Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative Materials for PVC Pipes

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The regular bursting of PVC pipes exposed by land erosion has been a great worry to consumers and water distribution companies. This work therefore, focuses on the use of multi-objective decision-making approach to choose alternative material that is non-toxic, corrosion resistant, cheap, UV radiations resistant and tough. Initial screening of the materials universe was done by using a set of non-negotiable requirements in CES EduPack software (Version 12.2.13). Performance equation and materials index were derived for a cylindrical pipe subjected to both internal and external pressure using a set of objectives and constraints. The index was plotted on a chart of fracture toughness against yield strength which returned six candidate materials. Digital logic method was then used to rank the candidate materials for the water pipe and the results showed that poly-ethylene terephthalate (PET) had the highest weighted property index followed by polyvinyl chloride blend (ASA/PVC (unfilled)), with the least being polyethylene ultra-high molecular weight (PE-UHMW). Employing stiffness and density criteria, ASA/PVC (unfilled) is the most suitable material for water pipe application in tropical environment.
Journal of Science and Technology
ISSN: 2456-5660 Volume 5, Issue 1, Jan-February 2020, PP 29-42 29 | Page
Material Selection for Water Pipes by the Multi-Objective
Decision-Making Method: The Case of Alternative Materials for
PVC Pipes
Emmanuel K. Arthur1, Emmanuel Gikunoo1, Frank O. Agyemang1, Salifu T.
Azeko2, Anthony Andrews1, Abigail Twenewaa1
1(Department of Materials Engineering, Kwame Nkrumah University of Science and Technology, Ghana)
2(Department of Mechanical Engineering, Tamale Technical University, Ghana)
Abstract: The regular bursting of PVC pipes exposed by land erosion has been a great worry to consumers and
water distribution companies. This work therefore, focuses on the use of multi-objective decision-making
approach to choose alternative material that is non-toxic, corrosion resistant, cheap, UV radiations resistant
and tough. Initial screening of the materials universe was done by using a set of non-negotiable requirements in
CES EduPack software (Version 12.2.13). Performance equation and materials index were derived for a
cylindrical pipe subjected to both internal and external pressure using a set of objectives and constraints. The
index was plotted on a chart of fracture toughness against yield strength which returned six candidate
materials. Digital logic method was then used to rank the candidate materials for the water pipe and the results
showed that poly-ethylene terephthalate (PET) had the highest weighted property index followed by polyvinyl
chloride blend (ASA/PVC (unfilled)), with the least being polyethylene ultra-high molecular weight (PE-
UHMW). Employing stiffness and density criteria, ASA/PVC (unfilled) is the most suitable material for water
pipe application in tropical environment.
Keywords: Water pipe, Material index, Weighted Property Index, polyvinyl chloride, polyvinyl chloride blend
1. Introduction
Portable drinking water is of major concern in most developing countries. The distribution of the
portable water plays a key role in transporting it to consumers [1]. The distribution cannot be possible without
channels connecting distribution centres to consumers. These water supplying channels includes pipes, fittings,
coating, valves, and other adjuncts with various materials. Generally, hollow cylindrical pipes are used to supply
water from treatment plants to consumers. The pipes come in various classes of materials (such as plastics,
metals and ceramics); and various sizes for the desired use.
Different materials are used to convey water and the type of material used depends on the type of
application and the quality of water needed. The most common pipe materials include concrete, reinforced
concrete and metals (ductile iron, copper, lead, stainless steel and galvanized steel). Other piping materials
include plastics such as high-density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP) and
cross-linked polyethylene (PEX)) [2]. PVC pipe is commonly used for conveying drinking water due to its
relatively low cost, moderate toughness, strength, chemical inertness, light weight and widely developed
processing methods [3, 4]. More often than not, PVC pipes used to transport water to buildings are laid
underground for safety reasons and to protect the pipes from UV radiations. However, the use of PVC pipes is
proving to be problematic since land erosion exposes these pipes. Due to the effect of climate change on the
ozone layers, the tropics are experiencing increasing amount of UV-radiations which poses danger to the
exposed PVC pipes [5, 6]. This embrittles the PVC materials degrades and fracture on the slightest impact [4, 7,
8]. Pipes laid underground but exposed in drains are also not spared as they are regularly pierced.
Maintenance cost and water that goes waste from such activities drain on the economy of the country. The
continuous wastage of water from the burst pipes creates gullies on untarred roads making it very difficult for
these roads to be accessible by cars. Hence there is the need for designers, engineers and manufacturers to
search for new and superior materials for performance improvements while maintaining or reducing the cost of
the material.
There are over 160,000 materials available with each having its own characteristics, applications, advantages,
and limitations [9]. Selecting quality materials for engineering designs therefore requires a better understanding
of the functional requirements for the product needs [10]. The quality of pipes for water distribution is known to
depend on the size of pipes, their composition, and properties. The economic aspects of the material, such as
availability, cost of raw materials, and cost of manufacturing, are also equally important [10, 11]. Several
engineering and technology journals [12, 13] emphasized on the need to apply technological innovations to the
material universe. Other researchers [14, 15, 16] also saw the need to apply technological management to
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 30 | Page
existing materials in the universe and this allows proper design concepts and utilization of materials. Therefore,
choosing the best suitable material using traditional design approach may result in materials with superior
performance being missed out during the selection process. This makes the selection of an optimal material for
our engineering design a multi-objective decision-making problem. This study is hoped to provide a high value
to the design and materials research community for the selection of suitable materials for any application.
2. Materials for Water Pipes
Water pipes have seen tremendous changes in materials since metals were first introduced. Polymers
and ceramics have all been used over the years. Numerous factors (viz.: properties of materials, performance
requirements, material’s reliability, safety, physical attributes, environmental conditions, availability,
disposability and recyclability, and economic factors [17, 18] affect the choice of these ranges of materials.
Generally, these pipes are grouped into three categories: metallic, concrete and plastic pipes. Metallic materials
commonly used for water pipe construction are copper, lead, steel and cast iron with plastics being high-density
polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP) and cross-linked polyethylene (PEX) [19,
20]. Copper piping are commonly used in the construction industry for transporting water and also
channeling refrigerant used in the heating, cooling, and air-conditioning systems. Copper pipes are used due to
their excellent corrosion resistance and reliability during connections. The pipes are mechanically strong and are
mostly installed above-ground due to its good UV resistance. Copper pipes can lose a lot of heat through the
walls if the pipe is not properly insulated because of its high thermal conductivity. Copper’s major disadvantage
is its relatively higher density and cost.
Lead is another metallic material used for conveying water. It is malleable, flexible and corrodes
relatively slowly [21]. Lead pipes were one of the first materials employed in the transportation of water to
households. It is therefore not a surprise for the term plumber to be derived from the Latin word for lead.
Intensive research which has associated certain health problems with the usage of lead has led to the banning of
its use in home water transportation with the exception of some vents and drainage systems [21, 22]. Lead that
can dissolve from the lead pipes into the drinking water is of major health concern, particularly as lead ingestion
has been demonstrated to reduce the intelligent quotient of young. The amount of lead that builds up in the
drinking water depends on its corrosivity and how long the water is in contact with the lead pipe [23]. However,
their extensive use in industry still continues due to their earlier discussed properties which are difficult to
obtain from other materials. In industries, lead with up to 6 wt.% antinomy find applications in areas which
include chemical plants, nuclear plants, paper manufacturing plants and hydro and plating applications.
Iron, another metallic material is commonly used. Its steel variant is used in the laying of pipelines and
for internal plumbing. Steel pipes are comparatively expensive, but are the strongest of all water pipes. They
have very low flexibility and can withstand high water pressure, come in convenient lengths and incur lower
installation costs. However, the use of steel pipes is problematic where water flow is slow or static for periods of
time because it causes rust from internal corrosion. Moreover, it has relatively high susceptibility to corrosion
and this can lead to heavy metal poisoning of consumers. They may also give an unpalatable taste and smell to
the water conveyed under corrosive conditions. Steel pipes are coated with zinc to reduce high susceptibility to
corrosion under the influence of water. This is because zinc is more active metal that oxidizes rapidly, thus
protecting steel pipes from corrosion. Steel pipes are therefore well suited for long-term installations and mostly
buried underground due to its hardiness and resistance to breakdown.
Concrete, another class of materials, are also employed in the water transportation system. Concrete are
materials produced from mixtures of mortar and coarse aggregates. Pipes made from concrete are noted for its
high strength and durability. They are mostly immune to the effects of environmental factors and therefore do
not rust, bend, or burn. They have the structural integrity needed to withstand an incredible amount of use over
decades. Although concrete is highly susceptible to fracture due to their brittle nature, they are used in piping
applications were property requirements discussed above permit. Concrete pipes are sometimes also reinforced
with still rods to impart some tensile properties. Reinforced concrete pipes are buried in areas where moisture
conditions are present. This allows for autogenous healing. Other disadvantages of concrete pipes include their
bulkiness and heaviness. They are also costlier to handle, install and transport. Concrete pipes however find
widespread applications in storm water drains, culverts and sewers.
Polymeric materials are the most used materials in pipping for water distribution. They have
appreciable fracture toughness, with the required flexibility. Polymer pipes installed in walls of buildings
usually melt during conditions such as fire outbreaks that result in high temperatures [24]. Polymeric materials
used for the manufacture of water pipes include polyethylene (PE), polyvinyl chloride (PVC), polypropylene
(PP) and cross-linked polyethylene (PEX).
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 31 | Page
PE pipes have recently found widespread application in water and sanitation systems. Their relatively
low prices, quick and easy implementation and repair speeds have contributed greatly to their increasing use
[25, 26]. These pipes have high UV radiation resistant, high impact strength and show resistance to cracking,
even at low temperatures. PE pipes have a long lifespan and are relatively easy to maintain. PE pipes, just like
most polymeric materials, are also stable in most aqueous media. Various additives are included in PE to modify
its properties for various applications. The modified versions are the high density polyethylene (HDPE),
medium density (MDPE) and low-density (LDPE) pipes. These modifications are required mainly due to the
high pressures sustained in the use of PE pipes [27]. Applications of PE pipes include usage in water supply
networks, rural sewage networks, drainages systems, fluid systems and industrial sewage, and irrigation
systems. PEX pipes are current modification of PE pipes. PEX pipes are variants of the HDPE with crosslink
structures. PEX pipes are gradually replacing copper and steel pipes in building services systems, hydronic
radiant heating and cooling systems, and domestic water piping system [28]. PEX pipes are highly susceptible to
UV radiation exposure and are therefore mainly used buried in the ground. PEX pipes have limited temperature
applications because of their low melting temperature of 400 °C. However, their thermal conductivity is much
lower than copper pipe and hence energy loss along the length of PEX pipes is minimized. Water movement
through PEX pipes is also quieter than through the metal pipes. Cost of PEX tubing is much lower and they are
flexible compared to copper and other metallic pipes. Hence their new use in household water heating systems
in place of copper pipings.
PP, another class of polymer, produces pipes that are lightweight with high impact strength and can
easily be joined using heat fusion welding. PPs have relatively high abrasion resistance and good thermal and
electrical insulating properties. They are resistant to many reagents such as aqueous solutions of acids, alkalis
and salts, and to a large number of organic solvents. However, PP pipes are not used in strong oxidizing
environments, such as chlorinated hydrocarbons solutions. PP melts at 170 °C and therefore can tolerate
temperatures up to 110 °C only for short periods. It is also able to retain its strength at temperatures as low as -
50°C. PP is thermoplastic material which can be recycled and hence do not pose environmental problems after
their use.
PVC is the last group of polymeric materials employed extensively in the construction of water pipes.
It is the second largest thermoplastics material by volume behind PE used for the production of water
transportation pipes [20]. It finds application mainly in piping for drainage, water supply and electrical
insulations. Of all the thermoplastics, PVC pipes are found to be the most rigid and strongest thermoset and thus
not flexible enough to withstand turbulent flows. It is relatively cheap, lightweight and has high tensile strength
and modulus of elasticity compared with other thermosets [29]. The melting point of PVC ranges between 100
°C and 260 °C depending on the additives to the PVC during manufacture. The rigid PVC has a small linear
expansion coefficient and also possesses good flame retardancy. Pipes made of PVC material has a maximum
operating temperature of 82 °C (its glass transition temperature) above which they begin to degrade and break
down. PVC although employed extensively in domestic applications, can therefore not be used in cases where
hot water transportation is involved.
The rigidity of PVC pipes makes them prone to fracture if exposed to the environment as shown in Fig.
1. PVC is amorphous and contains carbon chloride bonds which require less energy to cleave, further making it
a lot easier to crack or split. PVC pipes can easily be joined. Joining is mainly done by employing a gasket-
sealed joint. At temperatures below the freezing point of water, PVC joints tend to separate due to its high
shrinkage in the cold and also the its increase in brittles as the temperatures decreases below the freezing
temperature of water. Degradation of the PVC during its service life is attributed to the breakdown of the
molecular bond between the chlorine atoms and the polymer chain prior to its melting [20]. This can be
mitigated by adding stabilizers in the form of metal-based compounds to enhance PVC’s durability and stability.
Although, addition of stabilizers can sustain long service life compared with unplasticized PVC pipes, they
eventually become brittle when exposed to the UV radiations for long periods. This and other PVC adverse
environmental-induced oxidation during service leads to its deterioration in its performance during its lifespan
[30]. In light of this, the material to be selected as a replacement for PVC pipes, must be stable on exposure
to UV radiations, tougher than PVC, flexible, nonetheless chemically inert to water to avoid poisoning
consumers, and also relatively cheap to use.
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 32 | Page
(a) (b)
Fig. 1. picture showing (a) exposed pvc water pipes in gutter and (b) fractured above-ground pvc pipes.
3. Stages of Materials Selection
3.1 Design Requirements and Translation
A systematic design-oriented six-step approach (as shown in Fig. 2) was used to select an alternative
material for PVC water supply pipe. In a quest to find the material for the water pipe, the reason for choosing
the design, functional and environmental requirements for the water supply pipe were tabulated in Table 1. The
design requirements were further translated into function, objective, constraints and free variables as shown in
Table 2. Table 1. Design requirements for water supply pipe
Pipe requirement
Must be tough enough so that it cannot crack when exposed above-ground.
When an underground pipe line is exposed, any impact usually breaks the
pipe. This requires the pipe to have high fracture toughness.
Injection mouldable
Must be easily shaped into tubes for transporting water.
Corrosion resistant
It should not corrode/degrade when carrying water containing dissolve ions.
UV radiation resistant
It should not degrade when exposed to UV radiations from sun-light.
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 33 | Page
Fig. 2. a systematic design-oriented six-step materials selection approach.
Table 2. Translation of design requirements for water pipe
Water supply pipe
1. Injection mouldable
2. Higher fracture toughness than PVC (KIC 3.705 MPa.m1/2) *
3. Good hardness
4. Good corrosion resistance
5. Durability in fresh water
6. Durability in salt water
7. UV radiation resistant
Maximize fracture toughness
Free variable
1. Choice of material
2. Thickness of the pipe
*The fracture toughness constraint of 3.705 MPa.m1/2 is the fracture toughness mid-point value for un-
plasticized polyvinyl chloride (PVC). The value was obtained from CES Edupack software (Version 12.2.13).
3.2 Screening: Property Limits on Chart
The next stage of the selection process after translation of the design requirements involved screening
the materials universe by using the property limits. Using the advance level three (3) database of CES EduPack
software (Version 12.2.13), a few materials were obtained as a result of screening by setting the non-negotiable
requirements (constraints) on the material. Variety of constraints such as fracture toughness, corrosion resistant,
UV radiation resistant, durability in fresh water and salt water (shown in Table 3) were entered under the limit
stage of the CES EduPack software. All engineering materials in the software were used as starting materials for
the screening process. Table 3. Constraints set under limit stage.
The tree stage of advanced level three (3) database of the CES EduPack 2013 software was also used to
superimpose mouldability constraint. This eliminated a few of the materials. Further elimination of several
engineering materials was done by deriving the materials index using the objective and constraints set in Table
2. This was achieved by using both the design guidelines obtained from the material index and the graph stage
in the CES EduPack software.
3.3 Computer-Aided Screening: Derivation of Materials Index
The next step was obtaining from the subset of materials that meet the property limits, those that
maximize the performance of the water supply pipe. The performance equation for the pressure, p, of the
cylindrical tube under pressure from the flow of water was derived. For simplicity, the water supply pipe was
assumed to have a finite length with both uniform radial and axial pressure as shown in Fig. 3.
Durability: Fluids and Sunlight
Corrosion Resistance
Water (fresh)
Water (salt)
Set limits
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 34 | Page
Fig. 3. finite cylindrical tube under internal pressure (pi) and external pressure (po)
The cylindrical tube was considered to have a specified diameter, D, with a wall thickness, t, (the free
variable) smaller compared with D. When water tube is externally struck, the external pressure exerted on it
was obtained by using the relation deduced by Timoshenko and Gere (1961) for a finite thin-walled cylinder.
The critical elastic pressure, , for a thin-walled finite cylinder of a perfect circular shape was given as
where E is the elastic modulus, is the Poisson’s ratio, t is wall thickness of the cylinder and D is the diameter
of the cylinder.
The minimum tube thickness, t, needed to support the elastic pressure, p, (from (1)) is given as:
However, the water in the tube also generate internal pressure that act on the internal walls of the cylindrical
tube. The internal yield pressure is given as:
Materials selected for water pipping must be such that the external pressure on the water supply tube
should not exceed the yield stress of the material used to make the pipe. Therefore, the material for the water
supply tube should have the right mechanical properties (such as yield strength, hardness and fracture
toughness) and length-diameter and thickness-diameter ratios. The water tube should not fail by fast fracture;
this requires that the wall-pressure of the pipe must be less than . The water tube must be designed in such a
way that the stresses everywhere are less than that required to cause fracture (at crack length of ac). This
condition called leak-before-break criterion gives the allowable stress as [17]:
The wall thickness, t, of the pressure vessel must also contain the pressure, p, without yielding. From (3), this
means that:
Substituting (5) into (4) to eliminate the free variable t (with σ = σy) gives:
Using Ashby's material selection approach [18], the performance of the pipe under consideration was calculated
by the equation:
The material part of the (7) gives the material index and therefore from (6) the material index that maximizes
performance is given as:
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 35 | Page
3.3.1 Ranking: Material Index on Charts
The material index was further used to eliminate more materials which fall short of the requirements. A
chart with on the y-axis and on the x-axis was generated with the CES EduPack software as shown in
Fig. 4. The materials selection index derived in (8) and the predetermined constraints require that the best
processing route for the candidate material should be by the injection moulding technique. This is the most
suitable method of manufacturing hollow members. This further puts a restriction on the material to be selected
from the group of polymeric materials according to Fig. 4. A CES generated material selection chart of
against was plotted. A performance index (design guideline) which is a straight line with a slope of 0.5 was
plotted on the chart as shown in Fig. 4. All the engineering materials which lie on the line will perform equally
based on the 0.5 criterion. Those which lie above the 0.5 criterion will performer better, and those farther above
the line are the best materials [10]. The search engine rejects all materials with attributes that lie below the
plotted design guideline.
The materials obtained in the search region window are Acrylonitrile styrene acrylate + polyvinyl
chloride blend (ASA/PVC (unfilled)), polybutylene terephthalate (PBT), polycyclohexylene-dimethylene tere/
isopthalate copolyester (PCTA), polycyclohexylenedimethylene terephthalate glycol copolymer (PCTG),
polyethelene ultra high molecular weight (PE-UHMW) and poly-ethylene terephthalate (PET). This implies that
these materials are possible candidate materials for the manufacture of water pipes.
Fig. 4. CES generated material selection chart of against with performance index gradient line of 0.5.
It could be seen from the candidate materials that ceramics, metals and composites were screened out. Although,
ceramics/glasses and all alloys are known to have excellent UV radiation resistance, ceramics were eliminated
due to its low fracture toughness. Also, due to metallic alloys’ low corrosion resistance; all metallic alloys were
screened out. Metallic alloys which can even withstand corrosion are expensive to use for water pipes. Some
composites and polymers are known to have excellent UV radiation resistance but due to composites’ high cost,
they are not considered. The properties of the candidate materials are listed in Table 4. Digital logic (multi-
objective optimization) method was then used to select the best candidate material that can serve the purpose of
the water pipe. The multi-objective optimization method compromises between several conflicting objectives in
the material selection process.
Table 4. Properties of candidate materials obtained from CES EduPack software database
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 36 | Page
Note: (a) 5- Excellent, 4- Very good, 3- Good, 2-Fair, 1- Poor. Data obtained from [Ref.]. Mid-points of data
ranges were used.
(b) 5- Very inexpensive, 4- Inexpensive, 3- Moderate price, 2-Expensive, 1- Very expensive.
* Mouldability was scaled by using the upper end of melting temperature range from the CES Edupack
Where ASA/PVC = Acrylonitrile styrene acrylate + polyvinyl chloride blend,
PBT = polybutylene terephthalate (60% filled with long glass),
PCTA = polycyclohexylenedimethylene tere/isopthalate copolyester,
PCTG = polycyclohexylenedimethylene terephthalate glycol copolymer,
PE-UHMW = polyethelene ultra high molecular weight and
PET = polyethylene terephthalate.
3.3.2 Digital Logic Method
The digital logic method (DLM) was used to rank the candidate materials obtained with the CES
Edupack software in Section 3.1. Table 4 shows the properties of the candidate materials that were used for the
ranking purposes. In DLM, multiple properties such as mouldability, fracture toughness, corrosion resistance,
UV radiation resistance, elastic modulus and yield strength were considered for the optimum selection of the
materials. The properties of the materials were scaled based on their respective weighting factor and the
respective scale values obtained presented in Table 4.
The fracture toughness of water supply pipes is important to resist fracture when striked. While the UV
radiation resistance is given high rating to curb the degradation problem faced with the PVC pipes. Mouldability
was given next priority followed by corrosion resistance and elastic modulus. The properties with the 21 number
of decisions, and corresponding weighting factor are given in Table 5. From Table 4, it can be seen that
mouldability and corrosion resistance have the highest weighting factors followed by fracture toughness and UV
radiation resistance, whereas the least important properties are elastic modulus obtained lower weighting factor.
Materials with higher fracture toughness are more desirable for water piping applications. The scaled
values were calculated using (8). Materials properties such as fracture toughness, yield strength and hardness
must be relatively high. These properties were scaled using (9) (Maleque et al., 2010). Other properties that
cannot be measured (eg. mouldabiliy, UV resistance and cost) were rated in proportion.
The scaled values of properties of materials that can be measured were calculated in Eq. (8) and the results are
given in Table 6.
Journal of Science and Technology
ISSN: 2456-5660 Volume 5, Issue 1, Jan-February 2020, PP 29-42 37 | Page
Table 5. Determination of relative importance of properties using pairwise comparison
*where n is the number of properties considered.
The property that is considered to be the more important of the two is given a 1 and the less important property is given a 0.
Number of positive decisions, N
Factor (α)
1. KIC
2. UV resistance
3. Corrosion
4. Mouldability
5. Hardness
6. yield strength
7. Cost
Journal of Science and Technology
ISSN: 2456-5660 Volume 5, Issue 1, Jan-February 2020, PP 29-42 38 | Page
Table 6. Scaled values of properties of each candidate material
*Mouldability of the candidate polymers was scaled using upper limit of the melt temperature range from the
CES 2018 materials properties database. The upper limit usually applies to injection molding.
Weighted property indices ) were calculated using (9) (Maleque et al., 2010).
= (9)
where β is the scaled property, α is the weighting factor and i is summed over all the n
number of relevant properties.
Table 7. Calculated Weighted Property Performance Index
The corrosion and UV resistances of all the materials are 19 and 9 respectively.
Fig. 5 shows a plot of weighted property index against candidate materials. The digital logic index
showed that PET has the highest weighted performance index followed by ASA/PVC (unfilled), PBT (filled)
and PVC. Other materials having lower weighted performance index than PVC material are PCTA, PCTG and
PE-UHMW. Clearly, PCTA, PCTG and PE-UHMW were not considered because their respective weighted
property indices were below that of PVC which needs to be substituted. The weighted property index showed
that PET is a better candidate material than the other candidate materials when density and flexibility are not
considered. However, for easy transportation and installation, density must be considered while for ease of
installation around bends, flexibility is a necessity.
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 39 | Page
Fig. 5. Plot of weighted property index against the candidate materials.
PET (unfilled semi-crystalline) has a higher density of 1.39 kg/m3 compared to 1.21 kg/m3 for
ASA/PVC (CES EduPack Software, 2018). Also, PET has a Young’s modulus of 2.98 GPa higher than the 2.05
GPa of ASA/PVC. Therefore, the relatively high density and Young’s modulus of PET does not make it a better
choice for consideration in water piping materials. PBT with similar composition to PET, cost almost the same
as PET and its weighted property index is also similar to the weighted property index of PET. However, PBT is
a high-performance material with relatively high molecular weight, strong and stiffer than PET. As a result,
PBT was eliminated due to its relatively high density and rigidity compared to that of PET. PBT (filled) could
be candidate material but due to its relatively high cost it was also eliminated. Recent studies have shown that
several grades of PBT and PET are flammable and also need UV protection for outdoor uses. Improvement in
the UV and flammability properties of these polymers comes at a cost.
Relying on the weighted property index of ASA/PVC (unfilled), its light weight, flexibility, and
fracture toughness as summarised in Table 3, ASA/PVC (unfilled) has better material properties for use in
underground water transportation pipes. PVC alone softens when subjected to temperatures above 65 oC while it
becomes brittle when exposed to UV radiations (Zhang et al., 2013). Acrylate rubber in ASA provides
exceptional resistance to UV degradation. The acrylate polymer also gives high impact strength when added to
PVC. Addition of ASA fraction in PVC has been reported (Rimdusit et al., 2014) to show improved UV
radiation resistance and weatherability of the polymer for outdoor applications (Zhang et al., 2013). Researchers
have shown that ASA has a heat distortion temperature of 90°C at 1.8 MPa which is higher than the 70°C
exhibited by PVC. ASA also exhibits superior weathering durability, impact, and chemical resistances than PVC
(Han et al., 2009; Zhang et al., 2013). The ASA in PVC improves the HDT of PVC without sacrificing
Combination of PVC and ASA therefore reduces the challenge of photo degradation by UV rays
experienced by PVC while improving its properties exploited in water piping materials. The resulting ASA/PVC
material is stronger and resistant to adverse weather. Therefore, based on the multi-objective decision making
approach ASA/PVC blend is the most suitable material based on the aforementioned functional requirements of
water pipes. ASA+PVC blend satisfies the constraints and the objectives under consideration.
3.4 Implication of Results
Poor selection of material for water supply pipes, may lead not only to failure of the material but also
to unnecessary cost which can have significant implications on the economy, health and water scarcity. Failures
arising from PVC material selection are common in Africa where a significant quantity of water is lost via
leaking water pipes, causing huge financial loss and environmental pollution (Adedeji et al., 2017). Population
explosion and insufficient supply of water are already mitigating factors that researchers are looking into since
that is likely to be a major concern in the very near future in most of African countries. Hence the continuous
use of conventional PVC pipes, which has been a major source of water loss as a result of bursting of the PVCs
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 40 | Page
do result in supply deficiency. The deficiency arises as result of the reduction in the overall quantities and
pressure and in other cases the introduction of pollutants (Xu et al., 2011).
It worth to mention that, if PVC water supply pipes are continuously used, it can cause more financial
lost to water transporting utilities. It has been reported (Romer et al., 2005; Adedeji et al., 2017) that, water loss
constitutes major challenge to water utilities around the world. Also, when these pipes burst, pollutants can
affect the quality of portable water which can cause health challenges. With the adoption of proposed material
selected in this work, it will limit the high risk of pipe bursts and its associated menace.
A clearer fundamental understanding has also been provided on how to select materials, using the
materials indices method while meeting multiple and/or conflicting constraints. Knowledge provided in this
work will be able to guide designers, engineers, students and educators on how materials selection systematic
and efficient steps are used in selecting a suitable material for a given application.
This work has also addressed the challenges of frequent failure of PVC pipes by employing systematic
approach of screening and ranking engineering materials based on materials indices and digital logic method.
Moreover, the findings will ensure that water consumers use appropriate materials for transporting water to their
households. If proper material is not selected for water pipes, the reliability of the pipe will tend to be highly
unpredictable. Therefore with systematic materials selection procedures discussed in this paper, long term
success and integrity of the water pipes would be guaranteed.
4. Conclusions
In this paper, a case study on the selection of materials for water pipes is outlined. The CES Edu pack
software and Ashby’s material selection charts were used for the initial screening of the candidate materials.
Six polymeric materials namely ASA/PVC (unfilled), PBT, PCTA, PCTG, PE-UHMW and PET were
considered as candidate materials by following the design requirements. The digital logic method showed that
PET had the highest weighted property index followed by ASA/PVC (unfilled), PBT (filled), PVC, PCTA,
PCTG and PE-UHMW. However, ASA/PVC was considered the best candidate material for water pipes due to
its relatively low cost, light weight, flexibility and mouldability compared to PET material.
5. Acknowledgements
The authors are very grateful to Kwame Nkrumah University of Science and Technology and Tamale
Technical University for their financial support.
6. References
[1] J. Rajasärkkä, M. Pernica, J. Kuta, J. Lašňák, Z. Šimek, And L. Bláha, Drinking water
contaminants from epoxy resin-coated pipes: A field study, Water research, 103, 2016, 133-
[2] G.A. Burlingame, and C. Anselme, Distribution system tastes and odors. Advances in taste-and-
odor treatment and control,1995, 281-319.
[3] E. Charles, A. Charles, W. James and T. Mark, PVC handbook (Hanser Publications: Cincinnati,
[4] S. Rimdusit, P. Wongmanit, S. Damrongsakkul, D. Saramas, C. Jubsilp and I. Dueramae,
Characterizations of poly (vinyl chloride)/acrylonitrile styrene acrylate Blends for outdoor
applications, Engineering Journal, 18, 2014, 105-118.
[5] A.F. Bais, G. Bernhard, R.L. Mckenzie, P. Aucamp, P.J. Young,M. Ilyas, P. Jöckel, and M.
Deushi, Ozoneclimate interactions and effects on solar ultraviolet radiation, Photochemical
& Photobiological Sciences, 2019,
[6] E.L. Marron, W.A. Mitch, U.V. Gunten, and D.L. Sedlak, A tale of two treatments: the multiple
barrier approach to removing chemical contaminants during potable water reuse, Accounts
of chemical research, 52(3), 2019, 615-622.
[7] K.A. Jassim, W.H. Jassim, and S.H. Mahdi, the effect of sunlight on medium density polyethylene
water pipes. Energy Procedia, 119, 2017, 650-655.
[8] D.F. Shams, S. Islam, B. Shi, W. Khan, B. Gunawardana, M. Saad, M. Qasim, H.A. Javed, S,G.
Afridi, and M. Naeem, Characteristics of pipe corrosion scales in untreated water
distribution system and effect on water quality in Peshawar, Pakistan, Environmental Science
and Pollution Research, 26, 2019, 5794-5803.
[9] P. Ramalhete, A. Senos, And C. Aguiar, Digital tools for material selection in product design.
Materials & Design (1980-2015), 31, 2010, 2275-2287.
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 41 | Page
[10] M.F. Ashby, (Materials selection in mechanical design, Butterworth-Heinemann, 2005).
[11] A. Jahan, M. Ismail, S. Sapuan, and F. Mustapha, Material screening and choosing methodsa
review, Materials & Design, 31, 2010, 696-705.
[12] C. Petti, Y. Tang, and A. Margherita, Technological innovation vs technological backwardness
patterns in latecomer firms: An absorptive capacity perspective, Journal of Engineering and
Technology Management, 51, 2019, 10-20.
[13] K. Jeong, H. Noh, Y-K Song, and S. Lee, Essential patent portfolios to monitor technology
standardization strategies: Case of LTE-A technologies, Journal of Engineering and
Technology Management, 45, 2017, 18-36.
[14] D. Cetindamar, R. Phaal, D.R. Probert, Technology management as a profession and the
challenges ahead, Journal of Engineering and Technology Management, 41,2016, 1-13.
[15] M. Fargnoli, M. De Minicis, And M. Tronci, Design management for sustainability: an
integrated approach for the development of sustainable products, Journal of Engineering and
Technology Management, 34,2014, 29-45.
[16] E.W.T Ngai, D.C.K. Chau, E.W.T Lo, and C.F. Lei, Design and development of a corporate
sustainability index platform for corporate sustainability performance analysis, Journal of
Engineering and Technology Management, 34, 2014, 63-77.
[17] M. Ashby, (Materials selection in mechanical design, 5th Edition, Butterworth- Heinemann,
[18] M. Ashby,Y. Brechet, D. Cebon, and L. Salvo, Selection strategies for materials and processes,
Materials & Design, 25, 2004, 51-67.
[19] P. Tomboulian, L. Schweitzer, K. Mullin, J. Wilson and D. Khiari, Materials used in drinking
water distribution systems: contribution to taste-and-odor, Water Science and Technology,
49, 2004, 219-226.
[20] I. Janajreh, M. Alshrah, and S. Zamzam, Mechanical recycling of PVC plastic waste streams
from cable industry: A case study, Sustainable Cities and Society, 18, 2015, 13-20.
[21] R.L. Canfield, Jr, C.R. Henderson Jr, D.A. Cory-Slechta, C. Cox, T.A. Jusko, and B.P.
Lanphear, Intellectual impairment in children with blood lead concentrations below 10 μg per
decilite,. New England Journal of Medicine, 348, 2003, 1517-1526.
[22] B.B. Gump, P. Stewart, J. Reihman, E. Lonky, T. Darvill, P.J. Parsons, and D.A. Granger, Low-
level prenatal and postnatal blood lead exposure and adrenocortical responses to acute stress
in children, Environmental health perspectives, 116, 2007, 249-255.
[23] M. Karnib, A. Kabbani, H. Holail, and Z. Olama, Heavy metals removal using activated carbon,
silica and silica activated carbon composite, Energy Procedia, 50, 2014, 113-120.
[24] T. Marsden, M. Stirling, and C. Lang, High temperature test method for polymer pipes, Polymer
Testing, 68, 2018, 309-314.
[25] Y. Zhang, And P.-Y.B. Jar, Quantitative assessment of deformation-induced damage in
polyethylene pressure pipe, Polymer Testing, 47, 2015, 42-50.
[26] S. KIM, and K. LEE, Field performance of recycled plastic foundation for pipeline, Materials, 8,
2015, 2673-2687.
[27] D. Covas, I. Stoianov, H. Ramos, N. Graham, Č. Maksimović, and D. Butler, Water hammer in
pressurized polyethylene pipes: conceptual model and experimental analysis, Urban Water
Journal, 1, 2004, 177-197.
[28] D. Song, and R. Gupta, The use of thermosets in the building and construction industry,
Thermosets,2012, 165-188.
[29]G. Erhard, and M. Thompson, (Designing with plastics, hanser munich, germany, 2006).
[30] J. Yu, L. Sun, C. Ma, Y. Qiao, and H. Yao, Thermal degradation of PVC: A review, Waste
management, 48, 2016, 300-314.
Material Selection for Water Pipes by the Multi-Objective Decision-Making Method: The Case of Alternative
Materials for PVC Pipes 42 | Page
[31] J.M. Gere, and S.P. Timoshenko, (Theory of elastic stability, 2nd Edition, McGraw-Hill, New
York, 1961).
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