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Design.1PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems
d e s i g n
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 36
Trench Design 37
Allowable Bending Radius 38
Deflection Questionnaire – FAX BACK 39
Deflection Questionnaire – Vinidex locations 40
Thrust Block Supports 41
Electrical Conductivity 43
Vibration 43
Heat Sources 43
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Limitation of LiabilityThis manual has been compiled by Vinidex PtyLimited (“the Company”) to promote betterunderstanding of the technical aspects of theCompany’s products to assist users in obtainingfrom them the best possible performance.
The manual is supplied subject toacknowledgement of the following conditions:
• The manual is protected by Copyright and maynot be copied or reproduced in any form or byany means in whole or in part without priorconsent in writing by the Company.
• Product specifications, usage data and advisoryinformation may change from time to time withadvances in research and field experience. TheCompany reserves the right to make suchchanges at any time without notice.
• Correct usage of the Company’s productsinvolves engineering judgements which cannotbe properly made without full knowledge of allthe conditions pertaining to each specificinstallation. The Company expressly disclaimsall and any liability to any person whethersupplied with this publication or not in respectof anything and of the consequences of anythingdone or omitted to be done by any such personin reliance whether whole or partial upon thewhole or any part of the contents of thispublication.
• No offer to trade, nor any conditions of trading,are expressed or implied by the issue of contentof this manual. Nothing herein shall override theCompany’s Conditions of Sale, which may beobtained from the Registered Office or any SalesOffice of the Company.
• This manual is and shall remain the property ofthe Company, and shall be surrendered ondemand to the Company.
• Information supplied in this manual does notoverride a job specification, where such conflictarises, consult the authority supervising the job.
© Copyright Vinidex Pty LimitedABN 42 000 664 942
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d e s i g n
Pipe SelectionVinidex PE pipes are available in acomprehensive range of sizes up to1000mm diameter, and pressure classesin accordance with the requirements ofAS/NZS 4130 - Polyethylene (PE) pipesfor pressure applications.
Additional sizes and pressure classes toAS/NZS 4130 requirements are addedfrom time to time and subject tominimum quantity requirements, pipesmade to specific sizes, lengths orpressure classes are available.
The Standard AS/NZS 4130 includes arange of PE material designations basedon the Minimum Required Stress (MRS),and classified as PE63, PE80, andPE100. When pipes are made to thesame dimensions, but from differentrated PE materials, then the pipes willhave different pressure ratings.
The relationship between the dimensionsof the pipes, the PE materialclassification and the working pressurerating are as shown in Table 4.1.
For simplicity, the dimensions of the pipehave been referred in terms of theStandard Dimension Ratio (SDR) where:
Outside DiameterSDR =
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 factoris 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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d e s i g n
Pipe DimensionsTable 4.2 PE Pipe Dimensions AS/NZS 4130
Nom
inal
Size DN
SDR
41SD
R 33
SDR
26SD
R 21
SDR
17SD
R 13
.6SD
R 11
SDR
9SD
R 7.
4M
in. W
allTh
ickne
ss(m
m)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
Min
. Wall
Thick
ness
(mm
)
Mea
nI.D
.(m
m)
161.
613
1.6
131.
613
1.6
131.
613
1.6
131.
613
1.8
122.
211
201.
617
1.6
171.
617
1.6
171.
617
1.6
171.
916
2.3
152.
814
251.
622
1.6
221.
622
1.6
221.
622
1.9
212.
320
2.8
193.
518
321.
629
1.6
291.
629
1.6
291.
928
2.4
272.
926
3.6
244.
423
401.
637
1.6
371.
637
1.9
362.
435
3.0
343.
732
4.5
315.
528
501.
647
1.6
472.
046
2.4
453.
044
3.7
424.
640
5.6
386.
935
631.
660
2.0
592.
458
3.0
573.
855
4.7
535.
851
7.1
488.
645
751.
971
2.3
702.
969
3.6
674.
566
5.5
636.
861
8.4
5810
.353
902.
286
2.8
843.
583
4.3
815.
478
6.6
768.
273
10.1
6912
.365
110
2.7
105
3.4
103
4.3
101
5.3
996.
696
8.1
9310
.089
12.3
8415
.178
125
3.1
119
3.9
117
4.8
115
6.0
113
7.4
110
9.2
106
11.4
101
14.0
9617
.189
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
--
--
--
--
Po
lyeth
yle
ne P
ipe D
imen
sio
ns
(base
d o
n A
S/N
ZS 4
130-1
997,
Po
lyeth
yle
ne p
ipes
for
pre
ssu
re a
pp
lica
tio
ns.
)
SD
R –
No
min
al
rati
o o
f o
uts
ide d
iam
ete
r to
wall
th
ickn
ess
.
ID
– i
nte
rnal
dia
mete
r
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d e s i g n
AllowableOperating Pressure
Hydrostatic Design Basis
Vinidex pipes manufactured to AS/NZS4130, Series 1 have wall thickness andpressure ratings determined by theBarlow 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 hasbeen based on the static workingpressure operating continuously at themaximum value for the entire lifetime ofthe pipeline.
The value of maximum hoop stress usedin the selection of the pipe wall thicknessis known as the Hydrostatic DesignStress (S). This value is dependent uponthe type of PE material being used andthe pipe material service temperature. InAS/NZS 4131, materials are classified forlong term strength by the designationMinimum Required Strength (MRS).
The MRS is the value resulting fromextrapolation of short and long termtests to a 50 year point at 20°C.
Note: See Figure 2.1 for typical stressregression curves.
Table 4.3 Hydrostatic Design Stress andMinimum 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 polymerdependent and long term properties foreach pipe grade material are establishedby long term testing to the requirementsof ISO/DIS 9080 by the polymerproducers. Individual PE grades mayexhibit different characteristics and PEmaterials can be provided with enhancedspecific properties. In these cases theadvice of Vinidex engineers should beobtained.
Maximum AllowableOperating Pressure
where
MAOP is the maximum allowableoperating pressure in MPa.
PN is the pipe classification inaccordance with AS/NZS 4130.
F is the Design Factor.
For example, if the minimum value of F ischosen (F = 1.25), a PN10 pipe will havea MAOP of 1.0 MPa at 20°C.
T =PD
2S + P
S =MRS
F
MAOP =PN x 0.125
F
The Hydrostatic Design Stress (S) isobtained by application of a Design orSafety Factor (F) to the MRS.
See Table 4.3.
The specific value selected for theDesign Factor depends on a number ofvariables, including the nature of thetransmitted fluid, the location of thepipeline, and the risk of third partydamage.
The wall thickness values for Series 1pipes to AS/NZS 4130 were derivedusing a value of 1.25 for F, this being theminimum value applicable.
AS/NZS 4131 specifics MRS values of6.3 MPa, 8.0 MPa and 10.0 MPa for thegrades designated as PE63, PE80 andPE100 respectively.
The relationship between the S and MRSstandard values in AS/NZS 4131 is asshown in Table 4.3.
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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 forrecommendations.
Where installation applications are usedto carry fluids other than water, thenanother value of the Design Factor mayneed to be selected. The value selectedwill depend on both the nature of thefluid being carried and the location of thepipeline installation. For specificinstallations, the advice of Vinidexengineers should be obtained.
In the case of gas pipes in AS/NZS 4130,both Series 2 and Series 3, a DesignFactor ranging between F = 2.0 andF = 4.0 applies depending on the specificinstallation conditions; see Table 4.6.
Table 4.4Typical Design Factors
Pipeline Application Design Factor
20°C F
Water Supply 1.25
Natural Gas 2.0
Compressed Air 2.0
LPG 2.2
Where the Design Factor is varied, thenthe MAOP for the particular Series 1 pipePN rating can be calculated as follows:
In the particular case of gas distribution,then the type of gas, and the pipelineinstallation conditions need to beconsidered. In this case the DesignFactor is a combination of a number ofsub factors (fx) which must be factoredtogether to give the final value for F suchthat:
F = f0 x f1 x f2 x f3 x f4 x f5
MAOP =PN x 0.125
F
Table 4.5 PE Pipe Pressure Ratings
PN Rating Number Nominal Working Pressure
MPa Head MetresPN 3.2 0.32 32
PN 4 0.40 40PN 6.3 0.63 63PN 8 0.80 80PN 10 1.00 100PN 12.5 1.25 125PN 16 1.60 160PN 20 2.00 200PN 25 2.50 250
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d e s i g n
TemperatureInfluencesThe physical properties of Vinidex PEpipes are related to a standard referencetemperature of 20°C. Where physicalproperty values are quoted to ISO andDIN Standard test methods, these are forthe 20°C condition, unless otherwisequoted. Wherever PE pipelines operate atelevated temperatures, the pressureratings (PN) must be revised.
The temperature to be considered for there rating is the pipe material servicetemperature, and the actual operatingconditions for each specific installationmust be evaluated.
For long length installations atemperature gradient will exist along thelength of the pipe line. This gradient willbe dependent upon site conditions, andthe fluid being carried will approach theambient temperature of the surrounds.
The rate of temperature loss will bedetermined by inlet temperature, fluidflow rate, soil conductivity, ambienttemperature and depth of burial. Asthese factors are specific to eachinstallation, the temperature gradientcalculations are complex and in order toassist the designer, Vinidex havedeveloped computer software to predictthe temperature gradient along thepipeline.
This is available on request to Vinidexdesign engineers.
Service LifetimesThe design basis used in AS/NZS 4130for PN rating of PE pipes to determinethe minimum wall thickness for eachdiameter and PN rating provides for thesteady and continuous application of themaximum allowable working pressureover an arbitrary period of 50 years.
The selection of the long termhydrostatic design stress value (HDS) isdependent on the specific grade of PEand the pipe material servicetemperature. For the grades of PEmaterials contained in AS/NZS 4131the specific values are contained inTable 4.3.
As these values are polymer dependent,individual grades may exhibit differentcharacteristics and materials can beprovided with enhanced properties forcrack resistance or elevated temperatureperformance. In these cases the adviceof Vinidex design engineers should beobtained.
Vinidex PE pipes are continually tested incombinations of elevated temperature(80°C water conditions) and pressure toensure compliance with specificationrequirements.
The adoption of a 50 year design life inAS/NZS 4130 to establish a value of theHDS is arbitrary, and does not relate tothe actual service lifetime of the pipeline.
Where pipelines are used for applicationssuch as water supply, where economicevaluations such as present valuecalculations are performed, the lifetimesof PE lines designed and operated withinthe AS guidelines may be regarded as70–100 years for the purpose of thecalculations. Any lifetime values beyondthese figures are meaningless, as theassumptions made in other parts of theeconomic evaluations outweigh theeffect of pipe lifetime.
The grades of PE specified in AS/NZS4131 are produced by differentpolymerisation methods, and as suchhave different responses to temperaturevariations.
Pipe Classification (PN) is based oncontinuous operation at 20°C and thepressure rating will be reduced forhigher temperatures. In addition, as PEis an oxidising material, the lifetime ofsome grades will be limited by elevatedtemperature operation. Table 4.7 givestemperature rerating data for Vinidexpipes made to AS/NZS 4130.
In these tables, allowable workingpressures are derived from ISO 13761*and assume continuous operation at thetemperatures listed.
Extrapolation limit is maximum allowableextrapolation time in years, based ondata analysis in accordance with ISO/DIS9080**, and at least two years of test at80°C for PE80B and PE100. Actualproduct life may well be in excess ofthese values.
The performance of compounds used inthe manufacture of Vinidex pipes toAS/NZS 4130 has been verified byappropriate data analysis.
In addition, Vinidex offers pipes madefrom specialised compounds forparticular applications, such as elevatedtemperature use.
Contact Vinidex engineers for specialrequirements.
Note:
* Plastics pipes and fittings – pressurereduction factors for polyethylenepipeline systems for use attemperatures above 20°C.
** Plastics piping and ducting systems –determination of long-termhydrostatic strength ofthermoplastics materials in pipe formby extrapolation.
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d e s i g n
Pipe Design forVariableOperationalConditionsThe following examples assist in thedesign and selection of polyethylenepipes 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 elevatedtemperature it may be appropriate todecrease 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 andtemperature, estimate the proportion oflife ‘used up’ by using the time/temperature relationships in the table.
If the proportion is less than unity, thematerial is satisfactory.
1 25.x
The data in the tables are obtained fromthe use of ISO 13761 and ISO/DIS 9080,and are appropriate for compoundstypically used by Vinidex.
Example
Pumped system normally working at amaximum head, including surge of 60m.At startup, the mean pipe walltemperature is 55°C, dropping to 35°Cafter 1 hour. Pump operation is for 10hours per day, with a system life of 15years.
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 hasan 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, Lmin 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, Lmin for 35°C is 100 years,therefore proportion of time used is:
Total proportion is 8.2% of life used in15 years (6.25 years actual operation).
0.62524
= 0.026 = 2.6%
5.625100
= 0.056 = 5.6%
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d e s i g n
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 Years20 200 32 40 63 80 100 125 160 20025 100 30 38 59 75 94 117 150 18830 100 28 35 55 70 88 109 140 17535 100 26 32 50 64 80 100 128 16040 100 24 30 47 60 75 94 120 15045 60 22 28 44 56 70 88 112 14050 36 21 26 41 52 65 81 104 13055 24 19 24 38 48 60 75 96 12060 12 18 23 35 45 56 70 90 11365 8 17 21 33 42 53 66 84 10570 5 16 20 31 39 49 61 78 9875 2 14 18 28 36 45 56 72 9080 2 13 17 26 33 41 52 66 83
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 Years20 50 32 40 63 80 100 125 160 20025 50 29 36 57 72 90 113 144 18030 30 26 33 51 65 81 102 130 16335 18 23 29 46 58 73 91 116 14540 12 20 25 39 50 63 78 100 12545 6 18 23 35 45 56 70 90 113
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 Years20 200 32 40 63 80 100 125 160 200 25025 100 30 38 59 75 94 117 150 188 23330 100 28 35 55 70 88 109 140 175 21835 100 26 32 50 64 80 100 128 160 20040 100 24 30 47 60 75 94 120 150 18545 60 22 28 44 56 70 88 112 140 17550 36 21 26 41 52 65 81 104 130 16355 24 19 24 38 48 60 75 96 120 15060 12 18 23 35 45 56 70 90 113 14065 8 17 21 33 42 53 66 84 105 13070 5 16 20 31 39 49 61 78 98 12075 2 14 18 28 36 45 56 72 90 11380 2 13 17 26 33 41 52 66 83 105
Table 4.7 Temperature Rating Tables
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E ModulusThe E modulus of polyethylene varieswith temperature, duration of loading,stress, and the particular grade ofmaterial.
However, in order to facilitateengineering calculations, it is generallyappropriate to group materials intocategories and adopt ‘typical’ values of E.
Table 4.8 lists E values in MPa forPE80B (MDPE), PE80C (HDPE), andPE100 (HDPE).
PE 80B
Temp °C 3 min 1h 5h 24h 1y 20y 50y0 1050 830 740 650 410 320 300
20 700 550 490 430 270 215 20040 530 410 370 320 200 160 15060 400 300 280 250 160 - -
PE 80C
Temp °C 3 min 1h 5h 24h 1y 20y 50y0 1080 850 740 660 400 320 300
20 750 590 520 460 280 220 20540 470 370 320 290 180 140 13060 210 170 150 130 80 - -
PE 100
Temp °C 3 min 1h 5h 24h 1y 20y 50y0 1380 1080 950 830 520 410 380
20 950 750 660 580 360 280 26040 700 550 490 430 270 210 19060 530 420 370 320 200 - -
Table 4.8 E Values (MPa)
Selection of WallThickness forSpecialApplicationsFor a required nominal diameter (DN)and working pressure, the necessarywall thickness for special applicationsmay be calculated using the Barlowformula:
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
tP DNS P
=+
..2
SMRS
F= S MPa= =10
1 258 0
..
tx
mm=+
=0 9 63016 0 9
33 6.
..
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d e s i g n
Hydraulic Design
Design Basis
Vinidex Polyethylene (PE) pipes offeradvantages to the designer due to thesmooth internal bores which aremaintained over the working lifetime ofthe pipelines. The surface energycharacteristics of PE inhibit the build upof deposits on the internal pipe surfacesthereby retaining the maximum boredimensions and flow capacities.
The flow charts presented in this sectionrelate the combinations of pipediameters, flow velocities and head losswith discharge of water in PE pipelines.These charts have been developed forthe flow of water through the pipes.Where fluids other than water are beingconsidered, the charts may not beapplicable due to the flow properties ofthese different fluids. In these cases theadvice of Vinidex engineers should beobtained.
There are a number of flow formulae incommon use which have either atheoretical or empirical background.However, only the Hazen-Williams andColebrook-White formulae areconsidered in this section.
Hazen - Williams
The original Hazen-Williams formula waspublished in 1920 in the form:
v = C1 r0.63 s0.54 0.001-0.04
where
C1 = Hazen-Williams roughnesscoefficient
r = hydraulic radius (ft)
s = hydraulic gradient
Colebrook - White
The development from first principles ofthe Darcy-Weisbach formula results inthe 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 pipeapplications are likely to operate in thetransition zone between smooth and fullturbulence, the transition functiondeveloped by Colebrook-White isnecessary to establish the relationshipbetween f and R.
where
k = Colebrook-White roughnesscoefficient (m)
The appropriate value for PE pipes is:
k = 0.007 x 10 -3 m
= 0.007 mm
This value provides for the range ofpipe diameters, and water flowvelocities encountered in normalpipeline installations.
HfLvD g
=2
2
fR
= 64
12
3 72 51
1 2 10 1 2f
kD Rf/ /
log.
.= − +
The variations inherent with diameterchanges are accounted for by theintroduction of the coefficient C2 so that
C2 = C1 r0.02
Adoption of a Hazen-Williams roughnesscoefficient of 155 results in the followingrelationship for discharge in Vinidex PEpipes
Q = 4.03 x 10-5 D2.65 H0.54
where
Q = discharge (litres/second)
D = internal diameter (mm)
H = head loss (metres/100 metreslength of pipe)
Flow charts for pipe systems using theHazen - Williams formula have been inoperation in Australia for over 30 years.The charts calculate the volumes ofwater transmitted through pipelines ofvarious materials, and have been provenin practical installations.
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Head Loss in Fittings
Wherever a change to pipe cross section,or a change in the direction of flowoccurs in a pipeline, energy is lost andthis must be accounted for in thehydraulic design.
Under normal circumstances involvinglong pipelines these head losses aresmall in relation to the head losses dueto pipe wall friction.
However, geometry and inlet/exitcondition head losses may be significantin short pipe runs or in complexinstallations where a large number offittings are included in the design.
The general relationship for head lossesin 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 Kis dependent on the particular geometryof each fitting, and values for specificcases are listed in Table 4.9.
The total head loss in the pipelinenetwork is then obtained by addingtogether the calculations performed foreach fitting in the system, the head lossin the pipes, and any other design headlosses.
Worked Example
What is the head loss occurring in a250mm equal tee with the flow in themain 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 teesunder the same conditions, then the totalhead loss in the fittings is 15 x 0.07 =1.05 metres.
Flow Variations
The flow charts presented for PE pipesare based on a number of assumptions,and variations to these standardconditions may require evaluation as tothe effect on discharge.
Water Temperature
The charts are based on a watertemperature of 20°C. A watertemperature increase above this value,results in a decrease in viscosity of thewater, with a corresponding increase indischarge ( or reduced head loss )through the pipeline.
An allowance of approximately 1%increase in the water discharge must bemade for each 3°C increase intemperature above 20°C. Similarly, adecrease of approximately 1% indischarge occurs for each 3°C stepbelow 20°C water temperature.
Pipe Dimensions
The flow charts presented in this sectionare based on mean pipe dimensions ofSeries 1 pipes made to AS/NZS 4130 PEpipes for Pressure applications.
Surface Roughness
The roughness coefficients adopted forVinidex PE pipes result fromexperimental programs performed inEurope and the USA, and follow therecommendations laid down inAustralian Standard AS2200 - DesignCharts for Water Supply and Sewerage.
H KVg
=
2
2
H KVg
=
2
2
H = ××
0 35 22 9 81
2..
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Flow ChartWorked Examples
Example 1 - Gravity Main(refer Figure 4.1)
A flow of water of 32 litres/second isrequired to flow from a storage tanklocated on a hill 50 metres above anoutlet. The tank is located 4.5 km awayfrom 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 towithstand 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 ofPN6.3 class pipes in both PE80, andPE100 materials.
504500
100 1 11 100x m m= . /
Figure 4.1 Gravity Flow Example
Maximum differencein water level
50m
Discharge4,500m of
Vinidex PE Pipe
Storagetank
PE80 Material Option
PE80 PN6.3 pipe is SDR 21.
Use the SDR 21 flow chart, readintersection of discharge line at 32 l/sand head loss line at 1.11m/100m ofpipe. Select the next largest pipe size.
This results in a DN200 mm pipediameter.
PE100 Material Option
PE100 PN6.3 pipe is SDR 26.
Use the SDR26 flow chart, read theintersection of discharge line at 32 l/sand head loss line at 1.11m/100m ofpipe. Select the next largest pipe size.
This results in a DN180 mm pipediameter.
Hence for this application, there are twooptions available, either :
1. DN 200 PE80 PN6.3 or2. DN 180 PE100 PN6.3
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d e s i g n
3. Fittings head losses
From Figure 4.2, identify the type andnumber of different fittings used in thepipeline. Select the appropriate formfactor value K for each fitting type fromTable 4.9. Then:
Fitting Form Head Loss mFactor 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 Headvg
=2
2
= =1 02 9 81
0 052..
.x
0 5100
5000 25.
x m=
Example 2 - Pumped Main(refer Figure 4.2)
A line is required to provide 20 litres/second of water from a dam to a highlevel storage tank located 5000 metresaway. The tank has a maximum waterelevation of 100 m and the minimumwater elevation in the dam is 70 m.
The maximum flow velocity is required tobe limited to 1.0 metres/second tominimise 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 witha PN6.3 class pipe.
PE80 Option
From Table 4.1, PE80 PN6.3 pipe isSDR21.
Use the SDR 21 flow chart, find theintersection of the discharge line at 20 l/sand the velocity line at 1 m/s. Select thecorresponding or next largest size ofpipe. Where the discharge line intersectsthe selected pipe size, trace across to findthe head loss per 100m length of pipe.
This gives a value of 0.5m/100m.
Calculate the total friction head loss in thepipe:
Figure 4.2 Pumped Flow Example
Maximum differencein water level - 30m
90°Elbow
GateValve
Pump GateValve 2x90°
Elbows
Hinged Disc Foot Valve
with Strainer
RL 100m
RL 70m
Min Level of Dam
Reflux Valve45° Elbow
5,000mof Vinidex PE Pipe
45° Elbow
SquareOutlet
90° Elbow
Storage TankMax Level of Tank
Then from the flow chart, estimate thevelocity 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 anyprovision for surge allowance inpressure class selection.
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Part Full FlowNon pressure pipes are designed to runfull under anticipated peak flowconditions. However, for a considerableperiod the pipes run at less than full flowconditions and in these circumstancesthey act as open channels with a freefluid to air surface.
In these instances consideration must begiven to maintaining a minimumtransport velocity to prevent depositionof solids and blockage of the pipeline.
For pipes flowing part full, the mostusual self cleansing velocity adopted forsewers is 0.6 metres/second.
Example 3. Determineflow velocity anddischarge under part fullflow conditions
Given gravity conditions:
Pipe DN 200 PE80 PN6.3
Mean Pipe ID 180 mm ( Refer Table XXPE pipe dimensions, or AS/NZS 4130 )
Gradient 1 in 100
Depth of flow 80 mm
Problem:
Find flow and velocity
Solution:
Proportional DepthDepth of flow
Pipe ID=
= =80180
0 44.
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
Prop
ortio
nal D
epth
Figure 4.3 Part Full Flow
From Figure 4.3 Part Full Flow, for aproportional depth of 0.44, theproportional discharge is 0.4 and theproportional velocity if 0.95.
Refer to the Vinidex PE pipe flow chartfor the SDR 21 pipe.
For a gradient of 1 in 100 full flow is39 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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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 LossesElbows R/D < 0.6 45° 0.35
90° 1.10
Long Radius Bends (R/D > 2) 111/4° 0.05221/2° 0.1045° 0.2090° 0.50
Tees
(a) Flow in line 0.35
(b) Line to branch flow 1.00
Sudden EnlargementsRatio d/D
0.9 0.040.8 0.130.7 0.260.6 0.410.5 0.560.4 0.710.3 0.830.2 0.92
<0.2 1.00Sudden ContractionsRatio d/D
0.9 0.100.8 0.180.7 0.260.6 0.320.5 0.380.4 0.420.3 0.460.2 0.48
<0.2 0.50
Fitting Type K
Gradual EnlargementsRatio d/D q = 10° typical
0.9 0.020.7 0.130.5 0.290.3 0.42
Gradual ContractionsRatio d/D q = 10° typical
0.9 0.030.7 0.080.5 0.120.3 0.14
ValvesGate 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 strainerhinged disc valve 15.00unhinged (poppet) disc valve 10.00
Air Valves zero
Ball Valve 0.10
Pipe Exit LossesSquare Outlet 1.00
Rounded Outlet 1.00
Resistance CoefficientsTable 4.9 Valves, Fittings and Changes in Pipe Cross-Section
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d e s i g n
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZE A
ND CLASS (D
N/PN)
NOMINAL SIZE AND CLASS (DN/PN)
VE
LOC
ITY
m/s
1.5
3.0
2.5
2.0
1.75
1.25
1.0
0.5
0.25
16/1616/12.5
20/16 20/12.5
25/16 25/12.5 25/10 25/832/16 32/12.5
32/10
32/8
32/6.3
40/16 40/12.5 40/10
40/6.350/16
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 75/1075/8
75/6.3
Flow Chart for Small Bore Polyethylene Pipe – DN16 to DN75(PE80B, PE80C Materials)
Flo
w C
hart
fo
r Sm
all
Bo
re P
oly
eth
yle
ne P
ipe –
DN
16 t
o D
N75 (
PE8
0B
, PE8
0C
Mate
rials
)
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Flow Chart for Polyethylene Pipe – SDR 41(PE80: PN3.2 & PE100: PN4)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZENOMINAL SIZE
VE
LOC
ITY
m/s
90
110125
140
160180
200225
250280
315355
400450
500560
630710
800900
1000
4.0
2.0
3.0
1.5
1.0
0.5
0.25
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 4
1 (
PE80:
PN
3.2
& P
E1
00
: PN
4)
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d e s i g n
Flow Chart for Polyethylene Pipe – SDR 33(PE80: PN4)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZENOMINAL SIZE
VE
LOC
ITY
m/s
4.0
2.0
3.0
1.5
1.0
0.5
0.25
90
110125
140
160180
200225
250280
315355
400450
500560
630710
800900
1000
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 3
3 (
PE8
0: PN
4)
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Flow Chart for Polyethylene Pipe – SDR 26(PE100: PN6.3)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZE
NOMINAL SIZE
VE
LOC
ITY
m/s
ec
4.0
2.0
3.0
1.5
1.0
0.5
0.25
90
110125
140
160180
200225
250280
315355
400450
500560
630710
800900
1000
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 2
6 (
PE10
0: PN
6.3
)
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d e s i g n
Flow Chart for Polyethylene Pipe – SDR 21(PE80: PN6.3 & PE100: PN8)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZE
NOMINAL SIZE
VE
LOC
ITY
m/s
4.0
2.0
3.0
1.5
1.0
0.5
0.25
90
110125
140
160180
200225
250280
315355
400450
500560
630710
800900
1000
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 2
1 (
PE80:
PN
6.3
& P
E1
00
: PN
8)
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d e s i g n
Flow Chart for Polyethylene Pipe – SDR 17(PE80: PN8 & PE100: PN10)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZE
NOMINAL SIZE
VE
LOC
ITY
m/s
4.0
2.0
3.0
1.5
1.0
0.5
0.25
90
110125
140
160180
200225
250280
315355
400450
500560
630710
800900
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 1
7 (
PE80:
PN
8 &
PE1
00
: PN
10
)
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d e s i g n
Flow Chart for Polyethylene Pipe – SDR 13.6(PE80: PN10 & PE100: PN12.5)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZE
NOMINAL SIZE
VE
LOC
ITY
m/s
4.0
2.0
3.0
1.5
1.0
0.5
0.25
90
110125
140
160180
200225
250280
315355
400450
500560
630710
800
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 1
3.6
(PE80:
PN
10 &
PE1
00
: PN
12
.5)
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d e s i g n
Flow Chart for Polyethylene Pipe – SDR 11(PE80: PN12.5 & PE100: PN16)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZE
NOMINAL SIZE
VE
LOC
ITY
m/s
4.0
2.0
3.0
1.5
1.0
0.5
0.25
90
110125
140
160180
200225
250280
315355
400450
500560
630710
800
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 1
1 (
PE80:
PN
12.5
& P
E1
00
: PN
16
)
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d e s i g n
Flow Chart for Polyethylene Pipe – SDR 9(PE80: PN16 & PE100: PN20)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL SIZE
NOMINAL SIZE
VE
LOC
ITY
m/s
90
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
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 9
(PE80: PN
16
& P
E1
00
: PN
20
)
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d e s i g n
Flow Chart for Polyethylene Pipe – SDR 7.4(PE100: PN25)
Dis
char
ge
- L
itre
s p
er S
eco
nd
(L
/s)
Head Loss - Metres Head of Water per 100 metres of Pipe
NOMINAL S
IZE
NOMINAL SIZE
VE
LOC
ITY
m/s
90
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
Flo
w C
hart
fo
r Po
lyeth
yle
ne P
ipe –
SD
R 7
.4 (
PE1
00
: PN
25
)
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d e s i g n
Surge & FatigueSurge, or ‘water hammer’, is a temporarychange in pressure caused by a changein velocity of flow in the pipeline,whereas fatigue is the effect induced inthe pipe or fitting by repeated surgeevents.
For Vinidex PE pipes to AS/NZS 4130,operating under the following limitations,it is not necessary to make specificallowance for fatigue effects:
(a) The maximum pressure in the pipefrom all sources must be less than thepressure equivalent to the Classificationof the pipe (PN).
and
(b) The amplitude between minimum andmaximum pressure from all sourcesmust not exceed the pressure equivalentto the Classification of the pipe (PN).
Care must be taken to ensure that theminimum pressure does not reach alevel that may result in vacuum collapse(see External Pressure Resistance, pageDesign.36).
Surge may take the form of positive and/or negative pressure pulses resultingfrom change of flow velocity, such asarising from valve or pump operation.Such changes of flow velocity lead toinduced pressure waves in the pipeline.
Ptt
Pc
2 1=
tL
C= 2
C = W1K
+SDR
E
−03
.5
mx 10 / sec
P C V1 = .
This represents the case of a singlepipeline with the flow being completelyclosed off. The pressure rises generatedby flow changes in PE pipelines are thelowest generated in major pipelinematerials due to the relatively lowmodulus values.
Further, as medium density materialshave lower modulus values than highdensity materials, the pressure rise inPE80B materials will be lower than thatin PE80C and PE100 materials.
Water hammer (surge) analysis ofpipeline networks is complex and beyondthe scope of this Manual. Whererequired, detailed analysis should beundertaken by experts.
The velocity of the pressure wave,referred to as celerity (C), depends onthe pipe material, pipe dimensions, andthe liquid properties in accordance withthe following relationship:
where
W = liquid density (1000 kg/m3
for water)
SDR = Standard Dimension Ratioof the pipe
K = liquid bulk modulus (2150 MPa)
E = pipe material short termmodulus (MPa) refer Table 4.8
The time taken for the pressure wave totravel the length of the pipeline andreturn 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 closureis given by:
where:
P1 = pressure rise in kPa
v = liquid velocity in m/sec
If the valve closure time tc is greater thant, then the pressure rise is approximatedby:
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CelerityThe surge celerity in a polyethylenepipeline filled with liquid can bedetermined by:
where
W = liquid density (1000 kg/m3
for water)
SDR = Standard Dimension Ratioof the pipe
K = liquid bulk modulus (2150MPa)
E = pipe material ‘instantaneous’modulus (taken as 1000MPa forPE80B, 1200MPa for PE80C,1500MPa for PE100)
Table 4.10 Surge Celerity
Celerity m/sSDR MDPE (PE 80B) HDPE (PE 80C) HDPE (PE 100)
41 160 170 19033 170 190 21026 190 210 24021 220 240 26017 240 260 290
13.6 270 290 32011 300 320 3609 330 350 390
7.4 360 390 430
C WK
SDRE
x m= +
−1
100 5
3.
/ sec
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Slurry Flow
General DesignConsiderations
The abrasion resistance characteristicsand flexibility of Vinidex PE pipes makeslurry flow lines, such as mine tailings,ideal applications for the material andsuch installations are in widespread usethroughout Australia.
The transportation of Non Newtonianfluids such as liquids or liquid/liquid,liquid/solid mixtures or slurries is ahighly complex process and requires adetailed knowledge of the specific fluidbefore flow rate calculations can beperformed.
As distinct from water, many fluidsregarded as slurries have propertieswhich are either time or shear ratedependent or a combination of bothcharacteristics. Hence it is essential forthe properties of the specific fluid to beestablished under the operatingconditions being considered for eachdesign installation.
In addition to water flow, slurry flowdesign needs to take into account thepotential for abrasion of the pipe walls,especially at changes of direction orzones of turbulence.
The most usual applications of VinidexPE pipes involve liquid/solid mixturesand these must first be categorisedaccording to flow type:
• Homogeneous Suspensions
• Heterogeneous Suspensions
Homogeneous Suspensions
Homogeneous suspensions are thoseshowing no appreciable density gradientacross the cross section of the pipe.These slurries consist of materialparticles uniformly suspended in thetransport fluid.
Generally, the particle size can be used todetermine the flow type and suspensionswith particle sizes up to 20 microns canbe regarded as homogeneous across therange of flow velocities experienced.
Heterogeneous Suspensions
Heterogeneous suspensions are thoseshowing appreciable density gradientsacross the cross section of the pipe, andare those containing large particleswithin the fluid.
Suspensions containing particle sizes of40 microns and above may be regardedas heterogeneous.
In addition to the fluid characterisationsfor both types, the tendency for solids tosettle out of the flow means that aminimum flow velocity must bemaintained.
This velocity, the Minimum TransportVelocity, is defined as the velocity atwhich particles are just starting toappear on the bottom of the pipe.
The flow in short length pipelines differsin that these lines may be flushed outwith water before shut down ofoperations. Long length pipelines cannotbe flushed out in the same way and theselection of operating velocities and pipediameter needs to address this aspect.
The design of slurry pipelines is aniterative process requiring designassumptions to be made initially, andthen repeatedly being checked and testedfor suitability. The specific fluid underconsideration requires full scale flowtesting to be conducted to establish theaccurate flow properties for the liquid/particle combinations to be used in theinstalled pipeline.
Without this specific data, theassumptions made as to the fluid flowbehaviour may result in the operationalpipeline being at a variance to theassumed behaviour. The principles ofslurry pipeline design as outlined in themethods of Durand, Wasp, and Govierand Aziz are recommended in theselection of Vinidex PE pipes for theseapplications.
Note:
The published Vinidex PE pipe flowcharts relate ONLY to water or otherliquids which behave as Newtonianfluids.
They are not suitable for calculating theflow discharges of other fluids, includingslurries.
For further information on slurry pipelinedesign, the designer is referred to suchpublications as Govier G.W. and Aziz K,The Flow of Complex Mixtures in Pipes.Rheinhold, 1972. and Wasp E.J. SolidLiquid Flow - Slurry PipelineTransportation. Trans Tech Publications.1977.
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Pipe WearPolyethylene pipe has been a provenperformer over many decades inresisting internal abrasion due to slurry.It is particularly resistant to abrasionfrom particles less than 500 microns insize depending on particle shape.
The abrasive wear of any slurry handlingsystem is heavily dependent on thephysical characteristics of the solidsbeing transported. These characteristicsinclude angularity, degree of particleattrition, angle of attack, velocity, and theconcentration of solids in thetransporting fluid.
With metal pipes, corrosive wearinteracts synergistically with abrasivewear, producing rates of wear that can bemany times greater than a simplecombination of the two modes of wear.Corrosive attack on a piping material canlead to increasing roughness of thesurface, loss of pressure and localisededdying, and hence increase the abrasiveattack.
Factors Affecting Ratesof Wear
The wall of polyethylene pipes are wornby contact with the solids particles. Theprincipal causes of wear are as follows:
• Particle Size
• Particle Specific Gravity
• Velocity
• Angle of Attack
Particle Size
The size of the particle combined withthe requisite velocity is one of theprincipal factors which contribute towear. The rate of wear increases withparticle size with very little wearoccurring on polyethylene systemsbelow 300 microns. Above this size therate of wear will increase proportionallywith particle size with the maximumpractical D50 size around 1mm. Manyresearchers have attempted to developrelationships between particle size andrates of wear, however, these have notproven to be accurate due to the widevariation of slurry characteristics. Thewear mechanism involved is notthoroughly understood, however, it isbelieved the higher impact energyresulting from a combination of particlemass and the high velocity required totransport this larger particle are theprincipal contributing factors.
Particle Specific Gravity
Similarly, the specific gravity willincrease the mass of the particleresulting in increased wear. This is aresult of the increased impact energyfrom the mass of the particle combinedwith the faster carrier velocity.
Velocity
A minimum velocity is required toprovide the necessary uplift forces tokeep a solid particle in suspension. Thisvelocity also increases the impact energyof the particle against the wall of thepipe.
Angle of Attack
There are essentially two modes of wear,impingement and cutting. Cutting wearis considered to be caused by the lowangle impingement of particles. Inpractice, cutting wear comprises acutting action, and the accommodationof some of the energy of impact withinthe matrix of the material being worn.Hence, cutting wear also incorporates acomponent of deformation wear. Therequirement for wear is that some of thesolid particles must have sufficientenergy to penetrate and shear a material,perhaps gouging fragments loose. As aresult, a low modulus material such aspolyethylene has very good resistance tocutting wear due to the resultingdeformation upon impact. In the case ofangular particles the cutting action isincreased resulting in increased pipewear.
The simple theory of abrasive wearsuggests that specific wear (wear perunit mass transported) is proportional tonormal force at the pipe wall. Thereforethe wear rate will increase as the angle ofattack to the pipe wall increases. Theincrease in angle will also increase theamount of energy with which the particlestrikes the pipe wall. It is for this reasonthat accelerated wear is caused by:
i) Fittings which effect a change in theangle of flow such as tees and bends
ii) Butt weld joints. Butt weld internalbeads will cause eddying which willresult in increases in angle of attackof the particle to the pipe wall. As aresult accelerated wear generallyoccurs immediately downstream ofthe bead. This is usually prominent inD50 particle sizes over 300 microns.For coarse particle slurries theinternal bead should be removed.Irrigati
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Maintenance andOperationTo reduce the cost of wear on a pipelineasset it is general practice to rotate thepipes at the appropriate intervals, this isparticularly important when transportingsand slurries. In this respect mechanicaljoints are useful, although re-welding ofpipes over 500mm has been preferred insome cases to reduce capital costs.These mechanical joints are usuallyinstalled at every 20m pipe length toassist the pipe rotation process and alsopermit clearance of blockages.
Slurry pipelines are usually operated asclose to the critical settling velocity aspractical to reduce operating costs.Unfortunately, if an increase in particlesize occurs, then saltation willcommence increasing friction losseventually resulting in a blockage. Otherfactors that cause blockages areincreases in solids concentration, loss ofpump pressure due to power failure, orpump impellor wear. Polyethylenepipelines may be cleared of blockages byclear water pumping provided they havebeen installed on flat even ground.Sudden vertical ‘V’ bends with anglesover 10° may cause an accumulation ofsolids in the bore, preventing clearing byclear water pumping. If vertical bendsare unavoidable then they should beinstalled with mechanical joints to permittheir easy removal for clearing.
FittingsA range of mechanical joints areavailable for polyethylene slurrypipelines. They include stub flanges andbacking rings, Hugger couplings,shouldered end/Victaulic couplings,compression couplings and rubber ringjoint fittings.
References
The Transportation of Flyash and BottomAsh in Slurry Form, C G Verkerk
Relative Wear Rate Determinations forSlurry 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 ofmechanical fittings somemisalignment of the mating facesmay occur resulting in increasedangles of attack of the particles.
iv) Change in velocity. Somecompression fittings cause areduction in the internal diameter ofthe pipe under the fitting resulting inturbulence. A mismatching valvebore will also cause turbulence. It isfor this reason that the use of clearbore valves such as knife gate valvesis preferred for slurry pipelines.
v) Increased velocity. High velocitiesare required to create sufficientturbulence for the suspension ofheavy particles. This turbulenceincreases the angle of attack to thepipe wall, resulting in increased wearfor large particles.
vi) Insufficient velocity. When a systemis operated near its settling velocity,the heavier particles migrate towardsthe lower half of the pipe crosssection. This will cause a generalincrease in pipe wear in this area. Ifsaltation/moving bed occurs, thenthe heavy particles will impactagainst the pipe bottom, causing anaccelerated wave profile wear. Shoulddeposition occur on the floor of thepipe, then the particles above thisdeposition will cause the maximumamount of wear as they interact withthe flow. This is characterised by theformation of wave marks on the 5and 7 o’clock position of the pipe.
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Pneumatic FlowVinidex PE pipe systems are ideal for thetransmission of gases both in the highand low pressure range.
The use of compressible liquids in PEpipes requires a number of specificdesign considerations as distinct fromthe techniques adopted in the calculationof discharge rates for fluids such aswater.
In particular:
• Compressed air may be at a highertemperature than the surroundingambient air temperature, especiallyclose to compressor line inlets, andthe pressure rating of the PE pipesrequire temperature re ratingaccordingly.
For air cooled compressors, thedelivered compressed airtemperature averages 15°C above thesurrounding air temperature. Forwater cooled compressors, thedelivered compressed airtemperature averages 10°C above thecooling water temperature.
• For underground applications wherethe PE pipes are exposed to ambientconditions, the surrounding airtemperature may reach 30°C, and thepipe physical properties requireadjustment accordingly.
• High pressure lines must bemechanically protected from damageespecially in exposed installations.
• Valve closing speed must be reducedto prevent a build up of pressurewaves in the compressible gas flow.
• Where gaseous fuels such aspropane, natural gas, or mixtures arecarried, the gas must be dry and freefrom liquid contamination which maycause stress cracking of the PE pipewalls.
• Vinidex PE pipes should not beconnected directly to compressoroutlets or air receivers. A 21 metrelength of metal pipe should beinserted between the air receiver andthe start of the PE pipe to allow forcooling of the compressed air.
• Dry gases, and gas/solids mixturesmay generate static electrical chargesand these may need to be dissipatedto prevent the possibility ofexplosion. PE pipes will not conductelectrical charges, and conductinginserts or plugs must be inserted intothe pipe to complete an earthingcircuit.
• Compressed air must be dry, andfilters installed in the pipeline toprevent condensation of lubricantswhich can lead to stress cracking inthe PE pipe material.
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System DesignGuidelines for theSelection ofVinidexairCompressed AirPipelinesIt is customary to find the InsideDiameter of the pipe by using formulassuch as shown below. The formulas usedare generally for approximation purposesonly, surmising that the temperature ofthe compressed air corresponds roughlyto the induction temperature. Anacceptable approximation is obtainedthrough the following equation:
4 Using point (3) draw a diagonalline to the separation line.
5 Go to top of nomogram and usethe point indicating the Length ofPipe and draw a line down tomeet horizontal line from point(4).
6 Move to the Pressure Decrease inthe Pipe (∆p) at the bottom ofnomogram and draw a verticalline up to meet the diagonaldrawn from point (5).
7 The Nominal Diameter of Pipe cannow be found by reading frompoint (6) across to the left handside of the nomogram. From thisexample DN63 pipe should beselected. If the completednomogram falls between twosizes of pipe, always use thelarger size.
Correction factors forfittings
Table 4.11 indicates the approximatepressure loss for fittings in terms of anequivalent length of straight pipe inmetres. For each pipeline fitting, add theequivalent length of pipe to the originallength of pipeline. This length is used forthe calculation of the equation above orfor the nomogram, Figure 4.4.
The advantage of using the nomogram isthat no further conversion factors arerequired for pipe sizing. Also, when fourof the parameters are known the fifth canbe determined by reading directly fromthe nomogram.
Example for the use ofthe air-line nomogram(Figure 4.4) to determinethe 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 operatingfigures, proceed to mark thosepositions around the perimeter ofthe nomogram.
2 Locate the separation linebetween (∆p) & (p). (See base ofnomogram.)
3 Commencing at the lower righthand side of the nomogram drawa line up from the WorkingPressure (p) to the line indicatingthe 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 andeasier method to source information (seeFigure 4.4). In this nomogram thePressure Decrease (∆p) is indicated inbar, the Working Pressure (p) in bar, theVolumetric Flowrate (Q) in L/s, the PipeLength (LE) in m, and the Pipe NominalDiameter DN.
dL Qp pE= 450 185
5. .
.
.
∆
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Figure 4.4Compressed AirFlow Nomogram
0.002 0.01 0.05 0.1 0.2 0.5 1 2 4 6 10 15500
400
300
63
90
50
40
32
25
20
200
100
50
30
20
15
10
5
3
2
1.5
1
1 2 5 10 20 50 100 200 500 1000 2000
3
37
4
6
5
2
no
min
al d
iam
ete
r D
N vo
lum
etric
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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Expansion andContractionExpansion and contraction of PE pipesoccurs with changes in the pipe materialservice temperature.
This is in common with all pipe materialsand in order to determine the actualamount of expansion or contraction, theactual temperature change, and thedegree of restraint of the installedpipeline need to be known.
For design purposes, an average value of2.0 x 10-4/°C for Vinidex PE pipes may beused.
The relationship between temperaturechange and length change for differentPE grades is as shown in Figure 4.5.
Worked Example
A 100 metre long PE80C pipelineoperates during the day at a steadytemperature of 48°C and when closeddown at night cools to an ambienttemperature of 18°C. What allowance forexpansion/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 then6.0 x 100 = 600 mm.
Where pipes are buried, the changes intemperature are small and slow acting,and the amount of expansion/contractionof the PE pipe is relatively small. Inaddition, the frictional support of thebackfill against the outside of the piperestrains the movement and any thermaleffects are translated into stress in thewall of the pipe.
Accordingly, in buried pipelines the mainconsideration of thermal movement isduring installation in high ambienttemperatures.
Under these conditions the PE pipe willbe at it’s maximum surface temperaturewhen placed into a shaded trench, andwhen backfilled will undergo themaximum temperature change, andhence thermal movement.
In these cases the effects of temperaturechange can be minimised by snaking thepipe in the trench for small sizes (up toDN110) and allowing the temperature tostabilise prior to backfilling.
For large sizes, the final connectionshould be left until the pipe temperaturehas stabilised.
Above ground pipes require noexpansion/contraction considerations forfree ended pipe or where lateralmovement is of no concern on site.Alternatively, pipes may be anchored atintervals to allow lateral movement to bespread evenly along the length of thepipeline.
Where above ground pipes are installedin confined conditions such as industrialor chemical process plants theexpansion/contraction movement can betaken up with sliding expansion joints.Where these cannot be used due to thefluid type being carried ( such as slurriescontaining solid particles ) the advice ofVinidex design engineers should besought for each particular installation.
Figure 4.5 Thermal Expansion and Contraction for PE
0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
Expa
nsio
n an
d Co
ntra
ctio
n (m
m/m
)
Pipe Material Temperature Change (°C)0 10 20 30 40 50 60 70 80
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External PressureResistanceThe possibility of external pressure(buckling) being the controlling designcondition must be evaluated in thedesign of PE pipelines.
All flexible pipe materials can be subjectto buckling due to external pressure andPE pipes behave in a similar fashion toPVC and steel pipes.
For pipe of uniform cross-section, thecritical buckling pressure (Pc) can becalculated 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 timedependent, the advice of Vinidexengineers should be sought forappropriate values.
Where ovality exists in the PE pipes, theeffective value of the critical bucklingpressure will be reduced.
The reduction in Pc for various levels ofinitial 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 supportedby backfill soil, the additional support(Pb) may be calculated from:
Pb = 1.15 (Pc E´) 0.5
Where E´ = soil modulus fromAS/NZS2566 - Buried Flexible Pipelines.
Pc =2380 • E
SDR − 1( )3
Tabulations of the value of E´ for variouscombinations of soil types and compac-tions are contained in AS/NZS2566.
The value of Pc calculated requires afactor of safety to be applied and a factorof 1.5 may be applied for thoseconditions where the negative pressureconditions can be accurately assessed.
Where soil support is taken into accountthen a factor of 3 is more appropriatedue to the uneven nature of soil support.
In general terms, PN10 PE pipe shouldbe used as a minimum for pump suctionline installations.
Where installation conditions potentiallylead to negative pressures, considerationmay need to be given to modification ofconstruction technique. For example,ducting pipes may need to be sealed andfilled with water during concreteencasement.
In operation, fluid may be removed fromthe pipeline faster than it is suppliedfrom the source. This can arise fromvalve operation, draining of the line orrupture of the line in service. Air valvesmust be provided at high points in theline and downstream from control valvesto allow the entry of air into the line andprevent the creation of vacuumconditions. On long rising grades or flatruns where there are no significant highpoints or grade changes, air valvesshould be placed at least every 500-1000metres at the engineer’s discretion.
Soil Description E´ MPa
Gravel – graded 20
Gravel – single size 14
Sand and coarse-grained soilwith less than 12% fines 14
Coarse-grained soilwith more than 12% fines 10
Fine-grained soil (LL<50%)with medium to no plasticity andcontaining more than 25%coarse-grained particles 10
Fine-grained soil (LL<50%)with medium to no plasticity andcontaining 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 coverdepths for Vinidex PE pipes are listed inTable 4.12.
These cover depths are indicative only,and specific installations should beevaluated in accordance with AS/NZS2566 - Buried Flexible Pipelines.
The minimum cover depths listed maybe reduced where load reductiontechniques are used, such as loadbearing beams, concrete slabs, conduitsleeves, or increased backfillcompaction.
Trench WidthsIn general practice, the trench widthshould be kept to the minimum thatenables construction to readily proceed.Refer to Figures 4.6 and 4.7.
The trench width used with PE pipe maybe reduced from those used with otherpipe types by buttwelding, orelectrofusion jointing above ground, andthen feeding the jointed pipe into thetrench. Similarly, small diameter pipe incoil form can be welded or mechanicallyjointed above ground and then fed intothe trench.
The minimum trench width should allowfor adequate tamping of side supportmaterial and should be not less than200mm greater than the diameter of thepipe. In very small diameter pipes thismay be reduced to a trench width oftwice 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 SupportMaterial used for side support shouldcomply with the requirements of thebedding materials.
The side support material should beevenly tamped in layers of 75 mm forpipes up to 250mm diameter, and 150mm for pipes of diameters 315mm andabove.
Compaction should be brought evenly tothe design value required by AS/NZS2566 for the specific installation.
BackfillOnce the sidefill has been placed andcompacted as required over the top ofthe pipe, backfill material may be placedusing excavated material.
Trench backfills should not be used as adump for large rocks, builders debris, orother unwanted site materials.
The maximum trench width should berestricted as much as possible,depending on the soil conditions. This isnecessary to reduce the cost ofexcavation, and to develop adequate sidesupport.
Where wide trenches or embankmentsare encountered, then the pipe should beinstalled on a 75 mm layer of tamped orcompacted bedding material as shownon the cross section diagrams. Wherepossible a sub trench should beconstructed at the base of the maintrench to reduce the soil loadsdeveloped. AS/NZS 2566 provides fulldetails for evaluating the loads developedunder wide trench conditions.
BeddingPE Pipes should be bedded on acontinuous layer, 75 mm thick, ofmaterials complying with the followingrequirements:
• Sand, free from rocks or other hardor sharp objects retained on a13.2mm sieve.
• Gravel or crushed rock of suitablegrading up to a max. size of 15mm.
•. The excavated material, free fromrocks and broken up such that itcontains no clay lumps greater than75mm which would prevent adequatecompaction.
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Figure 4.7Narrow Trench Condition
Figure 4.6Wide Trench Condition
Allowable BendingRadiusVinidex PE pipes are flexible inbehaviour, and can be readily bent in thefield.
In general terms, a minimum bendingradius of 33 x outside diameter of thepipe (33D) can be adopted for PE80C,and PE100 material pipes, whilst a radiusof 20 x outside diameter of the pipe(20D) can be adopted for PE63, andPE80B material pipes during installation.
This flexibility enables PE pipes toaccommodate uneven site conditions,and, by reducing the number of bendsrequired, cuts down total job costs.
For certain situations, the designer maywish to evaluate the resistance to kinkingor the minimum bending radius arisingfrom strain limitation. The long termstrain from all sources should not exceed0.04 (4%).
Rk = SDR (SDR-1)1.12
100mm min
100mm minD
Bedding75mm min
100mmmin
100mmmin
Bedding75mm min
When bending pipes there are twocontrol conditions:
1. Kinking in pipes with high SDRratios.
2. High outer fibre strain in highpressure class pipes with low SDRratios.
For condition 1
The minimum radius to prevent kinking(Rk) may be calculated by:
For condition 2
The minimum radius to prevent excessstrain (Re) may be calculated by:
where
ε = outer fibre strain(maximum allowable = 0.04)
D = mean Di (mm)
RD
e =2
ε
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DeflectionQuestionnaire
AS/NZS 2566 DeflectionCalculation for BuriedFlexible Pipes
The following questionnaire is to assistdesigners in the calculation of deflectionfor 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 yournearest Vinidex office – refer over leaf.
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Thrust BlockSupportsPE pipes and fittings joined by buttwelding, electrofusion, or other end loadbearing joint system do not normallyrequire anchorage to withstand loadsarising from internal pressure and flow.
For joint types which do not resist endloads, plus fabricated fittings whichincorporate welded PE pipe segments,anchorage support must be provided inorder to prevent joint or fitting failure. Inaddition, appurtenances such as valves,should be independently supported inorder to prevent excessive shear loadsbeing 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 .10-3
2
R = 2 w a V2. sin φ.10-9
2
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 onlyat 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 incomparison to the pressure thrust.
The pressure used in the calculationsshould be the maximum working, or testpressure, applied to the line.
Bearing Loads of Soils
The thrust developed must be resistedby the surrounding soil. The indicativebearing capacities of various soil typesare tabulated below:
The figures in the table below are forhorizontal thrusts, and may be doubledfor downward acting vertical thrusts. Forupward acting vertical thrusts, theweight of the thrust block mustcounteract the developed loads.
In shallow (<600mm) cover installationsor in unstable conditions of fill, the soil
support may be considerably reducedfrom the values tabulated, and acomplete soil analysis may be needed.
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Thrust BlockSize Calculations
1. Establish the maximum pressure tobe applied to the line
2. Calculate the thrust developed at thefitting being considered
3. Divide (2) by the safe bearingcapacity of the soil type againstwhich the thrust block must bear.
Worked Example
What bearing area of thrust block isrequired for a 160 mm PN12.5 90° bendin hard, dry clay?
1. Maximum working pressure ofPN12.5 pipe is 1.25 MPa.
Test pressure is 1.25 x WP
= 1.56 MPa.
2.
3. Bearing capacity of hard, dry clay is15x104 N/m2
Thrust blocks may be concrete or timber.Where cast insitu concrete is used, anadequate curing period must be providedto allow strength development in theconcrete before pressure is introduced tothe pipeline. Where timber blocks areused, test pressures may be introducedimmediately, but care needs to be takento ensure that the blocks will not rot andwill not be attacked by termites or ants.
=4
Bearing area of thrust block 3.8 x 104
2
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 = 2 PA .sin φ.102
= 3.8 x 10-4
-3
N
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ElectricalConductivityVinidex PE pipes are non conductive andcannot be used for electrical earthingpurposes or dissipating static electricitycharges.
Where PE pipes are used to replaceexisting metal water pipes, the designermust consider any existing systems usedfor earthing or corrosion controlpurposes. In these cases the appropriateelectrical supply authority must beconsulted to determine theirrequirements.
In dry, dusty, or explosive atmospheres,potential generation of electricity mustbe evaluated and static dissipationmeasures adopted to prevent anypossibility of explosion.
Heat SourcesPE pipes and fittings should be protectedfrom external heat sources which wouldbring the continuous pipe materialservice temperature above 80°C.
Where the PE pipes are installed aboveground, the protection system usedmust be resistant to ultra violet radiationand the effects of weathering, PE pipesrunning across roofing should besupported above the roof sheeting inorder to prevent temperature build up.
See Table 4.7 Temperature Rating Table.
VibrationDirect connection to sources of highfrequency such as pump outlet flangesshould be avoided. All fabricated fittingsmanufactured by cutting and weldingtechniques must be isolated fromvibration.
Where high frequency vibration sourcesexist in the pipeline, the PE sectionsshould be connected using a flexiblejoint such as a repair coupling,expansion joint, or wire reinforcedrubber bellows joint. When used aboveground such joints may need to berestrained to prevent pipe end pullout.
d e s i g n
Irrigati
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www.polypipe.c
om.au
Ph 1300 661 417