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Some useful web sites and references

Borouge www.borouge.com

Borealis www.borealisgroup.com/pipe

Unicor GmbH www.unicor.com

Fränkische GmbH www.fraenkische.de

Corma Inc. www.corma.com

KWH Group Ltd. www.kwhpipe.com

The Gulf Plastic Pipes Academy www.yourppa.org

Plastics Pipes for Water Supply and Sewage Disposal Book by Lars-Eric Janson, 2003

Dreiling, G. “BorECO Polypropylene for sewage pipe systems” Dubai Plast Pro, April 2007

Barresi, S & Ek, C-G Plastics Pipes XII, April 2004“Large diameter spirally wound PP sewerage pipes installation in Italy”

Materials for Sewage Applications

PP GradesBorECO BA212E This is a high modulus PP-HM material, specifically designed for the production of non pressure sewage and drainage pipes. Due to its higher stiffness, it provides a 15% weight saving against standard PP-B and a 27% weight saving against PVC.

BorECO BA415EThis is an intermediate stiffness PP-B material, designed

specifically for the production of twin wall sewage and drainage pipes. It will produce high quality products at high output rates.

BA202EThis is a standard PP-B material suitable for a wide range of pipes, fittings, sheets and profiles.

Commercial Reference Material Type Modulus Application

BorECO BA212E PP-HM 1700 High stiffness extrusion grade

BorECO BA415E PP-B 1500 Intermediate stiffness for twin wall pipe extrusion

BA202E PP-B 1300 General purpose PP-B grade

PE GradesBorSafe HE3490-LS This is a PE100 pipe compound providing an excellent balance of production and end use properties. It is a high output material which is ideal for producing liner pipes for renovating gas, water and sewage systems.

Borsafe HE3490-LS-H This PE100 pipe compound has exceptional resistance to stress cracking, making the pipe less vulnerable to failure due to installation damage. Ideal for the outer layer of a

multilayer pipe installed using directional drilling or pipe bursting techniques.

BorSafe HE3490-IMThis is a PE100 compound with improved flow properties, which makes it ideal for the production of injection moulded fittings. The higher flow enables a lower melt temperature to be used. which reduces built in stresses (lower scrap rate) and the production cycle time (lower costs).

Commercial Reference Material Type Colour Application

BorSafe HE3490-LS PE100 Black Extrusion all pipe sizes 63 – 2000mm

BorSafe HE3490-LS-H PE100 High SCR Black Extrusion pipes for demanding conditions

BorSafe HE3490-IM PE100 High flow Black Injection moulded pressure fittings

Polypropylene materials for Non-Pressure Sewage & Drainage Systems

Polypropylene materials for non-pressure sewage and drainage systems

PP Sewage System Solutions

The principle design characteristic of a non-pressure pipe is

its ring stiffness, which is a measure of the pipes’ resistance to

applied loads. The ring stiffness of the pipe is a combination of

the stiffness of the material and the structural design of the wall.

In order to provide the optimum stiffness for minimum weight,

different designs are used for different size ranges of pipe.

Smaller diameter sewer pipesSmall diameter PP sewage pipes (110 – 315mm) are usually

made of solid walled construction with socketed ends, for easy

connection (see fig. 5). In recent years, high modulus PP-HM

materials have been developed, which provide the ideal balance

of stiffness, impact strength and long term properties for non-

pressure sewage and drainage pipes. These materials allow the

wall thickness of the pipe to be reduced, for a given stiffness class

and therefore, are more competitive against other materials.

Intermediate sized structured wall pipesFor larger diameters (250 – 800mm), structured wall PP designs

are usually used to improve the stiffness to weight ratio, and

thereby reduce the cost per metre. Common designs include

ribbed pipes (e.g. Ultrarib) or twin walled pipes, with a corrugated

outer and smooth inner wall.

To optimise the design of the pipe corrugation, profile design

needs to be matched to the material stiffness. A number of

specialised machine manufacturers, such as Unicor, Fränkische

and Corma, offer equipment and advice on how to produce these

pipe products.

Large diameter non – pressure pipesAt very larger diameters (800 – 4,000mm), it is usual to use a

spiral winding process rather than a conventional corrugator. This

is constructed from an extruded PP or PE profile that is wound

onto a mandrel and welded to the adjacent spiral. In this way, it is

possible to build up pipes up to 4,000mm in diameter. European

pipe manufacturers, such as KWH and Krah, offer expertise and

equipment for the manufacture of such pipes.

Fig. 2: Specific weight of sewer pipe materials

Fig 1: Rigid pipes fail in a brittle mode

Fig. 3: Hydraulic flow characteristics of sewer pipe materials

Market trends

Over 150 years ago, it was established that a piped sewage system provided a major improvement to public health. Today, however many of our sewers in the major cities are cracked and leaking into the environment.

Most old sewer pipes are made from rigid materials, like concrete or clay that are brittle and fail due to stone impingement or ground movement (see fig. 1). The generation of sulphuric acid also causes internal corrosion of concrete, which further weakens the structure and is a major problem in hot dry climates. Ground movement and tree root intrusion are also problems for traditional sewage systems.

Fig. 4: Abrasion resistance of different pipe materials

Average abrasion (am in mm)

2,0

1,5

1,0

0,5

0,25

00 50 100 150 200 250 300 350 400 450 n in 1000

Cement pipe

MC-DUR linedcement pipe FRP pipe

Clay pipe

PVC-pipe

PP or HDPE pipe

Number of load cycles (n in 1000)

The benefits of PP materials for sewage pipes:

• ChemicalResistance–Polyolefinmaterialsarevery resistant to sulphuric acid erosion. Indeed, they are used to renovate or protect concrete sewer pipes.

• Specificweight–PPhasthelowestspecificweight of all sewage pipe materials, producing a stiff lightweight system that is easy to install (see fig. 2).

• Hydraulicflow–PPpipesareverysmoothandhave the lowest friction factor of all sewer pipe materials. Therefore, solids can be transported even at low fluid flows, which is important in hot dry climates like the Middle East (see fig. 3)

• Abrasionresistance–Polymers,suchasPP,havea much higher resistance to abrasion than concrete, clay or iron pipes. This is particularly important in countries like the Middle East, where sand is trapped in the sewers and drainage systems (see fig. 4).

• Flexibility–PPistoughandflexibleandwillnotcrack or break at moderate levels of deformation, whereas concrete and clay pipes are very brittle and fail at very low levels of deformation.

• Weldability–wheretreerootintrusionisaserious problem, welded PP pipes systems can be used, forming an impenetrable barrier to tree roots.

Why PP for Sewer Systems?

Polypropylene (PP), like polyethylene (PE), is a polyolefin material that is easily processed to form pipes and fittings. PP is stiffer than polyethylene and therefore, ideal for producing non-pressure pipes and forming the socket joints, which are usually preferred by the installer.

Fig. 5: Solid wall PP sewage pipe

Fig. 6: Structured wall sewage pipes

Fig. 7: Large diameter spiral wound pipe

Read these case stories where polypropylene materials have provided a durable solution• Corrosionresistant• Highabrasionresistance• Highstiffnessmaterials• Highresistancetoacids&otherchemicals

Concrete

Iron

Steel

Clay

PP

Wall roughness factor0 0,5 1 1,5 2 2,5 3 3,5

Steel

Iron

Concete

Clay

GRP

PVC

PP

Specific Weight - kg/m3

0 1000 2000 3000 4000 5000 6000 7000 8000 9000