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Effast PVCu and ABS
High performance PVCu and ABS Pressure Pipe Systems
DECEMBER 2008EFF-TM2-IND
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Eff ast fr om Polypipe is a well establ ished brand name
that is recognised throughout both t he industri al
process market and const ruction industr ies for i ts
market-leading range of thermoplasti c pipework
systems suit able for use wi th in i ndustrial app lications.The company now provides these components to
customers all over the world and leads the way in the
research and development of advanced new solut ions
that satisfy the specifi c needs of the market .
Polypipe, wit h it s large UK based manuf acturing
capabilities, has developed Effasts comprehensive
product port fol io such that it now o ff ers a proven and
effective solut ion t o virt ually any requirement. No
matt er what t he project, t he Eff ast range can off er the
perfect combination of pressure pipe fi t t ings, ball,
butterfl y, diaphragm and actuated valves, compression
joint s, adaptors and other fi t ti ngs.
Normally available in both metric and imperial
dimensions these products are suit ed t o many
dif ferent commercial appl icat ions in such areas as
food and beverage processing, chemical manuf acture,
water t reatment and agriculture.
Outstanding performance and reliability have come
to represent the hallmarks by which Polypipes Eff ast
products are recognised. With these products also
carrying BSI Kite Mark accredit ation and conforming
to various other European standards they can be
specifi ed w it h complete confi dence.
Dedicated t o support ing it s customers at every stage
the company also complements its products and
systems with a full technical information and support
service, while a nationw ide distri but ion net work
means that products are readily available, even when
needed next day.
For fu rther in fo rmation please see our contact
details on the back cover of this brochure.
Effast
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Contents
Effast
Introduction to plastics 4 - 6
Material selection 7 - 11
Pressure and temperature relationships 12 - 17
Select ion of pipeline systems 18 - 22
Pipeline system design 23 - 27
Sto rage, handling and installat ion 28 - 35
Methods of joint ing 36 - 40
Pipe and fi t t ings dimensions 41 - 43
Guide to chemical resistance 44 - 79
Dimensions, uni ts and conversion tables 80 - 81
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Table 1.1 Monomers
Monomer name Formula Structure Polymer
Propylene C3
H6
Polypropylene
PP
Vinyl
C2H
3R
R can take manyforms (Including H,when it becomes
ethane).
Polyvinyl Chloride
PVC
Styrene C8H
8
PolystyrenePS
Introduction to plastics
1.1 Plastics: Polymers and mersPlasti cs are a group of engineering materials, belonging to
the larger family of polymers. Polymers are oft en
chain molecules and commonly t wo and t hree-dimensional
networks of repeating mer units, hence
poly-mers . The basic str ucture in p last ics is based on
carbon (C) and hydrogen (H); a range of other atoms
including chlorine (Cl), nitrogen (N), fl uorine (F) and
silicon (Si) may be present depending on the polymer.
The simplest C-H polymer is based on C2H
4(ethylene)
monomer f ormed int o chains of polyethylene (C2H2)n in
wh ich the monomers are linked end-on.
1.3 Macromolecule typesPolymer molecules are conventionally thought of as long
chains, but side br anches or cross-link ing between chains
can occur. The lat ter can pr oduce a 2-D or even a
3-D network, w ith propert ies such as Youngs modulus
increasing w ith the extent of the cross linking.
Putting this cross linking in place can be used to harden and
stiffen polymers; vulcanisation of rubber achieves this.
The structure of the molecular chains wil l determine how
closely they wi ll nest together and how crystalline
the result ing po lymer is.
1.4 Bond types and properties
Polymer molecules are held t ogether by t wo types of
bonds:-
Primary, covalent bonds between t he atoms in the chain
molecules. These are high strength bonds and can only be
broken irreversibly by hi gh t emperatures.
Secondary, hydrogen or van der Waals bonds, between
chain molecules. These bonds are easily broken down by
heating but r eform on cooling
1.2 Common monomers and polymers
Beyond the simplest common group above, there are a
number of others, some of which are easily recognisable by
name from t he polymers whi ch they make up.
Table 1.1 show s examples of monomers, their st ructu re,
and the result ing po lymer.
H C3H
3
C1
C2
H H
H H
C C
H Hn
H R
C C
H H
H H
C C
H H
H H
H HH
H CH2
C
Linear
Side-branched
Cross-linked
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1.4.1 Thermoplast ic plast icsThese consist of covalentl y bon ded chain mol ecules, perh aps
with some side chains, held in a solid by secondary bonds.
Heating sof tens and melt s th ese materi als, wh ich can be
remoulded and shaped; cooling allows them to hold a new
shape w hen t he secondary bonds refor m. Hence
thermoplastics can be recycled, although excessive heat will
break dow n the chains and change the material irr eversibly.
1.4.2 Thermosett ing plast ics
These mater ials consist of 2-D or 3-D net wo rks of heavily
cross linked chain molecules. The bonding is principally
prim ary covalent, so heati ng on ly serves to ult imat ely
dest roy t hem. Thermosets are not recyclable, so when
hardened, thermosets cannot be melted, deformed or fused.
Thermosets are usually reinforced w it h fi lling mater ials such
as glass fi bre, carbo n or t ext ile fi bres. Resins used in this case
include the following: -
Phenol ic resin (PF)
Polyester resin (UP)
Epoxy resin (EP)
1.4.3 ElastomersLike thermosets, these materials contain large amounts of
cross linking between chains. The progr essive st raigh tening
under t ension o f these long and convolut ed chains provides
the reversible elastic behaviour of these materials.
Elastomers resume their no rmal shape after being d istor ted
and also retain t heir elasticity at low t emperature.
Elastomers cannot be melted, f used or reshaped although
some thermoplastic elastomers have been developed.
Typical examples of elastomers are eth ylene propylene
rubber (EPDM), nit rile r ubber (NBR) and fl uorinerubber (FPM).
1.5 Structure of plastics PVCu,
ABS and PP
PVCu stands for unplasticised PVC. Polyvinyl chloride is
produced by polymerizati on of the monomer, vinyl chloride
as show n. PVCu is a hard plasti c that is made sof ter and more
fl exible by the addit ion o f p last icizers, the most w idely used
being pht halates.
ABS (acrylon it ril e but adiene styrene C8H
8C
4H
6C
3H
3N)
n
is a copolymer made by polymerizing styrene and
acrylonit rile in t he presence of polybutadiene.
The propor tions can vary from 15% t o 35% acrylonit rile,
5% t o 30% but adiene and 40% t o 60% styrene. The result is
a long chain of polybutadiene criss-crossed with shorter
chains of polystyrene-co-acrylonit rile. The nit rile groups from
neighbour ing chains, are polar and at tract each ot her
binding t he chains together w ith secondary bonds. Therefore
ABS is str onger than pu re pol ystyrene. The styrene group
gives the plastic a shiny, impervious surf ace wh ilst t he
butadiene, provides resilience even at low temperatures.
ABS can typicall y be u sed between -40 C and +60 C.
PP (polypropylene) is an addit ion polymer made fr om t hemonomer propylene, unusually resistant to many
chemical solvents, alkalis and acids and exhibit s a level o f
crystallinity intermediate between that of low density
polyethylene (LDPE) and high density po lyethylene (HDPE).
PPs Youngs modulus is also intermediate. Less tough than
LDPE, it is much less brittle than HDPE. This allows
polypropylene to be used as an alternat ive to engineering
plast ics, such as ABS. Polypropylene has very good resistance
to fatigue. The way in which the propylene group repeats
dow n t he chain det ermines crystallin it y and hence a lot of
properties of PP can be engineered at the polymerisation
stage, using pressure, temperature and type of catalyst to
cont rol t he structure as show n below.
Polyvinyl chloride
polymer
H H H H
C C C C
CI H CI H
Vinyl chlori de
monomer
H H
C C
CI H
CH2
N
Acrylonitrile
CH2
Styrene
CH2
H2C
1,3-butadiene
H H H H H H H H
C C C C C C C C
CH3
H CH3
H CH3
H CH3
H
CH3
H H H CH3
H H H
C C C C C C C C
H H CH3
H H H CH3
H
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Introduction to plastics
1.6 SynthesisOil, natural gas, coal and cellulose (vegetable in origin) are
the raw material sources from which plastics can be made.
When oil i s refi ned it is broken down by distil lation and
separated int o gr oups according t o evaporation rate. Gas
heads the group, f ollow ed by benzene, petroleum, gas oil and
fi nally t he bit umen residues. Benzene (used in t he producti on
of plastics) in its raw state is further subjected to the process
of heat cracking, which eff ectively breaks it down int o
ethylene, propylene, butylene and other hydrocarbons. These
are then modifi ed by using po lymerisation , polycondensation
or polyaddition processes to produce the required group o fplast ics.
1.6.1 Polymerisat ion
This is the most common of the processes used in plast ic
synthesis. In po lymerisation the basic molecules
(the monomers) are lined up to make macromolecular chains.
In t urn these macromolecular chains are aligned in their
entirety (no separation of by-product or other material) to
produce the plastic. Polyvinyl chloride (PVC), polypropylene
(PP) and polyethylene (PE), along wi th ot her p lasti cs are all
produced by pol ymerisation.
1.6.2 Polycondensat ionPolycondensat ion separates the by-products such as wat er or
acids fo rmed duri ng t he process whi le aligning both like and
unlike monomers, to produce macromolecular chains such as
polyamides and resins.
1.6.3 Polyaddit ion
Polyaddition is the creation of macromolecules from
molecules which are disimilar. During the process the
by-products are included and not subjected to separation.
Epoxide resins are produced in t his manner.
Table 1.2 Polymer groups
Plastics
Thermoplastics Thermosets Elastomers
AMORPHOUS(Random, unorganised molecular structure)
Vinylchlorides and Styroles
Polystyrene (PS)
Polycarbonate (PC)
Polyvinyl Chloride (PVC)
Acrylonitrile Butadiene Styrene (ABS)
SEMI-CRYSTALLINE(Partially ordered molecular structure)
Polyolefines
Polyethelene (PE)
Polypropylene (PP)
Polybutylene (PB)
RESINOUS POLYMER CHAINS(Hardener cross-linked on polymer chains)
Thermosets are usually reinforced by
using a filling material such as glass,
carbon or textile fibre producing:-
Glass-Fibre Plastic (GFK)
Carbon-Fibre Plastic (KFK) Carbon-Fibre Phenolic Resin (KF-PF)
Glass-Fibre Epoxy Resin (GF-EP)
ELASTIC PLASTICS(Synthetic and natural rubbers)
Natural Rubber (NR)
Latex
Synthetic Caoutchouc
Ethylene Propylene Rubber (EPDM)
Nitrile Rubber (NBR)
Chloroprene Rubber (CR)
Fluorine Rubber (FPM)
Silicone Rubber (SIR)
Thermally reversible They don't melt
Jointing by Chemical Welding Jointing by Fusion Welding Not suitable for jointing
Thermoelastomers
Thermoelastomers have similar properties to a thermoset, but
with almost the same hardness as the base thermoplastic.
i.e. Cross Linked Polyethelene (PEX).
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Material selection
2.0 Material selectionThere are a number of propert ies of engineering pl astics
which are key in making selection decisions. The range of
intrinsic physical properties largely depends on molecular
chain lengt h, molecular mass, crystallin ity, the proport ion of
primary bonds and the amount of cross linking .
The key properties and their relevance are detailed here:
2.1 General propert ies
Density (Mg/m3)
This represents the mass of a given volume, polymers havethe lowest density of all classes of engineering materials.
Energy content (MJ/kg)
The energy liberated during the combustion of the
substance.
Recycle fraction
Thermoplasti cs can be recycled, hi gher fr acti ons indicate
a more environmentally sensitive material. Thermosets
cannot be recycled, but may be dow n cycled by
incorporating t hem as a particulate fi ller in ot her
materials.
2.2 Mechanical propert ies
Youngs modulus or modulus of elasticity (GPa)
This modulus is a measure o f the materials resistance to
elastic defor mation . For t wo component s of the same
shape and size, a higher Youngs modulus will give a higher
sti ff ness of component .
Elastic limit (MPa)
Material can sustain certain stress due to axial loading
wit hout permanent def ormat ion. This is know n as Hookes
Law and is limited t o t he point know n as the Elasti c limit,
beyond which the material will not retain its original shape
if loading increased.
Tensile strength (MPa)
This is defi ned as the maximum load carried by the
component acting on the area of cross-section.
Poissons ratio
When a compo nent is placed in t ension, it s elast ic response
wil l be an increase in length , combined w ith a reduction in
cross sect ion (it gets longer and thinner). Poissons ratio is
a ratio of the narrowing (lateral) strain t o t he lengthening
(longit udinal) strain. As a number, typically around 0.4
fo r p last ics.
Hardness, VickersThis is the standard method for measuring the hardness of
materials; the surf ace is subjected to a standard pressure
fo r a standard lengt h of time by means of a pyramid
shaped diamond. Vickers Hardness is oft en g iven as a
hardness number rather t han a st ress.
Fracture toughness (MPa.m)
A measure of the ability of a material to withstand impact
and is not t he same as strength. A tough mat erial is the
opposite of a brittle one; an ideal material would be
strong and tough.
Ductility (%)The strain or proportional elongation at fracture. Higher
values imply a more ductile material. Ductilit y may be
quoted as a simple ratio e.g. 0.1 = 10%.
2.3 Thermal properties
Specific heat (J/kg.K)
A measure of the amount of energy required to raise the
temperature of a mass of material through a specifi ed
temperature. This propert y becomes import ant i n an
application w here sto rage or release of thermal energy is
an issue w ith higher values indicative of a material w hich
could store more heat.
Thermal expansion coefficient (mm/m.C)
This is the r ate of expansion o r contraction due t o a
change in t emperature and w hilst the un its of mm/m.C
seem quite small, this can lead to serious stresses in
materials which are constrained and experience
temperature changes. Where plastics are joined to other
materials of very different thermal expansion coeffi cients,
this difference can lead to stresses at the joint or
interface.
Thermal conductivity (W/m.K)Indication of the t ransfer of heat through the material.
Higher values indicate a material wh ich allows the
passage of heat more readily. Lower values imply a better
insulating material.
2.4 Elect rical propert ies
Dielectric constant
A dielectric material is a substance that is a poor
conductor of electr icity, but an effi cient support er of
electrostatic fi elds.
Resistivity (Ohms.m, in the range 1013 )The surface resistance of a plastic is, as the name
suggests, the resistance to t he fl ow of elect rical current
over i ts surf ace.
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Material selection
2.5 Selection of plastics for pipe systemsIn order to select the most suit able material f or a pipe system
the fol low ing f acto rs need to be addressed: -
The medium or fl uid conveyed and it s chemical composition
Operating pressure
Operating temperature
These factors are interlinked and only when all are addressed
can the correct materi al be selected. In addit ion t o t he above
it is necessary to be familiar with the characteristics of the
material f or t he pipe system.
Picture supplied courtesy of Sterling Hydrotec.
Table 2.1 Comparative properties of PVCu, ABS and PP
Property PVCu-Rigid ABS High Impact PP Homopolymer
General
Composition (CH2-CH-CI)
n(CH
2-CH-CH
2--CH-CN-C
6H
4)n
(CH2-CH-CH
3)n
Density (Mg/m) 1.35 to 1.55 1.03 to 1.07 0.90 to 0.92
Energy Content (Mj/kg) 85 to 106 85 to 120 90 to 110
Recycle Fraction 0.15 to 0.25 0.45 to 0.55 0.25 to 0.35
Mechanical
Young's Modulus of elasticity (GPa) 2.2 to 3.5 2.1 to 2.8 1 to 1.6
Elastic Limit (MPa) 35 to 52 40 to 45 28 to 33
Tensile Strength (MPa) 30 to 70 45 to 48 25 to 40
Compressive Strengh (MPa) 55 to 60 55 to 60 40 to 45
Ductility 0.1 to 3 0.06 to 0.07 1 to 2
Endurance Limit (MPa) 27 to 31.2 24 to 27 15.4 to 18.2
Fracture Toughness (MPa.m) 1 to 2 2.3 to 2.6 1.9 to 2.1
Hardness Vickers 10.6 to 15.6 5.6 to 12.2 9.3 to 11.2
Poisson's Ratio 0.38 to 0.43 0.38 to 0.42 0.4 to 0.45
Thermal
Normal Service Temperature (C) 0 to 60 -40 to 60 -10 to 110
Thermal Expansion (mm/m.C) 0.055 to 0.095 0.070 to 0.100 0.080 to 0.150
Specific Heat (J/kg.K) 1000 to 1100 1500 to 1510 1920 to 2100
Thermal Conductivity (W/m.K) 0.24 to 0.26 0.17 to 0.24 0.16 to 0.24
Electrical
Dielectric Constant 3.1 to 3.2 2.8 to 3.3 2.26 to 2.4
Resistivity (1013 ohm.m) 3.16 to 10 6.31 to 15.8 10 to 1000
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Plastic pipe systems have certain advantages when compared with metal pipe systems and the following
illust rates some of these advantages: -
Lightweight
Easier t o handle. Density range 0.9 - 1.8 g/cm
Elastic properties
Good impact resistance. Good bend stress resistance.
Heat loss
Plasti cs provide good
insulation and are poor
heat conductors.
Chemical stability
Good chemical resistance to a broad range of
materials conveyed.
Low temperature operation
Plastic pipelines can accommodate
ice expansion and t haw w ith out
damage.
Corrosion resistance
Plastic does not corrode, whereas many metals combine with
oxygen and corrode or rust.
Thermal expansion
Plasti cs expand much more than steel, as th ey are more
affected by thermal change.
Electrical conductivity
Plasti cs do not conduct electr ical
charge and t here is no electrolytic
reaction as wit h metals.
Smoother surface finish
Plastic pipes unlike metal pipes are not prone to
encrustat ion of lime-scale, etc; and t herefore w ill have
smaller pressure losses.
Colours
Plastic can be made in many permanent colours aiding
colour-code identifi cation and eliminati ng t he need for
paint maintenance.
SLURRY
Abrasion resistance
Plasti c is more resistant than
steel due to i ts lower fr ictional
characteristics.
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Material selection
2.6 Effast pipe system plastic materials2.6.1 Polyvinyl chloride (PVC)
Polyvinyl chloride, an amorphous thermoplastic is suitable for
injection moulding and extruding (i.e.reshaped with heat),
making it ideal for t he manufacture of pipes, fi tt ings and
valves. It can be heat welded or solvent cemented (chemically
welded). It can also be recycled and reprocessed. PVC in it s
natural stat e is a strong semi ri gid mat erial and is denot ed in
it s abbreviat ed form as PVCu or PVCuH where t he u
ident ifi es th e product as unp lasti cized and H as high impact.
PVCu pipes and fi tt ings are widely used wi th in t he Pot able
and Wastew ater t reatments industr ies. During t hemanufacturing process certain additives may be used to
enhance it s processabili ty and perf ormance characterist ics: -
Stabilizers:
Normally calcium or ti n based, provide p rot ection against
the adverse effects of heat degradati on and ult raviolet
(UV) radiation. Polymers used by Effast meet the
requirements of the many international regulatory bodies
governing the food and potable water industries.
Pigments:
These are colou rs that may assist in use ident ifi cation and
ease of maintenance.
Lubricants:
Are used to aid extrusion and the release of moulded
products from mould cavities.
These additives typically make up less than 5% of the
fi nished PVC component s mass. PVC pipe and fi tt ings can be
used in appli cations that require: -
Environment al resistance to aggressively caust ic or
acidic media
Good abrasion resistance
Operat ing temperat ure range: 0C to +60C
Solvent welding
2.6.2 Acrylonit ril e bu tadiene styrene (ABS)
Acrylonit rile but adiene styrene, an amorphous thermoplastic
is suitable for injection moulding and extruding
(i.e. reshaped wit h heat), making it suitable for the
manuf acture o f pipes, fi tt ings and valves. It can be solvent
cement ed (chemically welded). It can also be recycled and
reprocessed. ABS comprises a styrene and acrylonitrile
copolymer li nked t o po lybutadiene. The constit uents can be
changed in proportion and engineered to provide particular
propert ies required f or di ff erent appl ications such as the
cont ainment and conveyance of pot able wat er, slurri es
and chemicals.
ABS, being non-toxic, complies wi th the toxicolog ical
requirements of the British Plastics Federation/British
Industrial Biological Research Association (BIBRA) Code of
Practice for fo od usage 45/5.
ABS can be used in appli cat ions that requ ire: -
Good chemical resistance
Good abrasion resistance
Good material strength and hi gh impact resistance
Operating temperature range: -
- 40C to +60C- Suitable for low temperature usage
Solvent welding
2.6.3 Polypropylene (PP)
Polypropylene, a semi-crystalline thermoplasti c is suit able
for injection moulding and extruding (i.e. reshaped with
heat), making it suitable for the manuf actu re of pi pes,
fi ttings and valves. It can also be recycled and reprocessed.
Polypropylene is produced by polymerising propylene along
wit h a catalyst and ot her addit ives. The material can be
produced in eit her homo-polymer form (PP-H) and bl ock orrandom copolymers (PP-B or PP-R). Polypropylene is
adversely affected by UV radiati on and pipelines that are
installed ou tside or in direct sunligh t should be prot ected by
insulatio n o r p rot ective coating. Polypropylene is suit able
for use with foodstuffs, potable and ultra pure waters, as
well as wit hin the pharmaceutical and chemical industr ies.
Polypropylene can be used in applications that require: -
Environmental resistance to most organic and
inorganic chemicals
Good material strength and fat igue resistance
Operati ng t emperat ure range -10C to +110C
Fusion welding
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2.7 Specific environmental factorsfor pipe systems
2.7.1 Flammabi lit y
Mat erial fl ammabilit y can be measured by the Limiting
Oxygen Index (LOI) as defi ned under BS 2782 method
141 or ASTM 2863. Materials are assessed and given an
index number that refl ects their combustion characteristics.
For example materials wit h an index: -
Under 21, will support combusti on in air at ambient room
temperat ure (+15C)
Above 21, will not sustain combustion
Above 25, will burn onl y when there are extreme heat
condit ions i.e. where there is direct high temperatu re heat
applied (blowtor ch, etc.)
Plasti cs have a wide range of LOI and t he fo llow ing t able
demonstrates the LOI fo r d iff erent p lasti cs and it s effects
regarding fl ammabilit y and toxicity: -
Table 2.2 Flamabil ity properties
Thermoplasticmaterial
LOI Flammability Fumes' toxicity
PVCu 46 - 49 Self Extinguishing High
ABS 18 - 20 Burns Low to medium
PP 16 - 18 Burns Low to medium
2.7.2 Ultra violet light (UV)
The majorit y of p lastics when exposed to ult ra violet light
(present in sunligh t) w ill suffer degradation or loss of
properties to varying degrees. All plastics should be
prot ected and th is can be achieved by eit her lagging the
pipe where exposed or by painting with a weatherproof
wat er based paint.
2.7.3 Hot climat esApplications in hot climates should ensure storage and
installation to allow for thermal expansion, deformation
and degradati on due to excessive UV radiation or thermal
exposure.
2.7.4 Disinf ectants
Disinf ectant s are ant i-microbial agents in eit her an alcohol
or aqueous based solut ion, w ith detergent s to help spread
the agents th rough their str ong capillary actio n. The various
compositions of disinfectant s wil l have widely diff ering
eff ects on pl asti cs. It i s str ong ly advised when using p last ics
fo r a pipe system, that confi rmati on of compati bilit y wit h
the material should be sought from the disinf ectant
manufacturer.
Instr uctions for solvent cementing j oint s must be fo llow ed
rigidl y to avoid t he capillary acti on of solut ions.
The following table summarises certain thermoplastics for
use in d isinf ectant operating environment s: -
= Yes = No
* PVCu systems rated at 10 bar or above can only be used in
th is applicatio n when operated at 6 bar.
2.7.5 Electrostat ic charge
Plasti c pipe systems are not suit able f or electr ically conductive
applications. The build up of electrostatic charge may result
in a potentially explosive condit ion and in or der to avoid
such a situation t he foll owing guidelines must be followed: -
Stop electrostatic charge accumulating: By wrapping a
metallic earthing t ape fi rmly around t he pipecircumference or along the length of the pipe system or
painti ng t he pipe w ith a metalli c based, solvent
free, electr ically conducti ve paint.
Disperse the electrical charge: By ionizing the atmosphere,
increasing humidit y to over 65% or using an ant istat ic
hydroscopic soap.
2.7.6 Compressed air
Plasti c pipelines fo r compressed air appli cat ions can be
subject to damage from t he presence of oil, addit ives and
related vapour s. These contaminates should be removedfrom t he system t hrough fi ltrati on and t raps to ensure clean
and dry air.
The following table summarises certain thermoplastics for
use in compressed air systems: -
Table 2.3 Disinfectant suitability
Thermoplastic materialMaximum operating
pressure (bar)Suitability for
disinfectant use
PVCu 6 *
ABS NA
PP NA
PE and PVDF 10
Table 2.4 Compressor suitability
Thermoplastic materialSuitability as
compressed airlineEffects from
compressor oil
PVCu Poor suitability* Can become brittle
ABS Suitable Limited resistance
PP Unsuitable Drastically shortened life
PE and PB Very suitable Good resistance
* PVCu should only be used where t he air pressure does
not exceed 3 bar or t he applicati on is an open ended
dispersion system.
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Pressure and temperature
The required duration of operation for a given w orking
pressure and t emperature must be taken in to account when
plann ing a plastic pipe system. Pressures that can be
sustained f or a short time at a certain t emperature may not
be sustainable at a higher w orking temperature; or even at
the same pressure and t emperature should the wor king
durat ion o f the system be extended. It is possible t o w ork
out the maximum permitted working pressures at different
temperatures and the associated safety factors wit h t he
use of regression graphs. Safet y facto rs are used t o ensure
that plastic pipeline systems can operate under stress for theirgiven lifet ime wit hout damage or failure and is described as
the ratio between the maximum allowable circumferential
stress which a system can absorb and its operating stress.
Where P Permissible operat ing pressure (bar)
C Safet y facto r (see table 3.1)
20 Propor tionality constant
Circumferential stress (MPa), taken from
regression charts (3.1, 3.2 and 3.3) at t he end o f
this chapter.
e Pipes wall thickness (mm) D Pipes outside diameter (mm)
Note that fi tt ings and other component s, wit h the same
pressure rat ing as the pipe, are normally t hicker w alled and
therefore the lowest common denominator of wall thickness
(e) shou ld be used.
Table 3.1 Safety factors for thermoplastics (C)
Thermoplastic material
PVCu metric PVCu imperial ABS metric ABS imperial PP-H metric
Safety factor* 2.5 2.1 2.1 2.1 2.1
3.0 Pressure and temperature relationshipThe follow ing fo rmula is used to calculate t he permissible
working pressure for a pipeline system: -
* Safet y factors are based on 50 year expected li fe at 20C, wi th water.
The higher t he wor king t emperature of a plastic pipe system, t he lower wil l be the wor king pr essure that can be sustained
within the system, please refer to tables 3.2 to 3.5
(PN10) for 3 mm wall thickness
and
(PN10) for 3 mm wall thickness
and
(PN16) for 4.7 mm wall thickness (PN16) for 4.7 mm wall thickness
Worked example 3.1
Calculate the maximum operating pressure for a pipe system
wi th t he foll owing specifi cation :-
Mat erial type: PVCu
Intended operating lif e: 20 years
Maximum operat ing temperat ure: 20 C
Pipe dimension s: 63 x 3 mm and 63 x 4.7 mm
Solu t ion
Factor of safety C= 2.5 (from table 3.1).
Wit h li fe span 20 years and t emperat ure t = 20 C fi nd = 27
(from chart 3.1).
The fo rmula f or det ermining the operating pressure is used:-
Worked example 3.2
Calculate the maximum operating pressure for a pipe system
wit h the foll owing specifi cation :-
Mat erial type: PVCu
Intended operating lif e: 20 years
Maximum operat ing temperat ure: 30 C
Pipe dimensions: 63 x 3 mm and 63 x 4.7 mm
Solu t ion
Factor of safety C= 2.5 (from table 3.1).
Wit h li fe span 20 years and t emperat ure t = 30 C fi nd = 22
(from chart 3.1).
The fo rmula f or det ermining the operating pressure is used: -
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Table 3.2 Temperature and pressure relationship for pipes, PVCu imperial
Class C Class D Class E
Temperature (C) bar psi bar psi bar psi
0 9.0 130 12.0 174 15.0 217
20 9.0 130 12.0 174 15.0 217
30 8.1 117 10.8 156 13.5 195
35 7.2 104 9.6 139 12.0 174
40 6.3 91 8.4 121 10.5 152
45 5.4 78 7.2 104 9.0 130
50 4.0 58 5.4 78 6.7 97
55 2.7 39 3.6 52 4.5 65
60 1.3 18 1.8 26 2.2 31
Table 3.4 Temperature and pressure relationship for pipes, ABS imperial
Class C Class D Class E
Temperature (C) bar psi bar psi bar psi
-40 9.0 130 12.0 174 15.0 217
-20 9.0 130 12.0 174 15.0 217
0 9.0 130 12.0 174 15.0 217
20 9.0 130 12.0 174 15.0 217
30 8.1 117 11.3 163 13.5 195
40 6.3 91 8.5 123 10.5 152
50 4.5 65 6.3 91 7.5 108
60 2.7 39 3.8 55 4.5 65
Table 3.3 Temperature and pressure relationship for pipes,PVCu metric
Pipe pressure rating (bar)
Temperature (C) PN10 PN16
0 10.0 16.0
20 10.0 16.0
30 8.0 12.8
35 7.1 11.8
40 6.4 10.2
45 5.1 8.2
50 4.4 7.0
55 3.3 5.2
60 2.6 4.1
Table 3.5 Temperature and pressure relationship for pipes,PP-H metric (PN10)
Pipe pressure rating (bar)
Temperature (C) 50 Years 25 Years 10 Years 1 Year
20 10.0 10.6 11.0 12.3
40 6.2 6.6 6.9 8.0
60 3.8 4.1 4.3 5.2
80 - 1.6 2.0 3.5
95 - - 0.9 2.3110 - - - 1.6
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Solu t ionFrom table 3.3 for PVC at 20C, the pressure rat ing is 10 bar.
From tab le 3.6 for PVC at 20C, the permissible circumferent ial
stress = 10 MPa.
Hence
Scan also be calculated by:
alternatively:
It is recommended t hat i f the allowable negat ive pressure
(Pe) is less than 1 bar then the pipeline system will not sustain
vacuum. (1 bar = 0.98 Atmospheres.) Different thermoplastics
have diff erent operat ing t emperatures under a vacuum and
maximum installation temperatures must be observed, as
shown in table 3.7: -
Worked example 3.4
A PVCu pipe (PN10) operates under t he fo llow ing condit ion: -
Pipe out side diamet er: 110mm
Intended service lif e: 10 years
Safet y facto r: 2
Modulus of Elasti city 2200 MPa
Poissons Rat io 0.4
Determine the collapsing p ressure and det ermine whether t he
vacuum pressure can or can no t be sustained,
for t wo cases: -
Pipe wal l th ickness: 5.3mm
Pipe wal l th ickness: 3.0mm
Solu t ion
The collapsing pressure i s given by: -
(a) For e = 5.3mm, the collapsing and the vacuum pressure are
calculated: -
Therefore t he pipe w ill sustain t his condit ion,
asPe is greater t han 1.
(b) For e = 3mm, the collapsing and the vacuum pressure
are calculated: -
This pressure i s low er t han 1 b ar; hence the pipe system can
not support this condition.
3.3 Maximum working conditions for
negative pressureThe design safety factor for negative
pressure is 2.
Pipeline systems operat ing below atmospher ic pressure
(1 bar) are subjected to vacuum or negative pressure
and wil l tend t o collapse radially inwards due to t he
greater outside pressure.
The collapsing pressure can be shown by the following
formula: -
Where Pc Collapsing pressure (bar)
20 Propor tionality constant
E Modulus of elast icity (MPa) (See table 2.1)
Poissons ratio (See table 2.1)
e Pipe w all t hickness (mm)
D Pipe out side di ameter (mm)
C Safet y factor = 2 (Design safety f acto r f or
negat ive pressure)
The maximum allowable negative pressure (Pe) is obtained
from the collapsing pressure (Pc) and safety
factor (C) with: -
Table 3.7 Maximum installation temperatures forvacuum conditions
Thermoplastic material Maximum temperature under vacuum (C)
PN10 PN16
PVCu 40 60
ABS 60 60PP 80 80
+ +
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Pressure and temperature
100
504030
20
10
Load duration (hours)
Circum
ferentialstress(MPa)
1
0.10.1 1
20C30C40C
50C60C
10 100 103 104
1 5 10 25 50
Years
105 106
Chart 3.1 Life regression for PVCu
100
504030
20
10
Load duration (hours)
Circu
mferentialstress(MPa)
1
0.10.1 1
20C30C
40C50C
60C
10 100 103 104
1 5 10 25 50Years
105 106
Chart 3.2 Life regression for ABS
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100
504030
20
10
Load duration (hours)
Circum
ferentialstress(MPa)
1
0.10.1 1
20C30C40C
50C60C
70C80C
95C120C
10 100 103 104
1 5 10 25 50
Years
105 106
Chart 3.3 Life regression for PP-H
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Selection of pipeline systems
4.0 Pipeline system selectionPipeline system selection is usually based on a number
of parameters: -
The eff ect of working condit ions such as pressure,
temperat ure and t he fl uid carried as described in
chapter 3.
Flow rate of the fl uid usually governs the pipe size.
The relationship between the pipe size and the pressure
rating is show n in t ables 4.1 to 4.4 for the dif ferent types
of thermoplast ics; t hese tables also include pr essure
rat ings for pi pe fi t ti ngs and valves.
Table 4.1 PVCu (imperial sizes) pressure ratings -fittings, valves and pipes
Product Size - inchesPressure rating at 20C
psi bar
Fittings
Solvent cement - 6 217 15
8,10 and 12 130 9
Threaded /8 - 4 145 10
Union - 2 174 12
3 - 4 145 10
Flange Blanks
1 - 2 232 16
2 - 4 145 10
5 - 6 87 6
Valves
Ball/8 - 2 232 16
2 - 4 145 10
3 Way ball - 2 145 10
Diaphragm - 2 145 10
Butterfly 3 - 5 145 10
6 87 6
Knife gate 1 - 4 36 2.5
Check/8 - 2 232 16
2 - 3 145 10
Wafer check2 - 6 145 10
8 87 6
Pipes
Class E - 6 217 15
Class D 1 - 6 174 12
Class C 2 - 12 130 9
Class TThreading andmachining only
/8 - 2 174 12
Table 4.2 PVCu (metric sizes) pressure ratings -fittings, valves and pipes
Product Size - mmPressure rating at 20C
bar psi
Fittings
Solvent cement16 - 160 16 232
200 - 315 10 145
Metric solvent xBSP adaptor
16 x /8" -110 - 4"
10 145
Valves
Ball16 - 63 16 232
75 - 110 10 145
Diaphragm 20 - 63 10 145
Butterfly 90 - 140 10 145
160 6 87
Check16 - 63 16 232
75 - 90 10 145
Pipes
PN rated 16 - 315 10 and 16 145 and 232
Table 4.3 PP-H (metric sizes) pressure ratings -fittings, valves and pipes
ProductSize - mm(inches)
Pressure rating at 20C
bar psi
Fittings
Socket fusion 16 - 110 10 145
Valves
Ball union end/socket fusion
20 - 63("- 2")
10 145
Ball union end/threaded BSP
(" - 2") 10145
Butterfly
90 - 140(3" - 5")
10 145
160 - 225(6" - 8")
6 87
Check20 - 63
(" - 2")10 145
Pipes
PN rated 16 - 110 10 145
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Table 4.4 ABS (imperial sizes) pressure ratings -fittings, valves and pipes
ProductSize - inches
(mm)
Pressure rating at 20C
psi bar
Fittings
Solvent cement
- 4 217 15
5 - 6 174 12
8 145 10
Threaded BSP /8 - 3 145 10
Union - 2 174 12
3 - 4 145 10
Flange Blanks
1 - 2 232 16
2 - 4 145 10
5 - 6 87 6
Valves
Ball
/8 - 2(16 - 63mm)
232 16
2 - 4(75 - 110mm)
145 10
Check
/8 - 2(16 - 63mm)
232 16
2 - 3(75 - 90mm)
145 10
Pipes
Class E /8 - 4 217 15
Class D 6 174 12
Class C 1 - 8 130 9
Class TThreading andmachining only
/8 - 2 174 12
4.1 Valve selection
Valve select ion is based upon a number of key paramet ers: -
The primary valve body material is selected along wit h
the material best suit ed fo r t he pipe system.
Thereafter valve selecti on will depend on the propert ies
of the conveyed medium and the valve characteristics
themselves, as show n i n t able 4.5.
The compati bilit y of the seal material to the conveyed
medium within the known operating parameters must
be confi rmed, which can be determined by reference
to the valve seal behaviour in table 4.6.
Addit ionally, valves have another import ant characteristic
known as torque rating which is very important in
actuated applications. Charts 4.1 to 4.6 show the
tor que-valve diameter rat ing f or t hree types of valves.
Table 4.5 Valve select ion
Valve features Ball valve Butterfly valve Diaphragm valve
Standard seal EPDM, FPM EPDM, FPM EPDM
Flow Full Restricted Restricted
Flow adjustmentLimited,not positive
Good,positive
Good,positive
Frictionalpressure loss
Low Medium High
Behaviourwater hammer
Fair Limited Limited
Table 4.6 Valve seal behaviour
Seal features Ball valve Butterfly valve Diaphragm valve
Liquid, particlefree
Good Good Good
Liquid,particulate orcrystal forming
Limited, needsregular cleaning
Good, but needsoccasionalcleaning
Good
Liquid, viscous Good Limited Limited
Gases Good Good Limited
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Selection of pipeline systems
Chart 4.3 Torque for industrial ball valve PP
35
30
25
20
15
10
5
0
16 20 25 32 40Pipe diameter (mm)
Tor
que(Nm)
50 63 75 90
Chart 4.2 Torque for industrial ball valve PVCu and ABS
35
30
25
20
15
10
5
0
20 25 32 40 50
Pipe diameter (mm)
Torque(Nm)
63 75 90 110
Please note: Some 75mm ball valves are based on90mm bodies and thus have a higher tor ques rating.
Chart 4.1 Torque for economy ball valve PVCu
70
60
50
40
30
20
10
0
16 20 25 32 40
Pipe diameter (mm)
Torque(Nm)
50 63 75 90
110
Please note: Some 75mm ball valves are based on90mm bodies and thus have a higher tor ques rating.
Torque charts for ball valves
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Chart 4.5 Torque for butterfly valve PP
70
80
90
60
50
40
30
20
10
0
90 110Pipe diameter (mm)
T
orque(Nm)
140 160 225
Chart 4.4 Torque for butterfly valve PVCu
35
30
25
20
15
10
5
0
90 110Pipe diameter (mm)
Torque(Nm)
125 140 160
Torque charts for butterfl y valves
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Selection of pipeline systems
Chart 4.6 Torque for diaphragm valve PVCu
12
10
8
6
4
2
0
20Pipe diameter (mm)
Torque(Nm)
25 32 40 50 63
Torque chart for diaphragm valves
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Pipeline system design
Worked example 5.1(a) What size of PVCu pipe should be used if the volumetric
fl ow rate is 10 l/s and t he fl ow velocity is rest ricted t o
3m/s?
(b) What is the ef fect of using a smaller or larger size pipe
to do t he job? Take pipes of external diameters and w all
thicknesses as: -
(i) D = 50mm and e = 1.8mm.
(ii) D = 75mm and e = 2.2mm respectively.
Solu t ion
(a) The pipe int ernal diameter f ormula is used:-
(b) In case the suppliers do not have the exact diameter
determined above (65mm), let us examine two opt ions: -
(i) When the fl ow area is decreased to 50mm
diameter, then the velocity wil l increase as
shown by the Continuity equation in terms
of velocity: -
This is clearly over t he recommended design limit
of 3m/s for fl ow velocity of liquids in thi s pipeline
system and is not advisable.
(ii) When t he fl ow area is increased to 75mm
diameter, then the velocity will decrease as shown
by the Continuity equation: -
This fl ow velocity is lower than the maximum
recommended value of 3m/s and is therefor e
acceptable. Remember t hat low er fl ow velocity
means propor t ionately low er pressure losses,
therefore, always go f or t he next size up if your
calculated size is not available.
5.2 Flow regimes in pipeline system
Flow regimes in a pipe were classifi ed by Osborne Reynolds
(in the early tw entiet h century) into t hree categories: -
Laminar: Where the fl ow behaves in an orderly mannerrunnin g in parallel stream lines.
Turbulent: Where the fl ow st reams are inter linked.
Transient: An intermediate condit ion where the fl ow
is neither Laminar nor Turbulent.
This chapter describes the design calculati ons for a plastic
pipeline system by using t he fo llow ing criteria: -
Pipeline diameter for a given fl uid fl ow rat e
Frictional and pressure losses of t he system
Pumping power requirement
Pressure transient s (i.e. wat er hammer)
The above parameters are shown and worked examples are
provided to demonstrate the calculation
procedure for each aspect.
5.1 Pipe diameter calculation
Pipeline sizing is a thr ee-way relati onship betw een the
int ernal pipe fl ow area (A in m), the fl ow velocity
(u in m/s) and the volumetr ic fl ow rate (Q in m/s) as
given by: -
Where t he cross-sect ion of the pipes int ernal fl ow
area (A) is
The above relationship can be expressed in terms of the
internal pipe diameter (din m): -
If t he fl ow rate is expressed in lit res per second (l/s), then the
pipe diameter (mm) relation can be simplifi ed t o: -
Note t hat t here are tw o f actor s wh ich infl uence the selecti on
of fl ow velocity: -
In order to avoid increasing pressure losses due to f ricti on,
if the pipe int ernal diameter is reduced the fl ow velocit y
should be proport ionately reduced.
Noise generat ion increases rapid ly wi th velocity,
especially fo r gas fl ow applications and t he follow ing
limit ing velociti es are accepted f or the general design
of pipeline systems: -
Table 5.1 Noise limiting flow velocities inplastic pipeline systems
Medium carried Maximum velocity (m/s)
Liquid under suction 1
Liquid under delivery 3
Gas 25
mmu
Qd 65
3
1053 . 86 53 . 86 = ==
m/sd 5. 1905 3.6
53 . 86
10
53 . 862 2
=
=u Q=
m/su Q=d
2. 5557 4.4
53 . 8610
53 . 862 2
=
=
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Reynolds ident ifi ed t hese categori es by calculat ing a
dimension less group of three fl ow paramet ers, later given
the name Reynolds number , which is defi ned by:-
Where Re Reynolds number
u Flow velocity (m/s)
d Pipe int ernal diameter (m)
v Kinematic viscosity (m/s), see table 5.2 below
The friction factor (f) can also be determined graphically
using t he Moody diagram (Chart 5.1) shown at the end of
this chapter.
DArcy presented the follow ing relationship t o determine t he
Head loss ( ) due to fr ictional resistance to the fl ow
in p ipelines: -
Where f Coeffi cient of fr iction
L Length of pipe (m)
g Acceleration due to gravity (9.81m/s)
u Flow velocity (m/s)
d Pipe int ernal diameter (m)
Usually hydraul ic loss is evaluated in metres per 100m length
(i.e.L = 100) so the above formula can be simplifi ed to: -
5.4 Pressure losses due to obstructionsin pipeline systems
Obstruction losses are due t o t he presence of valves and fi tt ings
in p ipeline systems. These losses are grouped int o one lot
and the associated hydraulic loss ( ) is calculat ed as the
sum of all loss coeffi cients mul tiplied by the velocity head of the
approaching fl uid: -
Where g Acceleration due to gravity (9.81m/s)
u Flow velocity (m/s)
ki
The sum o f k-values fo r fi tt ings and valves for
the pipe system, see tables 5.5 and 5.6
Reynolds concluded that if Re is less than 2000 the fl ow is
clearly laminar and w henRe is over 4000 the fl ow is clearly
turbulent. How ever when Re is between 2000 and 4000 the
fl ow is tr ansient and the fl ow prediction i s not reliable.
5.3 Pressure losses due to frictionin pipelines
The coeffi cient o f fr iction w hich is an indication of the
resistance the pipe surf ace off ers to the fl ow is dependent on
the value of the Reynolds number and t he roughness of the
pipe int ernal surface. Plasti cs have a unique advantage over
metal pi pes in t hat they are considered perfectly smooth
when new and do not suff er from t he build up of rust or
coagulation; thus their original internal dimension is
retained. The friction factor f or plastic pipes is given in table 5.4
Pipeline system design
Table 5.2 Kinematic viscosity of water
Temperature Kinematic viscosity (m/s x 10-6)
0 1.752
5 1.501
10 1.300
15 1.137
20 1.004
25 0.893
30 0.800
35 0.722
40 0.656
45 0.600
50 0.551
Table 5.3 Reynolds flow regimes
Regime Reynolds number (Re ) Characteristics
Laminar 4000 Very mixed flow
Table 5.4 Friction coefficients
Regime Reynolds number (Re) Coefficient of friction (f)
Laminar 4000 0.079Re -0.25
g
u
d
f LHf
2
42 =
f u 2
d
02 .4 Hf =
Hf
( )g
u
2
2
= HO ik
HO
Table 5.5 Obstruction loss coefficient for fittings
Obstruction k
Pipe entry 0.5
Pipe exit 1.0
90 elbow 0.40
45 elbow 0.30
90 bend 0.60
45 bend 0.40
Tee straight through 0.80
Tee branch 90 0.95
Sudden enlargement diameter ratio
1:2 0.15
1:3 0.19
1:4 0.241:5 0.30
Sudden contraction diameter ratio
5:1 0.40
4:1 0.37
3:1 0.33
2:1 0.30
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Table 5.6 Obstruction loss coefficient for valves
Valve 25% Open 50% Open 75% Open 100% Open
Ball 10.53 5.54 1.25 0.28
Diaphragm 1.94 1.59 1.39 1.25
Butterfly 3.74 0.42 0.14 0.10
Non-return 6.37 3.5 2.1 1.0
5.5 Pump rating
5.5.1 Hydraul ic losses in pipeline systems
The pum p in a fl uid pipeli ne system has to: -
Overcome frict ional losses,
Overcome obstruction losses due to valves and fi t t ings,
The total hydrauli c loss (metres) is therefo re given by
Transfer t he fl uid at the requir ed fl ow rat e betw een
tw o stations,
The stat ic-lift is the physical dif ference in elevation betw een
the t wo stat ions in metres.
5.5.2 Pressure losses in pipel ine systems
The relationship between head loss and pressure loss is
given by: -
Where P Pressure lo ss (N/m or Pa)
Densit y of fl uid (kg/m)
g Accelerati on due t o gr avity (9.81m/s)
5.5.3 Energ y loss in pipeli ne system
The af orement ioned hydrauli c losses in a pip eline system
are to be accommodated in t he design process and t hese
losses should be considered when selecting the correctpump size (duty).
The pumps rating (pow er requirement in Wat ts) is given by: -
Where
Q Volumetr ic fl ow rate
Hydraulic effi ciency of pump
(Refer to manufacturers data)
Htotal
Total eff ecti ve head Htotal
=Hstatic-lift
+ Hlosses
(Due to pipe-friction, fi ttings, plus stat ic-lift )
Worked example 5.2A PVCu pipeline system, pumping water, comprises the
foll owin g items: -
Pipe Length 200m
Outside diameter 110mm
Wall thickness 10mm
Fit t ings 2x 90bends k = 0.6
1x pipe ent ry k = 0.5
1x pipe exit k = 1.0
1x but terfl y valve (25% open) k = 3.74
(a) Determin e the t ot al hydraulic and pressure losses of th is
system when the fl ow rate of w ater is 30 l/s if t he
oper ati ng t emperatu re is 10C. (Take th e viscosit y of
wat er from t able 5.2)
(b) Determine t he pump pow er to deliver this fl ow r ate to a
point situated 20m above the source given the pumps
hydrauli c effi ciency is 80%.
Solu t ion
(a)
Total hydraulic losses
Total pressure losses
(b) Total eff ecti ve head
Pump power
Hence fl ow
is tur bulent.
Hlosses =Hf + Ho = 33 + 7.2= 40.2 m
P = g Hlosses = 103 9.81 40.2394 kPa=
Htotal
=Hstatic- lift
+ Hlosses20 + 40.2
60.2 m==
Q g Htotal /10
330 10 -3 9.81 60.2 / 0.822.1 kW
=
=
=
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Pipeline system design
5.6 Pressure transients in pipelinesystems (water hammer)
There are times when either by poor design or abrupt
changes in t he fl ow condit ion t he pipeli ne system
undergoes a pressure surge, th is phenomenon know n as
Water Hammer , may be initiated by any of t he follow ing
acti ons in th e pipeli ne system: -
Abru pt valve closure
Pump start up, shut dow n or an abrupt change in speed
Ent rapped gas in the liquid fl ow
There are four important parameters to be considered
at t he design stage so t hat t he effect of water h ammer
is minimised: -
1. The velocity of the pressure wave (m/s)
Where K Bulk modu lus of elast icity f or fl uid (Pa)
Fluid densit y (kg/m3)
E Modulus of elasticity of pipe material (Pa)
d Pipe inside di ameter (mm)
e Pipe wall thickness (mm)
2. Pressure fl uctu atio n consist s of bot h an upper and lower
pressure limit and th ese must be kept w ithin the p ipes
pressure characteri sti cs, such th at the upper limit is wit hin
the pipes maximum operating pressure and the lower
limi t is above the pipes collapsing pressure, in order t o
avoid permanent damage to the pipe system.
The pressure fl uctuation is given by
Where u is the velocity change (m/s).
The pressure fl uctuat ion r esult s in up per and l ow er limi t s of
oper at ion and is defi ned as:-
The maximum pressure:
The m inim um pressure:
3. The eff ecti ve safet y facto r f or f requent surges should be
lower than the materials safety factor.
4. Critical wave period (seconds) given by
WhereL is pipe length (m)
Actuated valves must have closure t imes greater t han
this wave period in order to minimise the eff ect of
water hammer.
Worked example 5.3A PVCu pipeline system, PN6 rated, 300m in lengt h, w ith an
out side diamet er of 50mm and a wall t hickness of
1.8mm wit h an operati onal pr essure of 4.4 bar, has an
actu ated valve wi th a closing t ime of 2 seconds.
Where PVCus Youn gs modu lus (E) is 2.6 GPa and it s
circumf erent ial stress is 29 MPa; and wat ers bulk modu lus
of elasti city (K) is 2.05 GPa and i ts density o f 1000 kg/m .
Determine the water hammer characteristics where the
fl ow rat e is 10m/h and 20m/h.
Solution
PropertyFlow rate (m/h)
10 20
1. Pressure wave velocity
310 m/s 310 m/s
2. Initial wave velocity
1.643 m/s 3.285 m/s
3. Pressure fluctuation
5.09 bar 10.18 bar
3.1 Maximum pressure
9.49 bar 14.58 bar
3.2 Minimum pressure
-0.69 bar -5.78 bar
4. Critical wave period
1.9 second 1.9 second
Collapsing pressure
-2.88 bar -2.88 bar
Maximum allowablenegative pressure
-1.44 bar -1.44 bar
Effective safety factor
2.37 1.54
Statement
Pmin
is within thePe parameter, hence thesystem will withstand thenegative pressure.
Pmax
is less than themaximum permissiblepressure of 15 bar.
Pmin
is outside thePe parameter, hence thepipe will collapse.
Pmax
is less than themaximum permissiblepressure of 15 bar.
u
Note: In cases of negative pressure Chas a value of 2
as in section 3.3. In t his example the water hammer
procedure was followed (4 steps) in addition Pc and Pe
were calculat ed as out lined in sect ion 3.3 and Cmax
as
outlined in section 5.6.
Where is circumferent ial stress (MPa)
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Reynolds number
Frictionfa
ctor
Relativeroughness
Laminar flow
0.008
0.01
0.00001
0.0001
0.0005
0.001
0.005
0.01
0.02
0.03
0.04
0.05
0.02
0.03
0.04
0.05
0.06
0.07
0.08
103 104 105 106 107 108
Turbulent flow
Transientzone
Chart 5.1 The Moody diagram
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Storage, handling and installation
6.0 IntroductionOne of th e key part s of a successfu l install ation comes fr om
th e way that plasti c pipes and component s are
stored and handled. This chapter deals with the installation
of plastic pipeline systems and describes the
methods for preserving stru ctur al int egrity and
compensating for thermal expansion.
6.1 Storage and handling
Pipe is often stor ed directly on the gr ound o r support ed in
racks or pallets and the f ollow ing condition s
should be observed: -
Ensure th at t he ground surf ace is level and cleared of
debris to prevent the pipes from becoming bent, scored
and damaged.
Pipes should never be stacked more t han 6 layers high
and in hot climat es th is shoul d be restr icted t o 4 layers.
Large bo re pipes shoul d not be stacked greater than
1 metre high, t hus avoiding ovality due to heat
and pressure.
Pipes of di ff erent diamet ers and wall t hickness shoul d be
stacked separately. If t his is not practical th e larger
diameter and t hicker walled pipes should be sto red at t he
bott om of t he stack.
Pipe racks shoul d be const ructed to pr ovide ful l support
to each pipe layer. Side supports should be at least
100mm wide and be placed at regu lar int ervals of
1.2 metr es along t he pipe length .
Narrow straps to suppo rt t he pipe stack should
be avoided.
Pipes can be stored in pal let ised stacks as lon g as the
pallets and not the pipes support the stack weight andpallet s shoul d be stacked no more than 3 pallet s high fo r
shor t periods only.
Pipes and fi tt ings sto red for an extend ed period of ti me
should be pr otected from direct sunlight t o avoid UV
degradation. Fittings should be stored using a method
that allows air circulat ion such as por ous hessian sacks,
boxes or on shelves.
The whole purpose of correct handling is to avoid damage
to pipes and should encompass loadin g, t ransit and
unloading of the pi pes. The fol lowi ng guid elines should b e
addressed w hen handling p ipes: -
Pipes shoul d be loaded and unloaded manually wi th out
draggi ng t hem over t he ground , as th is causes damage.
However if handling pallets of pipe by forklif t ensure that
th e for ks do not cause damage.
Flatbed vehicles shoul d be used to distr ibut e pipe loads
and th e largest di ameter pi pe shoul d be loaded fi rst w it h
the smaller pipe loaded on top or nested inside to avoid
damage. Do not drop pipes off the vehicle whenoff loading but handle and stack them correctly.
6.2 Installation of plastic pipes
Thermoplasti cs expand and contract t o a far g reater extent
th an metals and t he fo llow ing sketch provides a compari son
between some metals and plastics: -
There are tw o facto rs to consider w hen calculating
expansion o r cont raction i n pipes: -
Environmental temperature (external temperature) at
which the pip e will stabilise prior t o installation .
Fluid temperature (internal temperature) whi ch is the
operational t emperature of the p ipeline system.
The change in length due to thermal expansion or
cont raction i n a pipelin e system i s determined by the
following f ormula: -
Where L Expansion (Le) or contraction (Lc) in mm
T Difference in temperature betw een the
installation and the operating
temperatu res in C (=Toperate- Tinstall)
L Length of pipe when in stalled
Coef fi cient o f expansion
Figure 6.1 Comparison of thermal expansion of
plastics and metals
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Mild steel
Stainless steel
Copper
PVCu
ABS
Polypropylene
Polyethylene
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Solution
StepOperating temperature (oC)
30 8
Calculate temperature difference
T (=Toperate- Tinstall)= 30 - 10
= +20C
= 8 - 10
= -2C*
Calculate change in length due to expansionand contraction
L = T x L x( = 0.078 for PVCu)
= 20 x 30 x 0.078= 46.8mm
= -2 x 30 x 0.078= -4.68mm*
Select length of flexiblearm or compensator
Take the greater value (change inlength) regardless of whether it is dueto expansion or contraction that canaccommodate the maximum movement.
In this caseL= 46.8mm
For example PVCu will expand 0.078mm per metre for
every 1C raised in mid-wall temperatu re above t he installatio n
temperature.
Please note t hat t he temperatu re diff erence is the di ff erence
between the installation temperature and t he working temperature,
in deg rees Celsius (C).
Table 6.1 Coefficient of linear expansion for thermoplastics ()
Thermoplasticmaterial
Coefficient (10-5m/mC)
Length/temperatureequivalent (mm/mC)
PVCu 7.8 0.078
ABS 10.1 0.101
PP 15.0 0.150
PE 20.0 0.200
* Please note a (-) minus value repr esents th e dif ference in
temperature (it is not a subzero) and hence it causes a contraction
of t he length of t he pipe.
Worked example 6.1Find t he expansion and cont raction on a 4 diamet er PVCu
pipe system installed at 10C, where t he maximum and
minimum operat ing temperatu res are 30C and 8C
respectively and the overall length of the installation is 30m.
Table 6.2 Calculated expansion for 1 metre length pipe
Temperaturedifference (C)
Expansion (mm) CommentPVCu ABS PP
1 0.078 0.101 0.150
2 0.156 0.202 0.300
3 0.234 0.303 0.450 For the temperaturerange not on thechart add the factors
4 0.312 0.404 0.600
5 0.390 0.505 0.750
6 0.468 0.606 0.900
7 0.546 0.707 1.050 i.e.For PVCu @ 37C
8 0.624 0.808 1.200
9 0.702 0.909 1.350 20C = 1.560mm
10 0.780 1.010 1.500 +17C = 1.326mm
11 0.858 1.111 1.650
12 0.936 1.212 1.800 37C = 2.886mm13 1.014 1.313 1.950
14 1.092 1.414 2.100
15 1.170 1.515 2.250
16 1.248 1.616 2.400
17 1.326 1.717 2.550
18 1.404 1.818 2.700
19 1.482 1.919 2.850
20 1.560 2.020 3.000
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Storage, handling and installation
6.3 Flexible arms in pipelineinstallations
Flexible arms or expansion bellow s are used in order t o
avoid the associated stresses generated from a pipes change
in length due to expansion or contraction. Expansion
bellows are not a prime concern of this document and th e
installer is advised t o seek specialist gu idance fro m t he
manuf acturers of such pr oducts. The fl exibilit y of plasti cs
permits expansion or contraction to be compensated for by
means of eith er directional change wit hin a pi pe system
(single fl exible arm) or by t he installati on of expansion l oops
consisti ng o f tw o fl exible arms (double fl exible arm), asshow n in t he follow ing illustr ations: -
6.5 Pre-stressing flexible arms
Somet imes changes of l engt h (L) can on ly be channelled in
one di rection, p ossibly du e to a fl exible secti on h aving t o
operate in a confi ned space. When this occurs the fl exible
arm can be pre-str essed achieving t he followi ng:-
The fl exible arm can be reduced in lengt h
The fl exible arm will straight en under working condit ions
thus relieving a large amount of stress
The installation w ill look bett er when in service
6.4 How to find the flexible arm (a)length
To calculate the lengt h of a fl exible arm () the fol low ing
fo rmul ae can be used: -
Single arm:
Double arm:
Where a Flexible arm lengt h (mm)
D Pipe out side diamet er (mm)
L Expansion o r Cont raction (mm ) for single
arm, for double arm useL/2
Cm Constant fo r mat erial, see table 6.3Figure 6.2 Single arm
Figure 6.3 Double arm (expansion loop)
(Lc) (Le)
a
(Lc)(Le)
ab
Fixed point
Table 6.3 Thermoplastic materia l constant (Cm)
Thermoplastic material Constant
PVCu 33.5
ABS 32.7
PP 30.0
PE 26.0
Solution
Single arm Double arm
a = 970mm a = 686mm
Worked example 6.2
A 40mm ABS pip e (Cm = 32.7) has expanded in lengt h by
22mm, what is the lengt h required f or single and double
fl exible arm arrangement s?
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Worked example 6.3A 15 metre lengt h of 63mm PVCu pipe (= 0.078 for PVCu)
was install ed at 10C, if th e workin g t emperature is 50C
determine the layout of the non pre-stressed and
pre-stressed arm arrangements.
Solution
Non pre-stressed Pre-stressed
There will be an expansion of 47mm,therefore the flexible arm length will be 1823mm.
Half of the expansion (23.5mm) is now pre-stressed,therefore the flexible arm length will be 1289mm.
FixedPoint
15m
a = 1823mm
= 47mmL
FixedPoint
15m - 23.5mm
a = 1289mm
= 23.5mm2L
( )a 33.5= 1823mm=63 47
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Storage, handling and installation
Full suppo rt of t he pipeline can be achieved by
running along suitable channel and restr aining it
fro m lateral movement.
Pipelines wh ich are suspended have to be suppo rt ed by
brackets spaced at predet ermined int ervals (see tables
6.4, 6.5 and 6.6).
Limit ing Rings PVCu and ABS: These can be made by
cutting a small length (dissecting 1/3rd of the
circumf erence) of class C o r 10 bar pipe of th e same
outside diameter of the carrier pipe. The remaining
segment can be sprun g open and t hen solvent w elded
into place on t he carrier pipe.
Figure 6.4 Support s, brackets and limit ing rings
6.7 BracketsPipe brackets need to be made with the inside diameter of
the bracket marginally larger t han the pipe out er diameter.
This allows free lineal movement of the pipe and avoids
inhibit ing expansion o r contr act ion. They shoul d also be
smoot h, to avoid damage to t he outer surface of t he pipe.
There are tw o basic types of bracket s, as shown in fi gures
6.5 and 6.6, namely loose brackets and fi xed br acket s.
Tables 6.4 and 6.5 are based on class E pip e (15 bar) or the
PN16 metric rating. For pi pes of a lower rat ing t he spacing
wi ll be closer, derate as fo llow s: -
Class D (12 bar) and PN12 rat ed pipe x 0.75
Class C (9 bar) and PN10 rat ed pip e x 0.62
Figu re 6.5 Loose brackets - axial movement is
required without constraint
A loose bracket
allow s axial
movement.
A sliding bracket
allows movement
along a fl at
supporting surface.
Hanging bracket
allows radial and
axial movement.
Figu re 6.5 Fixed brackets - axial movement
constrained or cont rolled
A bracket oneither side
prevents axial
movement.
A bracket betweentwo pipe sockets or
limiting rings
prevents axial
movement.
A bracket t o controlpipe movement in
one direction .
6.6 Plastic pipe systems supportand bracketing
Plast ic pipe systems requir e regu lar support wh ich can vary
according to pipe material, size and wall dimension o f the
pipe, the weight (density) of the liquid carried and the
temperature of the pi pe wall. There are three t ypes of
mechanism which support or restrain pipe movement:
Restrained within a channel; supported with clips or
brackets at pr edeterm ined int ervals (see tables 6.4, 6.5,
and 6.6) and limiting rings to restrict axial movement.
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Table 6.4 Bracket spacing for gases and liquids PVCu PN 16 metric pipe and class E (15 bar) imperial pipe
Pipe size Bracket spacing in metres
mm inch 20C 30C 40C 50C 60C
16 3/8
0.80 0.70 0.50 * *
20 0.90 0.80 0.60 * *
25 1.00 0.90 0.70 0.55 0.40
32 1 1.10 0.95 0.75 0.60 0.45
40 1 1.20 1.10 0.90 0.70 0.55
50 1 1.30 1.20 1.00 0.80 0.60
63 2 1.40 1.30 1.10 0.90 0.65
75 2 1.50 1.40 1.20 1.00 0.7090 3 1.60 1.50 1.30 1.20 0.85
110 4 1.90 1.80 1.60 1.30 1.10
125 - 2.10 2.00 1.85 1.60 1.25
140 5 2.20 2.10 1.90 1.65 1.35
160 6 2.30 2.20 2.00 1.75 1.50
225 8 2.60 2.45 2.30 2.00 1.75
250 - 2.80 2.70 2.55 2.20 1.95
280 10 3.20 3.00 2.85 2.50 2.15
315 12 3.60 3.40 3.20 2.80 2.45
Table 6.5 Bracket spacing for gases and liquids - ABS class E pipe (15 bar)
Pipe size Bracket spacing in metres
inch 20C 30C 40C 50C 60C
3/8
0.80 0.75 0.65 0.60 0.50
0.90 0.80 0.75 0.65 0.55
1.00 0.95 0.85 0.75 0.70
1 1.10 1.00 0.95 0.80 0.75
1 1.20 1.10 1.00 0.90 0.80
1 1.25 1.20 1.10 0.95 0.85
2 1.40 1.30 1.20 1.00 0.90
2 1.50 1.35 1.25 1.15 1.00
3 1.60 1.45 1.35 1.20 1.05
4 1.80 1.65 1.55 1.35 1.20
5 2.00 1.80 1.70 1.50 1.30
6 2.10 1.90 1.80 1.60 1.40
8 2.30 2.10 1.90 1.70 1.50
* Implies full support requirement.
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Storage, handling and installation
Table 6.6 Bracket spacing for gases and liquids - polypropylene metric 10 bar rated pipe
Pipe size Bracket spacing in metres
mm 20C 40C 60C 80C 100C
16 0.74 0.68 0.63 0.54 0.39
20 0.79 0.69 0.64 0.59 0.44
25 0.84 0.82 0.74 0.69 0.49
32 0.99 0.94 0.84 0.74 0.54
40 1.05 1.03 0.94 0.84 0.59
50 1.20 1.14 1.04 0.89 0.69
63 1.38 1.29 1.18 1.04 0.79
75 1.53 1.43 1.28 1.13 0.8490 1.63 1.53 1.43 1.23 0.93
110 1.84 1.73 1.58 1.38 1.04
6.8 The Z dimension
The fo llowi ng steps should b e undertaken in p reparation f or
a pipeline installation: -
Prepar e a basic sket ch of t he pipel ine system,
including fi tt ings.
Ent er the dimensions of t he pipes and fi tt ings and the
cent re to cent re measurement of each secti on eit her by
measuring on site or from the engineers drawings.
Calculate the cut length of each piece of pipe betw een
fi tt ings to enable correct o verall assembled leng th of
section as follows: -
L = M - Z1
- Z2
Where L Cut length of pipe
M Centre to centre length betw een fi tt ings
Z1
- Z2
Linear Dimensions of fi tti ngs
As an example, the install atio n not es fo r a PVCu pip e wou ld
appear as fo llow s: -
M cent re to cent re = 1200mm
Less Z1
fl ange = 4mm
Less Z2
bend = 80mm
- 84mm
L cut lengt h pipe = 1116mm
L
M
Z2
Z1
Figure 6.7 - Z dimension
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Chart 6.1 Length of flexible arm: general guide for PVCu & ABS
3000
1000
Change in length (mm)
Lengthofflexiblesection
(mm)
1001 10
12"
100 300
315
10"
280
8"
25022
520
06"
160
5"
140
125
4"
110
3"
9021/2"
752"
6311/2"50
11/4"
401"
32
3/4"251/2"203/8"16
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Methods of jointing
7.0 IntroductionThis chapter deals wit h t he fou r key methods of jo ining
plastic pipes and t he selection of a joint ing m ethod is
dependent on t he pipe mat erial and it s characteristi cs.
Table 7.1 is a guide t o the selecti on of t he type of join t
which can be used fo r t he particular pipe material.
= Suit able = Not suitable
Table 7.1 Thermoplastic jointing methods
MethodPVCu
Thermoplastic material
ABS PP and PE
Solvent cement
Solvent cement is formulated to chemically solvate the surfaces of pipes and fittings, so that when they are pushed together the softened surfaces intermix and cure into a
hard, strong and leak-free joint.
Materials welded this way must be alike, i.e. PVCu to PVCu and ABS to ABS. Not PVCu to ABS or vice versa.
Mechanical
This method uses threads and flanges to connect the different parts of pipeline systems.
Fusion
Fusion jointing involves heating the two components to be joined, so that the fusion/melt temperature on each surface is reached simultaneously. The two melted surfaces
are then brought together at a pressure designed to produce a homogenous joint when cooled. The resulting joint will have an equivalent strength and pressure rating as the
original pipe. Contact Polypipe for further details.
Compression
Compression jointing consists of compressing a rubber ring between the inner wall of the fitting and the outer wall of the pipe to be jointed. Compression joints can be used
to connect different types of pipe, both plastic and metal. As long as the correct fitting is selected, taking into account the outside diameters of the different types of pipe
work, then a satisfactory joint can be made. Note: Compression joints are designed primarily for use on water pipelines.
Contact Polypipe for further details.
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Table 7.2 PVCu and ABS solvent jointing procedure
Procedure Equipment
Important information: Always use Personal Protective Equipment - gloves
and eye protection
Always carry out work in a well ventilated area
Always refer to Material Safety Data Sheets
Dispose of waste responsibly
Failure to follow the jointing procedure may invalidate
any warranties given
1. Cut the pipe at right angles to its axis
and to the required length.
Deburr the cut end of the pipe with a
sharp knife or scraper.
Pipe cutter
SawScraper or knife
2. Chamfer the leading edge of the pipe at
approximately 15 to 30. This will prevent the
solvent cement being wiped from both the pipe
and fitting when mated together and will also
help to build up a ring of solvent around the
chamfer, thus ensuring a proper seal.
Pipe Size
38 (16mm)
- 1 (20 - 50mm)
2 - 8 (63 - 225mm)
Chamfer Size (mm)
2
3 - 4
5 - 6
Chamfering tool
Fine disc angle
grinder, file or
abrasive paper
80 - 100 grit
3. Mark the pipe back from the chamfered
end to a length equal to the socket
depth plus 5mm.
This mark will act as a visual indicator
to show that the pipe is fully inserted
into the socket.
Marker pen
4. Roughen the pipe surface (up to the
indicator mark) and the inside of the
socket with abrasive cloth or paper.
Do not roughen the pipe and fitting to the
extent that the clearance between them
is noticeably increased.
Abrasive
paper/cloth
80 - 100 grit
5. Clean the inner surface of the socket and the
surface of the pipe up to the mark using a lint
free cloth or absorbent paper dampened with
Effast solvent cleaner.
Lint free cloth or
absorbent paper
Effast solvent cleaner
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Methods of jointing
Table 7.2 PVCu and ABS solvent jointing procedure - continued
Procedure Equipment
6. Select the correct solvent cement, PVCu to PVCu,
ABS to ABS. (failure to use the recommended solvent
cement may invalidate any warranties given)
Apply the cement straight from the tin and ensure all
relevant surfaces are covered.
Read the instructions on the tin.
Avoid using excessive amounts of
solvent cement.
Effast PVCu cement
Effast ABS cement
Brush (half the diameter
of the socket)
Joints are normally made in temperatures between 5 - 25C and in dry conditions, damp or wet conditions can adversely effect the solvent jointing procedure. The maximum
time before the cement is too dry for jointing is approximately 3 minutes. In hot weather this time is reduced. The joint must be made whilst the cement is still wet.
At temperatures below 5C the curing time will be considerably increased.
7. Push fittings/pipe together without twisting andensure that they are aligned and fully engaged (the
indicator mark should be in line with the edge of
the socket) then hold the assembly for a short time
as specified.
Pipe Size
38 - 2 (16mm - 63mm)
2 - 4 (75 - 119mm)
5 - 8 (140 - 225mm)
10 - 12 (250 - 315mm)
Holding Time
(minutes)
1
2
When the joint is made, an O-ring of cement is formed between the pipe chamfer and the internal socket wall. This ring helps to ensure seal integrity. A bead of cement will
show around the external junction of the pipe and fitting, this should be wiped off leaving the outer part of the joint clean. Do not disturb for at least 10 - 15 minutes to
ensure that the weld integrity is maintained. After this period, the assembly can be carefully handled, prepared for further jointing or left for the recommended curing
time which is:
Up to 8 (225mm) ambient temperature constantly above 5C After 8 hours The joint will have cured enough to withstand the working pressure.
After 24 hours The pipe system can be fully pressure tested.
The number of operators:
For joints of up to 2 (75mm) 1 person is required, from 3 (90mm) up to 6 (160mm) 2 persons are needed, for 8 (225mm) and above 3 people are required.Pipe work should be ventilated during the joining and curing processes. Never seal a pipe system which has been newly jointed as the trapped vapours can cause damage.
Positive ventilation with a small air blower is recommended to purge systems with multiple joints.
Table 7.3 Recommended joints per litre of Effast cement
Pipe size Thermoplastic material
inch mm PVCu ABS
3/8
- 1 16 - 32 300 400
1 - 2 40 - 63 120 175
2 - 3 75 - 90 50 70
4 110 30 45
5 140 20 30
6 160 15 25
8 200 - 225 8 15
10 250 - 280 3 4
12 315 3 4
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7.1 Important point s Heavy equipment should be support ed independently
fr om t he pi peline. i.e. valves, str ainers, etc.
Pipe clips shoul d be made to allow linear expansion of
the pipeline and if l ined the lining should be of a
material compatible w ith t he pipeline.
Mast ics, int umescent mastics, adhesive tapes and labels
should not be used (as many degrade plastics), unless
manuf acturers provide document s of adhesive or
mastic compatibility.
Insulat ion must be considered very careful ly, as a numberof foam rubber in sulation products and t heir adhesives
may not be compatible with plastic pipes.
Adhesives should on ly be used to bon d t he foam edges
tog ether and should never be used to bond t he
insulation to the pip eline. Refer t o manuf actur ers for
compatibility data. For example, compatible insulations
are fi bre wools (Rockwool), polystyrene, etc.
Trace heating tapes: Dont u se tapes covered wit h
plasticized PVC as this can react with thermoplastic pipes.
Tapes wi th sheaths made from w oven wi re, polyester or
silicone r ubber are acceptabl e.
Oils: A number of synthetic oils are not suit able for use
with plastic pipelines. Oils such as esters, organic
phosphates and polyalkylene g lycols should be avoided.
Health and safet y: Solvent cement and cleaning fl uid
give off vapours that are dangerous to health. During
jointing the w ork place must b e well ventilated.
7.2 Solvent joint ing , " Do Nots"
Make joint s in rain or wet condit ions.
Use dirt y brushes or cleaning rags.
Use the same brushes wi th dif f erent solvent cement s.
Dilut e or thin solvent cements wi th cleaner.
Leave solvent cement t ins open as th e cont ents wi ll
evaporate and the cement performance will be reduced.
Use near naked ligh ts or smoke whi lst join ti ng as solvents
are high ly fl ammable.
Make join ts in a confi ned space as solvents emit
hazardous vapours.
7.3 Mechanical jointing procedure - threadedfi t t ings - plast ic to plast ic
An extensive range of th readed fi tt ings are available, mostl y
parallel threaded but some t apered. Thread compatibi lity is
an essenti al aspect of join ti ng. For jo int ing such part s fo llow
these steps: -
1. Select compatib le thread i.e. Parallel t o Parallel, never
Parallel t o t aper or vice versa.
2. Use PTFE tape to seal t he jo in t . If sealant pastes are used
they must be compatible with the plastic components.
3. Hand tight en and if n ecessary tighten f urt her to a
maximum of turn using a str ap wr ench.
PVCu class 7 and ABS class T pipes, sizes 38 up to 2 are
manufactur ed wit h a thick wall t o enable threads to be cut.
7.3.1 Flanges - plastic to p last ic/metal
Flanges are suit able for j oini ng metals or rubbers to p lasti cs.
Joint ing such part s fo llow th ese steps: -
1. Ensure fl anges are paral lel, close to each other and al low
a gap for the gasket.
2. Insert gasket, ensure th at t he bolt h oles are align ed.
3. Use fl at w ashers betw een bolt h ead, the nut and
the fl ange.
4. Tight en bolt s accord ing t o t he sequence fi gure 7.3
and table 7.4.
Rubber Gasket
Flange
Plastic Female Adaptor
Metal Union Nut
Gasket
Metal Adaptor
Figure 7.1 Flange joint
7.3.2 Composit e unions - metal t o pl ast ics union j oin t
Figu re 7.2 Composit e
NOTE: If metal th read
is used in conjunction
wit h a plastic thr ead
then the temperature
should not vary by
more than 5C.
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Methods of jointing
1
2
34
5
6 7
8
Table 7.4 Flange bolting torques (approximate)
Pipe sizeInch 1 1 1 2 2 3 4 - 5 6 - 8 10 12
mm 20 25 32 40 50 63 75 90 110 125 140 160 200 225 280 315
TorqueNM 8 9 10 18 24 32 36 40 44 48 50 62 74 76 76 76
Ft/Pdl 6 7 8 13 18 23 26 29 32 35 37 46 54 56 56 56
Figure 7.3 - Flange bo lt t igh tening sequence
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Pipe and fi ttings dimensions
DIN 8077/8078 PP-H (metric) pipe dimensions
Diameter (mm) Wall thickness (mm)
Outside diameter Mean outside diameter 6 bar 10 bar
Minimum Maximum Min Max Min Max
16 16 16.3 - - 2.0 2.4
20 20 20.3 1.8 2.2 2.5 3.0
25 25 25.3 1.8 2.2 2.7 3.2
32 32 32.3 2.0 2.4 3.0 3.5
40 40 40.4 2.3 2.8 3.7 4.3
50 50 50.5 2.9 3.4 4.6 5.3
63 63 63.6 3.6 4.2 5.8 6.6
75 75 75.7 4.3 5.0 6.9 7.8
90 90 90.9 5.1 5.9 8.2 9.3
110 110 111.0 6.3 7.2 10.0 11.2
EN1452 part 2 PVCu (metric) pipe dimensions
Outside diameter (mm)Average wall thickness (mm)
6 bar 10 bar 16 bar
16 - - -
20 - - 1.5
25 - - 1.9
32 - 1.6 2.4
40 1.5 1.9 3.0
50 1.6 2.4 3.7
63 2.0 3.0 4.7
75 2.3 3.6 5.6
90 2.8 4.3 6.7
110 3.2 4.2 6.6
125 3.7 4.8 7.4
140 4.1 5.4 8.3
160 4.7 6.2 9.5
180 5.3 6.9 10.7
200 5.9 7.7 11.9
225 6.6 8.6 13.4
250 7.3 8.6 14.8
280 8.2 10.7 16.6
315 9.2 12.1 18.7
Safet y facto r c = 2.5
Safet y facto r c = 2
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Pipe and fi ttings dimensions
DIN 8061 PVCu (metric) pipe dimensions DIN 8063 PVCu (metric) fitting dimensions
Diameter (mm) Average wall thickness (mm) Diameter (mm)
Outsidediameter
Mean outside diameter6 bar 10 bar 16 bar Nominal size
Mean socket internal diameterat midpoint of socket depth
Minimum Maximum Minimum Maximum
16 16 16.2 - - 1.2 16 16.1 16.3
20 20 20.2 - - 1.5 20 20.1 20.3
25 25 25.2 - 1.5 1.9 25 25.1 25.3
32 32 32.2 - 1.8 2.4 30 32.1 32.3
40 40 40.2 1.8 1.9 3.0 40 40.1 40.3
50 50 50.2 1.8 2.4 3.7 50 50.1 50.3
63 63 63.2 1.9 3.0 4.7 63 63.1 63.3
75 75 75.3 2.2 3.6 5.6 75 75.1 75.3
90 90 90.3 2.7 4.3 6.7 90 90.1 90.3
110 110 110.3 3.2 5.3 8.2 110 110.1 110.4
125 125 125.3 3.7 6.0 9.3 125 125.1 125.4
140 140 140.4 4.1 6.7 10.4 140 140.2 140.5
160 160 160.4 4.7 7.7 11.9 160 160.2 160.5
180 180 180.4 5.3 8.6 13.4 180 180.3 180.6
200 200 200.4 5.9 9.6 14.9 200 200.3 200.8
225 225 225.5 6.6 10.8 16.7 225 - -
250 250 250.5 7.3 11.9 18.6 250 - -
280 280 280.6 8.2 13.4 20.8 280 - -
315 315 315.6 9.2 15.0 23.4 315 - -
BS 3505 PVCu (imperial) pip