an introduction about pipeline

8/13/2019 An Introduction about Pipeline

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PAB 2073: FACILITIES ENGINEERING

MAZLIN IDRESS

EXT: 7067


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Pipeline An introduction

PAB 2073


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Learning outcome

At the end of this chapter, students should be

able to:

Differentiate between a pipeline and a tanker

and their application for transportation of

hydrocarbons.

Describe different types of pipelines and the

respective application.


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Pipelines Definition

A pipeline system is defined as a pipeline

section extending from an inlet point

(may be an offshore platform oronshore compressor station) to an

outlet point (may be another platform

or an onshore receiving station).


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Pipeline Classification

Pipelines can be classified as:

Onshore

Offshore

The onshore and/or offshore pipelines have

THREE (3)types:

Trunk or gathering

Transmission or transportation

Distribution


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Types of Pipeline: Gathering Line

These lines are used to transport oil from

field pressure and storage to large tank

where it is accumulated for pumping into the

long distance called trunk line.

Gathering pipelines typically consist of lines

ranging from 4-8 inside diameter.


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Types of Pipeline: Trunk Line

From large central storage, oil is movedthrough large diameter, long distancepipeline called trunk line to refineries.

Pump are required at the beginning of thetrunk line and pumping stations must also bespaced a long the pipeline to maintainpipeline pressure at the level required toovercome friction, change in the elevationand other losses.


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Crude trunk lines operate at higher pressure

than gathering systems. These lines are made

of steel and individual sections are joined by

welding.

These lines are almost buried below ground

surface are coated externally to protect

against corrosion.

Types of Pipeline: Trunk Line


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Transportation Pipelines - Mainly long pipes

with large diameters, moving products (oil,

gas, refined products) between cities,countries and even continents.

Types of Pipeline:Transmission/Transportation


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These transportation networks include

several compressor stations in gas lines or

pump stations for crude and multi-products

pipelines.

The large diameter may range from 24 to

60 inches

Example Trans ASEAN line

Types of Pipeline:Transmission/Transportation


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Types of Pipeline: Distribution Line


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Source: Oil and Gas Pipelines Miesnerand Leffler

Oil and Natural Gas Pipeline

The general principles governing oil and natural gas

pipelines are the same, except that gas is many times

more compressible. This is an important factor in

understanding the differences between oil andnatural gas pipelines


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Oil Pipelines

Crude oil is collected from field gathering systems

consisting of pipelines that move oil from the wellhead to

storage tanks and treatment facilities where the oil is

measured and tested.

Oil pipelines are made from steelor plastictubes with inner

diameter typically from 10 to 120 cm (about 4 to 48 inches).

Most pipelines are buried at a typical depth of about 1 - 2

meters (about 3 to 6 feet).

From the gathering system the crude oil is sent to a pump

station where the oil delivered to the pipeline.
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Oil Pipelines

The pipeline may have many collection anddelivery points along route. Booster pumpsare located along the pipeline to maintain

the pressure and keep the oil flowing usuallyflows at speed of about 1 to 6 m/s.

The delivery points may be refineries, wherethe oil is processed into products, or shippingterminals, where the oil is loaded ontotankers.


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Oil Pipelines

A pipeline may handle several types of crude oil. Thepipeline will schedule its operation to ensure that the rightcrude oil is sent to the correct destination.

The pipeline operator sets the date and place when and

where the oil is received and when the oil will arrive at itsdestination.

Crude oil may also move over more than one pipelinesystem as it journeys from the oil field to the refinery orshipping port.

Storage is located along the pipeline to ensure smoothcontinuous pipeline operation.


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Natural Gas Pipelines

Natural gas pipelines are used to move gasfrom the field to consumers. Gas producedfrom onshore and offshore facilities istransported via gathering systems and inter-and intra-state pipelines to residential,commercial, industrial, and utilitycompanies.

For natural gas, pipelines are constructed ofcarbon steel and varying in size from2 inches (51 mm) to 56 inches (1,400 mm) indiameter, depending on the type of pipeline.


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Natural Gas Pipelines

The gas is pressurized by compressor stations

and is odorless unless mixed with an odorant

where required by the proper regulating body.

Most natural gas pipelines operate using acomplex have become so automated that they

are capable of operating under command of a

computer system that coordinates the operationof valves, prime movers, and conditioning

equipment.
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Pipelines Components


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Initial Injection Station - Known also as

Supply or Inlet station, is the beginning of

the system, where the product is injected

into the line.

Storage facilities, pumps or compressors are

usually located at these locations.


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Compressor/Pump Stations - Pumps for

liquid pipelines and Compressors for gas

pipelines, are located along the line to move

the product through the pipeline.

The location of these stations is defined by

the topography of the terrain, the type of

product being transported, or operationalconditions of the network.


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Partial Delivery Station - Known also asIntermediate Stations, these facilities allowthe pipeline operator to deliver part of the

product being transported. Block Valve Station - These are the first line

of protection for pipelines.

With these valves the operator can isolateany segment of the line for maintenancework or isolate a rupture or leak.


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Block valve stations are usually located every 20

to 30 miles (48 km), depending on the type of

pipeline.

Even though it is not a design rule, it is a veryusual practice in liquid pipelines.

The location of these stations depends

exclusively on the nature of the product beingtransported, the trajectory of the pipeline

and/or the operational conditions of the line.


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Regulator Station - This is a special type of

valve station, where the operator can release

some of the pressure from the line.

Regulators are usually located at thedownhill side of a peak.


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Final Delivery Station- Known also as Outlet

stations or Terminals, this is where the

product will be distributed to the consumer.

It could be a tank terminal for liquid pipelinesor a connection to a distribution network for

gas pipelines.


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Maintenance

For pipeline companies, maintenance is about

understanding the condition of the asset. They

perform necessary inspections, correct potentially

unsafe conditions before they cause failures, andrepair failures after they occur


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Pipelines Inspection

Crude oil contains varying amounts of wax,

or paraffin, and in colder climates wax

buildup may occur within a pipeline.

Often these pipelines are inspected and

cleaned using pipeline inspection gauges

pigs, also known as, scrapersor Go-devils.


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How Pipelines Work

The operation of pipeline seems simple enough:

pump fluid in one end and take it out the other.

While the principles dictating the behaviour offluids are rather intuitive, the calculations

involved are fairly complex


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The Physics of Fluid Flow

Pressure makes fluid move

Pressure is a reflection of energy added to pipelinesby pumps, compressors or gravity

The pressure in a non-flowing pipeline along a levelroute is the same along its entire length

But in a route with elevation changes, pressure ishigher in valleys and lower in hilltops

Once the line start flowing, the pressure is almostalways lower as the fluid moves


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Compressor

stationLevel pipeline

Direction of flow

Energy Energy

Pressure at any point = Pressure at origin- Pressure loss due to friction

+/- Pressure due to elevation changes


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Friction losses, pipe lengths and flow rates

Friction causes resistance to flow

Faster flow rates produce more friction than slower rates

Changing one variable, pressure or flow rate, can change the

other, and changing the length changes both


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Hydraulic Properties of Hydrocarbon

Fluids

Important properties of fluid concerning pipeline operators:

Density

Viscosity

Pour Point

Vapor pressure (evaporation)

Pressure

Compressibility



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Hydraulic properties of hydrocarbon fluids

Density

Temperature and pressure both affect density

API gravitymeasure of density for fluids

Viscosity

Higher viscosity, more energy to move fluid Pour Point

Temperature can drop until reach pour point and cease to flow

Pressure

Absolute pressure (psia) = Gauge pressure (psig) + Atmosphericpressure



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Hydraulic properties of hydrocarbon fluids

Vapor pressure

Temperature and pressure determines if fluid stays as liquid orevaporate to gas

Higher vapor pressure means more volatility

Important consideration for oil and natural gas pipelines

When combination of gas pipeline operating P&T exceeds vapor pressureof the heavier molecules, they turn to liquid

When line pressure of oil pipeline drops below vapor pressure, bubblesform

Compressibility

Important for gas pipeline

How much work to force a given mass into smaller space



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Basic Flow principles and Equations

Principles:

First Law of Thermodynamics

Law of conservation of energy

Fundamental to pipeline hydraulics

Bernoullis Principle

Static pressure + Dynamic pressure + hydrostatic

pressure = Constant



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Basic Flow principles and Equations

Equations: Flow characteristics

Laminar, transitional turbulent, fully turbulent

Friction loss

Major factor why pumps and compressors are required Factors of viscosity, density, velocity, pipe length, roughness of

inside pipe

Elevation loss or gain How much decline or gain depends on weight of fluid and height

of hill

Flow rates and capacities Mass = density x area x velocity x time



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Corrosion

Almost all oil and natural gas lines are steel Steel corrode if not protected

Pipeline can leak or rupture if too much metal isremoved

Few different types of corrosionmost common isgalvanic corrosion

Corrosion outside pipe external corrosion

Corrosion inside pipe internal corrosion

Both can be influenced by bacteria, fungus and algaeliving on the surface of the pipes!



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To prevent external corrosion:

External corrosion is caused by current flowso stop flow

of electrons stop corrosion

Insulating coatings e.g. coal tar enamel, fusion-bondedepoxy applied to outside pipe wall

Reverse flow of electrons - cathodic protection

Sacrificial anodebury metal with higher

electrochemical potential than iron (anodes) in selectedlocations along the lines


Corrosion


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To prevent internal corrosion:

Internal corrosion occurs in low spots where contaminants

like water tend to collect

Regular pig runs

Inject corrosion inhibitors

It works by coating the internal of the pipe to prevent current flow

Interact with pipe materials to lower the pipes electrochemical

potential

React with oxygen etc before they corrode the pipe


Corrosion


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Major Components

When most people think of pipelines, they think of

pipe. But there are many other essential components

needed to build and operate pipelines. These include

pumps, compressors, meters, valves, fittings andmany more including hundreds of instruments,

sensors and so on. Nevertheless, the bulk of a

pipeline is pipe.


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Pipe

Today, steel is the material of choice for high-pressure pipelines

Low-pressure pipelines use various types of plasticsand fiberglass

Pipelines produced in standard sizes and strengthratings

Pipes selected based on their chemical and physicalproperties Chemical properties of metalcarbon affect strength,

ductility Physicalpipes stress must be below specified minimum

yield strength (SMYS) and return to original size whenpressure is relieved



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Coating

Properly protected pipe can last virtually forever

Most important is that coatings insulate line

electrically so protect from current flow and thus

corrosion Many types, for e.g. Fusion bond epoxy, Coal tar

Enamel, Plastics, Tape, Shrink sleeves, Concrete

coating



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Pumps, compressors, Prime Movers and VSD

Pumpsoil service

Compressorsnatural gas service

Positive Displacement (PD) and Centrifugal designs are forboth oil and gas pipelines

PD pumps/compressors add pressure (potential energy) byforcing more fluid in pipeline

Centrifugal pumps/comps spins -create kinetic energy, andthen slow downconvert to potential energy

Pumps and compressors get power from prime movers

Engines Electric motors

Turbines

Variable Speed Devices (VSD)control pumps andcompressors



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Meters and Provers

Function of metering Ensure pipeline customers receive the amount of oil/gas they put in

Ensure pipeline operates environmentally safe, no hazard

Classification

Direct volume metermeasure volume directly Inference meteruse flow properties to calculate flow rate

Main types

PD metersflow separate in chambers, count chambers as they go

Turbine metersmeasure speed of bladed rotor to calc. flow rate

Orifice metermeasure gas flow!

Coriolis meterworks for both oil and gas

Proversused to ensure accurate metering measurements.E.g. Master meters and Pipe provers



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Engineering and Design

The pipeline planners have developed a plan with preliminary

routes and volumes. The preliminary design document is then

handed off to the design group for detailed engineering. The

document includes the lines intended use, approximate

route, intended volumes, primary receipt and delivery points,as well as suggested operating pressures, diameters and wall

thickness. They may also include pumping and compression

needs, storage needs, metering, instrumentation and control


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DESIGN of pipeline system

Safety considerations

Route selection

Line size, Wall thickness, Looping

Systems curvesPressure vs. flow rate

Fittings, flanges, valves

Pumps, compressors, prime movers

Flow and pressure control

Stationsnumbers, locations, design and layout

Complex!


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ASSIGNMENT

In a group of 5 people, prepare a 10 minutes

presentation on FLOW ASSURANCE problems

in pipelines. State the problem and how to

mitigate the problem. Find out the newtechnology used in the industry to overcome

the problem.

A week to complete Presentation date: 28 and 29thMarch

an introduction about pipeline

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