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PIPELINES


DEFINITION


Pipelines consist of a series of pipes with pumps, valves, and control devices that convey
fluids (e.g. water, oil, etc.), gases (e.g. natural gas) or solids suspended in liquid (e.g.
sewage or some slurry mixtures used in industrial

or mining processes). Modern
communications lines such as fiber optics and electrical lines are also sometimes installed
within pipelines. Pipelines may be constructed above or below ground depending on the
conditions of the soil and the environment in
which the pipeline travels.


SYNOPSIS

Pipelines are susceptible to extensive damage during earthquakes and in high seismic
regions, often special connectors and fittings are used to allow the pipe to move
elastically. Since pipelines often carry materia
ls that are vital to sustain life and maintain
property, they are usually referred to as lifelines.
Pipeline networks may be placed above
or below ground or run underwater. For the most part, pipeline networks are constructed
below ground. All types of p
ipelines have been placed below ground including, energy
pipelines like oil, natural gas, and gasoline, as well as water lines, sewer lines, storm
sewers, telephone lines, television cables, and many types of electric lines.

Since natural resources like cr
ude oil and natural gas are found in vastly different
locations than where they are processed, it is necessary for pipeline networks to be placed
underground in order to avoid safety and minimize their appearance.



Above
-
ground pipelines are subject to
the same kinds of internal inertial loads as
buildings and other structures, and their supports must be designed for these expected
forces. Damage to buried pipeline systems can either be induced by permanent ground
deformations or by transient seismic wav
e propagation. Permanent ground deformations
can be categorized as surface faulting, landsliding, seismic compaction (settlement), or
liquefaction. Along with transportation and utility systems, pipelines are lifeline
components.


The United States has th
e largest network of energy pipelines, both oil and natural gas, of
any nation in the world. The oil pipeline network alone in the U.S. is more than 10 times
larger than that in Europe.



Components of Pipelines
:


Pipe sections are made from a variety of m
aterials including; reinforced concrete, steel,
polyurethane, clay, etc. The type of material used for an individual pipeline network is
specific to the type of material flowing through the pipe as well as the environment in
which the pipeline travels. O
ther important components of pipelines are the connectors,
such as couplings, tees, elbows, etc., shown in Figure 1. These connectors are used to
join lengths of individual pipe sections as well as to divert the pipeline in one or many
different direction
s. Welded steel pipe is generally more resistant than piping connected
with other methods to damage from inertial forces (above
-
ground piping, such as in
buildings or industrial facilities, or where transmission lines are above
-
ground) as well as
more res
istant to imposed soil deformations if buried. Incompatible motions between one
section of pipe and another at a right
-
angle connection or where a tank is connected to a
pipe, is often the most likely location of damage. Valves are another component of
p
ipelines that play an integral part in the pipeline network (Figure 2). These valves,
which are primarily used in fluid filled pipelines, are used to control the flow within and
around the pipeline network. For pipelines traveling up an incline, pumps ma
y be
required to push the fluid up the incline. The pump component is especially useful on
pipelines that travel through mountain regions, like the Alaskan Pipeline shown in Figure
3. The ability of pipelines to accommodate very large deformations, in th
is case from
faulting, if properly designed is shown by the performance of the Alaskan Pipeline in the

November

2003
, Denali Earthquake.



The Trans
-
Alaskan Pipeline: A Brief Description of the Trans
-
Alaskan Pipeline


Although used less frequently than bu
ried pipelines, above ground pipelines are just as
effective in transporting products from one location to another. However, a clear
disadvantage is that above ground pipelines may be visible to the public and are
susceptible to damage from humans. A we
ll known example of an above ground
pipeline is the Trans
-
Alaska Pipeline. This pipeline, which travels through the
environmentally sensitive Tundra, was build above ground in order to prevent the warm
oil inside the pipe from melting the permafrost. Thi
s elevated pipeline also features a
staggere
d shape, (Figure 4
) which provides elasticity to the system during earthquake
loads. It took $8 billion (U.S. dollars) and two years to build the Trans
-
Alaska Pipeline.
It is said to be one of the most difficult

engineering feats of all time. The pipeline is 5937
km long and has an outside diameter of 13.12 m. The pipeline carries crude oil from
Prudhoe Bay on the
Northern Slope of Alaska to the ice
-

free port of
Valdez in southern
Alaska. It crosses three mount
ain ranges, 34 major waterways, and 800 smal
l streams.
Figure 5 and Figure 6

detail the obstacles the pipeline had to overcome as well as the
route which the pipeline travels. The oil travels at 40.1 kph and takes 6.2 days to travel
the length of the pipe
line.














CONTENT IN DEPTH


Buried Pipelines: Chapter 23 of the Earthquake Engineering Handbook, edited by Wai
-
Fah Chen and Charles Scawthorn, discusses pipeline performance in past earthquakes, as
well as the various types of failure modes.

http://www.engnetbase.com

(search keyword “Pipelines”)


Construction of Marine and Offshore Structures, Second Edition: This site provides an
online copy of the book written by Ben C. Gerwick which outlines the proce
dures for
constructing marine and offshore structures.

http://www.engnetbase.com/ejournals/books/book_summary/toc.asp?id=502


Pipe Line & Gas Industry: This is an onlin
e publication that presents information on
general aspects of the oil and gas pipeline industry.

http://www.pipe
-
line.com/


Pipeline and Gas Journal.com: This site provides journal articles on a variety of pipeli
ne
related issues.

http://www.undergroundinfo.com/PGJ/pgj_home.html


The American Lifelines Alliance (ALA): This site provides information about the public
-
private partnership project, which

has a specific seismic mission, funded by the Federal
Emergency Management Agency (FEMA) and managed by the National Institute of
Building Sciences (NIBS). The Alliance has the goal of reducing risks to lifelines from
hazards.

http://www.americanlifelinesalliance.org/


The Association of Bay Area Governments (ABAG): This site provides information on a
variety of earthquake
-
related hazards (
http://quake.abag
.ca.gov/
). Also included in this
site, is a link that discusses the damaging effects of utility pipeline leaks.
(
http://www.abag.ca.gov/bayarea/eqmaps/liquefac/pipes.html
).


Endbr
idge Pipelines Inc.: This site is the homepage for Endbridge Pipelines Inc. which
operates the world's longest and most sophisticated crude oil and petroleum products
pipeline system.

http://www.enbridge.c
om/pipelines/


The Alyeska Pipeline Service Company: This site is the homepage of the company
responsible for the operation of the Trans
-
Alaska Pipeline.

http://www.alyeska
-
pipe.com/


Pacific Gas and Electric

(PG&E) Gas Transmission: Northwest: This site outlines the
steps that PG&E employees take to ensure the integrity of their pipelines and the safe
transmission of liquid natural gas.

http://www.pge
-
nw.com/company_info/?content=/safety/our_role.html&nav=nav.html?navObj=elThree


Southern California Gas Company: This site provides information on how to turn off
your natural gas lines in the event of a
n earthquake.

http://www.socalgas.com/general/safety/whattodo.shtml


Pacific Earthquake Engineering Research Center (PEER): Providing data, models, and
methods needed to improve the ear
thquake reliability and safety of lifelines systems,
including electric and gas transmission lines.

http://peer.berkeley.edu/



Pipeline Design


The design of a pipeline network is a process which must take a var
iety of factors into
consideration. Engineers must consider the types of loads that are going to be imposed
on the pipeline, the environment that the pipeline will travel in, and the type of material
that the pipeline is going to convey. Whether a pipeli
ne is onshore or offshore, there are
an assortment of different loads that could potentially damage the pipeline, including
bending moments, internal or external pressures, surrounding soil, and dynamic loading.
The capacity of a pipeline to resist bendin
g, as well as axial tension or compression, is
particularly important in areas where there is a potential for differential settlement or
during the construction process when lengths of pipe are placed on uneven surfaces.
While seismic considerations are i
mportant, th
ere are other criteria, such as

initial
construction cost and durability over the years with the associated maintenance cost,


When designing liquid pipeline networks such as fire fighting water network systems,
large cooling water systems, an
d long distance liquid pipelines, fatigue loading must be
taken into consideration. Fatigue loading can either be caused by a variation in internal
fluid pressure and/or temperature or by a phenomenon know as water hammer, were by a
severe dynamic shock f
orce and vibration on the piping structure is introduced due to the
sudden closer of a system valve. Dynamic loading of buried pipelines, including
earthquake loads, moving vehicle loads, railroad crossings, pile driving, blast loading and
impact loads du
e to falling objects, is another important design consideration that
engineers must take into account. Dynamic loading is a case that involves a variety of
different loading combinations, including flexural loads and fatigue loads. For example a
pipeline t
hat travels beneath a major truck route. The pipeline must be strong enough to
withstand the repeated flexural loads that are imposed every time a truck passes over as
well as the fatigue loads that are present ever time the pipe deforms. Designing a
pip
eline for earthquake imposed loads is difficult since there is such a variety of ways in
which the system might deform relative to the ground. However, through the use of
technologically advanced connections and state of the art materials, engineers are f
inding
ways to design pipelines to withstand a gamut of imposed loads.





Pipeline Construction


Unlike the planning phase for a building structure on one site, the planning phase of a
pipeline project is the most crucial and usually begins years in adv
ance. Some initial
steps in the planning process include determining market need, route selection, pipeline
design, land acquisition and permitting. Each of these steps, and many others, play an
intricate role in allowing the construction phase of the pr
oject to proceed without any
delays.

In general, the design and construction of a pipeline occurs in three stages; pre
-
construction, construction, and post
-
construction. The pre
-
construction phase involves
engineering and design, land acquisition, and e
nvironmental impact studies. In the
United States, all federal and state requirements must be met by the pipeline planning
team as well as obtaining any permits that pertain to the construction of the pipeline.
Planning teams must also respond to any and

all concerns that are brought forth by the
local community. In order to secure easement rights to place the pipeline along the
selected route, land or right
-
of
-
way agents, hired by the pipeline operator, are assigned to
work with potential landowners to
meet their needs.

On average, the actual construction phase of a project occurs in the shortest amount of
time. But the construction phase can only begin after all of the pre
-
construction actions
have been accomplished. Before the pipeline can be buried o
r erected, the right
-
of
-
way
must be cleared and prepared for construction. Once the right
-
of
-
way is ready, the
pipeline is assembled and is either lowered into a pre
-
dug trench, bored under waterways
or roads, or placed above ground on system of

columns an
d hangers. Figures 1

and
Figure
2

are examples of buried pipelines still in the placement stage of the construction
process.

The post
-
construction phase of a pipeline project primarily addresses the restoring of the
land affected by trenching and placemen
t of the pipeline. Before the pipeline goes on
line, the pipe and components are tested in the field with water pressure, weld x
-
rays and
an assortment of other inspection tests. Each stage of the post
-
construction process is
overseen by qualified inspecto
rs to ensure compliance with the engineering plan, codes,
permit conditions, landowner and easement agreements, and regulatory requirements.
For more information and photographs of the pipeline construction process, please visit
Welded Construction Compan
y, L.P at,
http://www.weldedconstruction.com/process.html
.

Pipeline Operation and Maintenance:

Whether they are carrying oil, water, or electrical power, most pipelines are required to
operat
e all
-
day, everyday. With the help of powerful pumps, oil additives and the laws of
physics, pipelines can transport product efficiently and effectively, with little or no down
time.

With today’s advancements in technology, pipeline operators can watch th
e rate, pressure
and movement of product at points along the system. This technology also enables
operators to detect any breaks in the pipeline, allowing for quick containment of spilled
product and minimization of environmental impact. While every pipel
ine company
strives to achieve incident
-
free operation, accidents do happen. Figure
3

shows the
aftermath of a ruptured

natural gas pipeline in Venezuela.
Pipeline operators are trained
to shut down pipeline systems quickly and safely when accidents do o
ccur.

One of the most crucial tasks in pipeline operation is maintenance. Just like the pipeline,
pipeline maintenance crews work all
-
day, everyday. Their job is to ensure the integrity
of pipeline infrastructure. These maintenance crews ensure that weldi
ng operations, valve
inspections, pipeline repairs, corrosion prevention system checks and electronic
equipment maintenance are performed safely and according to procedures that have been
established by code or by the company.

Under
-
sea Gas Transmission P
ipeline near Osaka, Japan:

In general, underwater pipelines are used to transport oil and gas products from offshore
drilling structures to mainland refineries. However, in countries where the ability to run a
new pipeline is limited due to for example, e
xisting infrastructure, if the continent or
region is near water, underwater pipelines may be placed offshore in order to alleviate
constructability issues. One example of this type of offshore pipeline is the gas
transmission pipeline connecting the Senb
oku Liquid Natural Gas (LNG) terminal to the
Hokko pressure regulating station near Osaka, Japan. Figure
4

shows the route of this
new pipeline. This pipeline is 96.5 km in length, 769 millimeters (mm) in diameter and
is buried 39.9 m below the seabed of

the Osaka Bay area. The pipeline is encased in a
shield tunnel, with an inner diameter of 2.4 m, which was designed to protect the pipeline
from the elements and external forces. If this pipeline had been run above ground, heavy
traffic in the Osaka Bay

area would have made construction very difficult.


To achieve the engineering feat of placing this pipeline under the seabed and through
reclaimed land, shielded tunnel and horizontal directional drilling methods were
implemented fo
r the installatio
n, see Figure 5
. Since the pipeline would be transitioning
between reclaimed lands (built of fill material) and the bays seabed, engineers had to
design this structure to resist the effects of subsidence and seismic forces. In order to
protect the pipeli
ne from the differential settlement of the reclaimed fill, flexible
segments were used at the interface between the reclaimed land and the seabed. To
protect against seismic activity, the joints of each tunnel segment were outfitted with
elastic washers t
hat provided flexibility for the system.







Examples of Pipeline Damage in Past Earthquakes


Figure
6

shows a few ways in which pipelines may be damaged due to ground
deformations. While permanent ground deformation vulnerability is predominantly
limit
ed to local sections of the pipeline system, the potential for a pipeline to be damaged
is extremely high. These large ground deformations are usually very dramatic, very
sudden, and confined locally. The hazards imposed by wave propagation on the other
hand usually affect the entire pipeline network, with a significantly smaller damage rate.


Failure modes for pipelines can be rupture due to tension forces or buckling due to
compression forces, as illustrated in Figures
7

and
8
. For segmented pipelines

with
relatively small diameters, flexural failures, especially in areas where the ground is
curved, are one type of failure mode that has been observed after seismic activity. On the
other hand, pipelines with larger diameters and comparatively thick wal
ls, the majority of
observed failures were due to distress at the pipeline joints (e.g. axial pull
-
out in tension,
crushing of bell and spigot in compression) (O’Rourke et al. 1999).


Presented below are a few examples of the amount and types of observed
pipeline
failures during previous seismic events.




The magnitude 8.3 1906 San Francisco, California earthquake resulted in
extensive damage to the cities water transmission lines, which in turn, hindered
the extinguishing of fires, resulting in a large por
tion of the city being burnt to the
ground, see Figure
9
.




The 1971 San Fernando, California earthquake resulted in 1400 breaks in various
piping systems. The city of San Fernando temporarily lost water, gas, and
sewage services. Liquefaction
-
induced lat
eral spreading along the eastern and
western shores of the Upper Van Norman Reservoir damaged water, gas, and
petroleum transmission lines (O’Rourke et al., 1985). See Figures 1
0

through 1
3

for pipeline damage photographs.




Although a large portion of the

cities structures suffered extensive damage during
the 1987 Ecuador earthquake, the major impact was the socio
-
economic loss that
the country incurred when a 40 kilometer section of the trans
-
Ecuadorian
pipeline was completely destroyed. At a cost of $85
0 million (1987 U.S. dollars)
in lost sales and reconstruction (O’Rourke et al., 1985), the loss of this one year
old structure sent the countries economy into a tailspin.




The 1994 Northridge, California earthquake resulted in extensive damage to
water
, gas, sewage and other utility lines, at costs in excess of $1.7 billion (1994
U.S. dollars). In one portion of Los Angeles County, 100% of the population
was without power for one day and approximately 15% of the population was
without water for eight d
ays. Similarly, 12% of the population was without
natural gas for almost two weeks (O’Rourk
e et al., 1995). See Figures 14
through 17

for pipeline damage photographs.




During the 2001 Nisqually, Washington earthquake, there was extensive
structural and n
on
-
structural damage caused by broken fire sprinkler and piping
systems. In one case, a nine story unreinforced masonry (URM) building that
had been seismically upgraded was closed due to damage to electrical fixtures
and water damage.




In November of 200
3 a magnitude 7.9 earthquake struck Alaska, rupturing the
Earth's surface for 209 miles along the Susitna Glacier, Denali, and Totschunda
Faults. Even though the Denali Fault shifted about 14 feet beneath the Trans
-
Alaska Oil Pipeline, the pipeline did not

break, averting a major economic and
environmental disaster