technical_manual_hdpe_pipes.pdf

8/20/2019 technical_manual_hdpe_pipes.pdf

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Contents

Page

Profile: Company Details 3

1 Polyethylene (PE - HDPE/MDPE) Pipe 5

2 Polyethylene (PE) Pipe: Benefits 6

3 GPPL‘S PE Pipe: Properties 8

4 BIS Standards 11

5 Design Considerations 12

5.1 Advantages by Using PE100 Grade Pipe 15

6 Polyethylene Pressure Pipes: Designing 17

7 Hydraulic Perspective: Design 21

7.1 Surge Design: Water Hammer Calculation 24

8 Laying And Jointing Of Polyethylene (PE) Pipes 26

9 Maintenance In PE Pipes 30

9.1 Testing Of The Pipe 32

10

Above Ground Installation 34

10.1 Distribution Or Service Connection 36

10.2 Electro Fusion 37

11 Frequent Queries 38

12 Contact Details 42

13 PE100 wall thickness sheet 43

14

Design Analysis 44

15 Project Execution pictures 49

GODAVARI POLYMERS PVT LTD

Head Office, #315, Minerva Complex, S. D. Road, Secunderabad – 500 003

Tel: +91 (40) 27842092, 27897733 Fax: +91 (40) 27819467 Email:[email protected]


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PROFILE

Godavari Polymers Pvt Ltd is one of the largest manufacturers of

Polyethylene (PE - HDPE/MDPE) pipes and fittings to suit the customer

requirements which are part of Water Management techniques by

constantly redefining our quality standards and focusing on surpassing of the

same thus adding value to end users and business associates.

Godavari Polymers Pvt ltd is one of the manufacturers of pressure rated

Polyethylene (HDPE/MDPE) pipes was incorporated in August, 1990 as a private

limited company with Register of companies, Andhra Pradesh with an objective

to manufacture High Density Polyethylene (HDPE) pipes and the unit is located at

Cherlapally, IDA , Secunderabad, Ranga Reddy Dist.

Godavari Polymers Pvt Limited having started operations and has a capacity of10000 tonnes per annum with pipe sizes from 20MM to 500 mm (as per BIS

Standards), today it is one on the largest manufacturers of PE( HDPE/MDPE) pipes,

Sprinkler and Drip Irrigation Systems in Indian sub-continent.

Godavari Polymers Pvt Ltd not only into manufacturing of PE piping and also

aimed to strengthen the operations and provide customers trouble free solutions

on piping undertakes projects on turnkey basis from designing to commissioning.

The products are also serviced in many critical applications of industrial slurry and

effluents spread over various segments.

Certifications:

Our manufacturing facility is accredited for Quality Management Systems as per

DIN EN ISO 9001:2000.

GPPL products are approved by Bureau of Indian Standards and also produced in

line with other international standards Viz., BS/DIN/ISO etc.

Quality Assurance:

Godavari Polymers Pvt Ltd well established Quality Assurance system supports and

ensures highest quality in the industry for the products manufactured with timely

supply to our customers which meet the requirement completely. Godavari

products are stringently checked at each stage of the production as well as post

production process.


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Infrastructure:

Our infrastructure plays an important role in enabling us to meet the exact

requirements and standards of the industry. We are empowered by a

sophisticated infrastructure, supported by highly experienced professionals.

All our equipment and machinery incorporate the latest technologies that enable

us to maintain our competitive edge in the market.

Godavari Polymers has skilled and trained manpower for execution of the works

with equipment imported for meeting best installation practises.

Godavari Polymers believes and promotes on updating the clients and users on

various developments of the product and its applications. The company

continuously organizes seminars and workshops to update on various subjects at

frequent intervals. Also organizes training programs on installation techniques forbenefit of users for best installation and maintenance practises.

Customer Satisfaction:

We satisfy the requirements of our clients by foreseeing their future demands, by

maintaining a constant relationship with our customers & understanding their

exact requirements and the client satisfaction is the at most motto of the

company.

Clients:

We cater to a wide and expanding network of clients, spread all across the

Indian sub-continent.

We executed many prestigious water development projects/schemes in Govt.,

public and private sectors which not only working efficiently and also serving the

important needs of the beneficiary.


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PART -1 POLYETHYLENE (PE - HDPE/MDPE) PIPE

Godavari Polymers Pvt Ltd (GPPL) is a proven performer in the industrial,

municipal, agricultural/irrigation, mining pipe markets. Engineered for

gravity flow systems and also pumping mains a wide range of PE (HDPE/MDPE)

pipe designs are available to meet specific standard and project requirements.

Characteristics and properties of PE pipes include the following:

Strength

The inherent flexibility of the PE pipe provides this product with its inherent minimum

pipe stiffness of 320 kPa or 210 kPa. The smooth inner wall provides longitudinal

stiffness which enables alignment and grade to be maintained in the trench during

installation.

Impact Resistance

PE pipes take the knocks and bumps of handling, moving in installation with ease.

As the Combination of non-brittleness of PE and its unique Properties makes PE pipe

capable of sustaining impact in both warm weather usage and cold weather

installations.

UV Resistance

PE pipe contains a minimum of 2% carbon black additive to protect the product

from ultraviolet light. This gives PE pipe maximum weather resistance in applicationswhere continuous exposure to the elements is expected.

Chemical Resistance

PE has the highest level of chemical resistance of all traditional sewer products. PE

pipe brings the gravity flow sewer market the same exceptional performance

remaining tough and resistant under conditions that could seriously damage pipe

made of other conventional materials.

Recommended pH Range

PE material provides excellent resistance to both acidic and alkaline environments

with strong acids through all bases, ranging pH 1.25 to 14.

Abrasion Resistance

Tests indicate that PE pipe is highly resistant to abrasion, giving it a significant

advantage over other pipe materials in both acidic and abrasive environments.


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PART-II Polyethylene (PE) pipe: Benefits

Piping made from polyethylene is a cost effective solution for a broad range of

piping problems in municipal, industrial, marine, mining, landfill, duct and

agricultural applications. It has been tested and proven effective for above

ground, surface, buried, slip lined, floating, and sub-surface marine applications.

Excellent flow characteristics

Leak free & High Joint Integrity

Corrosion, Abrasion and Chemical resistance

Excellent flow characteristics

Lightweight and Flexible

Ductility and Toughness

Advantages by using PE pipe

The design and construction of PE product offer a distinct weight advantage over

conventional pipe. They provide ease of handling, positioning, installing and

connecting those conventional pipes cannot match. PE pipe affords these

important benefits to the user:

1.

Savings on Installation

Due to its light weight, less manpower and lighter machinery is needed to transport,

handle and connect PE pipe compared to most of the other pipes. That's real

savings and real value added by using PE Pipe.

2. Fittings and Accessories

Godavari piping systems comes complete with a full range of fittings. Both

moulded fittings and adapters are available, as well as an extensive selection of

Made-to-order fabricated fittings to suit special project needs.

3. Faster Installation

The Continuous coils up to 500 meters can be achieved for the pipes with

diameters from minimal to 110 mm dia pipes. For more than 110 diameter pipe

standard length s up to 12 meter is produced and these 12 meter standard lengths

are easily handled and installed using minimal equipment.


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4. Impact Toughness

PE pipe is highly resistant to the rigors of installation handling in tough

environment prevailing at the site location. PE pipe can be installed with

confidence in the hottest of summer or the coldest of winter conditions.

5. Safer Handling

At less than 10% the weight per meter of concrete pipe, PE pipe gives the handler

and installer a big safety advantage. For example a 2.4 m length of 900 mm

diameter concrete pipe weighs more than 2,400 kg, while an equal length of 500

mm diameter PE pipe weighs less than 100 kg.


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PART-III: About GODAVARI PE PIPE

Godavari PE (HDPE) pipe can carry potable water, wastewater, slurries,

chemicals, hazardous wastes, and compressed gases. In fact, polyethylene

pipe has a long and distinguished history of service to the gas, oil, mining and

other industries.

Godavari PE pipe has the lowest repair frequency per meter of pipe per year

compared with all other pressure pipe materials used for distribution.

Polyethylene is strong, extremely tough and very durable. If the project is for long

service, trouble-free installation, flexibility, resistance to chemicals or a myriad of

other features, high-density polyethylene pipe will meet all your requirements.

Lower life cycle costs

o Corrosion resistance. Does not rust or corrode.

o Leak tight. Heat-fused joints create a homogenous, monolithic system.

The fusion joint is stronger than the pipe.

o Maintains optimum flow rates. Does not support tuberculation and has a

high resistance to scale or biological build-up.

o Excellent water hammer characteristics. Designed to withstand high

surge events.

o High strain allowance. Virtually eliminates breakage due to freezing

pipes.

o

Additional cost savings are achieved by lower instance of repairs.

o With no infiltration, potable water losses and groundwater treatment

costs encountered in traditional piping systems are eliminated.

Reduced installation costs

o Material of choice for trench less technology. Used in directional boring,

ploughing, river crossings, pipe bursting and slip lining.

o Fewer fittings due to pipe flexibility. Allowable bending radius of 20 to 25

times outside diameter of pipe.

o Lighter equipment required for handling and installation than with

metallic materials.

o Eliminates the need for thrust blocking. Heat fused joints are fully

restrained.

o Lightweight and longer lengths allow for significant savings in labour and

equipment.


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LEAK FREE.

o Polyethylene pipe is normally joined by heat fusion. Butt, socket,

sidewall fusion and electro fusion create a joint that is as strong as

the pipe itself, and is virtually leak free. This unique joining methodproduces significant cost reductions compared to other materials.

CORROSION, ABRASION AND CHEMICAL RESISTANT.

o Polyethylene piping’s performance in mining, dredging and similar

applications proves it will outwear many more costly piping materials

when conveying a variety of abrasive slurries.

o PE has excellent corrosion resistance and is virtually inert. It does not need

expensive maintenance or cathode protection. It offers better overall

resistance to corrosive acids, bases and salts than most piping materials.

o In addition, polyethylene is unaffected by bacteria, fungi and the most

“aggressive” naturally occurring soils. It has good resistance to many

organic substances, such as solvents and fuels.

EXCELLENT FLOW CHARACTERISTICS.

o Because polyethylene is smoother than steel, cast iron, ductile iron, or

concrete, a smaller PE pipe can carry an equivalent volumetric flow rate

at the same pressure. It has less drag and a lower tendency for

turbulence at high flow.

o Its superior chemical resistance and “non-stick” surface combine to

almost eliminate scaling and pitting and preserve the excellent hydraulic

characteristics throughout the pipe service life.

LIGHTWEIGHT AND FLEXIBLE

o Polyethylene pipe is produced in straight lengths or in coils. Made from

materials about one-eighth the density of steel, it is lightweight and does

not require the use of heavy lifting equipment for installation.

o It reduces the need for fittings, is excellent in shifting soils and performs

well in earthquake-prone areas. PE resists the effects of freezing and

allows bending without the need for an excessive number of fittings.

Since PE is not a brittle material, it can be installed with bends over

uneven terrain easily in continuous lengths without additional welds or

couplings. DUCTILITY AND TOUGHNESS.

o Polyethylene pipe and fittings are inherently tough, resilient and resistant

to damage caused by external loads, vibrations, and from pressure

surges such as water hammer. Even in cold weather polyethylene pipe is

tolerant to handling and bending.


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MANUFACTURED UNDER RECOGNIZED STANDARDS.

o Polyethylene pipe is listed and approved by the standards or

committees of the agencies like BIS, EEI etc.

AVAILABLE IN DIAMETERS FROM 12mm TO 500mm o Polyethylene pipe is available in a wide range of diameters and wall

thickness, with flanges, elbows, tees, wyes, and valves, providing a total

system solution. PE pipe is also available in Iron Pipe Size (IPS), Ductile Pipe

Size (DIPS) as well as metric sizes. Plastic Pipe Institute members can

provide pipe, fittings and other appurtenances.


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PART-IV BIS Standards

Godavari Polymers Pvt Ltd well established Quality Assurance system

supports and ensures highest quality in the industry for the products

manufactured with timely supply to our customers which meet the

requirement completely. Godavari PE Products are stringently checked at each

stage of the production as well as post production process.

Godavari Polymers Pvt Ltd manufacturing facility is accredited for Quality

Management Systems as per DIN EN ISO 9001:2000

IS No. Title

IS 4984:1995 Specification for High Density Polyethylene pipes for

potable water supplies (fourth revision)

IS 8008(Part 6-8):2003 Specification for injection moulded PE fittings for potable

water supplies: Part 6 Specific requirements for pipe

ends, Part 7 Specific requirements for sandwich flanges,

Part 8 Specific requirements for reducing tests

IS 8008(Part 9):2003 Injection moulded/machined high density polyethylene

(PE) fittings for potable water supplies - Specification

Part 9 Specific requirements for ends caps (first revision)

IS 8360(Part 1 - 3):1977 Specification for fabricated high density polyethylene

(PE) fittings for potable water supplies:

• Part 1 General requirements

• Part 2 Specific requirements for 90 tees

• Part 3 Specific requirements for 90 bends

IS 14333:1996 High density polyethylene pipes for sewerage -

Specification

IS 7328:1992 Specification for PE material Moulding and Extrusion

IS 7634:1975 Specification for Laying & Jointing of PE Pipes: Part 2


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PART-V Design Considerations

Designing a pressure pipe line:

The primary elements in determining the minimum acceptable diameter of

any pipe network are system design flow rates and pressure drops. The design flow

rates are based on system demands that are normally established in the process

design phase of a project.

Before the determination of the minimum inside diameter can be made, service

conditions must be reviewed to determine operational requirements such as

recommended fluid velocity for the application and liquid characteristics such as

viscosity, temperature, suspended solids concentration, solids density and settling

velocity, abrasiveness and corrosivity. This information is then used to determine the

minimum inside diameter of the pipe for the piping system.

PIPE SPECIFICATIONS

1. Velocity:

The maximum allowable fluid velocity in a PE Piping system is a function of the

design of a specific system and its operational conditions. For normal liquid service

applications, the acceptable velocity in pipes is 1.0 m/sec to 2.1 m/sec (3.83 ft/sec

to 7 ft/sec) with a maximum velocity limited to 2.1 m/s (7 ft/s) at piping discharge

points including pump suction lines.

Recommended liquid velocities:

Recommended Velocity

Water and similar liquids High viscous liquids

Pipe size Gravity system Pumping system Gravity system Pumping system

75-250 mm 1 - 1.5 m /sec 1 - 2.1 m/sec 1 - 1.5 m /sec 1 - 2.1 m/sec

250- 500 mm 1 - 1.5 m /sec 1.2 - 2.1 m/sec 1 - 1.5 m /sec 1 - 1.82 m/sec

2. Pressure :

The pressure rating of a piping system is determined by identifying the maximum

steady state pressure, and determining and allowing for pressure transients. The

determination of maximum steady state design pressure and temperature is based

on an evaluation of specific operating conditions


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The evaluation of conditions must consider all modes of operation. Piping

components shall be designed for an internal to hydraulic conditions based

on operating pressures, potential back pressures, surges in pressures or

temperature fluctuations, control system performance variations andprocess upsets must be considered.

Pressure drops throughout the piping network are designed to provide an optimum

balance between the installed cost of the piping system and operating costs of the

system pumps.

Pressure drop, or head loss, is caused by friction between the pipe wall and the

fluid, and by minor losses such as flow obstructions, changes in direction, changes

in flow area, etc. Fluid head loss is added to elevation changes to determine pump

requirements.

PE Pipes are classified by the pressure rating corresponding to the maximum

permissible working pressure at the required temperature. Depending upon the

material strength the grades of the pipe is differentiated.

3. Material classification:

Proper raw materials with specified grades (PE63, PE80, and PE100) are selected for

production and these polyethylene’s’ are polymerized in controlled environment

thus producing PE pipes of high quality products, superiority on nature.

Polyethylene (PE100) pipes can carry potable water, waste water, slurries,

chemicals, hazardous wastes and compressed gases. In fact, PE100 is strong,

extremely tough and very durable when compared to it preceding material like PE

80 grade and PE63 grade. PE100 pipe has superior qualities in terms of mechanical

and all also other properties when compared to PE80, PE63.

The Polyethylene material used for the manufacture of pipeline systems are

classified and dimensioned by long term performance under hydrostatic pressure in

accordance with IS 4984:1995.

The design basis used in IS4984:1995 for Pressure rating (PN rating) of PE pipes inorder to determine the minimum wall thickness for each diameter and PN rating

provides for the steady and continuous application of the maximum allowable

working pressure over an arbitrary period of 50 years.

The selection of the long term hydrostatic design stress value (HDS) is dependent on

the specific grade of PE and the pipe material service temperature. For the grades

of PE materials contained in IS4984:1995, the specific values of the different grades


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are shown in Table. As these values are polymer dependent, individual grades may

exhibit different characteristics and materials can be provided with

enhanced properties for crack resistance or elevated temperature

performance.

This classification of PE piping grade material is based on the Minimum Required

Strength (MRS), which is the hydraulic stress that would cause failure after 50 years.

PE Pipe material is evaluated by the minimum required strength (MRS)

o When PE80 pipes are hydrostatically tested at 20 °C, a minimum required

strength at 50 years of 8 Mpa – MRS will be 8 Mpa

o When PE100 pipes are hydrostatically tested at 20 °C, a minimum required

strength at 50 years of 10 Mpa – MRS Will be 10Mpa

Typical Stress Regression Curves:

The relationship between the curves in the regression curves as shown in fig.01 for

different test temperatures enables prediction of the position of the curve at 20°C,

based on a known position at elevated temperature – see Figure .This in turn

enables prediction of life at 20°C. The value of the predicted hoop stress (97.5%

lower confidence limit) at the 50 year point is used to determine the MRS of the

material, i.e. 6.3, 8.0 or 10.0 MPa.

FIG: Stress Regression Curves

The enhanced performance of PE100 allows the pipes to be produced with thinner

pipe walls compared to PE80 pipes of equivalent SDR rating and In addition to the


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superior qualities, PE100 also has the greater resistance to rapid crack propagation

compared to PE80.

PE 80 piping system can be advantageously replaced by PE100 material,

ensuring safety, reliability and economic benefits under similar operating

conditions with out affecting the proceeded benefits derived from the

Polyethylene (PE) piping system.

Prime Advantages derived by using PE100 material for Polyethylene piping system:

o Durability and sustainability of the Pipe can be achieved by using the piping

material PE100.

o Due to higher superiority and durability of PE100 piping system, the overall

efficiency of the piping system can be maximized.

o Excellent hydraulic properties with low friction resistance throughout life of PE

100 thus long service life is achieved and it can able to withstand higher water

hammer when compared to PE80 Pipe., As thickness of the PE100 pipe is less as

compared to PE80 pipe, Volumetric flow (Discharge of the material) from the

pipe of PE100 pipe is comparatively higher than PE80.

o Due to its low weight of PE100 for same SDR of PE80, Material handling of PE100

Pipe is lot simplified.

o As butt welding is directly dependent on thickness of the pipe, Time required for

Installation and jointing of PE100 pipe is less when compared to PE80 pipe.

o Due to higher discharge and inner diameter of the PE100 pipe , the loading

factors on the pump assembled with the piping system can be minimized thus

saving the not only the pumping costs and maintenance costs but also

maximizing the life and efficiency of the pump, thus the overall efficiency of the

piping system can be maximized.

Representation of PE80 PipeRepresentation of PE100 Pipe

Representation of PE100 Pipe & PE80 of same Nominal (Outer) diameter and

Pressure Rating


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Tabular Representation of Properties of PE100 & PE80:

S. no Polymer data Unit PE80 PE100

1 Density at 23 °c gram/cm ³ 0.947 0.956

2 Viscosity number cm³/gram 360 360

3 Melt Flow Rate at 190° C / 5 kg gram/ 10 min 0.3-0.5 0.2-0.5

Mechanical properties

4 Yield stress(tensile) Mpa 21 23

5 Elongation at yield % 8 9

6 Tensile modulus(Short Term) Mpa 750 900

7 Notched impact strength

At 23°C

At 20°C

Kj/m²

Kj/m²

24

11

26

13

Other Properties

8Oxidation - induction time at 210

°cMin ≥20

9 Carbon black content % 2.3± 0.2 2.3± 0.2

10 Dispersion ----- 25

14 Elongation at break % >600 >600

15 Linear thermal expansion % 1.8 2.4

Electrical properties

16 Electric strength kv/mm 53 53

17 Volume resistively Ω m >10 ^13 >10 ^13


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Part VI POLYETHYLENE PRESSURE PIPES

Design Aspects

The parameters of the Polyethylene (PE) pipe for the application are

depended on various factors which are discussed as below:

Pressure Determinations:

Barlow's Formula is commonly used to determine the pressure with is the main

factor in determining the pressure rating of the piping system:

1. Internal Pressure at Minimum Yield

2. Ultimate Bursting Pressure

3.

Maximum Allowable Working Pressure

Hoop Stress, Internal Pressure & Wall Thickness

Tensile Creep Curves

Polyethylene has no true elastic constants, such as elastic modulus or

proportional limit, nor do they have sharply defined yield points.

Hydrostatic Pressure

The hydrostatic pressure capacity of plastic pipe is related to a number of

variables:

o Standard Dimension Ratio (SDR): The ratio between the outside

diameter and the wall thickness

• The hydrostatic design stress of the polymer

• Operating temperature

• The duration and variability of the stress applied by the internal

hydrostatic pressure

Although plastic pipes can withstand short-term hydrostatic pressures at levels

substantially higher than the pressure rating, the duty is always based on the

long-term strength at 20°C to ensure a design life of at least 50 years.


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The relationship between the internal pressure, diameter, wall thickness

and the hoop stress in the pipe wall, is given by the Barlow formula,

which can be expressed as follows:

Where

P = Maximum Allowable Operated Pressure; dm = mean outside diameter

(mm); Wt = wall thickness (mm) ; δ s = hoop stress (Mpa)

This formula has been standardized for use in design, testing and research and is

applicable at all levels of pressure and stress. For design purposes, p is taken as themaximum allowable working pressure and δs the maximum allowable hoop stress

at 20°C.

Minimum required strength (MRS)

Polyethylene (PE) Pipe and fittings material are evaluated by their

minimum required strength (MRS)

o When PE80 pipes are hydrostatically tested at 20 °C, a minimum

required strength at 50 years of 8 Mpa => MRS will be 80

kg/cm2

o When PE100 pipes are hydrostatically tested at 20 °c, a minimum

required strength at 50 years of 10 Mpa => MRS Will be 100 kg/cm2

Design stress

o The design stress for Polyethylene (PE) -PE80 grade pipes is 8 Mpa. The

following table shows the comparison between the 50 years MRS values

for PE (PE80) and PE (PE100) pipes.

o The enhanced performance allows Polyethylene (PE) pipes to be

produced with thinner pipe walls.


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Standard dimension ratio (SDR)

For Polyethylene (PE) Pipe of 25 mm nominal size and above, the pipe wall

thickness bears a constant ratio to the outside diameter, for a given pressure rating.

This is known as the standard dimension ratio (SDR), which can be defined as theratio of nominal diameter to the wall thickness which is calculated as follows:

SDR = Nominal outside Diameter / Minimum wall thickness

Carbon Black content

Another important factor of the specification is the Carbon Black content. The

carbon black content and dispersion are so specified that the pipe, when exposed

to sun light has no damaging effects. This is particularly important as the

Polyethylene (PE) pipe can be laid over ground and stored openly, as the carbon

black content in the resin takes care of the effect of UV light.

Pressure rating

The pressure rating of Polyethylene (PE) Pipe is generally referred to in 'bar', where 1

bar equals 10.2m head (approx).

Table gives the pressure rating and SDR of both PE 80 and PE100 pipes.

Design stress calculation:

The design stress is obtained by considering the design factors, safety factors etc.

Where S= Design Stress ; MRS=Minimum Required Strength;

F=Design Factors

Pipe

Material

Grade

Nominal

Diameter

Minimum Required

Strength ( MRS in

Mpa)

Design Stress in

Mpa

Pressure Rating as

per IS4984

Specification

In mm t 20 oC & 50

YEARS

t 20oC

t 30oC

In bar

PE100

Grade16-500 10 6.3 8.0 6,8,10,12.5,16 IS 4984:1995

PE80

Grade16-500 8 5 6.3 2.5,4,6,8,10,12.5,16 IS 4984:1995

PE63

Grade16-315 6.3 4 5 2.5,4,6,8,10,12.5,16 IS 4984:1995


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Design Factors(F):

The value of the design factors or safety factors depends not only the pipe

material but also on the numerous factors like application of the piping

systems transporting material nature & properties and operation risks

involved in the application . In general, Design /Safety factors for water

applications of 1.25 valve times is the minimal applicable value and in vast the

design factor.

Maximum Allowable Operated Pressure(MAOP)

Considering the design factors, IS4984 standard specifies the design stress values of

6.3 Mpa, 8 Mpa & 10 Mpa are designated as PE63, PE80 & PE100 respectively.

Maximum Allowable Operated pressure (MAOP) is important criteria considered for

prescribing the pressure rating of the Polyethylene.

Where

MAOP = Max. Allowable Operated

Pressure

PN = Pressure Rating; F= design factors;

F = Fd X Ft

• Fd = design factors nature of the fluid;

• Ft = temperature factors


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Part VII HYDRAULIC PERSPECTIVE: Design

Design formulae which are used for determining the required diameter of a

pipeline are often interpreted with a great deal of precision, but it is oftenoverlooked the starting point for such computations is the design flow - a

parameter which is derived from often less accurate hydrological data using

calculations based on methods.

Pipe Flow Formulae

When designing a pipeline or conduit carrying liquid, an engineer faces ambiguous

in the choosing an appropriate flow formula on which to base the calculation, so

proper selection of the design formula has to be taken in selecting the proper

formula among numerous formulae. Some of the commonly used formulae are:

Hazen-Williams equation

Manning’s equation

Darcy-Weisbach equation, incorporating the Colebrook-White

equation for the determination of friction factor.

The Hazen-Williams and the Manning’s equations are both empirical and contain

dimensional coefficients which take account of the roughness of the pipe.

Selection of Pipe dimensions

Considering the frictional flow co-efficient factor:

It is important to realize that, whilst the inherent surface roughness of a pipe is an

important characteristic property which could be expected to be a constant for a

specific pipe, the roughness coefficient used in energy loss computations is a

parameter which is dependent on both the pipe surface and the service

conditions.

Firstly, Coefficients may need to be varied/selected depending upon the followingreasons:

Biological growths and other obstructions.

Slime deposits, encrustation, detritus and other debris.

Irregularities at joints such as:


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Abrupt decrease/increase in diameter

Protrusions of jointing materials

Amount and size of material to be transported

Disturbance of flow due to branches

The ‘C’ factor in the Hazen and William’s formula is 155 for plastics and

less for metallic pipes. Also, because of its corrosion resistance this factor

does not change with time as there will be no deposits or incrustations

unlike metallic pipes.

A combination of Hazen-William formula and Darcy-Weisbach

formula is frequently employed for calculating head losses,

particularly in computerized calculations:

The variables a, b are Coefficients which are dimension less. .Designbased on flow velocities exceeding 3 meters /sec are not

recommended.

Flow velocities in the range of 1.0-2.5 meters/sec are considered

hydraulically and economically optimal.

Because of high surface elasticity coefficient, Polyethylene (PE) pipes

effected from water impact will be very minimal when compared to the

other pipe types, as this the main reason that in pipe lining ,smallerdimension PE100 pipe can be used for the same work of the alternative

pipes.

Depending upon the flow coefficients as discussed, Hazen Williams’ formula can be

derived as below:

The Hazen-Williams formula

Q= 1002 X C X d2.65 X S0.54

• S = Pressure loss due to friction, in mtr / mtr

• Q =Volumetric flow rate, in meter3/Hour

• d = Inside diameter, in meter

•

C =Flow Factor Coefficient =150 for

Polyethylene (PE)


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Gravity Mains

For buried gravity flow lines such as sewers and OHSR feeder water lines, the

requisite wall thickness must be established in accordance with externalstress conditions caused by earth pressure and traffic.

In the Crown Loading Test , Polyethylene (PE) pipe does not fracture. Under

increasing crushing load it deform but no stress cracks form. Basically, it must be

noted that even with sewer pipes of conventional materials, the soil in the vicinity of

pipe must be compacted in accordance with the laid down specifications. If

compacted soils are not locally available they must be obtained. Polyethylene (PE)

pipes are no exception to this rule.

The minimum cover depth for road traffic loads should be 0.8m; for pipes of D>

0.8m it should be equal to the pipe diameter and for rail and road traffic, minimum

cover depths of >1.5D >1.2m should be provided.

Polyethylene (PE) pipe are dimensioned so that the long-term deformation after 50

years does not exceed 6%. It is observed that pipe equal to or less than SDR ratio of

PN6 class pipe is best suited for such deformation criteria.

Pumping Mains

A water supply distribution system consists of a complex network of interconnected

pipes, service reservoirs and pumps which deliver water from the source to the

consumer. Water demand is highly variable, both by day and season. Supply, by

contrast is normally constant. Consequently, the distribution system must include

storage elements, and must be capable of flexible operation.

Water pressures within the system are normally kept between a maximum (70m

head) and a minimum (20m head) value. This ensures that the consumer demand

is met, and that undue leakage due to excess pressure does not occur.

DESIGN FOR DYNAMIC STRESSES:

Polyethylene pressure pipes are designed on the basis of a burst regression line for

pipes subjected to constant internal pressure. From this long term testing and

analysis, nominal working pressure classes are allocated to pipes as a first indicationof the duty for which they are suitable. However, there are many other factors

which must be considered, including the effects of dynamic loading. Whilst most

gravity pressure lines operate substantially under constant pressure, pumped lines

frequently do not and it is essential that the effects of this type of loading be

considered in the pipeline design phase to avoid premature failure. This note is


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intended to assist in the selection of pipe class for polyethylene pipes in

applications involving transient and cyclic operating pressures.

Pressure fluctuations in pumped mains result from events such as pump

start-up and shutdown or valves opening and closing. The approach

adopted for pipe design and class selection when considering these events

depends on the anticipated frequency of the pressure fluctuation as follows:

For random, isolated surge events, for example, those which result from

emergency shutdowns, the designer must ensure that the maximum and

minimum pressures experienced by the system are within acceptable limits;

and

For frequent, repetitive pressure variations, the designer must consider the

potential for fatigue and design accordingly.

Surge events are characterized by high pressure rise rates with no time

spent at the peak pressure. The maximum duration of a surge event is

about 5 minutes.

The key factors to consider are the size and frequency of the repeated

event. For large pressure cycles, a lower number of events can be

tolerated in the pipe lifetime.

For smaller pressure changes, a greater number of events are acceptable.

The only design consideration required for this type of pressure fluctuation is

that the maximum pressure should not exceed the pressure rating of the

pipe.

Surge design

It has long been recognized that polyethylene pipes are capable of handling short-

term stresses far greater than the long-term loads upon which they are designed.

Field tests of installed pipelines are conducted to verify the pipeline design and

construction. These tests are generally carried out at a pressure of 1.25 times the

maximum system operating pressure. Since the test pressure is generally the highest

pressure a pipeline will experience, the field test serves to demonstrate that all

system components, including items such as anchor blocks which are formed in-

situ, will be satisfactory for the operating conditions.

The demonstrated ability of polyethylene pipes to accommodate short-term surge

pressures can be utilized to advantage by allowing some over-pressurization.

However, it is recommended that the peak design pressure is limited to the field test

pressure of that pipeline in order to ensure that the pipeline as a whole is capable

of performing under these conditions. Where the generation of negative pressures


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is anticipated, the possibility of transverse buckling should be considered. This topic

is well covered in other technical literature.

Water Hammer:

Water hammer is an increase in pressure in the pipe caused by a sudden change

in the velocity. The velocity change usually results from the closing of a valve,

starting the pump etc;

The maximum surge pressure encountered is a function of the wave velocity as

follows:

Where,

C = Wave velocity (in m/sec) ; d =Pipe I.D. (in mm);

t = wall thickness (in mm)

k = Fluid bulk modulus of elasticity= (2.08 X 108 for water in Kg/m 2 )

E = Modulus of elasticity of the pipe;

for PVC pipe in Kg/m2: 3 X 108 & For polyethylene in Kg/m2 : 9X

107

The maximum surge pressure, P,

Where

C = Wave velocity (m/sec), as defined above

V = Maximum change in velocity ( in m/sec)

g = Acceleration due to gravity (9.81 m/sec2)

To determine the maximum change in velocity, a worst-case scenario should be

considered. This would occur when all the pumps are running at minimum static

head condition (this is the maximum velocity the pumps will produce), and are

suddenly shut down. The minimum static head would occur when the system has

the maximum water level present.


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Part VII LAYING AND JOINTING OF POLYETHYLENE (PE) PIPES

The jointing of Polyethylene is confined to IS7634 (Part 2) standard which

gives guidance for the proper methods of laying and jointing of

polyethylene (PE) pipe work for the potable water supplies.

Jointing of PE PIPE with a PE pipe or with PE special can be jointed by making use of

jointing process called “BUTT WELDING “ procedure which is an most efficient type

of HEAT FUSION process.

BUTT WELDING:

The principle of heat fusion is to heat two surfaces to a designated temperature,

and then fuse them together by application of force. This pressure causes flow of

the melted materials, which causes mixing and thus fusion. When the polyethylenematerial is heated, the molecular structure is transformed from a crystalline state

into an amorphous condition. When fusion pressure is applied, the molecules from

each polyethylene part mix. As the joint cools, the molecules return to their

crystalline form, the original interfaces are gone, and the two pipes become one

homogeneous unit.

Butt Fusion Machine Procedure

The principle operations include:

Clamping - The pipe pieces held axially to allow all subsequentoperations to take place.

Facing - The pipe ends must be faced to establish clean, parallel mating

surfaces perpendicular to the centreline of the pipes.

Alignment - The pipe ends must be aligned with each other to

minimize mismatch or high-low of the pipe wall.

Heating - A melt pattern that penetrates into the pipe must be formed

around both pipe ends.

Joining - The melt patterns must be joined with a specified force. The

force must be constant around the interface area.

Holding - The molten joint must be held immobile with a specified force

until adequately cooled.


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WELD PERFORMANCE CRITERIA IN DETAIL:

The key features in attaining the required quality Butt Weld are:

1. Identifying materials being used in the installation as compatible for

welding

2. calculating appropriate welding parameters to be used

3. Maintaining and calibrating welding equipment

4. Performing welding

5.

Assessing quality of welded joints made.

Polyethylene (PE) Pipes fusion procedures require specific tools and equipment for

the fusion type and for the sizes of pipe and fittings to be joined. The process can be

detailed as below:

1. Identify materials as being compatible for welding.

1.1. Identify materials as polyethylene (PE) from specifications and work site

instructions

1.2. Identify PE materials and pipes supplied as being compatible for

welding from specifications.2. Calculate appropriate pipe welding parameters.

2.1. Identify welding machine type and operating data

2.2. Check whether the welding machine is automatic or semi-automatic or

manual.

2.3. 2.2 Identify pipe materials and dimensions

2.4. Check for the Diameter with in OVALITY are same


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2.5. Perform welding parameter calculations for individual welding

machines and pipe details

3.

Maintain and calibrate welding equipment.3.1.

Set up welding equipment and work area

3.1.1. Welding equipment consists of Heating Plate(mirror ), trimmer,

pressure jack or hydraulic jack

3.2. Ensure safety equipment is available and operational

3.3.

Check operation and calibrate where required, heating, trimming, and

pressure systems.

4. Perform welding.

4.1.

Assemble pipeline components in welding machine

4.2. Clean, align and trim pipe ends

4.2.1. Perform heating, welding, and cooling phases using calculated

welding parameters

4.3.

Monitor and record achieved weld parameters for each joint as per

enterprise requirement

4.4.

Clean up equipment when completed as per enterprise procedures

4.5. Clean up work site, dispose of scrap materials as per enterprise

procedures

4.6. Use personal protective equipment as per enterprise requirements.

5. Assess quality of completed joints.

5.1. Identify quality requirements for joints

5.2. Assess joints against specification requirements, and report results

5.3.

Identify and report non-conformances as per enterprise requirements

6. Identify materials as being compatible for welding.

6.1. Identify materials as polyethylene (PE) from specifications and work site

instructions

6.2. Identify PE materials and pipes supplied as being compatible for

welding from specifications.

7. Calculate appropriate pipe welding parameters.

7.1.

Identify welding machine type and operating data

7.2.

Check whether the welding machine is automatic or semi-automatic ormanual.

7.3. 2.2 Identify pipe materials and dimensions

7.4. Check for the Diameter with in OVALITY are same

7.5.

Perform welding parameter calculations for individual welding

machines and pipe details


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8. Maintain and calibrate welding equipment.

8.1. Set up welding equipment and work area

8.1.1. Welding equipment consists of Heating Plate(mirror ),

trimmer, pressure jack or hydraulic jack8.2.

Ensure safety equipment is available and operational

8.3.

Check operation and calibrate where required, heating, trimming, and

pressure systems.

9. Perform welding.

9.1.

Assemble pipeline components in welding machine

9.2. Clean, align and trim pipe ends

9.2.1. Perform heating, welding, and cooling phases using calculated

welding parameters

9.3. Monitor and record achieved weld parameters for each joint as per

enterprise requirement

9.4.

Clean up equipment when completed as per enterprise procedures

9.5.

Clean up work site, dispose of scrap materials as per enterprise

procedures

9.6.

Use personal protective equipment as per enterprise requirements.

10. Assess quality of completed joints.

10.1. Identify quality requirements for joints

10.2. Assess joints against specification requirements, and report results

10.3.

Identify and report non-conformances as per enterprise requirements


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Part IX MAINTANENCE IN PE PIPES

1. Puncher in PE line.

2. Replacements in PE pipe line.

3. Replacement of specials in PE pipe line.

4. Re-routing in PE pipeline.

5. Different options in joining of PE pipe lines.

6. Training of Department personal.

1 Puncher in PE pipe line:

PE material is a viscous-elastic material and because of which it has high elastic

expansion limit. Punchers are not usually a part of such material. Such things can

only happen when a sharp object is pierced with a considerable force. Also it

happens if it comes in contact with a hot object (+200°C) for some time. At sites this

can happen while excavating with sharp shovel and its sharp teeth punchers the

pipe. It can rectified immediately by wrapping a rubber sheet over the puncher

portion of pipe and clamping it with a suitable PVC / MS saddle pieces.

The other option for this is using compression fittings by cutting the damaged

portion and joining the pipeline with compression fitting up to a size limit of 110mm.

2. Replacing in PE pipe line:

If the above case is with a greater damage where a bigger portion of pipe has tobe removed, then that piece of pipe has to be completely replaced with a new

piece by arranging a piece of same size and connecting them with flanges at both

ends of pipe.

If there is a requirement of replacing PE pipe with other type of pipe material for a

specific application, than PE pipe can undoubtedly be attached through the

flanges.

3. Replacing of specials in PE pipelines:

It is difficult that a fitting getting failed in the process of functioning. A new spare PEfitting is simply replaced with at least joining one end by welding and the other by

flange.

If the PE fittings are not available in the department stores section then the

immediate solution is to replace with any existing fitting of same size in the

department stores made from MS /CI which are flanged at both ends. Hence it is


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recommended to keep in hand some spare fittings in the stores after any PE

pipeline is completed.

4. Re-routing of PE pipeline:

In any case if sudden modification of pipeline has to be done and the proposed

line has to be diverted to some other locations, then a ‘Tee/Bend’ is placed in the

required position. A suitable reducer is welded in that Tee and the other end is

blind flanged.

Repair and Maintenance of the Piping system:

Pipe Laying:

For laying down the PE pipes, it is enough to make a trench which has a place at

each side of the pipe for the operation of the compaction machine .There is no

need to bring sand for bedding and It is enough to prepare the trench bottom

surface with an angle of 120 degree. The earth derived from the excavation can

be used as filling sand after eliminating the big size stones and sharp object that

may damage the pipe .In rocky place, the sharp sides of the rocks are covered by

sand in order not to allow it to damage the pipe.

All road, railway and canal crossings should be done by laying pipe within larger

diameter sleeve pipes having a minimum of once and half times the diameter of

the main. The sleeve provides an access for repairs and servicing, without the need

to disturb traffic.

The advantage of less need of brining special filling sand out of the site, less

excavation and less filling sand need.


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Advantages

1. Since there is no need to bring special filling sand from out of the

excavated area, filling sand cost is minimum.

2. Since less excavation is done, excavation and filling costs are minimum

compared to the other pipe types.

Testing of the pipe and joint integrity:

Pipes before completely buried in the trenches are to be tested for withstanding

the designed water pressure. The pressure rating given in IS 4984:1995 is for the pipe

to withstand continuous rated pressure for 50 years at 300C.

As explained in earlier, Polyethylene (PE) pipes have the ability to withstand much

higher loads for short term. Testing of the welded pipe is necessary to ensure the

joint strength.

Prior to testing, the entire PE pipeline should be checked to ensure all debris and

construction materials are removed from contact with the pipes and fittings. Where

concrete anchor or thrust blocks are used no pressure testing should take place

within 7 days of casting the blocks. All mechanical ring seal joints must be

restrained either by sand bags, or by partial backfilling of the line leaving the joints

open for visual inspection. Where thermal fusion jointing has been used, no testing

should take place until the joints have completely cooled to ambient temperature.

In order to test the effectiveness of PE piping system, PE Pipeline should be checked

to ensure the leak free system. The line should be tested in smaller sections of not

more than 1000mtrs. All air the valve should be serviced and both ends should be

plugged. At the higher end an air vent pipe with a valve should be provided. The

Pipe line is to be pressurized with the help of a hydraulic test pump (Manual or

motorized)

The test pressure of 1.5 times the maximum working pressure should be maintained

for a maximum period of 8 hours or for the time necessary to visually inspect all

joints in the line.

A smaller drop in pressure may be observed due to thermal expansion or

circumferential expansion of the pipe diameter. However, this does not indicate

leakage in the pipeline. Where the installation consists of small additions to existing

pipelines the test pressure period may be 15 minutes.


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The following procedure is recommended for PE pipe Testing.

1. When PE pipes are tested by pressurizing, there will be reduction in

pressure over time (or pressure decay) even in a leak free system,

as a result of the creep characteristics of the material. The PE pipe

expands during pressurization.

2. Polyethylene pipelines must not be pressure tested unless the wall

temperature is kept below 300C. Pipe exposed to hot summer weather

should not be tested unless the ambient temperature comes to 300 C. After

filling, the pipe line shall be left to stabilize at its temperature for a minimum

period of 1 hour.

3. Fusion joints may be covered during testing. Flanged or other threaded

type joints shall be kept open for visual inspection. The pipe line shall be

filled and pressure tested from the lowest point. 4. During the test period, make-up water is continuously added to maintain

the pressure. Under no circumstance, air is to be used instead of water for

testing.

5. The test pressure shall be 1.5 times the rated pressure of pipes or of the

proposed maximum design pressure of the section. Apply the pressure by

continuously pumping at a constant rate.

6. Tests should be performed on reasonable lengths of pipelines. Long lengths

more than 2000mtrs may make leak detection more difficult.

7. Acceptance Criteria: If the pressure remains steady (within 5% of the target

value) for one and half hour, leakage is not indicated. Flanged and otherthreaded connections shall be visually inspected.

8. If the test is not complete because of leakage or equipment failures, the

test section shall be depressurized and allowed to ‘relax’ for at least eight

hours, before starting the next testing sequence.

9. Testing outside the trench is to be avoided, as pipe rupture may involve

safety issues.

10. Hydraulic test proves duly signed by the inspection authorities are to be

maintained by the contractor, manufacturer and consumer.


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Part X ABOVE GROUND INSTALLATION

Polyethylene pipe provides unique joint integrity, toughness, flexibility and

low weight. These factors combine to make its use practical for many

“above-ground” applications. Basically the pipe may be installed over the

ground in an unrestrained manner, thus allowing the pipe to move freely in

response to temperature change. Or the pipe may be anchored by some means

that will control any change of physical dimensions; anchoring can take

advantage of polyethylene’s unique stress relaxation properties to control

movement and deflection mechanically.

For exposed supported above

ground pipe work, proper anchorage

is essential. The structure and

anchorages must resist or

accommodate thermal stresses or

movement over the ambient

temperature range to which the pipe

system will be subjected. It is

preferable that a polyethylene pipe is

installed at or near the maximum

operating temperature such that pipes are thermally expanded whereby at that

point clamps or supports can be bolted into position thus restraining the pipe from

further movement. As the pipeline cools, tensile stresses are developed and thepipeline will remain straight between supports. If the pipeline then warms to its

original installation temperature, it returns to its installation condition and sag

between pipe supports is minimized.

Support spacing:

Support spacing is based on pipe material

and dimensions, nature of the flow

medium, operating temperature and the

specials & appurtenances.

Pipe clips used for anchorage and support

should have flat, non-abrasive contact

faces, or be-lined with rubber sheeting and

should not be over-tightened. The width of support brackets and hangers should

normally be either 100mm or half the nominal pipe bore diameter, whichever is the

greater.


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If the supports are to resist the temperature controlled or thermal movement, then

the stress induced in pipes, fittings and supports should be assessed and span

distance should be specified.

Thrust Block Anchoring:

PE pipes and fittings joined by butt welding, electro fusion, or other end load

bearing joint system do not normally require anchorage to withstand loads arising

from internal pressure and flow. Thrust blocks are required for the piping

applications where the pressures are high in which the joints cannot resist the

longitudinal loading on the piping.

For joint types which do not resist end loads, plus fabricated fittings which

incorporate welded PE pipe segments, anchorage support must be provided in

order to prevent joint or fitting failure. In addition, appurtenances such as valvesshould be independently supported in order to prevent excessive shear loads being

transferred to the PE pipe.

Thrust block sizing is selected based on the following:

1. Depending upon the soil type, loads arising from internal pressure, flow of the

fluid, temperature of the medium, proper fitting and specials are selected and

the block should be designed after considering this factors.

2. Sizing of the thrust block is mainly dependent on the size of the pipe and pressure

exerted by the pipe on the surrounding soil, so in order to build a block the

maximum pressure should be considered.

Mostly Thrust blocks are made from concrete and the blocks should be adequately

cured for specified period in order to allow the bonding of the concrete in order to

develop the strength before the pressure is introduced in to the piping system. The

contact point between the pipe and thrust block must be protected in order to

prevent the abrasion of the pipe.


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Distribution or service connection considerations

Tapping Saddles

Service connections may be provided in PE pipe systems using tappingsaddles which are either electro fusion or mechanically connected. Tapping

saddles should not be installed closer than 100mm to prevent reduction in pressure

capacity in the pipeline. Tapping saddles may be used for tapping’s up to 30% of

the size of the main pipe or a maximum diameter of 50mm. Where larger off take

sizes are required, then a reducing tee section should be used.

Tapping saddles of the mechanical strap type should not be used on curved pipes.

Tapping saddles of the saddle fusion, or electro fusion type should only be used on

the top of curved lines, and not be closer to the end of the pipe than 500mm.

Connection may then be made without loss of the operating service. Alternatively,

tapping may be performed on new main lines prior to pressurization, and entry into

service using the same techniques.

Direct Tapping

The tapping of services directly into the pipe wall by drilling and tapping a thread in

the wall material is not recommended in PE pipes. This practice may lead to

premature failure of the system.


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New development in Polyethylene (PE) pipes:

Electro Fusion:

Electro fusion is the technique of heat fusion joining is somewhat different

from the conventional fusion joining thus far described. The main difference

between conventional heat fusion and electro fusion is the method by which the

heat is applied. In conventional heat fusion joining, a heating tool is used to heat

the pipe and fittings surfaces. The electro fusion joint is heated internally, either by a

y coil at the interface of the joint or, as in one design, by a conductive polymer.

Heat is created as an electric current is applied to the conductive material in the

fitting.

General steps to be followed while performing electro fusion joining are:

1. Prepare the pipe

2. Clamp the fitting and pipe (S)

3. Apply the electric current

4. Cool and remove the clamps

1. Prepare the pipe:

First clean the pipe surface in the joint area. Cut the end of the pipe square (omit

this operation for saddle-type electro fusion or joints). Mark on the pipe. Surface the

proper positioning of the fitting to be installed. Scrape the surface of the pipe area

to be joined, removing all surface degradation and contamination. Exercise

caution to avoid contamination of the scraped pipe surfaces. There are tools

available to a system operator in this procedure.

2. Clamp the fitting and pipe :

Place the pipes and fitting in the clamping fixture to prevent movement of the pipe

or fitting. Give special attention to the proper positioning of the fittings on the

prepared pipe surfaces.

3. Apply electric current:

Connect the electro fusion control box to the fitting and to the power source.

Apply electric current to the fitting as specified in the manufacturer’s instructions. If

the control does not do so automatically, turn of the current when the proper time

has elapsed to heat the joint properly.

Allow the joint to cool for the clamping fixtures. Premature removal from the clamps

and any strain on a joint that has not fully cool can be detrimental to joint

performance.


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Part XI F.A.Q’s:

Q. What fittings are available for PE pipe?

A. Godavari Polymers Pvt Ltd (GPPL) offers PE fittings in standard

configurations, including: straight and reducing tees, elbows, crosses,

concentric and eccentric reducers, flanges, mechanical-joint adaptors, outlet

branch-saddles, etc. These can be fused directly to the PE pipe. Custom fittings are

also available upon request.

Q. In what lengths is PE pipe available?

. .

• (110 ).

140 ,

• Pipe is normally available in straight lengths up to 18mtr in length.

Q. How long has PE been used in sewer and water applications?

A. Polyethylene has been used in various parts like in USA, European countries and

also in Asia for sewer force mains, gravity flow sewers, and pressure water main

applications for approximately 50 years. After many years of field proven

performance, it became a standardized material and product.

Q. Is GPPL PE PIPE certified for potable water use?

A. Yes. GPPL PE PIPE piping or fittings can be used for potable water.

Q. What is the life expectancy of PE pipe?

A. THE US EPA expects 100-year service life from PE pipes. Buried solid wall or profile

wall PE pipe should last at least as long. PE pressure pipe was first used in water

service over 50 years ago. Current accelerated testing methods predict that

today’s PE pressure pipes will last much longer than 50 years. Everything points to a

service life of at least 100 years in a properly designed and installed PE pipe system.

Q. Is polyethylene pipe affected by chemicals?

A. NO. Plastics are not subject to galvanic corrosion, as are metals, since they are

not conductors.

Q. Will sunlight adversely affect PE pipe?

A. NO. PE pipe can sustain the higher temperatures like sunlight etc. Black PE pipe

has been stabilized with carbon black, which is the most effective ultraviolet


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stabilizer. PE pipe with carbon black UV stabilization (the normal black PE pipe),

may be used indefinitely outdoors.

Q. What is the temperature range across which PE pipe may be used?

A. The upper limit temperature for pressure service is 50oC. The low

temperature limit is usually regarded as -40oC. Cold temperatures do not adversely

affect PE in static applications.

Q. Will PE pipe wear less than other materials in a slurry application?

A. Yes. In general terms, with adequate particulate suspension, PE pipe has an

extremely high resistance to abrasion from slurries. In some applications, PE pipe has

outlasted steel pipe by as much as 4 to 1 for a given situation.

Q. Can PE pipe be used in permanent above ground installations?

A. Yes. In many mining and industrial applications, PE pipe has been installed

above ground and has provided and continues to provide excellent service after

15 to 25 years, with the potential to remain in service for many more years.

Q. How are PE solid wall pipe and components joined and connected?

A. PE pipe is normally joined by heat fusion. Butt fusion, socket fusion, sidewall fusion

and electro-fusion are all heat fusion methods that create a leak free joint stronger

than the pipe itself. The butt-fusion procedure is most frequently used joining

procedure.

Q. How long does it take to make a butt fusion joint?

A. The time required to make a butt fusion joint is dependent upon the pipe wall

thickness and diameter, and the field weather conditions. Typically the thicker the

pipe being joined the longer it takes to make a butt fusion joint, due to heating and

cooling time requirements.

Q. What inspection criteria are used to provide assurance about the quality of heat-

fusion joints?

A. The fusion joint has to be made following the pipe manufacturer’s

recommended fusion procedures, which include the procedures described instandards. The time-proven method used for field inspection of fusion joints is visual

examination of the melt bead.

Q. Are gaskets required between the faces of PE flanges/ joints?

A. Gaskets are not required between PE to PE connections. Elastomeric gaskets are

normally used for flanges between PE flange adapters and metal flanges.


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Q. How can PE pipe be connected to pipe made from other materials (PVC,

Ductile, Iron, and Corrugated)?

A. For non-pressure ‘drainage’ applications, flexible rubber couplings are

used. These flexible couplings are made for joining all types of gravity flowdrainage pipe, including transitions from one type or size of pipe to another.

For pressure applications and low-pressure sewer applications, PE transition fittings,

PE flanges, and standard metal couplings are recommended.

Q. Will mechanical joint valves and fittings work with PE pipe?

A. Yes. Mechanical joint /flange joints which are fused to PE pipe are available as

standard products. These joints are fully restrained.

Q. Will PE pipe of the same OD size as DI pipe deliver the same flow?

A. The inside surface of PE is extremely smooth and has a very low long-term design

coefficient of friction. The smooth bore of PE pipe is maintained throughout its

service life. It is often possible to use a polyethylene pipe with a smaller inside

diameter than the comparably sized ductile iron pipe, and still achieve an equal or

greater flow. The roughness co-efficient to use with Ductile Iron pipe recognizes the

likelihood that the ID roughness will degrade over time.

Q. To avoid kinking the pipe, what is the allowable bending radius of PE pipe?

A. For Godavari PE PIPE the rule of thumb is to use a minimum bending radius of 50

times the nominal diameter of the pipe.

Q. Is expansion and contraction of PE pipe a problem?

A. No. All objects expand and contract. As with all materials, expansion and

contraction must be taken into consideration when designing a PE piping system.

The resistance to movement provided by friction between the pipe and its’

embedment is usually sufficient to prevent thermal expansion and contraction.

Q. Are thrust blocks required with PE pipelines?

A. No. PE pipe and fittings joined by heat fusion are self-restrained and do not

require thrust blocks. It is only at the transition to unrestrained bell and gasketedpipe that provision must be made to limit the transmission of axial forces to the

‘other’ piping system.

Q. Is PE pipe suitable for use under railroads?

A. Yes, PE pipe is suitable for direct burial under railroads with just 4-5 feet of cover.

An engineering burial analysis is recommended.


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Q. How are service connections made on PE pipe mains?

A. PE pipe can be cold or hot (under pressure) tapped using saddle fusion

tapping tees which are readily available in the industry. There are bolt-on

mechanical connections qualified for use with PE pipelines as well.

Q. What are the recommended procedures to pressure test a polyethylene

pipeline?

A. GPPL PE PIPE is pressure tested in a procedure similar to that used to test other

pipes. Normally 1.5 times of working pressure is recommended for testing the pipe.

Q. Can PE pipe be threaded using the same tapping tools commonly used for

tapping PVC or ductile iron pipe?

A. No. Tapping of PVC or ductile iron pipe relies on cutting threads into the pipe

wall. Un-reinforced PE threads loose compression of the taper threads by creep-strain, leading to drip leaks over time.

Q. How are PE pipelines located?

A. A tracer wire can be buried above the PE pipe at the time of installation to

facilitate future locates. If no metal wire was installed above the plastic pipe,

ground-penetrating radar or acoustic resonance may be used.

Q. Is it possible to repair a damaged PE pipe?

A. Yes, a full saddle clamp can be used as a temporary repair. The damaged zone

should be replaced within a scheduled maintenance period using a PE sectioneither heat-fused or flanged into place.

Q. How will using PE save money?

A. Using PE pipe you create a leak-free system with an exceptionally long

service life, that will save money annually on reduced leakage losses,

improved water conservation, a reduction in the need for new water

treatment plants, reduced warehousing requirements, a reduction in

maintenance crews, reduced seasonal water-main breaks, less

maintenance, and less rehabilitation and restoration. Savings will accrue for

many years to come.


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Ten good reasons why PE water pipe systems provide a

superior solution:

1.

PE pipes are flexible and tough, ensuring highest

durability and a long service life at low maintenance costs

2. PE pipes are corrosion-free, with the lowest rate of water

leakage of any material

3. Leak-tight fusion welded joints can even resist soil movement

like the shocks due to earthquakes

4. Wide product range offering pressure ratings up to 16 bars

and pipe diameters from 20 to 500 mm

5. Well adapted to cost-saving modern trench less installation

techniques, and to renovation of old pipe networks

6. PE, as a material, is neutral towards water;

7. The light weight of PE pipes makes them easy to transport

and install, reducing the overall installation cost

8.

Environmentally friendly: low energy consumptions and low

CO2 emissions over their life-cycle. PE is easy to recycle and

can be converted into energy at the end of its service life

9. Successful track record of almost 50 years

10. Innovative mindset has allowed constant improvement of

the PE materials and pipe solutions

For further details regarding the PE piping, please do contact:

technical_manual_hdpe_pipes.pdf

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