PE Design

User Manual: PE

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Design.1

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contents

Pipe Selection 3

Pipe Dimensions 4

Allowable Operating Pressure 5

Temperature Influences 7

Service Lifetimes 7

Pipe Design for Variable Operating Conditions 8

E Modulus 10

Selection of Wall Thickness for Special Applications 10

Hydraulic Design 11

Flow Chart Worked Examples 13

Part Full Flow 15

Resistance Coefficients 16

Flow Charts 17-26

Surge and Fatigue 27

Celerity 28

Slurry Flow 29

Pipe Wear 30

Maintenance and Operation 31

Fittings 31

Pneumatic Flow 32

System Design Guidelines for the Selection of Vinidexair Compressed Air Pipelines 33

Expansion And Contraction 35

External Pressure Resistance

Trench Design

Allowable Bending Radius

Deflection Questionnaire – FAX BACK

Deflection Questionnaire – Vinidex locations

Thrust Block Supports

Electrical Conductivity

Vibration

Heat Sources

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Design.2

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Limitation of Liability

This manual has been compiled by Vinidex Pty

Limited (“the Company”) to promote better

understanding of the technical aspects of the

Company’s products to assist users in obtaining

from them the best possible performance.

The manual is supplied subject to

acknowledgement of the following conditions:

• The manual is protected by Copyright and may

not be copied or reproduced in any form or by

any means in whole or in part without prior

consent in writing by the Company.

• Product specifications, usage data and advisory

information may change from time to time with

advances in research and field experience. The

Company reserves the right to make such

changes at any time without notice.

• Correct usage of the Company’s products

involves engineering judgements which cannot

be properly made without full knowledge of all

the conditions pertaining to each specific

installation. The Company expressly disclaims

all and any liability to any person whether

supplied with this publication or not in respect

of anything and of the consequences of anything

done or omitted to be done by any such person

in reliance whether whole or partial upon the

whole or any part of the contents of this

publication.

• No offer to trade, nor any conditions of trading,

are expressed or implied by the issue of content

of this manual. Nothing herein shall override the

Company’s Conditions of Sale, which may be

obtained from the Registered Office or any Sales

Office of the Company.

• This manual is and shall remain the property of

the Company, and shall be surrendered on

demand to the Company.

• Information supplied in this manual does not

override a job specification, where such conflict

arises, consult the authority supervising the job.

ABN 42 000 664 942

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Design.3

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Pipe Selection

Vinidex PE pipes are available in a

comprehensive range of sizes up to

1000mm diameter, and pressure classes

in accordance with the requirements of

AS/NZS 4130 - Polyethylene (PE) pipes

for pressure applications.

Additional sizes and pressure classes to

AS/NZS 4130 requirements are added

from time to time and subject to

minimum quantity requirements, pipes

made to specific sizes, lengths or

pressure classes are available.

The Standard AS/NZS 4130 includes a

range of PE material designations based

on the Minimum Required Stress (MRS),

and classified as PE63, PE80, and

PE100. When pipes are made to the

same dimensions, but from different

rated PE materials, then the pipes will

have different pressure ratings.

The relationship between the dimensions

of the pipes, the PE material

classification and the working pressure

rating are as shown in Table 4.1.

For simplicity, the dimensions of the pipe

have been referred in terms of the

Standard Dimension Ratio (SDR) where:

Outside Diameter

SDR =

Wall Thickness

Table 4.1 Comparison of SDR & Pressure Ratings (PN)

SDR 41 33 26 21 17 13.6 11 9 7.4

PE80 PN3.2 PN4 - PN6.3 PN8 PN10 PN12.5 PN16 PN20

PE100 PN4 - PN6.3 PN8 PN10 PN12.5 PN16 PN20 PN25

Notes:

PE Long term rupture stress at 20°C (MPa x 10) to which a minimum design factor

is applied to obtain the 20°C hydrostatic design hoop stress.

PN Pipe pressure rating at 20°C (MPa x10).

SDR Nominal ratio of outside diameter to wall thickness.

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Design.4

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Pipe Dimensions

Table 4.2 PE Pipe Dimensions AS/NZS 4130

Nominal

Size

SDR 41 SDR 33 SDR 26 SDR 21 SDR 17 SDR 13.6 SDR 11 SDR 9 SDR 7.4

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

Min. Wall

Thickness

(mm)

Mean

I.D.

(mm)

16 1.6 13 1.6 13 1.6 13 1.6 13 1.6 13 1.6 13 1.6 13 1.8 12 2.2 11

20 1.6 17 1.6 17 1.6 17 1.6 17 1.6 17 1.6 17 1.9 16 2.3 15 2.8 14

25 1.6 22 1.6 22 1.6 22 1.6 22 1.6 22 1.9 21 2.3 20 2.8 19 3.5 18

32 1.6 29 1.6 29 1.6 29 1.6 29 1.9 28 2.4 27 2.9 26 3.6 24 4.4 23

40 1.6 37 1.6 37 1.6 37 1.9 36 2.4 35 3.0 34 3.7 32 4.5 31 5.5 28

50 1.6 47 1.6 47 2.0 46 2.4 45 3.0 44 3.7 42 4.6 40 5.6 38 6.9 35

63 1.6 60 2.0 59 2.4 58 3.0 57 3.8 55 4.7 53 5.8 51 7.1 48 8.6 45

75 1.9 71 2.3 70 2.9 69 3.6 67 4.5 66 5.5 63 6.8 61 8.4 58 10.3 53

90 2.2 86 2.8 84 3.5 83 4.3 81 5.4 78 6.6 76 8.2 73 10.1 69 12.3 65

110 2.7 105 3.4 103 4.3 101 5.3 99 6.6 96 8.1 93 10.0 89 12.3 84 15.1 78

125 3.1 119 3.9 117 4.8 115 6.0 113 7.4 110 9.2 106 11.4 101 14.0 96 17.1 89

140 3.5 133 4.3 131 5.4 129 6.7 126 8.3 123 10.3 118 12.7 114 15.7 108 19.2 99

160 4.0 152 4.9 150 6.2 148 7.7 144 9.5 140 11.8 136 14.6 130 17.9 123 21.9 114

180 4.4 171 5.5 169 6.9 166 8.6 163 10.7 158 13.3 153 16.4 145 20.1 138 24.6 128

200 4.9 190 6.2 188 7.7 184 9.6 180 11.9 175 14.7 170 18.2 162 22.4 154 27.3 143

225 5.5 215 6.9 211 8.6 207 10.8 203 13.4 198 16.6 191 20.5 183 25.1 173 30.8 161

250 6.2 238 7.7 235 9.6 230 11.9 225 14.8 219 18.4 212 22.7 203 27.9 192 34.2 179

280 6.9 267 8.6 263 10.7 258 13.4 253 16.6 246 20.6 238 25.4 228 31.3 215 38.3 200

315 7.7 300 9.7 296 12.1 290 15.0 285 18.7 278 23.2 268 28.6 256 35.2 242 43.0 226

355 8.7 338 10.9 333 13.6 328 16.9 320 21.1 311 26.1 301 32.2 289 39.6 273 48.5 255

400 9.8 380 12.3 376 15.3 370 19.1 362 23.7 351 29.4 340 36.3 326 44.7 307 54.6 287

450 11.0 429 13.8 422 17.2 415 21.5 406 26.7 395 33.1 382 40.9 366 50.2 347 61.5 322

500 12.3 476 15.3 470 19.1 462 23.9 452 29.6 440 36.8 424 45.4 407 55.8 384 - -

560 13.7 534 17.2 526 21.4 518 26.7 506 33.2 494 41.2 475 50.8 455 ----

630 15.4 600 19.3 592 24.1 582 30.0 570 37.3 554 46.3 535 57.2 512 - - - -

710 17.4 676 21.8 667 27.2 656 33.9 641 42.1 624 52.2 603 - - ----

800 19.6 762 24.5 752 30.6 739 38.1 723 47.4 704 58.8 679 - - - - - -

900 22.0 858 27.6 846 34.4 831 42.9 814 53.5 791 --------

1000 24.5 953 30.6 940 38.2 924 47.7 904 59.3 880 - - - - ----

Polyethylene Pipe Dimensions (based on AS/NZS 4130-1997, Polyethylene pipes for pressure applications.)

SDR – Nominal ratio of outside diameter to wall thickness. ID – internal diameter

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Allowable

Operating Pressure

Hydrostatic Design Basis

Vinidex pipes manufactured to AS/NZS

4130, Series 1 have wall thickness and

pressure ratings determined by the

Barlow formula as follows:

T = minimum wall thickness (mm)

P = normal working pressure

of pipe (MPa)

D = minimum mean OD (mm)

S = hydrostatic design stress

at 20°C (MPa)

See Table 4.2.

Hydrostatic Design Stress

The design of AS/NZS 4130 pipes has

been based on the static working

pressure operating continuously at the

maximum value for the entire lifetime of

the pipeline.

The value of maximum hoop stress used

in the selection of the pipe wall thickness

is known as the Hydrostatic Design

Stress (S). This value is dependent upon

the type of PE material being used and

the pipe material service temperature. In

AS/NZS 4131, materials are classified for

long term strength by the designation

Minimum Required Strength (MRS).

The MRS is the value resulting from

extrapolation of short and long term

tests to a 50 year point at 20°C.

Note: See Figure 2.1 for typical stress

regression curves.

Table 4.3 Hydrostatic Design Stress and

Minimum Required Strength – Values

Material Designation Minimum Required Strength Hydrostatic Design Stress

(MRS) MPa (S) MPa

PE63 5.0 6.3

PE80 6.3 8.0

PE100 8.0 10.0

These standard values are polymer

dependent and long term properties for

each pipe grade material are established

by long term testing to the requirements

of ISO/DIS 9080 by the polymer

producers. Individual PE grades may

exhibit different characteristics and PE

materials can be provided with enhanced

specific properties. In these cases the

advice of Vinidex engineers should be

obtained.

Maximum Allowable

Operating Pressure

where

MAOP is the maximum allowable

operating pressure in MPa.

PN is the pipe classification in

accordance with AS/NZS 4130.

F is the Design Factor.

For example, if the minimum value of F is

chosen (F = 1.25), a PN10 pipe will have

a MAOP of 1.0 MPa at 20°C.

T=PD

2S +P

S=MRS

MAOP =PN x 0.125

The Hydrostatic Design Stress (S) is

obtained by application of a Design or

Safety Factor (F) to the MRS.

See Table 4.3.

The specific value selected for the

Design Factor depends on a number of

variables, including the nature of the

transmitted fluid, the location of the

pipeline, and the risk of third party

damage.

The wall thickness values for Series 1

pipes to AS/NZS 4130 were derived

using a value of 1.25 for F, this being the

minimum value applicable.

AS/NZS 4131 specifics MRS values of

6.3 MPa, 8.0 MPa and 10.0 MPa for the

grades designated as PE63, PE80 and

PE100 respectively.

The relationship between the S and MRS

standard values in AS/NZS 4131 is as

shown in Table 4.3.

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Design.6

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Table 4.6 Design Factors – Gas Pipes

Installation Conditions Design Factor Value

Fluid type Natural Gas f0 2.0

LPG 2.2

Pipe Form Straight length f1 1.0

Coils 1.2

Soil Temperature (Av. °C) -10 < t < 0 f2 1.2

0 < t < 20 1.0

20 < t < 30 1.1

30 < t < 35 1.3

Designation Distribution f3 1.0

Transport 0.9

Rapid Crack Resistance f4 1.0

Population density & area loading

Open field f5 0.9

Less trafficed roads in inbuilt areas 1.05

Heavy trafficed roads in inbuilt areas 1.15

Roads in populated area 1.20

Roads in industrial area 1.25

Private area habitation 1.05

Private area industry 1.20

Note: Where factor values are not listed, consult with Vinidex engineers for

recommendations.

Where installation applications are used

to carry fluids other than water, then

another value of the Design Factor may

need to be selected. The value selected

will depend on both the nature of the

fluid being carried and the location of the

pipeline installation. For specific

installations, the advice of Vinidex

engineers should be obtained.

In the case of gas pipes in AS/NZS 4130,

both Series 2 and Series 3, a Design

Factor ranging between F = 2.0 and

F = 4.0 applies depending on the specific

installation conditions; see Table 4.6.

Table 4.4

Typical Design Factors

Pipeline Application Design Factor

20°CF

Water Supply 1.25

Natural Gas 2.0

Compressed Air 2.0

LPG 2.2

Where the Design Factor is varied, then

the MAOP for the particular Series 1 pipe

PN rating can be calculated as follows:

In the particular case of gas distribution,

then the type of gas, and the pipeline

installation conditions need to be

considered. In this case the Design

Factor is a combination of a number of

sub factors (fx) which must be factored

together to give the final value for F such

that:

F = f0 x f1 x f2 x f3 x f4 x f5

MAOP =PN x 0.125

Table 4.5 PE Pipe Pressure Ratings

PN Rating Number Nominal Working Pressure

MPa Head Metres

PN 3.2 0.32 32

PN 4 0.40 40

PN 6.3 0.63 63

PN 8 0.80 80

PN 10 1.00 100

PN 12.5 1.25 125

PN 16 1.60 160

PN 20 2.00 200

PN 25 2.50 250

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Temperature

Influences

The physical properties of Vinidex PE

pipes are related to a standard reference

temperature of 20°C. Where physical

property values are quoted to ISO and

DIN Standard test methods, these are for

the 20°C condition, unless otherwise

quoted. Wherever PE pipelines operate at

elevated temperatures, the pressure

ratings (PN) must be revised.

The temperature to be considered for the

re rating is the pipe material service

temperature, and the actual operating

conditions for each specific installation

must be evaluated.

For long length installations a

temperature gradient will exist along the

length of the pipe line. This gradient will

be dependent upon site conditions, and

the fluid being carried will approach the

ambient temperature of the surrounds.

The rate of temperature loss will be

determined by inlet temperature, fluid

flow rate, soil conductivity, ambient

temperature and depth of burial. As

these factors are specific to each

installation, the temperature gradient

calculations are complex and in order to

assist the designer, Vinidex have

developed computer software to predict

the temperature gradient along the

pipeline.

This is available on request to Vinidex

design engineers.

Service Lifetimes

The design basis used in AS/NZS 4130

for PN rating of PE pipes 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 AS/NZS 4131

the specific values are contained in

Table 4.3.

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. In these cases the advice

of Vinidex design engineers should be

obtained.

Vinidex PE pipes are continually tested in

combinations of elevated temperature

(80°C water conditions) and pressure to

ensure compliance with specification

requirements.

The adoption of a 50 year design life in

AS/NZS 4130 to establish a value of the

HDS is arbitrary, and does not relate to

the actual service lifetime of the pipeline.

Where pipelines are used for applications

such as water supply, where economic

evaluations such as present value

calculations are performed, the lifetimes

of PE lines designed and operated within

the AS guidelines may be regarded as

70–100 years for the purpose of the

calculations. Any lifetime values beyond

these figures are meaningless, as the

assumptions made in other parts of the

economic evaluations outweigh the

effect of pipe lifetime.

The grades of PE specified in AS/NZS

4131 are produced by different

polymerisation methods, and as such

have different responses to temperature

variations.

Pipe Classification (PN) is based on

continuous operation at 20°C and the

pressure rating will be reduced for

higher temperatures. In addition, as PE

is an oxidising material, the lifetime of

some grades will be limited by elevated

temperature operation. Table 4.7 gives

temperature rerating data for Vinidex

pipes made to AS/NZS 4130.

In these tables, allowable working

pressures are derived from ISO 13761*

and assume continuous operation at the

temperatures listed.

Extrapolation limit is maximum allowable

extrapolation time in years, based on

data analysis in accordance with ISO/DIS

9080**, and at least two years of test at

80°C for PE80B and PE100. Actual

product life may well be in excess of

these values.

The performance of compounds used in

the manufacture of Vinidex pipes to

AS/NZS 4130 has been verified by

appropriate data analysis.

In addition, Vinidex offers pipes made

from specialised compounds for

particular applications, such as elevated

temperature use.

Contact Vinidex engineers for special

requirements.

Note:

* Plastics pipes and fittings – pressure

reduction factors for polyethylene

pipeline systems for use at

temperatures above 20°C.

** Plastics piping and ducting systems –

determination of long-term

hydrostatic strength of

thermoplastics materials in pipe form

by extrapolation.

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Design.8

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Pipe Design for

Variable

Operational

Conditions

The following examples assist in the

design and selection of polyethylene

pipes for variable operating conditions

Given Operating Conditions

Pressure/Temperature/Time Relationship

Determine

Material

Class of pipe

Life

Steps

1. Assume a material

2. Determine Class from

Temperature Rating Table 4.7

Note: For brief periods at elevated

temperature it may be appropriate to

decrease the safety factor to a value of x,

i.e. multiply the working pressure by:

3. By the following process,

assess whether life is ‘used up’

For each combination of time and

temperature, estimate the proportion of

life ‘used up’ by using the time/

temperature relationships in the table.

If the proportion is less than unity, the

material is satisfactory.

125.

The data in the tables are obtained from

the use of ISO 13761 and ISO/DIS 9080,

and are appropriate for compounds

typically used by Vinidex.

Example

Pumped system normally working at a

maximum head, including surge of 60m.

At startup, the mean pipe wall

temperature is 55°C, dropping to 35°C

after 1 hour. Pump operation is for 10

hours per day, with a system life of 15

years.

1. Assume PE 80B

2. Determine Pipe Class

The worst situation is operation at 55°C.

From Table 4.7, PN10 pipe at 55°C has

an allowable working head of 60m.

PN10 pipe is therefore satisfactory.

3. Determine Life

Total time at 55°C

= 1 x 365 x 15 = 5475h = 0.625y.

From

Table 4.7

, L

min

for 55°C is 24 years,

therefore proportion of time used is:

Total time at 35°C

= 9 x 365 x 15 = 49275h = 5.625y.

From the table, L

min

for 35°C is 100 years,

therefore proportion of time used is:

Total proportion is 8.2% of life used in

15 years (6.25 years actual operation).

0.625

24 = 0.026 = 2.6%

5.625

100 = 0.056 = 5.6%

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PE80B

Extrapolation Permissible System Operating Head (m)

Temp Limit PN 3.2 PN 4 PN 6.3 PN 8 PN 10 PN 12.5 PN 16 PN20

C Years

20 200 32 40 63 80 100 125 160 200

25 100 30 38 59 75 94 117 150 188

30 100 28 35 55 70 88 109 140 175

35 100 26 32 50 64 80 100 128 160

40 100 24 30 47 60 75 94 120 150

45 60 22 28 44 56 70 88 112 140

50 36 21 26 41 52 65 81 104 130

55 24 19 24 38 48 60 75 96 120

60 12 18 23 35 45 56 70 90 113

658 17213342536684105

705 1620313949617898

752 1418283645567290

802 1317263341526683

PE80C

Extrapolation Permissible System Operating Head (m)

Temp Limit PN 3.2 PN 4 PN 6.3 PN 8 PN 10 PN 12.5 PN 16 PN20

C Years

20 50 32 40 63 80 100 125 160 200

25 50 29 36 57 72 90 113 144 180

30 30 26 33 51 65 81 102 130 163

35 18 23 29 46 58 73 91 116 145

40 12 20 25 39 50 63 78 100 125

456 18233545567090113

PE100

Extrapolation Permissible System Operating Head (m)

Temp Limit PN 3.2 PN 4 PN 6.3 PN 8 PN 10 PN 12.5 PN 16 PN20 PN25

C Years

20 200 32 40 63 80 100 125 160 200 250

25 100 30 38 59 75 94 117 150 188 233

30 100 28 35 55 70 88 109 140 175 218

35 100 26 32 50 64 80 100 128 160 200

40 100 24 30 47 60 75 94 120 150 185

45 60 22 28 44 56 70 88 112 140 175

50 36 21 26 41 52 65 81 104 130 163

55 24 19 24 38 48 60 75 96 120 150

60 12 18 23 35 45 56 70 90 113 140

658 17213342536684105130

705 1620313949617898120

752 1418283645567290113

802 1317263341526683105

Table 4.7 Temperature Rating Tables

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Design.10

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E Modulus

The E modulus of polyethylene varies

with temperature, duration of loading,

stress, and the particular grade of

material.

However, in order to facilitate

engineering calculations, it is generally

appropriate to group materials into

categories and adopt ‘typical’ values of E.

Table 4.8 lists E values in MPa for

PE80B (MDPE), PE80C (HDPE), and

PE100 (HDPE).

PE 80B

Temp °C 3 min 1h 5h 24h 1y 20y 50y

0 1050 830 740 650 410 320 300

20 700 550 490 430 270 215 200

40 530 410 370 320 200 160 150

60 400 300 280 250 160 - -

PE 80C

Temp °C 3 min 1h 5h 24h 1y 20y 50y

0 1080 850 740 660 400 320 300

20 750 590 520 460 280 220 205

40 470 370 320 290 180 140 130

60 210 170 150 130 80 - -

PE 100

Temp °C 3 min 1h 5h 24h 1y 20y 50y

0 1380 1080 950 830 520 410 380

20 950 750 660 580 360 280 260

40 700 550 490 430 270 210 190

60 530 420 370 320 200 - -

Table 4.8 E Values (MPa)

Selection of Wall

Thickness for

Special

Applications

For a required nominal diameter (DN)

and working pressure, the necessary

wall thickness for special applications

may be calculated using the Barlow

formula:

where

t = minimum wall thickness (mm)

P = maximum working pressure (MPa)

DN = nominal outside diameter (mm)

S = design hoop stress (MPa)

where

F = design factor,

typically 1.25 for water

Example

P = 900kPa = 0.9MPa

DN = 630

MRS = 10 (PE100)

F = 1.25

tPDN

SMRS

S MPa==

125 80

txmm=+=

0 9 630

16 0 9 33 6

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Design.11

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Hydraulic Design

Design Basis

Vinidex Polyethylene (PE) pipes offer

advantages to the designer due to the

smooth internal bores which are

maintained over the working lifetime of

the pipelines. The surface energy

characteristics of PE inhibit the build up

of deposits on the internal pipe surfaces

thereby retaining the maximum bore

dimensions and flow capacities.

The flow charts presented in this section

relate the combinations of pipe

diameters, flow velocities and head loss

with discharge of water in PE pipelines.

These charts have been developed for

the flow of water through the pipes.

Where fluids other than water are being

considered, the charts may not be

applicable due to the flow properties of

these different fluids. In these cases the

advice of Vinidex engineers should be

obtained.

There are a number of flow formulae in

common use which have either a

theoretical or empirical background.

However, only the Hazen-Williams and

Colebrook-White formulae are

considered in this section.

Hazen - Williams

The original Hazen-Williams formula was

published in 1920 in the form:

v = C1 r0.63 s0.54 0.001-0.04

where

C1= Hazen-Williams roughness

coefficient

r = hydraulic radius (ft)

s = hydraulic gradient

Colebrook - White

The development from first principles of

the Darcy-Weisbach formula results in

the expression

where

and

f = Darcy friction factor

H = head loss due to friction (m)

D = pipe internal diameter (m)

L = pipe length (metres)

v = flow velocity (m/s)

g = gravitational acceleration

(9.81 m/s2)

R = Reynolds Number

This is valid for the laminar flow region

(R 2000), however, as most pipe

applications are likely to operate in the

transition zone between smooth and full

turbulence, the transition function

developed by Colebrook-White is

necessary to establish the relationship

between f and R.

where

k = Colebrook-White roughness

coefficient (m)

The appropriate value for PE pipes is:

k = 0.007 x 10 -3 m

= 0.007 mm

This value provides for the range of

pipe diameters, and water flow

velocities encountered in normal

pipeline installations.

HfLv

1237

251

12 10 12

DRf

log .

=− +











The variations inherent with diameter

changes are accounted for by the

introduction of the coefficient C2 so that

C2 = C1 r0.02

Adoption of a Hazen-Williams roughness

coefficient of 155 results in the following

relationship for discharge in Vinidex PE

pipes

Q = 4.03 x 10-5 D2.65 H0.54

where

Q = discharge (litres/second)

D = internal diameter (mm)

H = head loss (metres/100 metres

length of pipe)

Flow charts for pipe systems using the

Hazen - Williams formula have been in

operation in Australia for over 30 years.

The charts calculate the volumes of

water transmitted through pipelines of

various materials, and have been proven

in practical installations.

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Design.12

design

Head Loss in Fittings

Wherever a change to pipe cross section,

or a change in the direction of flow

occurs in a pipeline, energy is lost and

this must be accounted for in the

hydraulic design.

Under normal circumstances involving

long pipelines these head losses are

small in relation to the head losses due

to pipe wall friction.

However, geometry and inlet/exit

condition head losses may be significant

in short pipe runs or in complex

installations where a large number of

fittings are included in the design.

The general relationship for head losses

in fittings may be expressed as:

where

H = head loss (m)

V = velocity of flow (m/s)

K = head loss coefficient

g = gravitational acceleration

(9.81 m/s2)

The value of the head loss coefficient K

is dependent on the particular geometry

of each fitting, and values for specific

cases are listed in Table 4.9.

The total head loss in the pipeline

network is then obtained by adding

together the calculations performed for

each fitting in the system, the head loss

in the pipes, and any other design head

losses.

Worked Example

What is the head loss occurring in a

250mm equal tee with the flow in the

main pipeline at a flow velocity of 2 m/s?

where

K = 0.35 (Table 4.9)

V = 2 m/s

g = 9.81 m/s

If the total system contains 15 tees

under the same conditions, then the total

head loss in the fittings is 15 x 0.07 =

1.05 metres.

Flow Variations

The flow charts presented for PE pipes

are based on a number of assumptions,

and variations to these standard

conditions may require evaluation as to

the effect on discharge.

Water Temperature

The charts are based on a water

temperature of 20°C. A water

temperature increase above this value,

results in a decrease in viscosity of the

water, with a corresponding increase in

discharge ( or reduced head loss )

through the pipeline.

An allowance of approximately 1%

increase in the water discharge must be

made for each 3°C increase in

temperature above 20°C. Similarly, a

decrease of approximately 1% in

discharge occurs for each 3°C step

below 20°C water temperature.

Pipe Dimensions

The flow charts presented in this section

are based on mean pipe dimensions of

Series 1 pipes made to AS/NZS 4130 PE

pipes for Pressure applications.

Surface Roughness

The roughness coefficients adopted for

Vinidex PE pipes result from

experimental programs performed in

Europe and the USA, and follow the

recommendations laid down in

Australian Standard AS2200 - Design

Charts for Water Supply and Sewerage.

























H=×

035 2

2981

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Design.13

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Flow Chart

Worked Examples

Example 1 - Gravity Main

(refer Figure 4.1)

A flow of water of 32 litres/second is

required to flow from a storage tank

located on a hill 50 metres above an

outlet. The tank is located 4.5 km away

from the outlet.

Hence the information available is :

Q = 32 l/s

Head available = 50 metres

Length of pipeline = 4500 metres

Minimum PN rating of pipe available to

withstand the 50 m static head is PN6.3.

Head loss per 100 m length of pipe is :

Use Table 4.1 to select the SDR rating of

PN6.3 class pipes in both PE80, and

PE100 materials.

4500 100 1 11 100xmm=./

Figure 4.1 Gravity Flow Example

Maximum difference

in water level

50m

Discharge

4,500m of

Vinidex PE Pipe

Storage

tank

PE80 Material Option

PE80 PN6.3 pipe is SDR 21.

Use the SDR 21 flow chart, read

intersection of discharge line at 32 l/s

and head loss line at 1.11m/100m of

pipe. Select the next largest pipe size.

This results in a DN200 mm pipe

diameter.

PE100 Material Option

PE100 PN6.3 pipe is SDR 26.

Use the SDR26 flow chart, read the

intersection of discharge line at 32 l/s

and head loss line at 1.11m/100m of

pipe. Select the next largest pipe size.

This results in a DN180 mm pipe

diameter.

Hence for this application, there are two

options available, either :

1. DN 200 PE80 PN6.3 or

2. DN 180 PE100 PN6.3

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Design.14

design

3. Fittings head losses

From Figure 4.2, identify the type and

number of different fittings used in the

pipeline. Select the appropriate form

factor value K for each fitting type from

Table 4.9. Then:

Fitting Form Head Loss m

Factor K

Foot valve 15.0 15 x 0.05 = 0.75

Gate valve 0.2 2 x 0.2 x 0.05 = 0.02

Reflux valve 2.5 2.5 x 0.05 = 0.125

90° elbow 1.1 4 x 1.1 x 0.05 = 0.220

45° elbow 0.35 2 x 0.35 x 0.05 = 0.035

Square outlet 1.0 1.0 x 0.05 = 0.050

Total fittings head loss = 1.2

Velocity Head v

2981005

100 5000 25

.xm=

Example 2 - Pumped Main

(refer Figure 4.2)

A line is required to provide 20 litres/

second of water from a dam to a high

level storage tank located 5000 metres

away. The tank has a maximum water

elevation of 100 m and the minimum

water elevation in the dam is 70 m.

The maximum flow velocity is required to

be limited to 1.0 metres/second to

minimise water hammer effects.

The maximum head required at the pump

= static head + pipe friction head

+ fittings form loss

1. Static head

= 100 - 70 = 30 m

2. Pipe friction head

Considering the data available, start with

a PN6.3 class pipe.

PE80 Option

From Table 4.1, PE80 PN6.3 pipe is

SDR21.

Use the SDR 21 flow chart, find the

intersection of the discharge line at 20 l/s

and the velocity line at 1 m/s. Select the

corresponding or next largest size of

pipe. Where the discharge line intersects

the selected pipe size, trace across to find

the head loss per 100m length of pipe.

This gives a value of 0.5m/100m.

Calculate the total friction head loss in the

pipe:

Figure 4.2 Pumped Flow Example

Maximum difference

in water level - 30m

90°

Elbow

Gate

Valve Pump Gate

Valve 2x90°

Elbows

Hinged Disc

Foot Valve

with Strainer

RL 100m

RL 70m

Min Level

of Dam

Reflux Valve

45° Elbow

5,000m

of Vinidex PE Pipe

45° Elbow

Square

Outlet

90° Elbow

Storage Tank

Max Level of Tank

Then from the flow chart, estimate the

velocity of flow

This gives 1 m/s.

4. Total pumping head

= 30 + 25 + 1.2 = 56.2 m

allow 57 m.

Note: The example does not make any

provision for surge allowance in

pressure class selection.

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Part Full Flow

Non pressure pipes are designed to run

full under anticipated peak flow

conditions. However, for a considerable

period the pipes run at less than full flow

conditions and in these circumstances

they act as open channels with a free

fluid to air surface.

In these instances consideration must be

given to maintaining a minimum

transport velocity to prevent deposition

of solids and blockage of the pipeline.

For pipes flowing part full, the most

usual self cleansing velocity adopted for

sewers is 0.6 metres/second.

Example 3. Determine

flow velocity and

discharge under part full

flow conditions

Given gravity conditions:

Pipe DN 200 PE80 PN6.3

Mean Pipe ID 180 mm ( Refer Table XX

PE pipe dimensions, or AS/NZS 4130 )

Gradient 1 in 100

Depth of flow 80 mm

Problem:

Find flow and velocity

Solution:

Proportional Depth Depth of flow

Pipe ID

180 044.

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Discharge

Velocity

Proportional Discharge & Velocity

Proportional Depth

Figure 4.3 Part Full Flow

From Figure 4.3 Part Full Flow, for a

proportional depth of 0.44, the

proportional discharge is 0.4 and the

proportional velocity if 0.95.

Refer to the Vinidex PE pipe flow chart

for the SDR 21 pipe.

For a gradient of 1 in 100 full flow is

39 l/s and the velocity is 1.6 m/s.

Then, for part full flow

Discharge = 0.4 x 39

= 15.6 l/s

Velocity = 0.95 x 1.6

= 1.52 m/s

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Design.16

design

Fitting Type K

Pipe Entry Losses

Square Inlet 0.50

Re-entrant Inlet 0.80

Slightly Rounded Inlet 0.25

Bellmouth Inlet 0.05

Pipe Intermediate Losses

Elbows R/D < 0.6 45°0.35

90°1.10

Long Radius Bends (R/D > 2) 111/4°0.05

221/2°0.10

45°0.20

90°0.50

Tees

(a) Flow in line 0.35

(b) Line to branch flow 1.00

Sudden Enlargements

Ratio d/D

0.9 0.04

0.8 0.13

0.7 0.26

0.6 0.41

0.5 0.56

0.4 0.71

0.3 0.83

0.2 0.92

<0.2 1.00

Sudden Contractions

Ratio d/D

0.9 0.10

0.8 0.18

0.7 0.26

0.6 0.32

0.5 0.38

0.4 0.42

0.3 0.46

0.2 0.48

<0.2 0.50

Fitting Type K

Gradual Enlargements

Ratio d/D q = 10° typical

0.9 0.02

0.7 0.13

0.5 0.29

0.3 0.42

Gradual Contractions

Ratio d/D q = 10° typical

0.9 0.03

0.7 0.08

0.5 0.12

0.3 0.14

Valves

Gate Valve (fully open) 0.20

Reflux Valve 2.50

Globe Valve 10.00

Butterfly Valve (fully open) 0.20

Angle Valve 5.00

Foot Valve with strainer

hinged disc valve 15.00

unhinged (poppet) disc valve 10.00

Air Valves zero

Ball Valve 0.10

Pipe Exit Losses

Square Outlet 1.00

Rounded Outlet 1.00

Resistance Coefficients

Table 4.9 Valves, Fittings and Changes in Pipe Cross-Section

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Design.17

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Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE AND CLASS (DN/PN)

VELOCITY m/s

1.5

3.0

2.5

2.0

1.75

1.25

1.0

0.5

0.25

16/16

16/12.5

20/16

20/12.5

25/16

25/12.5

25/10

25/8

32/16

32/12.5

32/10 32/8

32/6.3 40/16

40/12.5

40/10

40/6.3 50/16

40/8

50/12.5

50/10

50/8 50/6.3

63/16

63/12.5

63/10

63/6.3 63/8

75/16

75/12.5

75/10 75/8

75/6.3

Flow Chart for Small Bore Polyethylene Pipe – DN16 to DN75

(PE80B, PE80C Materials)

Flow Chart for Small Bore Polyethylene Pipe – DN16 to DN75 (PE80B, PE80C Materials)

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Design.18

design

Flow Chart for Polyethylene Pipe – SDR 41

(PE80: PN3.2 & PE100: PN4)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

900

1000

4.0

2.0

3.0

1.5

1.0

0.5

0.25

Flow Chart for Polyethylene Pipe – SDR 41 (PE80: PN3.2 & PE100: PN4)

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Flow Chart for Polyethylene Pipe – SDR 33

(PE80: PN4)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

4.0

2.0

3.0

1.5

1.0

0.5

0.25

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

900

1000

Flow Chart for Polyethylene Pipe – SDR 33 (PE80: PN4)

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Design.20

design

Flow Chart for Polyethylene Pipe – SDR 26

(PE100: PN6.3)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/sec

4.0

2.0

3.0

1.5

1.0

0.5

0.25

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

900

1000

Flow Chart for Polyethylene Pipe – SDR 26 (PE100: PN6.3)

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Flow Chart for Polyethylene Pipe – SDR 21

(PE80: PN6.3 & PE100: PN8)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

4.0

2.0

3.0

1.5

1.0

0.5

0.25

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

900

1000

Flow Chart for Polyethylene Pipe – SDR 21 (PE80: PN6.3 & PE100: PN8)

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Design.22

design

Flow Chart for Polyethylene Pipe – SDR 17

(PE80: PN8 & PE100: PN10)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

4.0

2.0

3.0

1.5

1.0

0.5

0.25

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

900

Flow Chart for Polyethylene Pipe – SDR 17 (PE80: PN8 & PE100: PN10)

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Flow Chart for Polyethylene Pipe – SDR 13.6

(PE80: PN10 & PE100: PN12.5)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

4.0

2.0

3.0

1.5

1.0

0.5

0.25

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

Flow Chart for Polyethylene Pipe – SDR 13.6 (PE80: PN10 & PE100: PN12.5)

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Design.24

design

Flow Chart for Polyethylene Pipe – SDR 11

(PE80: PN12.5 & PE100: PN16)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

4.0

2.0

3.0

1.5

1.0

0.5

0.25

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

Flow Chart for Polyethylene Pipe – SDR 11 (PE80: PN12.5 & PE100: PN16)

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Flow Chart for Polyethylene Pipe – SDR 9

(PE80: PN16 & PE100: PN20)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

110

125

140

160

180

200

225

250

280

315

355

400

450

4.0

3.0

2.0

1.5

1.0

0.5

0.25

Flow Chart for Polyethylene Pipe – SDR 9 (PE80: PN16 & PE100: PN20)

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Design.26

design

Flow Chart for Polyethylene Pipe – SDR 7.4

(PE100: PN25)

Discharge - Litres per Second (L/s)

Head Loss - Metres Head of Water per 100 metres of Pipe

NOMINAL SIZE

VELOCITY m/s

110

125

140

160

180

200

225

250

280

315

355

400

450

4.0

3.0

2.0

1.5

1.0

0.5

0.25

Flow Chart for Polyethylene Pipe – SDR 7.4 (PE100: PN25)

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Design.27

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Surge & Fatigue

Surge, or ‘water hammer’, is a temporary

change in pressure caused by a change

in velocity of flow in the pipeline,

whereas fatigue is the effect induced in

the pipe or fitting by repeated surge

events.

For Vinidex PE pipes to AS/NZS 4130,

operating under the following limitations,

it is not necessary to make specific

allowance for fatigue effects:

(a) The maximum pressure in the pipe

from all sources must be less than the

pressure equivalent to the Classification

of the pipe (PN).

and

(b) The amplitude between minimum and

maximum pressure from all sources

must not exceed the pressure equivalent

to the Classification of the pipe (PN).

Care must be taken to ensure that the

minimum pressure does not reach a

level that may result in vacuum collapse

(see External Pressure Resistance, page

Design.36).

Surge may take the form of positive and/

or negative pressure pulses resulting

from change of flow velocity, such as

arising from valve or pump operation.

Such changes of flow velocity lead to

induced pressure waves in the pipeline.













C=W

SDR





 









 





−0

x 10 / sec

PCV

This represents the case of a single

pipeline with the flow being completely

closed off. The pressure rises generated

by flow changes in PE pipelines are the

lowest generated in major pipeline

materials due to the relatively low

modulus values.

Further, as medium density materials

have lower modulus values than high

density materials, the pressure rise in

PE80B materials will be lower than that

in PE80C and PE100 materials.

Water hammer (surge) analysis of

pipeline networks is complex and beyond

the scope of this Manual. Where

required, detailed analysis should be

undertaken by experts.

The velocity of the pressure wave,

referred to as celerity (C), depends on

the pipe material, pipe dimensions, and

the liquid properties in accordance with

the following relationship:

where

W = liquid density (1000 kg/m3

for water)

SDR = Standard Dimension Ratio

of the pipe

K = liquid bulk modulus (2150 MPa)

E = pipe material short term

modulus (MPa) refer Table 4.8

The time taken for the pressure wave to

travel the length of the pipeline and

return is

where:

t = time in seconds

L = length of pipeline

If the valve closure time tc is less than t,

the pressure rise due to the valve closure

is given by:

where:

P1 = pressure rise in kPa

v = liquid velocity in m/sec

If the valve closure time tc is greater than

t, then the pressure rise is approximated

by:

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Design.28

design

Celerity

The surge celerity in a polyethylene

pipeline filled with liquid can be

determined by:

where

W = liquid density (1000 kg/m3

for water)

SDR = Standard Dimension Ratio

of the pipe

K = liquid bulk modulus (2150MPa)

E = pipe material ‘instantaneous’

modulus (taken as 1000MPa for

PE80B, 1200MPa for PE80C,

1500MPa for PE100)

Table 4.10 Surge Celerity

Celerity m/s

SDR MDPE (PE 80B) HDPE (PE 80C) HDPE (PE 100)

41 160 170 190

33 170 190 210

26 190 210 240

21 220 240 260

17 240 260 290

13.6 270 290 320

11 300 320 360

9 330 350 390

7.4 360 390 430

SDR

Exm=+























−

110

/ sec

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Design.29

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design

Slurry Flow

General Design

Considerations

The abrasion resistance characteristics

and flexibility of Vinidex PE pipes make

slurry flow lines, such as mine tailings,

ideal applications for the material and

such installations are in widespread use

throughout Australia.

The transportation of Non Newtonian

fluids such as liquids or liquid/liquid,

liquid/solid mixtures or slurries is a

highly complex process and requires a

detailed knowledge of the specific fluid

before flow rate calculations can be

performed.

As distinct from water, many fluids

regarded as slurries have properties

which are either time or shear rate

dependent or a combination of both

characteristics. Hence it is essential for

the properties of the specific fluid to be

established under the operating

conditions being considered for each

design installation.

In addition to water flow, slurry flow

design needs to take into account the

potential for abrasion of the pipe walls,

especially at changes of direction or

zones of turbulence.

The most usual applications of Vinidex

PE pipes involve liquid/solid mixtures

and these must first be categorised

according to flow type:

• Homogeneous Suspensions

• Heterogeneous Suspensions

Homogeneous Suspensions

Homogeneous suspensions are those

showing no appreciable density gradient

across the cross section of the pipe.

These slurries consist of material

particles uniformly suspended in the

transport fluid.

Generally, the particle size can be used to

determine the flow type and suspensions

with particle sizes up to 20 microns can

be regarded as homogeneous across the

range of flow velocities experienced.

Heterogeneous Suspensions

Heterogeneous suspensions are those

showing appreciable density gradients

across the cross section of the pipe, and

are those containing large particles

within the fluid.

Suspensions containing particle sizes of

40 microns and above may be regarded

as heterogeneous.

In addition to the fluid characterisations

for both types, the tendency for solids to

settle out of the flow means that a

minimum flow velocity must be

maintained.

This velocity, the Minimum Transport

Velocity, is defined as the velocity at

which particles are just starting to

appear on the bottom of the pipe.

The flow in short length pipelines differs

in that these lines may be flushed out

with water before shut down of

operations. Long length pipelines cannot

be flushed out in the same way and the

selection of operating velocities and pipe

diameter needs to address this aspect.

The design of slurry pipelines is an

iterative process requiring design

assumptions to be made initially, and

then repeatedly being checked and tested

for suitability. The specific fluid under

consideration requires full scale flow

testing to be conducted to establish the

accurate flow properties for the liquid/

particle combinations to be used in the

installed pipeline.

Without this specific data, the

assumptions made as to the fluid flow

behaviour may result in the operational

pipeline being at a variance to the

assumed behaviour. The principles of

slurry pipeline design as outlined in the

methods of Durand, Wasp, and Govier

and Aziz are recommended in the

selection of Vinidex PE pipes for these

applications.

Note:

The published Vinidex PE pipe flow

charts relate ONLY to water or other

liquids which behave as Newtonian

fluids.

They are not suitable for calculating the

flow discharges of other fluids, including

slurries.

For further information on slurry pipeline

design, the designer is referred to such

publications as Govier G.W. and Aziz K,

The Flow of Complex Mixtures in Pipes.

Rheinhold, 1972.

and Wasp E.J.

Solid

Liquid Flow - Slurry Pipeline

Transportation. Trans Tech Publications.

1977.

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Design.30

design

Pipe Wear

Polyethylene pipe has been a proven

performer over many decades in

resisting internal abrasion due to slurry.

It is particularly resistant to abrasion

from particles less than 500 microns in

size depending on particle shape.

The abrasive wear of any slurry handling

system is heavily dependent on the

physical characteristics of the solids

being transported. These characteristics

include angularity, degree of particle

attrition, angle of attack, velocity, and the

concentration of solids in the

transporting fluid.

With metal pipes, corrosive wear

interacts synergistically with abrasive

wear, producing rates of wear that can be

many times greater than a simple

combination of the two modes of wear.

Corrosive attack on a piping material can

lead to increasing roughness of the

surface, loss of pressure and localised

eddying, and hence increase the abrasive

attack.

Factors Affecting Rates

of Wear

The wall of polyethylene pipes are worn

by contact with the solids particles. The

principal causes of wear are as follows:

• Particle Size

• Particle Specific Gravity

• Velocity

• Angle of Attack

Particle Size

The size of the particle combined with

the requisite velocity is one of the

principal factors which contribute to

wear. The rate of wear increases with

particle size with very little wear

occurring on polyethylene systems

below 300 microns. Above this size the

rate of wear will increase proportionally

with particle size with the maximum

practical D50 size around 1mm. Many

researchers have attempted to develop

relationships between particle size and

rates of wear, however, these have not

proven to be accurate due to the wide

variation of slurry characteristics. The

wear mechanism involved is not

thoroughly understood, however, it is

believed the higher impact energy

resulting from a combination of particle

mass and the high velocity required to

transport this larger particle are the

principal contributing factors.

Particle Specific Gravity

Similarly, the specific gravity will

increase the mass of the particle

resulting in increased wear. This is a

result of the increased impact energy

from the mass of the particle combined

with the faster carrier velocity.

Velocity

A minimum velocity is required to

provide the necessary uplift forces to

keep a solid particle in suspension. This

velocity also increases the impact energy

of the particle against the wall of the

pipe.

Angle of Attack

There are essentially two modes of wear,

impingement and cutting. Cutting wear

is considered to be caused by the low

angle impingement of particles. In

practice, cutting wear comprises a

cutting action, and the accommodation

of some of the energy of impact within

the matrix of the material being worn.

Hence, cutting wear also incorporates a

component of deformation wear. The

requirement for wear is that some of the

solid particles must have sufficient

energy to penetrate and shear a material,

perhaps gouging fragments loose. As a

result, a low modulus material such as

polyethylene has very good resistance to

cutting wear due to the resulting

deformation upon impact. In the case of

angular particles the cutting action is

increased resulting in increased pipe

wear.

The simple theory of abrasive wear

suggests that specific wear (wear per

unit mass transported) is proportional to

normal force at the pipe wall. Therefore

the wear rate will increase as the angle of

attack to the pipe wall increases. The

increase in angle will also increase the

amount of energy with which the particle

strikes the pipe wall. It is for this reason

that accelerated wear is caused by:

i) Fittings which effect a change in the

angle of flow such as tees and bends

ii) Butt weld joints. Butt weld internal

beads will cause eddying which will

result in increases in angle of attack

of the particle to the pipe wall. As a

result accelerated wear generally

occurs immediately downstream of

the bead. This is usually prominent in

D50 particle sizes over 300 microns.

For coarse particle slurries the

internal bead should be removed.

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Design.31

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Maintenance and

Operation

To reduce the cost of wear on a pipeline

asset it is general practice to rotate the

pipes at the appropriate intervals, this is

particularly important when transporting

sand slurries. In this respect mechanical

joints are useful, although re-welding of

pipes over 500mm has been preferred in

some cases to reduce capital costs.

These mechanical joints are usually

installed at every 20m pipe length to

assist the pipe rotation process and also

permit clearance of blockages.

Slurry pipelines are usually operated as

close to the critical settling velocity as

practical to reduce operating costs.

Unfortunately, if an increase in particle

size occurs, then saltation will

commence increasing friction loss

eventually resulting in a blockage. Other

factors that cause blockages are

increases in solids concentration, loss of

pump pressure due to power failure, or

pump impellor wear. Polyethylene

pipelines may be cleared of blockages by

clear water pumping provided they have

been installed on flat even ground.

Sudden vertical ‘V’ bends with angles

over 10° may cause an accumulation of

solids in the bore, preventing clearing by

clear water pumping. If vertical bends

are unavoidable then they should be

installed with mechanical joints to permit

their easy removal for clearing.

Fittings

A range of mechanical joints are

available for polyethylene slurry

pipelines. They include stub flanges and

backing rings, Hugger couplings,

shouldered end/Victaulic couplings,

compression couplings and rubber ring

joint fittings.

References

The Transportation of Flyash and Bottom

Ash in Slurry Form,

C G Verkerk

Relative Wear Rate Determinations for

Slurry Pipelines,

C A Shook, D B Haas,

W H W Husband and M Small

Warman Slurry Pumping Handbook,

Warman International Ltd.

iii) Fittings joints. At connections of

mechanical fittings some

misalignment of the mating faces

may occur resulting in increased

angles of attack of the particles.

iv) Change in velocity. Some

compression fittings cause a

reduction in the internal diameter of

the pipe under the fitting resulting in

turbulence. A mismatching valve

bore will also cause turbulence. It is

for this reason that the use of clear

bore valves such as knife gate valves

is preferred for slurry pipelines.

v) Increased velocity. High velocities

are required to create sufficient

turbulence for the suspension of

heavy particles. This turbulence

increases the angle of attack to the

pipe wall, resulting in increased wear

for large particles.

vi) Insufficient velocity. When a system

is operated near its settling velocity,

the heavier particles migrate towards

the lower half of the pipe cross

section. This will cause a general

increase in pipe wear in this area. If

saltation/moving bed occurs, then

the heavy particles will impact

against the pipe bottom, causing an

accelerated wave profile wear. Should

deposition occur on the floor of the

pipe, then the particles above this

deposition will cause the maximum

amount of wear as they interact with

the flow. This is characterised by the

formation of wave marks on the 5

and 7 o’clock position of the pipe.

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Design.32

design

Pneumatic Flow

Vinidex PE pipe systems are ideal for the

transmission of gases both in the high

and low pressure range.

The use of compressible liquids in PE

pipes requires a number of specific

design considerations as distinct from

the techniques adopted in the calculation

of discharge rates for fluids such as

water.

In particular:

• Compressed air may be at a higher

temperature than the surrounding

ambient air temperature, especially

close to compressor line inlets, and

the pressure rating of the PE pipes

require temperature re rating

accordingly.

For air cooled compressors, the

delivered compressed air

temperature averages 15°C above the

surrounding air temperature. For

water cooled compressors, the

delivered compressed air

temperature averages 10°C above the

cooling water temperature.

• For underground applications where

the PE pipes are exposed to ambient

conditions, the surrounding air

temperature may reach 30°C, and the

pipe physical properties require

adjustment accordingly.

• High pressure lines must be

mechanically protected from damage

especially in exposed installations.

• Valve closing speed must be reduced

to prevent a build up of pressure

waves in the compressible gas flow.

• Where gaseous fuels such as

propane, natural gas, or mixtures are

carried, the gas must be dry and free

from liquid contamination which may

cause stress cracking of the PE pipe

walls.

• Vinidex PE pipes should not be

connected directly to compressor

outlets or air receivers. A 21 metre

length of metal pipe should be

inserted between the air receiver and

the start of the PE pipe to allow for

cooling of the compressed air.

• Dry gases, and gas/solids mixtures

may generate static electrical charges

and these may need to be dissipated

to prevent the possibility of

explosion. PE pipes will not conduct

electrical charges, and conducting

inserts or plugs must be inserted into

the pipe to complete an earthing

circuit.

• Compressed air must be dry, and

filters installed in the pipeline to

prevent condensation of lubricants

which can lead to stress cracking in

the PE pipe material.

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Design.33

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System Design

Guidelines for the

Selection of

Vinidexair

Compressed Air

Pipelines

It is customary to find the Inside

Diameter of the pipe by using formulas

such as shown below. The formulas used

are generally for approximation purposes

only, surmising that the temperature of

the compressed air corresponds roughly

to the induction temperature. An

acceptable approximation is obtained

through the following equation:

4 Using point (3) draw a diagonal

line to the separation line.

5 Go to top of nomogram and use

the point indicating the Length of

Pipe and draw a line down to

meet horizontal line from point

(4).

6 Move to the Pressure Decrease in

the Pipe (∆p) at the bottom of

nomogram and draw a vertical

line up to meet the diagonal

drawn from point (5).

7 The Nominal Diameter of Pipe can

now be found by reading from

point (6) across to the left hand

side of the nomogram. From this

example DN63 pipe should be

selected. If the completed

nomogram falls between two

sizes of pipe, always use the

larger size.

Correction factors for

fittings

Table 4.11 indicates the approximate

pressure loss for fittings in terms of an

equivalent length of straight pipe in

metres. For each pipeline fitting, add the

equivalent length of pipe to the original

length of pipeline. This length is used for

the calculation of the equation above or

for the nomogram, Figure 4.4.

The advantage of using the nomogram is

that no further conversion factors are

required for pipe sizing. Also, when four

of the parameters are known the fifth can

be determined by reading directly from

the nomogram.

Example for the use of

the air-line nomogram

(Figure 4.4) to determine

the required pipe size

Working Pressure 7 bar

Volumetric Flowrate 30 L/s

Nominal length 200 m

Pressure Decrease 0.05 bar

1 Utilising the above operating

figures, proceed to mark those

positions around the perimeter of

the nomogram.

2 Locate the separation line

between (∆p) & (p). (See base of

nomogram.)

3 Commencing at the lower right

hand side of the nomogram draw

a line up from the Working

Pressure (p) to the line indicating

the Volumetric Flowrate (Q).

where

d = Pipe Internal Diameter in mm

LE= Pipe Length in m

Q = Volumetric Flowrate in L/s

Dp = Pressure Decrease in bar

p = Working Pressure in bar

Table 4.11 Pressure Loss for Fittings

Fitting equivalent pipe length in m

DN 20 DN 25 DN 32 DN 40 DN 50 DN 63 DN 90

socket welding joint

0.2 0.2 0.3 0.4 0.5 0.6 1.1

45° bend 0.2 0.3 0.4 0.6 0.9 1.2 2.3

90° bend 0.4 0.7 1.0 1.3 1.8 2.3 4.5

tees 0.8 1.4 1.9 2.4 2.8 3.8 7.5

reducer 0.3 0.4 0.5 0.6 0.7 0.9 2.1

The use of a nomogram is a quicker and

easier method to source information (see

Figure 4.4). In this nomogram the

Pressure Decrease (∆p) is indicated in

bar, the Working Pressure (p) in bar, the

Volumetric Flowrate (Q)

in L/s, the Pipe

Length (L

) in m, and the Pipe Nominal

Diameter DN.

dLQ

=450

185

∆

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Design.34

design

Figure 4.4

Compressed Air

Flow Nomogram

0.002 0.01 0.05 0.1 0.2 0.5 1 2 4 6 10 15500

400

300

200

100

1.5

1 2 5 10 20 50 100 200 500 1000 2000

nominal diameter DN

volumetric flow rate (Q) in L/s

pressure decrease in the pipe (∆p) in bar

length of the pipe (L) in m

working pressure (p) in bar

Sources:

Feldmann, K.H.:

Druckluftverteilung in der Praxis

(Munchen 1985)

Atlas Copco :

information sheets

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Design.35

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Expansion and

Contraction

Expansion and contraction of PE pipes

occurs with changes in the pipe material

service temperature.

This is in common with all pipe materials

and in order to determine the actual

amount of expansion or contraction, the

actual temperature change, and the

degree of restraint of the installed

pipeline need to be known.

For design purposes, an average value of

2.0 x 10-4/°C for Vinidex PE pipes may be

used.

The relationship between temperature

change and length change for different

PE grades is as shown in Figure 4.5.

Worked Example

A 100 metre long PE80C pipeline

operates during the day at a steady

temperature of 48°C and when closed

down at night cools to an ambient

temperature of 18°C. What allowance for

expansion/contraction must be made?

1. The temperature change experienced

= 48 - 18 = 30°C.

2. The thermal movement rate

(Figure 4.5) in mm/m for 30°C

= 6.0 mm/m.

3. The total thermal movement is then

6.0 x 100 = 600 mm.

Where pipes are buried, the changes in

temperature are small and slow acting,

and the amount of expansion/contraction

of the PE pipe is relatively small. In

addition, the frictional support of the

backfill against the outside of the pipe

restrains the movement and any thermal

effects are translated into stress in the

wall of the pipe.

Accordingly, in buried pipelines the main

consideration of thermal movement is

during installation in high ambient

temperatures.

Under these conditions the PE pipe will

be at it’s maximum surface temperature

when placed into a shaded trench, and

when backfilled will undergo the

maximum temperature change, and

hence thermal movement.

In these cases the effects of temperature

change can be minimised by snaking the

pipe in the trench for small sizes (up to

DN110) and allowing the temperature to

stabilise prior to backfilling.

For large sizes, the final connection

should be left until the pipe temperature

has stabilised.

Above ground pipes require no

expansion/contraction considerations for

free ended pipe or where lateral

movement is of no concern on site.

Alternatively, pipes may be anchored at

intervals to allow lateral movement to be

spread evenly along the length of the

pipeline.

Where above ground pipes are installed

in confined conditions such as industrial

or chemical process plants the

expansion/contraction movement can be

taken up with sliding expansion joints.

Where these cannot be used due to the

fluid type being carried ( such as slurries

containing solid particles ) the advice of

Vinidex design engineers should be

sought for each particular installation.

Figure 4.5 Thermal Expansion and Contraction for PE

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

Expansion and Contraction (mm/m)

Pipe Material Temperature Change (°C)

0 1020304050607080

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Design.36

design

External Pressure

Resistance

The possibility of external pressure

(buckling) being the controlling design

condition must be evaluated in the

design of PE pipelines.

All flexible pipe materials can be subject

to buckling due to external pressure and

PE pipes behave in a similar fashion to

PVC and steel pipes.

For pipe of uniform cross-section, the

critical buckling pressure (Pc) can be

calculated as follows:

where

Pc= critical buckling pressure, kPa

E = modulus, MPa from Table 4.8

SDR = pipe SDR from Table 4.1

As the modulus is temperature and time

dependent, the advice of Vinidex

engineers should be sought for

appropriate values.

Where ovality exists in the PE pipes, the

effective value of the critical buckling

pressure will be reduced.

The reduction in Pc for various levels of

initial ovality are as follows:

Ovality % 0 1 2 5 10

Reduction 1.0 0.99 0.97 0.93 0.86

Where pipes are buried and supported

by backfill soil, the additional support

(Pb) may be calculated from:

Pb = 1.15 (Pc E´) 0.5

Where E´ = soil modulus from

AS/NZS2566 - Buried Flexible Pipelines.

2380

•

SDR −1

()

Tabulations of the value of E´ for various

combinations of soil types and compac-

tions are contained in AS/NZS2566.

The value of Pc calculated requires a

factor of safety to be applied and a factor

of 1.5 may be applied for those

conditions where the negative pressure

conditions can be accurately assessed.

Where soil support is taken into account

then a factor of 3 is more appropriate

due to the uneven nature of soil support.

In general terms, PN10 PE pipe should

be used as a minimum for pump suction

line installations.

Where installation conditions potentially

lead to negative pressures, consideration

may need to be given to modification of

construction technique. For example,

ducting pipes may need to be sealed and

filled with water during concrete

encasement.

In operation, fluid may be removed from

the pipeline faster than it is supplied

from the source. This can arise from

valve operation, draining of the line or

rupture of the line in service. Air valves

must be provided at high points in the

line and downstream from control valves

to allow the entry of air into the line and

prevent the creation of vacuum

conditions. On long rising grades or flat

runs where there are no significant high

points or grade changes, air valves

should be placed at least every 500-1000

metres at the engineer’s discretion.

Soil Description E´ MPa

Gravel – graded 20

Gravel – single size 14

Sand and coarse-grained soil

with less than 12% fines 14

Coarse-grained soil

with more than 12% fines 10

Fine-grained soil (LL<50%)

with medium to no plasticity and

containing more than 25%

coarse-grained particles 10

Fine-grained soil (LL<50%)

with medium to no plasticity and

containing less than 25%

coarse-grained particles 10

Fine-grained soil (LL<50%)

with medium to high plasticity NR

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Trench Design

Minimum Cover

The recommended minimum cover

depths for Vinidex PE pipes are listed in

Table 4.12.

These cover depths are indicative only,

and specific installations should be

evaluated in accordance with AS/NZS

2566 - Buried Flexible Pipelines.

The minimum cover depths listed may

be reduced where load reduction

techniques are used, such as load

bearing beams, concrete slabs, conduit

sleeves, or increased backfill

compaction.

Trench Widths

In general practice, the trench width

should be kept to the minimum that

enables construction to readily proceed.

Refer to Figures 4.6 and 4.7.

The trench width used with PE pipe may

be reduced from those used with other

pipe types by buttwelding, or

electrofusion jointing above ground, and

then feeding the jointed pipe into the

trench. Similarly, small diameter pipe in

coil form can be welded or mechanically

jointed above ground and then fed into

the trench.

The minimum trench width should allow

for adequate tamping of side support

material and should be not less than

200mm greater than the diameter of the

pipe. In very small diameter pipes this

may be reduced to a trench width of

twice the pipe diameter.

Installation Condition Cover over Pipe Crown (mm)

Open country 300

Traffic Loading No pavement 450

Sealed pavement 600

Unsealed pavement 750

Construction equipment 750

Embankment 750

Table 4.12 Minimum Cover

Side Support

Material used for side support should

comply with the requirements of the

bedding materials.

The side support material should be

evenly tamped in layers of 75 mm for

pipes up to 250mm diameter, and 150

mm for pipes of diameters 315mm and

above.

Compaction should be brought evenly to

the design value required by AS/NZS

2566 for the specific installation.

Backfill

Once the sidefill has been placed and

compacted as required over the top of

the pipe, backfill material may be placed

using excavated material.

Trench backfills should not be used as a

dump for large rocks, builders debris, or

other unwanted site materials.

The maximum trench width should be

restricted as much as possible,

depending on the soil conditions. This is

necessary to reduce the cost of

excavation, and to develop adequate side

support.

Where wide trenches or embankments

are encountered, then the pipe should be

installed on a 75 mm layer of tamped or

compacted bedding material as shown

on the cross section diagrams. Where

possible a sub trench should be

constructed at the base of the main

trench to reduce the soil loads

developed. AS/NZS 2566 provides full

details for evaluating the loads developed

under wide trench conditions.

Bedding

PE Pipes should be bedded on a

continuous layer, 75 mm thick, of

materials complying with the following

requirements:

• Sand, free from rocks or other hard

or sharp objects retained on a

13.2mm sieve.

• Gravel or crushed rock of suitable

grading up to a max. size of 15mm.

•. The excavated material, free from

rocks and broken up such that it

contains no clay lumps greater than

75mm which would prevent adequate

compaction.

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Design.38

design

Figure 4.7

Narrow Trench Condition

Figure 4.6

Wide Trench Condition

Allowable Bending

Radius

Vinidex PE pipes are flexible in

behaviour, and can be readily bent in the

field.

In general terms, a minimum bending

radius of 33 x outside diameter of the

pipe (33D) can be adopted for PE80C,

and PE100 material pipes, whilst a radius

of 20 x outside diameter of the pipe

(20D) can be adopted for PE63, and

PE80B material pipes during installation.

This flexibility enables PE pipes to

accommodate uneven site conditions,

and, by reducing the number of bends

required, cuts down total job costs.

For certain situations, the designer may

wish to evaluate the resistance to kinking

or the minimum bending radius arising

from strain limitation. The long term

strain from all sources should not exceed

0.04 (4%).

=SDR (SDR-1)

1.12

100mm

min

100mm

min

Bedding

75mm min

100mm

min

100mm

min

Bedding

75mm min

When bending pipes there are two

control conditions:

1. Kinking in pipes with high SDR

ratios.

2. High outer fibre strain in high

pressure class pipes with low SDR

ratios.

For condition 1

The minimum radius to prevent kinking

(Rk) may be calculated by:

For condition 2

The minimum radius to prevent excess

strain (Re) may be calculated by:

where

ε= outer fibre strain

(maximum allowable = 0.04)

D = mean Di (mm)

e=2ε

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Deflection

Questionnaire

AS/NZS 2566 Deflection

Calculation for Buried

Flexible Pipes

The following questionnaire is to assist

designers in the calculation of deflection

for buried flexible pipe.

Company _______________________________________________________________________________

Name __________________________________________________________________________________

Phone ______________________ Fax ________________________ Email ________________________

PIPE DETAILS

Pipe Size and SDR or Class _________________________________________________________________

Pipe Material (ie. PE80/PE100) ______________________________________________________________

TRENCH DETAILS

Depth of Cover (from crown) _________________________________________________________________

Width (at pipe) ___________________________________________________________________________

Depth to Water Table (if above pipe) __________________________________________________________

LOADS

Live Load _______________________________________________________________________________

Dead Load ______________________________________________________________________________

SOIL TYPE

Native Soil ______________________________________________________________________________

Embedment Material ______________________________________________________________________

Degree of Compaction _____________________________________________________________________

Please photocopy before completing this form.

Retain this master for future use.

Complete all information and forward to your

nearest Vinidex office – refer over leaf.

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Design.40

design

Vinidex Locations

Sydney

254 Woodpark Rd, Smithfield NSW 2164

Tel (02) 9604 2422, Fax (02) 9604 4435

Melbourne

86 Whiteside Road, Clayton VIC 3168

Tel (03) 9543 2311, Fax (03) 9543 7420

Mildura

5 Corbould Court, Mildura VIC 3500

Tel (03) 5022 2616, Fax (03) 5022 1938

Brisbane & Export

224 Musgrave Rd, Coopers Plains QLD 4108

Tel (07) 3277 2822, Fax (07) 3277 3696

Townsville

49 Enterprise Avenue, Bohle QLD 4816

Tel (07) 4774 5044, Fax (07) 4774 5728

Adelaide

550 Churchill Road, Kilburn SA 5084

Tel (08) 8260 2077, Fax (08) 8349 6931

Perth

Sainsbury Road, O’Connor WA 6163

Tel (08) 9337 4344, Fax (08) 9331 3383

Darwin

3846 Marjorie Street, Berrimah NT 0828

Tel (08) 8932 8200, Fax (08) 8932 8211

Launceston

15 Thistle St, Sth Launceston TAS 7249

Tel (03) 6344 2521, Fax (03) 6343 1100

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Design.41

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design

Thrust Block

Supports

PE pipes and fittings joined by butt

welding, electrofusion, or other end load

bearing joint system do not normally

require anchorage to withstand loads

arising from internal pressure and flow.

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 valves,

should be independently supported in

order to prevent excessive shear loads

being transferred to the PE pipe.

Static Pressure Thrust

where

R = resultant thrust (kN)

P = pressure (MPa)

A = area of pipe cross section (mm2)

φ= angle of fitting (degrees)

For blank ends, tees and valves

R = PA 10-3

For reducers

R = P(A1 - A2) 10-3

R=2PA . sin φ.10

R=2waV

.sin φ.10

Soil Type Safe Bearing Capacity

(N/m2)

Rock and sandstone (hard thick layers) 100 x 105

Rock- solid shale and hard medium layers 90 x 104

Rock- poor shale, limestone 24 x 104

Gravel and coarse sand 20 x 104

Sand- compacted, firm, dry 15 x 104

Clay- hard, dry 15 x 104

Clay- readily indented 12 x 104

Clay/Sandy loam 9 x 104

Peat, wet alluvial soils, silt Nil

Velocity (Kinetic) Thrust

The velocity or kinetic thrust applies only

at changes of direction.

where

w = fluid density (kg/m3)

a = inside pipe cross section area

(mm2)

V = flow velocity (m/s)

The velocity thrust is generally small in

comparison to the pressure thrust.

The pressure used in the calculations

should be the maximum working, or test

pressure, applied to the line.

Bearing Loads of Soils

The thrust developed must be resisted

by the surrounding soil. The indicative

bearing capacities of various soil types

are tabulated below:

The figures in the table below are for

horizontal thrusts, and may be doubled

for downward acting vertical thrusts. For

upward acting vertical thrusts, the

weight of the thrust block must

counteract the developed loads.

In shallow (<600mm) cover installations

or in unstable conditions of fill, the soil

support may be considerably reduced

from the values tabulated, and a

complete soil analysis may be needed.

Irrigation Warehouse Group Pty Ltd

www.polypipe.com.au

Ph 1300 661 417

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Design.42

design

Thrust Block

Size Calculations

1. Establish the maximum pressure to

be applied to the line

2. Calculate the thrust developed at the

fitting being considered

3. Divide (2) by the safe bearing

capacity of the soil type against

which the thrust block must bear.

Worked Example

What bearing area of thrust block is

required for a 160 mm PN12.5 90° bend

in hard, dry clay?

1. Maximum working pressure of

PN12.5 pipe is 1.25 MPa.

Test pressure is 1.25 x WP

= 1.56 MPa.

3. Bearing capacity of hard, dry clay is

15x104 N/m2

Thrust blocks may be concrete or timber.

Where cast insitu concrete is used, an

adequate curing period must be provided

to allow strength development in the

concrete before pressure is introduced to

the pipeline. Where timber blocks are

used, test pressures may be introduced

immediately, but care needs to be taken

to ensure that the blocks will not rot and

will not be attacked by termites or ants.

Bearing area of thrust block 3.8 x 10

15 x 10

=0.25m

Figure 4.8 Thrust Blocks

Closed end and hydrant anchorage

Valve anchorage

Bend in vertical plane anchorage

Bend in horizontal plane anchorage

Tee anchorage

R=2PA.sin φ.10

=3.8 x10

Irrigation Warehouse Group Pty Ltd

www.polypipe.com.au

Ph 1300 661 417

Design.43

PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems

Electrical

Conductivity

Vinidex PE pipes are non conductive and

cannot be used for electrical earthing

purposes or dissipating static electricity

charges.

Where PE pipes are used to replace

existing metal water pipes, the designer

must consider any existing systems used

for earthing or corrosion control

purposes. In these cases the appropriate

electrical supply authority must be

consulted to determine their

requirements.

In dry, dusty, or explosive atmospheres,

potential generation of electricity must

be evaluated and static dissipation

measures adopted to prevent any

possibility of explosion.

Heat Sources

PE pipes and fittings should be protected

from external heat sources which would

bring the continuous pipe material

service temperature above 80°C.

Where the PE pipes are installed above

ground, the protection system used

must be resistant to ultra violet radiation

and the effects of weathering, PE pipes

running across roofing should be

supported above the roof sheeting in

order to prevent temperature build up.

See Table 4.7 Temperature Rating Table.

Vibration

Direct connection to sources of high

frequency such as pump outlet flanges

should be avoided. All fabricated fittings

manufactured by cutting and welding

techniques must be isolated from

vibration.

Where high frequency vibration sources

exist in the pipeline, the PE sections

should be connected using a flexible

joint such as a repair coupling,

expansion joint, or wire reinforced

rubber bellows joint. When used above

ground such joints may need to be

restrained to prevent pipe end pullout.

design

Irrigation Warehouse Group Pty Ltd

www.polypipe.com.au

Ph 1300 661 417

PE Design

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