CALIFORNIA STATE UNIVERSITY, NORTHRIDGE
SPIRAL WOUND PIPE
AS A REHABILITATION METHOD
A graduate project submitted in partial fulfillment of the requirements
For the Degree of Master of Science in Structural Engineering
By
Christopher Tomes
December 2020
The graduate project of Christopher Tomes is approved:
________________________________
________________
Dr. David Boyajian
Date
_________________________________
_________________
Dr. Tadeh Zirakian
Date
_________________________________
_________________
Dr. Sami Maalouf, Chair
Date
California State University, Northridge
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Table of Contents
Signature Page
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Table of Contents
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Abstract
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Chapter 1: Introduction
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Should Spiral-Wound Pipe Liner be used in a structural capacity?
When is Spiral Wound Pipe Liner a viable repair option?
Chapter 2: The Installation Method
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How Spiral Wound Pipe Rehab is Installed
3 Methods of Installation
Construction Benefits for Spiral Wound Pipe
Chapter 3: Material and Structural Properties
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Spiral Wound Material Properties
Spiral Wound Structural Properties
Spiral Wound Pipe Sizes and Restrictions
Spiral Wound as a Structural Liner
Chapter 4: Alternative Methods
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Slip Lining
CIPP Lining/UV Lining
HDD (Horizontal Directional Drilling) & Pipe Bursting
Remove & Replace (Open Trench)
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Chapter 5: Conclusion – When to use Spiral-wound?
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References/Works Cited
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Appendix A: Tables
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Appendix B: Figures
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ABSTRACT
SPIRAL WOUND PIPE
AS A REHABILITATION METHOD
By
Christopher Tomes
Master of Science in Structural Engineering
The goal of this project is to study the spiral wound pipe rehabilitation method, looking at all the
potential benefits of rehabbing pipe with this method. It will also try to determine if there are
any drawbacks or downsides. An analysis of the materials, structural properties, and
construction methods used to install this pipe will be conducted to figure out the most
economical and practical applications for spiral wound pipe rehab.
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Chapter 1: Introduction
Spiral-wound pipe rehabilitation is a method of trenchless pipe repair that uses strips of
interlocking PVC or HDPE that are spirally wound around in the inside of a host pipe to create a
plastic lining on the inner wall of the pipe. Spiral-wound pipe lining can take practically any
shape and any diameter. One of the main spiral-wound pipe lining manufacturers in the field
currently is Sekisui Pipe Rehabilitation (SPR). They have spiral-wound pipe lining options for
pipe diameters of 6” through 217”, and they can create or tailor their installation machines to
meet practically any pipe shape. The majority of the pipes in which the spiral-wound method
has been used are either storm drains, culverts or sewer pipes, and all the installations that I have
found to date are in gravity fed pipe networks. According to the Sekisui website, “Spiral Wound
rehabilitates corrugated metal, brick, concrete, clay and other pipe materials.” This method was
first developed in the late 1970s in Australia and has been widely used globally since the late
1980s. The gain in this method’s popularity is due in large part to trenchless installation and the
compact area needed above ground for installation. Theoretically, any pipe can be lined using
the spiral wound pipe rehabilitation method with access to the pipe only via the pipes upstream
and/or downstream maintenance holes. Spiral-wound pipe rehabilitation has many important
benefits in addition to trenchless installation that make it an appealing method to choose to repair
a damaged or aging host pipe. In this paper these benefits will be examined and analyzed. Any
potential drawbacks or downsides to using this method will also be studied in order to get a clear
picture about when it makes sense to use spiral-wound pipe rehab to rehab a pipe and when it
might be advantageous to use another method. We will also analyze claims made by spiral
wound pipe manufacturers about their products and see if they hold up to testing. Specifically,
we will look at the structural and material testing that has gone in to the development of products
that are currently on the market. These test results will be compared with ASTM (American
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Society for Testing and Materials) standards. We will also compare spiral wound test results
against other lining rehab methods available today as well as various traditional trenched remove
and replace pipe options. After all this data is compiled and the comparisons between the
different methods are made, we will hopefully have a clearer picture about when spiral-wound
pipe rehabilitation can be used most effectively and perhaps when other methods of pipe repair
might be more advantageous for a specific project. Spiral-wound pipe rehabilitation is a fairly
new method of pipe repair in the United States and government and private entities alike are
excited by the prospect of a low impact way to repair pipes without excavation and disruption to
communities and the environment. In this paper we will examine the potential that spiral-wound
pipe has to offer as well as look at the possible limitations that this method.
Spiral-Wound pipe manufacturers claim that their products are fully structural. This
means that they are capable of carrying the full structural loads that are typically placed on
buried pipelines. One of the questions that we will seek to answer in this paper is, can spiralwound liners stand up to full soil loadings and actually be used in a structural capacity? And
should we as engineers design systems to use spiral-wound liners structurally?
The second question that this paper will answer is, when is Spiral Wound Pipe Liner a
viable repair option? There are many repair options that are on the market that are available to
engineers today. These methods include a variety of trenchless methods as well as more
traditional trenched remove and replace methods. Knowing what method is best suited to a
particular project can be difficult given the large number of variables, constraints, factors that go
into choosing a repair method. Different methods are better suited to certain repair situations
than others. We will try to identify the situations where spiral wound liners are most
advantageous, and where other methods may be more applicable.
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Chapter 2: The Installation Method
In this chapter we will take an in depth look at the installation process and procedure of
spiral-wound pipe lining. We will break down the construction process and investigate the
benefits that this method offers for installation. There are three different installation methods
that will be analyzed in this paper. These three methods are used by Sekisui SPR, which is one
of the largest installers of spiral-wound pipe lining in the world. Each method corresponds to a
pipe diameter range for which that method is best suited. Finally, after looking at all of the
installation methods for spiral-wound pipe lining we will analyze the benefits of using this
trenchless lining method. The potential benefits that could be uncovered are threefold. The first
benefit is ease of installation. The second benefit is a cost-effective solution to pipe
rehabilitation. The third benefit that we expect to see from the use of this method is a very
limited impact on the communities and environment in which spiral-wound pipe rehab is
installed.
Let us start by taking a step by step look at how spiral wound PVC or HDPE is used to
rehabilitate pipe. Spiral-wound pipe liner is manufactured in ribbed strips of either PVC
(polyvinyl chloride) or HDPE (high density polyethylene). The PVC strips of pipe range from
approximately 2” to 4” in width. We will go deeper into the shape, structure, and material
properties of the pipe strips in a later chapter. One can see the general shape of the strips used in
spiral-wound pipe lining in Figure A.
These pipe strips arrive by truck at the construction site
in large spools. The spool size correlates to the length and diameter of the pipe to be lined.
Figure B shows an example of a spiral wound spool feeding into a maintenance hole at an
installation site. The liner strips are fed from the inside of the strip spool directly into the
maintenance hole, which is the only access point needed for this method to be installed. The
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next part of the installation process diverges and is different based on the pipe diameter and the
mechanical equipment being used for installation.
First, let us look at the process for the smallest pipes. Pipes that are typically repaired
using this method range between 6” and 42” in diameter. In this method the PVC strips are
wound directly into the pipeline with a machine that sits in one of the access points at the
entrance of the pipe. The machine, known as a winding machine, fits inside the maintenance
hole structure and is stationary at the opening of the pipe (Figure C). The compact size of the
machine allows the installation to take place completely inside the maintenance hole with no
additional excavation required. It spins in place and pulls the PVC strip in a circular motion
locking the edge of the strips into place with the strip in front of it. The machine moves the
strips down the length of the host pipe in a spiral motion locking the edge of each strip into place
with the spiral in front of it (Figure D). This corkscrew or spiral motion continues to push the
locked in place spiral-wound strips down the pipe until the entire pipe is lined. In order for this
process to work and be effective, the spiral-wound pipe liner must be smaller than the host pipe.
The spiral-wound liner must be smaller than the host pipe in order to limit any unnecessary
friction or uneven pipe surfaces or offsets in the pipe that may be present. If the liner were to run
into any of these offsets or see a large amount of friction during the installation process, the
winding machine would be unable to push the spirals down the pipe and this method would not
be able to be used. Since the spiral liner must be smaller than the host pipe during installation,
something must be done to fill in the annular space between the liner and the pipe. Traditionally,
this annular space or gap would be filled using a concrete grout or slurry. However, spiralwound pipe lining manufacturers have found a clever way to eliminate the need for grout. In
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their method of eliminating the gap between liner and host pipe, Sekisui’s website explains the
process like this,
“SPR™EX is initially wound at a fixed diameter smaller than the host pipe, resulting in a
gap between the pipe liner and host pipe. Once the SPR™EX reaches the far end
manhole (typically the upstream manhole), the profile’s expansion process begins. A wire within
the liner is pulled, severing a secondary lock within the profile. This allows successive wraps of
PVC profile to expand each other, increasing the diameter for a tight fit against the pipeline
wall. As the wire is pulled, the process travels back towards the winding machine. Once the
liner is expanded and the ends are sealed, the pipe rehabilitation process is complete (2019).”
The secondary lock that is broken by the pulling of the expansion wire allows the
interlocked spiral strips to slide against each other. This sliding action allows the strips to
expand and fit snuggly against the host pipe’s walls. As the expansion is occurring more
SPR™EX is fed into the pipe to accommodate the extra length necessary to expand the liner to
fill in the gap with the host pipe. In this method laterals are able to be reinstated by using a
robotic cutting tool that is inserted into the lined pipe.
The second method of spiral-wound pipe liner that we will investigate is intended
for medium to large diameter culverts, sewers, and storm drains (Figure E). This method is able
to accommodate a range of pipe sizes from 40” to 60” in diameter. Like the first method, this
trenchless lining system requires no annular space grouting. This spiral-wound liner is installed
by laying PVC liner directly against the host pipe wall. The way that this system works is with a
compact liner winding machine that traverses the diameter and shape of the host pipeline while
tightly lining PVC lining strips from a spool on the surface against the pipe wall. Also, like the
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first method, this method claims to be fully structurally independent and capable of handling the
full soil load on it own in the absence of the host pipe. The PVC strip profile consists of steel
reinforced T-bars with single tongue-and-groove profile locking which ensures lasting friction
locking of the system in the windings. Here is how Sekisui describes the installation process,
“The trenchless pipe lining process begins by feeding PVC profile from an above ground
spool directly into the host pipe. SPR™TF traverses the length of a deteriorated pipeline while
pulling profile to construct the PVC liner. Wraps of PVC are locked together as the winding
machine continues down the pipeline. The machine ‘lays’ profile directly against the pipe wall,
resulting in no space between liner and pipe. Since the profile is installed directly against the
pipe wall, no annular space grouting is required. The fully structural pipe rehabilitation process
is complete once the liner reaches the far end manhole and the ends are sealed (2019).”
The winding machine is a self-propelled system and winds the liner in the pipe with a
tight fit against the existing pipe wall. Because of the way that the machine moves around the
pipe and lays the spiral-wound liner directly against the host pipe there is no gap between liner
and pipe wall and thus no need for annular space grouting. There is also no need for the liner to
have a secondary expansion lock, so that it can expand since it is already as expanded as far as
possible against the host pipe.
The third and final method that we will discuss here is meant for large diameter pipes and
irregular and non-circular shapes. It can accommodate pipe diameters from 32” to 217”. In this
method, not only is the system of installation different but the material is also switched. Instead
of a PVC liner like the previous two methods, this method uses HDPE strips that are reinforced
with “fully encapsulated steel strips” (unitracc.com). The system that is used to install the spiral6
wound pipe liner is a type of traversing winding machine (Figure F). The machine consists of a
frame that matches the pipes cross-sectional shape. The shapes that can be lined vary widely
from box structures to horseshoes, teardrops, arches and many others. It fits inside the host
pipe’s cross-section and can be custom designed and built to work in a specific pipe structure and
for a specific project. The machine’s frame has a track around the edge which feeds spiralwound strips around the frame’s shape, which installs the liner. The machine travels down the
length of pipe laying strips of pipe as it moves. In this method, grout is added after the liner is
installed, either as a structural component to the liner or simply as a way to fill in the annular
space between the liner and the host pipe. The type and function of the grout depends on the
dimensions of the pipe and the overall project conditions that are being faced. Grouting occurs
in lifts through a series of ports within the liner. After the grouting is completed, the final result
is a fully structural lined pipe. The Sekisui company calls this method of installation SPRTM.
Now that we have taken an in depth look at these three methods of spiral-wound pipe
lining, we can analyze the construction benefits that each of these methods might offer to the
installation process. From the start, one of the main benefits for most spiral-wound pipe lining
systems is that site excavation is not required. Installations are able to be done entirely within
the access structures and the pipeline itself. All three of the winding machines that have been
discussed above are able to be assembled, disassembled, and moved through standard
maintenance hole structures.
Another construction benefit for two of the three spiral-wound installation methods is that
the PVC strips or profiles can be formed directly into the shape and diameter of the damaged
host pipe and do not require the use of grout to fill annular spaces. The structural properties of
the PVC and HDPE profiles, which include T-bars and steel reinforcement, along with the liner’s
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tight fit against the pipe wall alleviate the need for grouting after lining. These gaps are
eliminated by allowing the lining profile to fit snugly against the pipe wall and is aided by the
fact that the spiral-wound liners are fully structural lining elements. The elimination of the need
for grout allows the installation to be much quicker, and it eliminates concerns about voids
occurring in the grout. Voids that are left after grouting can cause uneven loading on the liner
and create structural weak spots in the line. The lack of grouting also allows for a much easier
installation procedure.
Another apparent benefit of the spiral-wound pipe lining methods in construction is that
the whole installation is portable and can be easily set up in remote access project locations.
This has huge benefits over traditional excavation and remove and replace projects, as well as
slip lining jobs, which both require excavation and a large amount of equipment for construction
as well as flow by-pass. The potential that spiral-wound has over these more traditional methods
are huge. It can be installed virtually anywhere, since all that is needed is maintenance hole
access. This ability unlocks options for pipe rehab in remote and hard to reach locations that
earlier would have required far more expensive alternatives. Difficult access reaches (DARs) are
a prime candidate for this method of repair, which will be far more economical, have a lower
impact, and be easier than most of the other rehab options currently available.
One final construction benefit of spiral-wound liners is that they can, in most cases, be
installed in live flow conditions. This ability eliminates the need for flows to be bypassed
around the pipe reach that is being rehabilitated. Apart from taking a long time to set up an
effective pipe bypass system, they are also very expensive to set up and operate. Eliminating the
need for bypassing a line during rehabilitation is a huge benefit to both a project’s schedule as
well as its budget.
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Chapter 3: Material and Structural Properties
The material and structural properties of a pipeline are a main concern for engineers in
determining which method and type of pipe to use during an installation or pipe rehabilitation.
Having pipes that can stand up to the environment that they will be placed in is of the utmost
importance to pipe system designers. The material properties of a pipe or pipe liner allow
engineers to know if the pipe they have selected will be compromised or not when the pipes are
exposed to hazardous and corrosive environments. The structural properties of a pipe liner allow
us to look at whether the liner can be classified as fully structural or not. A fully structural liner
is defined as a liner that is able to stand alone and take the entirety of the structural load of the
pipe. In other words, a structural liner is a stand-alone structural pipe inside a pipe. In this
chapter we will look at the materials and the material properties of spiral-wound pipe liners. We
will study where they are best suited and if there are any environments where they can be
compromised. We will also examine the claims that spiral-wound pipe liners are fully structural
liners that are able to take on the full loading of the host pipe. We will look at the latest
structural and material testing results from spiral-wound manufacturers and analyze the numbers
and the results of those tests. By the end of this chapter, we will have a much clearer
understanding of the capabilities and limitations of spiral-wound pipe liners. After looking at all
the material and structural properties of Spiral-wound pipe, we will aim to make a determination
about whether or not spiral-wound pipe liners are truly structural liners. We will also try to
answer the question, “should they be used in a structural capacity?”.
Material Properties:
First, we will dive into the materials that spiral-wound manufacturers use to create their
spiral-wound profile strips. The predominant material that is used for the majority of spiral9
wound liners is PVC or polyvinyl chloride. PVC is the third most produced synthetic plastic
polymer in the world. It comes in two basic forms: flexible and rigid. The PVC used in spiralwound pipe liners is of the flexible variety. The flexibility comes from the addition of
plasticizers to the PVC. Plasticized PVC is also known as PVC-P. PVC polymers are linear in
structure and strong. The mass of PVC is comprised of about fifty-seven percent chlorine. This
composition gives PVC a higher density than other structurally similar plastics such as
polyethylene and polypropylene. Relative to other plastics, PVC has a high hardness. Its
mechanical properties are also aided by increasing the molecular weight and are hurt by
increasing the temperature. PVC has a very poor heat stability. PVC is a great insulator of
electricity. The chemical properties of PVC are also very impressive. PVC has proven to be
chemically resistant to a wide spectrum of acids, bases, fats or lipids, salts, and alcohols. These
chemical properties make it a great candidate as a material in sewers. It’s resistance to a wide
range of corrosive effects that are commonly found in sewers means that PVC is widely used in
sewer piping systems. Roughly half of all PVC that is made each year is manufactured for its
use in making pipes. PVC in sewer pipe applications account for a large portion of those pipes.
However, the added plasticizers which make the flexible PVC in spiral-wound pipe liners easier
to work with and able to be spiral wound also make them susceptible to damage from solvents.
Solvents are often found in industrial areas. For areas in which it is possible for solvents to be
present, it is important for the long-term performance of pipes conveying flow to be resistant to
solvent-based chemicals. In cases where high temperatures and solvent-based chemicals exist,
temperature and solvent sensitive plastic (PVC) materials should be avoided.
Another material that is also used in spiral-wound pipe lining manufacturing is highdensity polyethylene or HDPE. HDPE is a thermoplastic polymer made from the ethylene
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monomer. HDPE is known to have a high strength to density ratio. The density of HDPE can
range from 930 to 970kg/m^3. The high density gives it a higher tensile strength and stronger
intermolecular forces than lower density plastics. One of HDPE’s main uses worldwide is in
corrosion resistant piping. Unlike PVC, HDPE is resistant to many different solvents and is also
used in a large variety of applications. HDPE is also known to be safer and more durable than
PVC.
Structural Properties
There is a tendency to think of sewer pipes from a hydraulic standpoint and forget the
critical fact that these pipes are structural elements as well. They must be able to achieve and
maintain structural integrity. The same way that normal structural members in ordinary above
ground structures use “mechanics” to calculate live loads on members, underground pipe
element design involves the application of “soil mechanics” for finding the design loads on the
pipe. The amount of load that a pipe can support can be computed with a safe and accurate
result. To determine a reliable equation for computing the relationship between various kinds of
loads and the necessary test strength of pipe elements, the Marston Equation was developed by
the engineering department at what is now Iowa State University and published in 1930. Today
the Marston equation is widely accepted as a conservative equation for computing trench loads
on pipe. A deeper study into trench load calculations on pipes reveals that there are three main
factors that contribute to loads on underground buried pipes. To properly analyze the loads
imposed on pipes, it is necessary to decide, for each pipe size, what the minimum practicable
design trench width at the top of the pipe is, and still allow for proper installation. The design
trench width, the depth of ill over the pipe, and the soil properties, will give you the load which
must be supported by the pipe and its bedding. Since we are dealing primarily with trenchless
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pipe repair methods in this study, we will not go into too much depth regarding load calculations
on pipe. I bring up the issue of loads on pipes simply to show that the trench width, backfill
process and material, and depth of fill all make major contributions to the loads that a pipe will
be able to support. For example, a pipe that is put in a three-foot-wide trench at the top of the
level of the pipe and backfilled with a full crushed stone encasement will have a load supporting
strength double that of a trench that is backfilled with a class D pipe bedding (Table 4). In this
example of two identical pipes, one can have a loading capacity that is double that of the other
based on nothing but the bedding that is used to support the pipe. The trench width at the top of
the pipe is one of the most crucial factors in determining the load on the pipe. The load on the
pipe increases in relation to the square of the trench width. Therefore, even a relatively small
increase in the width of the trench results in a large increase of the load. The point here is that
pipe construction and installation methods, including trench width, bedding, soil material, and
depth of fill are key in determining what loads the pipe will see in its service life. And it is far
too simple to say that a pipe or pipe liner is fully structural without a solid understanding about
what factors go into determining the loads that a pipe will see. When installing spiral-wound
pipe liners, which claim to have full structural capabilities, into a host pipe does the engineer
know what types of loads that pipe is experiencing? Do they know the trench width that was
used when that host pipe was constructed, or the type of bedding, or the type of backfill soil? All
these things play a role in the loads on that pipe. In this chapter we will seek to understand if
spiral-wound pipe lining designers have accounted for all these variables with their claim that
they make truly structural pipe elements. Spiral-wound liner does conform to the relevant
ASTM standards including ASTM F1697 and ASTM F1741, which define standard practices for
machine installations of spiral-wound PVC. Spiral-wound also adheres to the following
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structural tests, ASTM D256: Izod Pendulum impact resistance of Plastics, ASTM D638: Test
for Tensile Properties in plastics, ASTM D790: Test for Flexural Properties in plastics, ASTM
D2412: Test for determination of external loading characteristics on plastic pipes, and ASTM
D2444: Test for Impact resistance of Thermoplastic pipe and fittings. The minimum dimensions
and initial stiffness factors are specified in (Table 3). Spiral wound pipes are made from ribbed
strip structures. This gives the strips a relatively high strength to weight ratio. For any given
stiffness, less material is required for a spiral-wound pipe liner than a traditional solid wall liner
or pipe. This material efficiency makes spiral-wound a very cost-effective method from a
material perspective.
Sizes of Spiral-wound pipe liner currently range from between six inches and twohundred-seventeen inched in diameter. These are the sizes that are currently advertised by
spiral-wound pipe manufacturers, however since spiral-wound liners come in strips that can fit
practically any shape, they could theoretically be much larger. In theory there is no diameter size
or pipe shape that cannot be lined using this method. In practice though, there are few pipes will
ever exceed the 217” diameter size. On the small end there is a limit to how tight a spiral-wound
liner can be wrapped. This limit is determined by the material properties of the PVC and the
amount of bending or flex it can take before it fails. For practical purposes, most applications of
spiral-wound liners will be larger than six inches.
Now that we have been able to look at all the different material and structural aspects that
make up a spiral-wound pipe liner, we can draw some conclusions about its capabilities. Based
on the material properties present in spiral-wound liners, they have a wide range of applications
from storm drain pipes to most sewer pipes. They have passed a wide spectrum of corrosion
tests, including the Green Book section 211-2 Chemical Resistance (Pickle Jar Test). With this
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information, I would confidently use spiral-wound liners from a materials point of view in most
sewer applications where there are corrosive characteristics. And since spiral-wound pipe is
required to use extruded un-plasticized PVC strips meeting the minimum requirements as
defined in ASTM D1784, the presence of solvent based chemicals should not affect the spiralwound material. These conditions are typically limited to industrial sewers.
From a structural perspective it seems that spiral-wound pipes can match and even
exceed other forms of trenchless construction liners such as CIPP. On the other hand, there is
very little doubt that these liners cannot match the structural bearing capacities of vitrified clay
pipe or reinforced concrete pipe. These rigid pipes are clearly superior to any liner on the market
in terms of pipe strength. The question then becomes is lining a damaged or deteriorated pipe
with a liner an acceptable form of pipe rehabilitation. According to ASTM and other agencies
responsible for setting pipe standards and approving different products, spiral-wound pipe is an
acceptable option for repairing pipe with structural damage. Although I tend to agree with that
assessment for the vast majority of situations, there are situations in which the host pipe has
suffered severe structural deterioration and needs to be structurally rehabilitated, and the
surrounding soil conditions are not known. When the soil bearing requirements are unknown,
how can you properly identify if a liner is structurally sufficient or not. If you were to directly
bury spiral-wound pipe liner without a host pipe around it, you would have to make sure to
trench, provide good pipe bedding, and properly backfill and compact the soil in order for that
“structural” liner to be adequate on its own. When you are lining a host pipe with a trenchless
spiral-wound liner, most of the time the existing force being exerted on the host pipe is not
known, and the ideal pipe bedding, trench width, and soil characteristics are not available. That
means that the pipe could be seeing up to double the soil bearing load as the same pipe with ideal
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conditions. In conclusion, yes, spiral-wound liner can be used in a fully structural capacity,
given that the surrounding soil bearing conditions are known. This means that special care and
attention needs to be given when determining whether or not spiral-wound pipe liners are
adequate structural members. Spiral-wound pipe liners are definitely advantageous when being
used in a non-structural application. However, when being used in a structural capacity, the
condition of the host pipe is actually important in the decision to use spiral-wound liner. In this
regard, it must be concluded that although spiral-wound liner can be fully structural and support
the full soil bearing weight, in the absence of that soil bearing demand information this liner
should not be used in a fully structural capacity.
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Chapter 4: Alternative Methods
In this chapter, we will explore several different repair alternatives to spiral-wound pipe
liner. We will look at a few different aspects of these competing methods, including ease of
construction, cost, environmental impact, and construction timetable. By the end of this chapter,
we will try to draw some conclusions from this analysis about the main advantages to each
construction method and what situations each method is best suited for.
The first alternative construction method to spiral-wound pipe rehab is a method known
as slip-lining. Slip lining is a method of trenchless pipe rehabilitation. The method works by
pushing precast pipe segments into the host pipe via an access pit. The slip lining segments are
made from layers of fiberglass and resin that are wrapped around a mold. Often two access pits
are required for this method of lining installation. The first pit acts as a pushing or pipe jacking
pit while the other pit is used as a receiving pit. The pipe is pushed into the host pipe either by a
jacking machine that pushes each consecutive segment into the pipe or by manned entry into the
pipeline. Jacking a slip liner into place is done one segment at a time. Each new segment of slip
line pipe pushes the segment in front of it further down the line. This process is repeated until
the liner reaches the downstream, receiving, pit. After the liner is in place the annular space is
filled with grout. This approach to installing slip liner is used in the vast majority of slip lining
projects. The other way in which slip-liner is installed is by manned entry. This approach is
typically only used as a last resort or when jacking simply is not possible. An example of when
manned entry to push pipe is necessary is when slip lining around a curve in a pipe. In this case,
a jacking machine is not able to push the segments of pipe around a curve, so a worker must push
these segments in by hand. Manned entry is also only possible for slip lining of pipes greater
than approximately forty-two inches in diameter. The main advantage that slip lining has as a
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method of pipe rehabilitation is its effectiveness at lining large diameter pipes. Traditional CIPP
(cured in place pipe) liners have a maximum diameter of 120” but are often most effective as
structural liners at a much smaller diameter. Slip liner pipe, on the other hand can be used as a
fully structural option. It can also be constructed relatively quickly, as pipe liners must be
preordered prior to the start of construction. Once the pits are opened, the lining segments can
be installed in a short time frame. It is also a trenchless rehab method, which limits the impact
on the environment and community. However, slip lining is often slower than other lining
methods, since two large pits must be excavated in order to install the pipe segments. The need
for pits during installation make this method more expensive, slower, and they cause a larger
impact in the area where they are installed. The pits necessary for slip lining are one of its main
drawbacks as a construction method. In contrast, large diameter pipes can be lined using spiralwound pipe rehab without excavating large pits to push and receive pipe. Spiral-wound pipe
installation can be done completely through the host pipe’s maintenance holes.
The second method that we will examine is cured in place pipe or CIPP. CIPP lining is a
method of trenchless rehabilitation that is used to rehabilitate existing pipes. CIPP liners have
two components. The first component is a textile liner tube, and the second component is a
liquid resin that hardens after the tube is installed in the host pipe. The fabric tube consists of
one or more layers of non-woven absorbent felt, felt/ fiberglass, or fiberglass. This fabric must
comply with standards put forth by ASTM. The fabric also needs to be capable of both
absorbing and carrying resins. The resin is a corrosion resistant polyester or vinyl ester resin and
catalyst system of epoxy and hardener. When it is properly cured, the resin saturated fabric tube
liner should meet the requirements of ASTM standards. The process starts with what is known
as a wet-out stage. At this time, a textile liner is saturated with a resin mixture with an epoxy
17
base that is hardened with a preset hardener. The method that triggers the epoxy to harden
ranges from hot water, steam, and ambient atmosphere, to UV light. The next step is to install
the resin impregnated liner. The liner is inverted into the pipe using air pressure. At this point
the resin is on the outside of the liner against the host pipe wall. After, the liner is in place a
calibration tube is inserted into the line in order to activate the resin and harden the liner inside
the host pipe. The result of the curing process creates a fitted, smooth, and corrosion-resistant
new pipe wall. In order to reinstate any lateral connections into the newly lined pipe, a robotic
cutting device can be inserted. The typical standard design life of CIPP liners is fifty years.
CIPP liners can be produced both as structural and non-structural liners. Several factors
contribute to the determination of whether a CIPP liner is structural or non-structural. According
to NAASCO, “The physical properties and characteristics of the finished liner will vary
considerably depending on the types and mixing proportions of the materials used, and the
degree of cure executed. It shall be the responsibility of the Contractor to control these
variables and to provide a CIPP system which meets or exceeds the minimum properties” (p.11
NAASCO Performance Specification Guideline). Several physical minimum physical properties
and design parameters are listed in (Table 1). CIPP liners have many benefits as a repair
method. They are a low impact repair method. Many CIPP liners can be installed through the
maintenance hole of the pipe and do not have the need for a pit to be excavated. They also do
not need to be grouted after installation. Rehabbing a pipe using CIPP is also a fast process.
Most installations can be completed in a single day. The installation is also improved by the use
of a UV catalyst to which only hardens the resin mixture in the presence of UV light. UV cured
liners have a more stable curing process than traditional steam cured CIPP. Another advantage
that CIPP has in addition to short construction time and low environmental impact, is that it is
18
relatively inexpensive. Compared with slip lining and even spiral-wound liners, CIPP is a
bargain. A downside of CIPP is that for larger pipes the maintenance hole doesn’t have enough
space, and excavation at the access points is necessary. CIPP also cannot line certain noncircular and irregular pipe shapes. Spiral-wound pipe liners on the other hand can line any shape
pipe and can line any size from within the maintenance hole.
The third method that we will analyze is called Horizontal Directional Drilling. We will
also look at a method that is also similar to Horizontal Directional Drilling called Pipe Bursting.
Both of these methods follow similar procedures to rehabilitate a pipeline. They both require the
excavation of two pits at either end of the alignment in order to install the new lines. One access
pit acts as a pushing, jacking, or bursting pit, into which the new pipe is fed into the alignment.
The other pit serves as a receiving pit, which receives the boring or bursting head that goes in
front of the pipe. The receiving pit can also be used in tandem with the feeding pit to pull the
alignment as it is being pushed or jacked from the other end. This method is not a pipe
rehabilitation method but a trenchless pipe replacement method. In both cases a boring head or
bursting head leads new pipe into the alignment by creating a void in the soil into which a pipe
can be pushed. Pipe bursting utilizes the existing pipe and goes along an existing alignment.
The bursting head is inserted into the pipe and quickly expands outward breaking the host pipe
and creating room to pull a new pipe behind it. This method is often used when an existing pipe
needs to be upsized in order to accommodate a larger demand. Horizontal Directional Drilling,
or HDD on the other hand is used to create entirely new pipelines and alignments. This method
uses a drilling head to drill a hole in the earth into which a new pipeline can be fed. Both
methods can utilize multiple pipe materials in their construction, however HDD is most often
paired with a PVC or HDPE pipe which can be fused together at the jacking pit to create one
19
long segment of uninterrupted pipe. Similarly, pipe bursting often uses a plastic pipe that can be
end welded to form a jointless line which can be pulled or pushed into place easily. The main
advantage for both of these methods of pipe replacement and construction is the fact that they are
trenchless and limit the impact that they have on the surface environment and the community in
which they are installed. Downsides for these methods are that they are expensive and time
consuming. There is a lot of equipment and expensive machinery required in these installation
methods, and pits must be opened in order to construct the pipelines. We have also seen that
PVC and HDPE are generally good materials for most applications, however they do have
weaknesses when exposed to heat and solvent based chemicals. With this in mind, use of these
methods should only be used when it is known that there won’t be any long term or sustained
exposure to these elements. On additional positive for these methods is that since you are either
drilling into native soil or bursting pipe and compacting the soil surrounding the pipeline, soil
compaction concerns shouldn’t be a problem when using these methods.
The last method of constructing or replacing pipe in the ground is to dig a trench down to
the pipe level and repair or install new pipe. This is the most traditional method of pipe repair
and construction. Open trench remove and replace is the oldest and the most straight forward
method available to civil engineers. In this method a trench is excavated along the alignment,
trench shoring is installed, and the pipe is repaired by workers in the trench. This method also
allows for the repair of a small segment of pipe along a pipe alignment instead of removing and
replacing the entire pipe reach. These small segment repairs are known as spot repairs. Open
trench remove and replace has a wide range of pipe materials available for use. These include:
vitrified clay pipe (VCP), reinforced concrete pipe (RCP), PVC, HDPE, and cast-iron pipe (CIP).
Essentially all pipe materials that are available today can be used in open trench construction.
20
Open trench construction has the benefit of controlling almost every aspect of pipe installation
from a structural perspective. The open trench method gives the engineer complete control over
the structural longevity and viability of the pipe by allowing them to make choices about every
facet installation from the choice of the pipe material and trench width, to backfill material, and
pipe bedding material. When an engineer chooses to remove and replace a pipeline, he or she
can monitor and tailor the factors that have structural significance to the pipe. For this reason,
pipes chosen to be replaced using this method are often in the most severe need of rehabilitation.
When the structural integrity of a pipeline has degraded past a certain point, simply lining the
reach is not advisable or at times not even possible. In these cases, the pipe must be dug up,
removed, and replaced. In our study of this method we will look specifically at vitrified clay
pipe as a pipe material that is often used in sewer pipe construction. Vitrified clay pipe or VCP
is one of the strongest pipe materials available today. Tests to determine the bearing strength of
VCP are set by the American Society for Testing and Materials (ASTM) and are standard across
the country. The three-edge bearing strength tested for a 12” VCP is 2600 pounds per linear
foot. Compare this bearing strength with that of other pipe and liner strength tests. Across the
board, the National Clay Pipe Institute, insists that its testing of its pipes is the most rigorous and
meets the strictest standards in the industry. This strict adherence to high standards is born from
the fact that in decades past VCP has failed to meet the requirements necessary for sewer pipe.
This failure was due in large part to the fact that vitrified clay pipe is a rigid conduit. This
rigidity gave the pipe strength to bear large soil loads but made the pipe joints weak when loaded
with shear loads at the joints. In order to alleviate these shear force failures, the clay pipe
industry introduced flexible compression joints to clay pipes in the form of rubber compression
couplings to straight joints and polyurethane or polyester gaskets and O-rings to bell and spigot
21
joints. In addition to these improved joints the NCPI created new tests to prove that the flexible
joints had solved the problems of joint cracking and leaking joints. These tests included a
compression joint test, which simulates joint performance under conditions of shear load and
angular deflection. When loaded with 150 pounds per inch of nominal diameter and filled with
10 feet of head water pressure the joint “shall not leak” for a test period of 1-hour. This test and
several others have made the VCP manufacturing process one of the strongest, and vitrified clay
pipe meets the highest of standards set forth by ASTM. VCP has many other properties which
make it ideal for service in the corrosive conditions found in many sewer lines. It is made of
sustainable material. It has a high level of rigid strength, and flexible watertight joints. It is an
inert material and will not rust, corrode, shrink, elongate, bend, deflect, erode, oxidize, or
deteriorate over time. There are VCP pipes in service today that are over two hundred years old
and going strong. VCP has many advantages and positives as a sewer, or storm drain pipe
material. It is also able to be jacked into place using trenchless methods. However, the majority
of VCP is still installed using open trench construction. Open trench is often the cheapest option
available. It also allows for the best possible structural scenarios for pipe installation. On the
negative side though, it is often a lengthy construction process because of the excavation
required. It also causes the greatest impact to the community and the environment. Because of
these downsides open trench construction is often looked at as a last resort, especially in crowded
urban settings where disrupting the surface comes with a large amount of coordination and
negative effects including street closures, traffic problems, and political pressure. On the other
hand, the thought of 100-200 year design life after installation is a tempting reason to consider
this method of repair, especially when the alternative liner is often more expensive to install and
comes with a max design life of 50 years.
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Chapter 5: Conclusion: When to use Spiral-wound
Spiral-wound pipe liners are a very attractive new method for rehabbing pipe. There are
many benefits and positive aspects to repairing pipe using this method. Chief among these
benefits are the ability to rehabilitate pipe entirely within the hosts pipe maintenance holes. In
addition to this advantage, spiral-wound pipes can line pipe in live flow conditions of up to thirty
percent flow in the host pipe. They are also simple to install, can line any pipe shape, and are a
very cost-effective repair option when compared with other more conventional pipe repair
methods. Spiral-wound pipes have an advantage over slip lining because they don’t need access
pits to be excavated in order to repair damaged pipe. They also have that same advantage over
traditional pipe and trench or remove and replace options as they do not require any excavation.
They also have advantages over CIPP liners, which are probably the most direct competition for
spiral-wound pipe liners. The advantage that spiral-wound has over CIPP is ease of installation
and no pipe size or shape restrictions. CIPP resins need to be cured for the liner to be hardened.
This curing process can be tedious and difficult and opens the door to flaws forming in the liner.
CIPP also cannot line pipe over about thirty-six inches in diameter without additional excavation
as the liner fabric tube has difficulty fitting through the maintenance hole lid. Shape restrictions
are also a problem for CIPP. Although, liners can be custom ordered to fit any shape, the most
common CIPP liners are circular. Ordering a non-circular CIPP liner will incur additional costs,
whereas spiral-wound strips have the ability and versatility to line any shape for the same cost
per linear foot.
With all these advantages being noted, there are applications and situations in which
spiral-wound pipe liners are not the best choice for a pipe repair. For instance, a host pipe with
severe structural damage that is relatively close to the surface might be better served by a
23
trenched remove and replace method. Remove and replace gives the engineer a greater deal of
control over the pipe loading, because you can choose the trench width at the top of pipe, pipe
bedding case, and soil and backfill. These factors have the ability to greatly affect the loading a
pipe will see in its service life (Table 4). Structural liners in general cannot be prepared for the
loads they might see while in service because the loads are unknown and unknowable in
trenchless construction situations. A liner might be very competent when loaded with a typical
structural bearing load, however loads on host pipes can be very atypical in certain
circumstances. It is hard to claim that a liner is a structural member when the knowledge about
the loading varies drastically from case to case.
In conclusion, spiral-wound pipe liners are an intriguing and very versatile new
technology that has a wide range of applications in pipe repair and rehabilitation. It is a perfect
answer to many of the problems that face engineers working in the pipe rehab industry. It is easy
to install, versatile, low impact, and cost effective. It fills several gaps in the market that other
methods cannot, and it provides certain unique features like the ability to fit entirely inside a
maintenance structure without excavation and the ability to fit host pipes of any shape and size.
It is definitely a competitor to other lining methods that offers many advantages over the
competition. At the same time there are areas and situations where spiral-wound is not ideally
suited. Spiral-wound pipe makes the claim of being fully structural. However, based on the
evidence provided, it seems to be missing some key data that would allow it to be the best choice
as a fully structurally capable liner. In that respect, if a structural liner of any kind is needed to
rehab a pipe that is severely damaged, it seems that the best option for the long-term
serviceability of that pipeline is to remove and replace the pipe with a rigid pipe material such as
vitrified clay pipe (VCP). VCP is even a better than reinforced concrete pipe because of its inert
24
properties and long service life in the presence of corrosive conditions. The impressive material
and structural properties of VCP make it the ideal pipe material for severely damaged pipe
replacement. Spiral-wound simply isn’t the best option in these situations. In the end, spiralwound works in many other situations, and is often the best option for lining pipe that is mild or
moderately deteriorated. Trenchless construction is becoming more and more advantageous and
necessary in today’s busy cities where traffic, community, and environmental impact concerns
are taking center stage in the construction of underground pipe systems. Spiral-wound’s ability to
act as a truly trenchless construction method make it hugely appealing to water resource and
water collection engineers.
25
References
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(2017). PDF.
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https://en.wikipedia.org/wiki/High-density_polyethylene.
Known Limitations of Cured-in-Place Pipe (CIPP) Technology. (2018). Retrieved December 2,
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Langenbach, K., & Melville, S. (2018, November 2). PDF.
NASSCO Tech Tips - Spiral Wound Liners. (2019, June 7). Retrieved October 29, 2019, from
https://sekisuispra.com/spiral-wound-nassco/.
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Polyvinyl chloride. (2019, November 1). Retrieved November 4, 2019, from
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Rehab Technology Selection Guide. (2019, July). Underground Construction, 29–41.
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Spiral Wound Liners: Pipe Rehabilitation. (n.d.). Retrieved November 09, 2019, from
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SRP-EXP Spiral Ribbed Pipe. (n.d.). Retrieved November 10, 2019, from
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Tinberg, F. Specifications For Machine Spiral Wound PVC Liner Using The SPRTM EX Method.
(2010). https://www.nassco.org/sites/default/files/091211%20-%20SPR%20EX.pdf. Roseville.
TT Staff. (2015, October 23). Kansas City Water Services Turns to Spirally Wound Relining.
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What is CIPP? - Flow-Liner® Systems. (2018). Retrieved November 14, 2019, from https://flowliner.com/cipp.
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Appendix A: Tables
Table 1: CIPP Liner
Table 2: SPR Profiles
28
Table 3: Spiral Wound Properties
29
Table 4: Pipe Strength/Bedding Cases
30
Appendix B: Figures
Figure A:
Figure B:
Figure C:
31
Figure D:
Figure E:
Figure F:
32
Figure G:
Figure H:
33