile was calculated using equation of pressure loss due to friction considering all

assumed velocity and their corresponding diameters in equation above. First, I calculate pressure

profile for the normal water flow using all the velocities from the considered range.

Figure 4. Effect of velocity on pressure profile

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I.5. Pumps and valves

A pump is a device that moves fluids by mechanical action. Pumps consume energy to perform

mechanical work by moving the fluid. They operate via many energy sources, including manual

operation, electricity, engines or wind power, come in many size from microscopic for use in medical

application to large industrial pumps.

Pump performance calculations:

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We calculate the total energy of our profile in terms of head using the new parameters i.e.

pressure loss due to friction and elevation!"

!" =0 since water is to be delivered at atmospheric pressure.

The ideal pump for any give pipe system will produce the required flow rate at the required pressure.

The maximum efficiency of the pump will occur at these conditions. If a given pump is to work with a

given system, the operating point must be common to each. In other words H=h at the required flow

rate.

Figure 5. Best efficiency point between pump and system



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We choose a pump with head and proper capacity for our conditions. From the pump’s curve,

we get the equation with which we calculate for each situation the pump power.

y = -0.002x2 – 0.3054x +221 where y is the pump head [m] and x the flow rate in m3/hr.

Figure 6. Commercial pump curve

Figure 7. Best efficiency point

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Using just one pump, in some situation is not enough. So, pump can work in parallel or in series

in the same pump station. When working in parallel or series, their performance curve is obtained by

adding their flow rated at the same head, as indicated in the figures:

Figure 8. Parallel/series system of pumps

Figure 9. PAHT Pumps Danfoss

For my purpose I choose a commercial high-pressure pump for water. The specifications of the

pump are presented in Table 2.

Table 4. Pump specification

Manufacturer Danfoss

Pump size Up to 150 l/min

Continuous pressure Up to 140 bar

Fluid temperature 3 to 50!

Efficiency 90%



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A valve is a device that regulates, direct or controls the flow of a fluid by opening, closing or

partially obstructing various passageways. We will use valves to obstruct our flow and to cause energy

losses where the liquid overcome the maximum allowable pressure on the pipe.

Cv = !

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Cv, is the valve sizing coefficient determined experimentally for each type and size of valve.

Numerically, the discharge coefficient is equal to the number of U.S. gallons of water at 60F that will

flow through the valve in one minute when the pressure differential across the valve is one pound per

square inch.

A correction for viscosity must be applied due to the fact that the sizing equation is based on the

water flow.

The most used types of valves are check valve, globe valve and ball valve. The one used forregulation of flow is the globe valve while ball valve is just providing the opening or closing of the

pipeline flow.

Because we will need to regulate our flow, we will use globe ball, having the following

coefficients:

Table 5. Cv for ball valve

The pressure profiles, using each diameter and the flow variation are presented in the following plots:

OPEN 2/3 1/2 1

18 0.28 0.16



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In the case of D1, we used a pump at the beginning of the flow line and as we can see, the pipe

is supporting good even the flow variations.For D2, as for D1 we used one pump, but when we have

smaller flow in the pipe, pressure drops too much and is not anymore in the allowable range. Cavitation

can occur.For D3, we used two pumps in the pump station to overcome the pressure drop and flow

variations.For D4, even with 3 pump in the pump station it is not possible to overcome the pressure

drop.

In conclusion, the best solution are D1 and D3, while the cheapest solution will be D1 because

used less equipment.

I.6. Other consideration

Water storage is mandatory for any community, for different purposes as fire suppression,

agricultural farming, chemical manufacturing, irrigation agriculture, drinking water, etc. Various

materials are used for making water tank: plastics, fiberglass, concrete, stone, steel.

By design, a water tank should do no

harm to the water. Water is susceptible to a

number of ambient negative influences,

including bacteria, viruses, changes in pH or

accumulation of minerals. Industrial water tanks

can be fixed root type, used for liquids with very

high flash points. Water pipes do not need any

special treatment, just regular corrosion

protection.

Figure 14. Water storage



!+

II. OIL PIPELINE

II.1. Oil properties

Following the same procedure describe previous in Chapter I, we will proceed to the sizing of

the pipe for oil.

For oil, even a small variation in temperature will modify the parameters as viscosity and

density. That’s why for the sizing of the oil pipe, we will take into account a variation of the

viscosity, thus a variation of density as well due to temperature change.

In the following tables, will be presented just the final results.

Table 6. Oil properties

Propriety Value Unit

Temperature 21 !

Density 800 Kg/m

Viscosity 0,0075 Pa/s

Vapor pressure 0,0526 bar

II.2. Oil pipeline sizing

Oil transportation return a high profit, that’s why the equipment used must be high - quality in

order to have a higher efficiency. Steels used for the pipes must be high – graded with sufficient

strength to erosion.

Figure 15. Effect of velocity on pressure profile

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For D1 and D2 we considered just one pump station with one pump, while for D3 with three

pumps and for D4 with four pumps. Having more pump increase the cost. But, D2 is not supporting

very good the variation in flow and viscosity of oil, that’s why I suggest the use of D1 which gives

enough flexibility for variations.

II.3. Other considerations

Oil pipes are usually buried at depth of about 1 – 2m, so special protection methods from

impact, abrasion and corrosion must be used. These can include wood lagging, concrete coating,

rockshield, sand padding, etc.

Crude oil contains varying amounts of paraffin wax and in colder climate wax buildup may

occur within a pipeline. For our simulation, we consider wax and paraffin free oil. Often, the pipelines

are inspected and cleaned using pipeling inspection gauges, scrapers also known as pigs. Smart pigs are

used to detect anomalies in the pipe such as dents, metal loss caused by corrosion, cracking or other

mechanical damage. Once launched, they either clean wax deposits and material that may have

accumulated inside the line or inspects and records the condition of the line.

Figure 28. Pipe pigging

The storage of oil is made in floating roof tanks after has been stabilized to a vapour pressure of

less than 11.1 psia. The goal with all floating-roof tanks is to provide safe, efficient storage of volatile

products with minimum vapour loss to the environment. The external floating roof floats on the surface

of the liquid product and rises or falls as product is added or withdrawn from the tank [5].



#%

III. CONCLUSIONS

A comparison plot between water pressure profile and oil pressure profile is done in Figure 29.

Figure 29. Compared pressure profiles

At the same temperature, oil has a higher density and viscosity then water. So, the Reynolds

number will be less, meaning that will create less turbulence in the pipe. The turbulence in the pipe

increase the friction in the pipe, so oil flow will have less energy losses along the pipe than water.

Oil transportation return high profit, so high qualitative equipment is used. On the contrary, for

water transportation can be done in pipes with regular steel.

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Bibliography

[1]. http://en.wikipedia.org/wiki/Transport#Other_modes

[2]. http://academic.evergreen.edu/g/grossmaz/SUPPESBJ/

[3]. Munson, B.R. (2006). Fundamentals of Fluid Mechanics 5th Edition. Hoboken, NJ: Wiley & Sons.

[4]. http://www.engineeringtoolbox.com/nominal-wall-thickness-pipe-d_1337.html

[5]. http://petrowiki.org/Floating_roof_tanks

[6]. http://www.engineeringtoolbox.com/ansi-steel-pipes-d_305.html

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