PE Design
User Manual: PE
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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 17-26 Flow Charts 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 41 Thrust Block Supports Electrical Conductivity y Vibration Pt p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri Heat Sources Ltd 43 43 43 I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.1 d e s i g n 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. Ltd y t • Information supplied in this manual does not override a job specification, where such conflict arises, consult the authority supervising the job. © Copyright Vinidex Pty Limited ABN 42 000 664 942 P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.2 PE 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 Pipe Selection Table 4.1 Comparison of SDR & Pressure Ratings (PN) 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. SDR 41 33 26 21 17 PE80 PN3.2 PN4 - PN6.3 PN8 PE100 PN4 - PN6.3 PN8 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. 13.6 11 9 7.4 PN10 PN12.5 PN16 PN10 PN12.5 PN16 PN20 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. 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 Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.3 Design.4 400 355 315 280 250 225 I P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri 676 858 953 22.0 24.5 600 15.4 762 534 13.7 17.4 476 12.3 19.6 429 11.0 30.6 27.6 24.5 21.8 19.3 17.2 15.3 13.8 12.3 10.9 9.7 8.6 7.7 6.9 6.2 5.5 4.9 4.3 3.9 940 846 752 667 592 526 470 422 376 333 296 263 235 211 188 169 150 131 117 103 38.2 34.4 30.6 27.2 24.1 21.4 19.1 17.2 15.3 13.6 12.1 10.7 9.6 8.6 7.7 6.9 6.2 5.4 4.8 4.3 3.5 2.9 2.4 2.0 1.6 1.6 17 924 831 739 656 582 518 462 415 370 328 290 258 230 207 184 166 148 129 115 101 83 69 58 46 37 29 22 1.6 47.7 42.9 38.1 33.9 30.0 26.7 23.9 21.5 19.1 16.9 15.0 13.4 11.9 10.8 9.6 8.6 7.7 6.7 6.0 5.3 4.3 3.6 3.0 2.4 1.9 1.6 1.6 17 904 814 723 641 570 506 452 406 362 320 285 253 225 203 180 163 144 126 113 99 81 67 57 45 36 29 22 1.6 59.3 53.5 47.4 42.1 37.3 33.2 29.6 26.7 23.7 21.1 18.7 16.6 14.8 13.4 11.9 10.7 9.5 8.3 7.4 6.6 5.4 4.5 3.8 3.0 2.4 1.9 1.6 SDR – Nominal ratio of outside diameter to wall thickness. 1000 900 800 710 630 560 500 450 300 7.7 338 267 6.9 380 238 6.2 8.7 215 5.5 9.8 171 190 152 4.0 4.4 133 3.5 4.9 119 3.1 3.4 84 70 59 47 37 29 1.6 1.6 21 SDR Mean Min. Wall I.D. Thickness (mm) (mm) 13 1.6 880 791 704 624 554 494 440 395 351 311 278 246 219 198 175 158 140 123 110 96 78 66 55 44 35 28 22 17 17 - - 679 603 535 475 424 382 340 301 268 238 212 191 170 153 136 118 106 93 76 63 53 42 34 27 21 1.9 - - - - 57.2 50.8 45.4 40.9 36.3 32.2 28.6 25.4 22.7 20.5 18.2 16.4 14.6 12.7 11.4 10.0 8.2 6.8 5.8 4.6 3.7 2.9 2.3 - - - - 512 455 407 366 326 289 256 228 203 183 162 145 130 114 101 89 73 61 51 40 32 26 20 16 - - - - - - 55.8 50.2 44.7 39.6 35.2 31.3 27.9 25.1 22.4 20.1 17.9 15.7 14.0 12.3 10.1 8.4 7.1 5.6 4.5 3.6 2.8 2.3 11 SDR Mean Min. Wall I.D. Thickness (mm) (mm) 13 1.8 ID – internal diameter - - 58.8 52.2 46.3 41.2 36.8 33.1 29.4 26.1 23.2 20.6 18.4 16.6 14.7 13.3 11.8 10.3 9.2 8.1 6.6 5.5 4.7 3.7 3.0 2.4 1.9 1.6 17 SDR 13.6 SDR Mean Min. Wall Mean Min. Wall I.D. Thickness I.D. Thickness (mm) (mm) (mm) (mm) 13 1.6 13 1.6 - - - - - - 384 347 307 273 242 215 192 173 154 138 123 108 96 84 69 58 48 38 31 24 19 15 - - - - - - - 61.5 54.6 48.5 43.0 38.3 34.2 30.8 27.3 24.6 21.9 19.2 17.1 15.1 12.3 10.3 8.6 6.9 5.5 4.4 3.5 2.8 - - - - - - - 322 287 255 226 200 179 161 143 128 114 99 89 78 65 53 45 35 28 23 18 14 9 SDR 7.4 Mean Min. Wall Mean I.D. Thickness I.D. (mm) (mm) (mm) 12 2.2 11 g 200 180 160 105 2.7 2.8 2.3 2.0 1.6 1.6 1.6 17 22 26 SDR Mean Min. Wall I.D. Thickness (mm) (mm) 13 1.6 i 140 125 110 71 60 1.6 86 47 1.6 1.9 37 1.6 2.2 29 1.6 1.6 1.6 33 SDR Mean Min. Wall I.D. Thickness (mm) (mm) 13 1.6 s 90 75 63 17 22 1.6 1.6 41 SDR Mean Min. Wall I.D. Thickness (mm) (mm) 13 1.6 e 50 40 32 25 20 SDR Nominal Size Min. Wall DN Thickness (mm) 16 1.6 Polyethylene Pipe Dimensions (based on AS/NZS 4130-1997, Polyethylene pipes for pressure applications.) d n Pipe Dimensions Table 4.2 PE Pipe Dimensions AS/NZS 4130 Ltd y t PE 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 Allowable Operating Pressure Table 4.3 Hydrostatic Design Stress and Minimum Required Strength – Values Hydrostatic Design Basis Material Designation Vinidex pipes manufactured to AS/NZS 4130, Series 1 have wall thickness and pressure ratings determined by the Barlow formula as follows: T= PD 2S + P T = minimum wall thickness P = normal working pressure of pipe D = minimum mean OD S = hydrostatic design stress at 20°C See Table 4.2. (mm) Minimum Required Strength (MRS) MPa Hydrostatic Design Stress (S) MPa PE63 5.0 6.3 PE80 6.3 8.0 PE100 8.0 10.0 The Hydrostatic Design Stress (S) is obtained by application of a Design or Safety Factor (F) to the MRS. 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. See Table 4.3. (MPa) (mm) S= MRS F (MPa) 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. n 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. Maximum Allowable Operating Pressure 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. MAOP = PN x 0.125 F where 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. MAOP is the maximum allowable operating pressure in MPa. PN is the pipe classification in accordance with AS/NZS 4130. The relationship between the S and MRS standard values in AS/NZS 4131 is as shown in Table 4.3. 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. Ltd y t Note: See Figure 2.1 for typical stress regression curves. P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.5 d e s 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 i g Table 4.5 PE Pipe Pressure Ratings PN Rating Number F 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: PN x 0.125 MAOP = F Nominal Working Pressure PN 3.2 MPa 0.32 Head Metres 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 Table 4.6 Design Factors – Gas Pipes Installation Conditions Fluid type Natural Gas Design Factor 20°C n Design Factor Value f0 LPG Pipe Form 2.2 Straight length f1 Coils Soil Temperature (Av. °C) Designation F = f0 x f1 x f2 x f3 x f4 x f5 1.0 1.2 -10 < t < 0 f2 1.2 0 < t < 20 1.0 20 < t < 30 1.1 30 < t < 35 1.3 Distribution f3 Transport 1.0 0.9 Rapid Crack Resistance f4 1.0 f5 0.9 Population density & area loading Open field 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: 2.0 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. Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.6 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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. e s i g n Service Lifetimes The grades of PE specified in AS/NZS 4131 are produced by different polymerisation methods, and as such have different responses to temperature variations. 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. 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. 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. 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. 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. The performance of compounds used in the manufacture of Vinidex pipes to AS/NZS 4130 has been verified by appropriate data analysis. Vinidex PE pipes are continually tested in combinations of elevated temperature (80°C water conditions) and pressure to ensure compliance with specification requirements. In addition, Vinidex offers pipes made from specialised compounds for particular applications, such as elevated temperature use. 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. Contact Vinidex engineers for special requirements. 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 Ltd y t the these figures are meaningless, Pas p u assumptions made in other parts ro .au of the G e om the economic evaluations 7 us eoutweigh .c o h ip 1 41 effect of piperelifetime. p 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. 6 a W poly 0 6 n . 0 io w 3 at ww h 1 g i P rr I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.7 d e s i g n Example 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 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. Determine Material PN10 pipe is therefore satisfactory. Class of pipe 3. Determine Life Life Total time at 55°C Steps = 1 x 365 x 15 = 5475h = 0.625y. 1. Assume a material From Table 4.7, Lmin for 55°C is 24 years, therefore proportion of time used is: 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: 1.25 x 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. 0.625 = 0.026 = 2.6% 24 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: 5.625 = 0.056 = 5.6% 100 Total proportion is 8.2% of life used in 15 years (6.25 years actual operation). If the proportion is less than unity, the material is satisfactory. The data in the tables are obtained from Ltd the use of ISO 13761 and ISO/DIS 9080, y Pt p and are appropriate for compounds u ro u typically used by Vinidex. e G m.a s o ou pe.c 417 h e pi 61 ar W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.8 PE 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 Table 4.7 Temperature Rating Tables PE80B Extrapolation Temp Limit PN 3.2 °C Years 20 25 30 35 40 45 50 55 60 65 70 75 80 200 100 100 100 100 60 36 24 12 8 5 2 2 32 30 28 26 24 22 21 19 18 17 16 14 13 Permissible System Operating Head (m) PN 4 PN 6.3 PN 8 PN 10 PN 12.5 PN 16 40 38 35 32 30 28 26 24 23 21 20 18 17 63 59 55 50 47 44 41 38 35 33 31 28 26 80 75 70 64 60 56 52 48 45 42 39 36 33 100 94 88 80 75 70 65 60 56 53 49 45 41 125 117 109 100 94 88 81 75 70 66 61 56 52 160 150 140 128 120 112 104 96 90 84 78 72 66 PN20 200 188 175 160 150 140 130 120 113 105 98 90 83 PE80C Extrapolation Temp Limit PN 3.2 °C Years 20 25 30 35 40 45 50 50 30 18 12 6 32 29 26 23 20 18 Permissible System Operating Head (m) PN 4 PN 6.3 PN 8 PN 10 PN 12.5 PN 16 40 36 33 29 25 23 63 57 51 46 39 35 80 72 65 58 50 45 100 90 81 73 63 56 125 113 102 91 78 70 160 144 130 116 100 90 PN20 200 180 163 145 125 113 PE100 Extrapolation Temp Limit PN 3.2 °C Years 20 25 30 35 40 45 50 55 60 65 70 75 80 200 100 100 100 100 60 36 24 12 8 5 2 2 32 30 28 26 24 22 21 19 18 17 16 14 13 Permissible System Operating Head (m) PN 4 PN 6.3 PN 8 PN 10 PN 12.5 PN 16 40 38 35 32 30 28 26 24 23 21 20 18 17 63 59 55 50 47 44 41 38 35 33 31 28 26 80 75 70 64 60 56 52 48 45 42 39 36 33 100 94 88 80 75 70 65 60 56 53 49 45 41 125 117 109 100 94 88 81 75 70 66 61 56 52 160 150 140 128 120 112 104 96 90 84 78 72 66 PN20 PN25 200 188 175 160 150 140 130 120 113 105 98 90 83 250 233 218 200 185 175 163 150 140 130 120 113 105 Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.9 d e s E Modulus i n Table 4.8 E Values (MPa) 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. PE 80B Temp °C 3 min 1h 5h 24h 1y 20y 50y 0 20 40 60 1050 700 530 400 830 550 410 300 740 490 370 280 650 430 320 250 410 270 200 160 320 215 160 - 300 200 150 - PE 80C Table 4.8 lists E values in MPa for PE80B (MDPE), PE80C (HDPE), and PE100 (HDPE). Selection of Wall Thickness for Special Applications Temp °C 3 min 1h 5h 24h 1y 20y 50y 0 20 40 60 1080 750 470 210 850 590 370 170 740 520 320 150 660 460 290 130 400 280 180 80 320 220 140 - 300 205 130 - PE 100 Temp °C 3 min 1h 5h 24h 1y 20y 50y 0 20 40 60 1380 950 700 530 1080 750 550 420 950 660 490 370 830 580 430 320 520 360 270 200 410 280 210 - 380 260 190 - For a required nominal diameter (DN) and working pressure, the necessary wall thickness for special applications may be calculated using the Barlow formula: t = g P.DN 2.S + P Example where P = 900kPa P = maximum working pressure (MPa) DN = 630 DN = nominal outside diameter (mm) MRS = 10 (PE100) S = design hoop stress (MPa) F = 1.25 S = 10 1.25 t = 0.9 x 630 = 33.6mm 16 + 0.9 t = minimum wall thickness S = MRS F where F = design factor, typically 1.25 for water (mm) = 0.9MPa = 8.0MPa Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.10 PE 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 Colebrook - White 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. The development from first principles of the Darcy-Weisbach formula results in the expression The variations inherent with diameter changes are accounted for by the introduction of the coefficient C2 so that C2 = C1 r0.02 f = internal diameter (mm) H = head loss (metres/100 metres length of pipe) 64 R = Darcy friction factor H = head loss due to friction (m) D = pipe internal diameter (m) where D f = and Q = 4.03 x 10-5 D2.65 H0.54 = discharge (litres/second) fLv2 D 2g where Adoption of a Hazen-Williams roughness coefficient of 155 results in the following relationship for discharge in Vinidex PE pipes Q H= L = pipe length (metres) v = flow velocity (m/s) g = gravitational acceleration (9.81 m/s2) R = Reynolds Number 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. 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. 1 f 1/ 2 k 2.51 = −2 log10 + 1/ 2 3 7 D . Rf where Hazen - Williams k = Colebrook-White roughness coefficient (m) The original Hazen-Williams formula was published in 1920 in the form: The appropriate value for PE pipes is: k = 0.007 x 10 -3 m v = C1 r0.63 s0.54 0.001-0.04 = 0.007 mm where This value provides for the range of td L pipe diameters, and water flowPty up u velocities encountered inro normal .a G pipeline installations. se com 7 C1 = Hazen-Williams roughness coefficient r = hydraulic radius (ft) s = hydraulic gradient 1 ou e. eh pip 61 4 r a ly 6 W po 0 ion ww. 130 t ga w Ph rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.11 d e s i g n Flow Variations Head Loss in Fittings Worked Example 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. 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. 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? 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. 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: V2 H = K 2g where K= 0.35 (Table 4.9) V= 2 m/s g= 9.81 m/s H= 0.35 × 22 2 × 9.81 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. where Pipe Dimensions H = head loss (m) 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. V = velocity of flow (m/s) Surface Roughness 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 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. V2 H = K 2g K = head loss coefficient g = gravitational acceleration (9.81 m/s2) 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. Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.12 PE 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 Flow Chart Worked Examples Example 1 - Gravity Main PE80 Material Option (refer Figure 4.1) PE80 PN6.3 pipe is SDR 21. 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. 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. 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 : 50 x 100 = 1.11m / 100m 4500 Use Table 4.1 to select the SDR rating of PN6.3 class pipes in both PE80, and PE100 materials. 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 Figure 4.1 Gravity Flow Example Storage tank Maximum difference in water level 50m 4,500m of Vinidex PE Pipe Discharge Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.13 d e s Example 2 - Pumped Main i g 3. Fittings head losses (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 n Velocity Head = = 4. Total pumping head = 30 + 25 + 1.2 = 56.2 m v2 2g allow 57 m. Note: The example does not make any provision for surge allowance in pressure class selection. 1.02 = 0.05 2 x 9.81 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 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 2. Pipe friction head 90° elbow 1.1 4 x 1.1 x 0.05 = 0.220 Considering the data available, start with a PN6.3 class pipe. 45° elbow 0.35 2 x 0.35 x 0.05 = 0.035 PE80 Option Total fittings head loss 1. Static head = 100 - 70 = 30 m Square outlet 1.0 Head Loss m 1.0 x 0.05 = 0.050 = 1.2 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. Figure 4.2 Pumped Flow Example RL 100m 0.5 x 5000 = 25m 100 90° Elbow Maximum difference in water level - 30m Square Outlet Gate Pump Gate Valve 2x90° 90° Valve Elbows Elbow This gives a value of 0.5m/100m. Calculate the total friction head loss in the pipe: Storage Tank Max Level of Tank 45° Elbow 5,000m of Vinidex PE Pipe RL 70m Min Level of Dam 45° Elbow Hinged Disc Foot Valve with Strainer Reflux Valve Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri Then from the flow chart, estimate the velocity of flow This gives 1 m/s. I Design.14 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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. e s i g n Example 3. Determine flow velocity and discharge under part full flow conditions 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. Given gravity conditions: Pipe DN 200 PE80 PN6.3 Refer to the Vinidex PE pipe flow chart for the SDR 21 pipe. Mean Pipe ID 180 mm ( Refer Table XX PE pipe dimensions, or AS/NZS 4130 ) For a gradient of 1 in 100 full flow is 39 l/s and the velocity is 1.6 m/s. Gradient 1 in 100 Depth of flow 80 mm Then, for part full flow Problem: Discharge = 0.4 x 39 = 15.6 l/s Find flow and velocity Solution: Velocity Depth of flow Pr oportional Depth = Pipe ID = = 0.95 x 1.6 = 1.52 m/s 80 = 0.44 180 Figure 4.3 Part Full Flow 1.0 0.9 0.8 Proportional Depth 0.7 0.6 Discharge 0.5 0.4 0.3 Velocity 0.2 Ltd y t 0.1 0 0.1 P p u o au 0.2 0.3 0.4 0.5 0.6 0.7 0.8 . 1.0 Gr 0.9 m e Velocity s o Proportional Discharge & c u 17 o e. eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems 1.1 1.2 Design.15 d e s i g n Resistance Coefficients Table 4.9 Valves, Fittings and Changes in Pipe Cross-Section 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 Long Radius Bends (R/D > 2) 45° 90° 0.35 1.10 111/4° 221/2° 45° 90° 0.05 0.10 0.20 0.50 Fitting Type K Gradual Enlargements Ratio d/D q = 10° typical 0.9 0.7 0.5 0.3 0.02 0.13 0.29 0.42 Gradual Contractions Ratio d/D q = 10° typical 0.9 0.7 0.5 0.3 0.03 0.08 0.12 0.14 Valves Gate Valve (fully open) 0.20 Reflux Valve 2.50 Globe Valve 10.00 Tees (a) Flow in line 0.35 (b) Line to branch flow 1.00 Sudden Enlargements Ratio d/D 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 <0.2 0.04 0.13 0.26 0.41 0.56 0.71 0.83 0.92 1.00 Sudden Contractions Ratio d/D 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 <0.2 0.10 0.18 0.26 0.32 0.38 0.42 0.46 0.48 0.50 Butterfly Valve (fully open) 0.20 Angle Valve 5.00 Foot Valve with strainer hinged disc valve unhinged (poppet) disc valve 15.00 10.00 Air Valves zero Ball Valve 0.10 Ltd y t Pipe Exit Losses Square Outlet Rounded Outlet P 1.00 p u ro .au e G om s ou e.c 17 eh pip 61 41.00 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.16 PE 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 NO M IN AL SI AN D CL AS /8 6 63 3/16 50 6 /6 3 /6 63 /12 .3 .3 /1 .5 0 75 63 7 /8 7 /1 2 7 .3 5/10.5 5/1 6 5/ 6 /8 32 3 /1 32 2/1 6 /1 2.5 0 2 25 5/1 6 2 /12 5 25 /10.5 /8 20 20 /16 / 12 .5 ) PN DN / AL S I ZE A N D 1 CL 1 6/ 6 A /1 16 SS 2. 5 ( VE LO CIT Ym 0.2 5 /s 0.5 5 1.0 3 6. /8 32 1.2 ) 32 / 1.5 4 40 0/16 40/12. /1 5 0 3 1.7 PN 6. 5 40 2.0 N/ 40 / 2.5 (D 50 50 50/ /16 / 8 50 12. /1 5 0 3.0 S Discharge - Litres per Second (L/s) ZE 75 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) IN M NO Ltd y t P p u ro .au e G om s ou e.c 17 Head Loss - Metres Head of Water per 100 metres of Pipe eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.17 d e s i g n Flow Chart for Polyethylene Pipe – SDR 41 (PE80: PN3.2 & PE100: PN4) NO MI LS 00 10 IZE 0 90 0 4.0 80 0 3.0 71 0 63 2.0 0 50 1.5 0 45 0 40 1.0 5 35 5 31 0.5 0 28 0 25 5 0.2 5 LO CIT Ym /s 22 VE Discharge - Litres per Second (L/s) 0 56 0 20 0 18 0 16 0 14 5 12 0 11 90 Flow Chart for Polyethylene Pipe – SDR 41 (PE80: PN3.2 & PE100: PN4) NA IZE AL S N MI NO Ltd y t P p u ro .au e G om s Head Loss - Metres Head of Water per 100 metres of Pipe ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr Design.18 PE 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 Flow Chart for Polyethylene Pipe – SDR 33 (PE80: PN4) NO MI NA LS IZE 00 10 0 80 4.0 0 71 0 0 56 0 2.0 50 0 45 1.5 0 40 5 1.0 35 5 31 0 28 0.5 0 25 5 22 0 VE LO CIT Ym /s 20 0.2 5 Discharge - Litres per Second (L/s) 3.0 63 0 18 0 16 0 14 Flow Chart for Polyethylene Pipe – SDR 33 (PE80: PN4) 0 90 5 12 0 11 90 IZE AL S N MI NO Ltd y t P p u ro .au e G om s Head Loss - Metres Head of Water per 100 metres of Pipe ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.19 d e s i g n Flow Chart for Polyethylene Pipe – SDR 26 (PE100: PN6.3) NO MI NA LS 00 10 0 90 0 80 4.0 0 71 0 0 56 0 2.0 50 0 45 1.5 0 40 5 1.0 35 5 31 0 28 0.5 0 25 5 5 CIT Ym /se c 22 VE LO 0.2 Discharge - Litres per Second (L/s) 3.0 63 0 20 0 18 0 16 0 14 Flow Chart for Polyethylene Pipe – SDR 26 (PE100: PN6.3) IZE 5 12 0 11 90 IZE AL S N MI NO Ltd y t P p u ro .au e G om s Head Loss - Metres Head of Water per 100 metres of Pipe ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr Design.20 PE 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 Flow Chart for Polyethylene Pipe – SDR 21 (PE80: PN6.3 & PE100: PN8) NO NA LS IZE 00 10 0 90 0 4.0 80 0 71 3.0 0 Discharge - Litres per Second (L/s) 63 0 2.0 56 0 50 0 1.5 45 0 1.0 40 5 35 5 31 0 0.5 28 0 25 5 22 VE LO C ITY 0.2 5 m/ s 0 20 0 18 0 16 0 14 5 12 0 11 90 Flow Chart for Polyethylene Pipe – SDR 21 (PE80: PN6.3 & PE100: PN8) MI IZE AL S N MI NO Ltd y t P p u ro .au e G om s Head Loss - Metres Head of Water per 100 metres of Pipe ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.21 d e s i g n NO MI NA LS 0 90 IZE 4.0 0 80 0 3.0 71 0 2.0 56 0 50 1.5 0 45 0 1.0 40 5 35 5 31 0.5 0 28 0 25 5 /s 22 VE LO CIT 0.2 5 Ym Discharge - Litres per Second (L/s) 0 63 0 20 0 18 0 16 0 14 5 12 Flow Chart for Polyethylene Pipe – SDR 17 (PE80: PN8 & PE100: PN10) Flow Chart for Polyethylene Pipe – SDR 17 (PE80: PN8 & PE100: PN10) 0 11 90 IZE AL S N MI NO Ltd y t P p u ro .au e G om s ou e.c 17 Head Loss - Metres Head of Water per 100 metres of Pipe eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr Design.22 PE 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 NO MI NA LS 4.0 0 80 IZE 0 3.0 71 0 Discharge - Litres per Second (L/s) 2.0 63 0 56 0 1.5 50 0 45 1.0 0 40 5 35 5 0.5 31 0 28 0 25 5 VE LO CIT Ym 0.2 5 /s 22 0 20 0 18 0 16 0 14 5 12 0 11 90 Flow Chart for Polyethylene Pipe – SDR 13.6 (PE80: PN10 & PE100: PN12.5) Flow Chart for Polyethylene Pipe – SDR 13.6 (PE80: PN10 & PE100: PN12.5) IZE AL S N MI NO Ltd y t P p u ro .au e G om s Head Loss - Metres Head of Water per 100 metres of Pipe ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.23 d e s i g n NO MI NA LS IZE 0 4.0 80 0 Discharge - Litres per Second (L/s) 71 3.0 0 63 0 2.0 56 0 50 0 1.5 45 0 1.0 40 5 35 5 31 0 0.5 28 0 25 5 22 0 0.2 Ym 5 /s 0 20 CIT 18 0 LO 16 VE 0 14 5 12 Flow Chart for Polyethylene Pipe – SDR 11 (PE80: PN12.5 & PE100: PN16) Flow Chart for Polyethylene Pipe – SDR 11 (PE80: PN12.5 & PE100: PN16) 0 11 90 IZE AL S N MI NO Ltd y t Head Loss - Metres Head of Water per 100 metres of Pipe P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.24 PE 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 NO M 4.0 IN AL 0 3.0 45 SI ZE 0 2.0 40 Discharge - Litres per Second (L/s) 5 35 5 1.5 31 0 1.0 28 0 25 5 22 0 0.5 20 0 18 0 16 0 m/s 5 12 LO C ITY 0.25 14 0 VE 11 90 Flow Chart for Polyethylene Pipe – SDR 9 (PE80: PN16 & PE100: PN20) Flow Chart for Polyethylene Pipe – SDR 9 (PE80: PN16 & PE100: PN20) ZE AL SI IN OM N Head Loss - Metres Head of Water per 100 metres of Pipe Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.25 d e s i g n NO M 4.0 IN AL 0 3.0 45 SI ZE 0 Discharge - Litres per Second (L/s) 40 2.0 5 35 5 1.5 31 0 28 1.0 0 25 5 22 0 0.5 20 0 18 0 16 /s 0 0.25 11 LO CIT 5 VE Ym 14 12 Flow Chart for Polyethylene Pipe – SDR 7.4 (PE100: PN25) Flow Chart for Polyethylene Pipe – SDR 7.4 (PE100: PN25) 0 ZE 90 AL SI IN NO M Ltd y t P p u ro .au Head Loss - Metres Head of Water per 100 metres of Pipe e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr Design.26 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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. e s 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: 1 SDR C = W + E K 3 x 10 m/ sec where (a) The maximum pressure in the pipe from all sources must be less than the pressure equivalent to the Classification of the pipe (PN). SDR = Standard Dimension Ratio of the pipe (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. W = liquid bulk modulus (2150 MPa) E = pipe material short term modulus (MPa) refer Table 4.8 n 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. = liquid density (1000 kg/m3 for water) K g 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. −0 .5 For Vinidex PE pipes to AS/NZS 4130, operating under the following limitations, it is not necessary to make specific allowance for fatigue effects: and i 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 time taken for the pressure wave to travel the length of the pipeline and return is t= 2L C 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: P1 = C.V 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: Ltd y t t P2 = P1 t c P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.27 d e s Celerity − 0.5 x 103 m / sec where W g n Table 4.10 Surge Celerity The surge celerity in a polyethylene pipeline filled with liquid can be determined by: 1 SDR C = W + E K i = liquid density (1000 kg/m3 for water) SDR 41 33 26 21 17 13.6 11 9 7.4 Celerity m/s MDPE (PE 80B) HDPE (PE 80C) 160 170 190 220 240 270 300 330 360 170 190 210 240 260 290 320 350 390 HDPE (PE 100) 190 210 240 260 290 320 360 390 430 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) Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.28 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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 e s i g n 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. 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 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. 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. Note: The published Vinidex PE pipe flow charts relate ONLY to water or other liquids which behave as Newtonian fluids. 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. They are not suitable for calculating the flow discharges of other fluids, including slurries. 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. For further information on slurry pipeline design, the designer is referred to such publications as Govier G.W. and Aziz K, 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 Flow of Complex Mixtures in Pipes. Rheinhold, 1972. and Wasp E.J. Solid Liquid Flow - Slurry Pipeline Transportation. Trans Tech Publications. 1977. Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.29 d e s i g n Pipe Wear Particle Size Angle of Attack 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 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. 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 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 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. 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 td of the particle to the pipe wall. As aty L P p result accelerated wear generally u ro .au occurs immediately downstream e G om of s .c 417 ou peprominent the bead. This isehusually in i r a lyp 661 D50 particleWsizes poover0300 microns. on w. 30 ti wparticle 1 Forgacoarse w Ph slurries the i r r I internal bead should be removed. Design.30 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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. e s i Maintenance and Operation g n 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. 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. 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 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. Warman Slurry Pumping Handbook, Warman International Ltd. Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.31 d e s Pneumatic Flow i 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. 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. n • 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. g Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.32 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d e s i System Design Guidelines for the Selection of Vinidexair Compressed Air Pipelines 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. 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: Example for the use of the air-line nomogram (Figure 4.4) to determine the required pipe size d=5 450.L E.Q 1.85 ∆ p.p 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 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 (LE) in m, and the Pipe Nominal Diameter DN. Working Pressure 7 bar Volumetric Flowrate 30 L/s Nominal length 200 m Pressure Decrease 0.05 bar g n 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. 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.) Correction factors for fittings 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). 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. 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 L ty2.3 90° bend 0.4 0.7 1.0 1.3 tees 0.8 1.4 1.9 2.4 reducer 0.3 0.4 0.5 0.6 td P up 2.3 ro .au 4.5 G m 2.8 use c3.8 . o 417 7.5 o e eh pip 60.9 1 2.1 ar 0.7 ly 1.8 6 W o n w.p 300 o i t 1 ga ww Ph rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.33 d e s i g n length of the pipe (L) in m Figure 4.4 Compressed Air Flow Nomogram 1 2 5 10 20 50 100 200 500 1000 2000 Sources: Feldmann, K.H.: Druckluftverteilung in der Praxis (Munchen 1985) 1 1.5 Atlas Copco : information sheets 5 2 20 3 25 volumetric flow rate (Q) in L/s nominal diameter DN 5 32 10 40 15 20 4 50 3 30 7 50 63 3 100 90 6 200 300 2 400 500 0.002 0.01 0.05 0.1 0.2 0.5 1 2 4 6 10 15 Ltd y t P u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri working pressure (p) in bar p pressure decrease in the pipe (∆p) in bar I Design.34 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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. s i g n Figure 4.5 Thermal Expansion and Contraction for PE 20.0 Expansion and Contraction (mm/m) Expansion and Contraction e 17.5 15.0 12.5 10.0 7.5 5.0 2.5 0 0 10 20 30 40 50 Pipe Material Temperature Change (°C) Accordingly, in buried pipelines the main consideration of thermal movement is during installation in high ambient temperatures. 60 70 80 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. 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. Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.35 d e s 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: Pc = 2380 • E ( SDR − 1) 3 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 Reduction 1.0 1 2 0.99 0.97 5 10 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´) i g n Tabulations of the value of E´ for various combinations of soil types and compactions 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 Ltd y t 0.5 Where E´ = soil modulus from AS/NZS2566 - Buried Flexible Pipelines. P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.36 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d e s Trench Design Table 4.12 Minimum Cover Minimum Cover Installation Condition The recommended minimum cover depths for Vinidex PE pipes are listed in Table 4.12. Open country Traffic Loading 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. i g n Cover over Pipe Crown (mm) 300 No pavement 450 Sealed pavement 600 Unsealed pavement 750 Construction equipment 750 Embankment 750 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. 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. Ltd y t P p u o u •. The excavated material, free from Gr m.a e s o rocks and broken up such that it ou e.c 17 eh pip 61 4 r contains no clay lumps greater than a W poly 0 6 n . 75mm which would prevent adequate 0 tio ww 13 a w Ph compaction. ig Irr PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.37 d e 100mm min s 100mm min Bedding 75mm min Figure 4.6 Wide Trench Condition 100mm min D i g n Allowable Bending Radius When bending pipes there are two control conditions: Vinidex PE pipes are flexible in behaviour, and can be readily bent in the field. 1. Kinking in pipes with high SDR ratios. 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. For condition 1 The minimum radius to prevent kinking (Rk) may be calculated by: 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%). 100mm min 2. High outer fibre strain in high pressure class pipes with low SDR ratios. Rk = SDR (SDR-1) 1.12 For condition 2 The minimum radius to prevent excess strain (Re) may be calculated by: Re = D ε 2 where ε = outer fibre strain Bedding 75mm min (maximum allowable = 0.04) D = mean Di (mm) Figure 4.7 Narrow Trench Condition Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.38 PE 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 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. 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. 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 ______________________________________________________________________________ Ltd y t P ro .au e G om s ou e.c 17 Degree of Compaction _____________________________________________________________________ eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph ig Irr Embedment Material ______________________________________________________________________ up PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.39 d e s i g n 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 Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.40 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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 2PA . sin φ .10-3 R= 2 where R = resultant thrust (kN) e s i Velocity (Kinetic) Thrust n 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. The velocity or kinetic thrust applies only at changes of direction. R= g 2 w a V 2. sin φ .10-9 2 In shallow (<600mm) cover installations or in unstable conditions of fill, the soil where w = fluid density (kg/m3) support may be considerably reduced from the values tabulated, and a complete soil analysis may be needed. 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: P = pressure (MPa) A = area of pipe cross section (mm2) Soil Type Safe Bearing Capacity (N/m2) φ = angle of fitting (degrees) For blank ends, tees and valves R = PA 10-3 For reducers R = P(A1 - A2) 10-3 100 x 105 Rock and sandstone (hard thick layers) 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 9 x 104 Clay/Sandy loam Peat, wet alluvial soils, silt Nil Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.41 d e s i Thrust Block Size Calculations g n Figure 4.8 Thrust Blocks 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. Tee anchorage 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. Bend in horizontal plane anchorage Test pressure is 1.25 x WP = 1.56 MPa. 2. R = 2 PA .sin φ. 10-3 2 = 3.8 x 10-4 N Bend in vertical plane anchorage 3. Bearing capacity of hard, dry clay is 15x104 N/m2 Bearing area of thrust block = 3.8 x 10 4 15 x 10 4 = 0.25m 2 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. Valve anchorage Ltd y t Closed end and hydrant anchorage P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I Design.42 PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems d 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. e s i g n Vibration Heat Sources 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. 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. 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. See Table 4.7 Temperature Rating Table. Ltd y t P p u ro .au e G om s ou e.c 17 eh pip 61 4 r a W poly 0 6 n . 0 tio ww 13 a w Ph g rri I PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems Design.43
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