Metallic industrial piping Part 6: Additional requirements for buried piping

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1 BSI Sandards Publicaion Meallic indusrial piping Par 6: Addiional requiremens for buried piping NO COPYING WITOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGT LAW raising sandards worldwide

2 BRITIS STANDARD Naional foreword This Briish Sandard is he UK implemenaion of EN :01. I supersedes BS EN :004 which is wihdrawn. The UK paricipaion in is preparaion was enrused o Technical Commiee PVE/10, Piping sysems. A lis of organizaions represened on his commiee can be obained on reques o is secreary. This publicaion does no purpor o include all he necessary provisions of a conrac. Users are responsible for is correc applicaion. The Briish Sandards Insiuion 01. Published by BSI Sandards Limied 01 ISBN ICS Compliance wih a Briish Sandard canno confer immuniy from legal obligaions. This Briish Sandard was published under he auhoriy of he Sandards Policy and Sraegy Commiee on 31 July 01. Amendmens issued since publicaion Dae Tex affeced

3 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCE NORM EN June 01 BS EN :01 ICS Supersedes EN :004 English Version Meallic indusrial piping - Par 6: Addiional requiremens for buried piping Tuyaueries indusrielles méalliques - Parie 6: Exigences complémenaires relaives aux uyaueries enerrées Meallische indusrielle Rohrleiungen - Teil 6: Zusäzliche Anforderungen an erdgedecke Rohrleiungen This European Sandard was approved by CEN on 8 May 01. CEN members are bound o comply wih he CEN/CENELEC Inernal Regulaions which sipulae he condiions for giving his European Sandard he saus of a naional sandard wihou any aleraion. Up-o-dae liss and bibliographical references concerning such naional sandards may be obained on applicaion o he CEN-CENELEC Managemen Cenre or o any CEN member. This European Sandard exiss in hree official versions (English, French, German). A version in any oher language made by ranslaion under he responsibiliy of a CEN member ino is own language and noified o he CEN-CENELEC Managemen Cenre has he same saus as he official versions. CEN members are he naional sandards bodies of Ausria, Belgium, Bulgaria, Croaia, Cyprus, Czech Republic, Denmark, Esonia, Finland, France, Germany, Greece, ungary, Iceland, Ireland, Ialy, Lavia, Lihuania, Luxembourg, Mala, Neherlands, Norway, Poland, Porugal, Romania, Slovakia, Slovenia, Spain, Sweden, Swizerland, Turkey and Unied Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCES KOMITEE FÜR NORMUNG Managemen Cenre: Avenue Marnix 17, B-1000 Brussels 01 CEN All righs of exploiaion in any form and by any means reserved worldwide for CEN naional Members. Ref. No. EN :01: E

4 Conens Page Foreword Scope...5 Normaive references General Safey Roues Deph of insallaion Pipes marking and recording Inernal inspecion provisions Conens removal Trench drainage Maerials Design and calculaion Minimum wall hickness for buried piping Design Insallaion Trenches Pipe laying Back filling Sleeves or casings Corrosion proecion General Coaings Cahodic proecion Examinaion and esing...11 Annex A (normaive) Calculaions for buried piping...1 Annex Y (informaive) isory of EN Annex ZA (informaive) Relaionship beween his European sandard and he essenial requiremens of EU Direcive 97/3/EC...36 Bibliography...37

5 Foreword This documen (EN :01) has been prepared by Technical Commiee CEN/TC 67 Indusrial piping and pipelines, he secrearia of which is held by AFNOR. This European Sandard shall be given he saus of a naional sandard, eiher by publicaion of an idenical ex or by endorsemen, a he laes by December 01, and conflicing naional sandards shall be wihdrawn a he laes by December 01. Aenion is drawn o he possibiliy ha some of he elemens of his documen may be he subjec of paen righs. CEN [and/or CENELEC] shall no be held responsible for idenifying any or all such paen righs. This documen has been prepared under a mandae given o CEN by he European Commission and he European Free Trade Associaion, and suppors essenial requiremens of EU Direcive(s). For relaionship wih EU Direcive(s), see informaive Annex ZA, which is an inegral par of his documen. This European Sandard EN for meallic indusrial piping consiss of seven inerdependen and no dissociable pars which are: Par 1: General; Par : Maerials; Par 3: Design and calculaion; Par 4: Fabricaion and insallaion; Par 5: Inspecion and esing; Par 6: Addiional requiremens for buried piping; CEN/TR , Guidance on he use of conformiy assessmen procedures; Par 8: Addiional requiremens for aluminium and aluminium alloy piping. Alhough hese Pars may be obained separaely, i should be recognised ha he Pars are iner-dependan. As such he manufacure of meallic indusrial piping requires he applicaion of all he relevan Pars in order for he requiremens of he Sandard o be saisfacorily fulfilled. This European Sandard will be mainained by a Mainenance MD working group whose scope of working is limied o correcions and inerpreaions relaed o EN The conac o submi queries can be found a hp://porailgroupe.afnor.fr/public_espacenormalisaion/centc67wg8/index.hm. A form for submiing quesions can be downloaded from he link o he MD websie. Afer subjec expers have agreed an answer, he answer will be communicaed o he quesioner. Correced pages will be given specific issue number and issued by CEN according o CEN Rules. Inerpreaion shees will be posed on he websie of he MD. 3

6 This documen supersedes EN :004+A1:005. This new ediion incorporaes he Amendmens/he corrigenda which have been approved previously by CEN members, and he correced pages up o Issue 17 wihou any furher echnical change. Annex Y provides deails of significan echnical changes beween his European Sandard and he previous ediion. Amendmens o his new ediion may be issued from ime o ime and hen used immediaely as alernaives o rules conained herein. I is inended o deliver a new Issue of EN 13480:01 each year, consolidaing hese Amendmens and including oher idenified correcions. According o he CEN/CENELEC Inernal Regulaions, he naional sandards organizaions of he following counries are bound o implemen his European Sandard: Ausria, Belgium, Bulgaria, Croaia, Cyprus, Czech Republic, Denmark, Esonia, Finland, France, Germany, Greece, ungary, Iceland, Ireland, Ialy, Lavia, Lihuania, Luxembourg, Mala, Neherlands, Norway, Poland, Porugal, Romania, Slovakia, Slovenia, Spain, Sweden, Swizerland, Turkey and he Unied Kingdom. 4

7 1 Scope This documen specifies requiremens for indusrial piping eiher oally buried or parly buried and parly run in sleeves or similar proecion. I is used in conjuncion wih he oher six pars of EN Where buried piping subjec o his sandard connecs o piping insalled under oher jurisdicion such as pipelines, he ransiion should be made a a closing elemen e.g. an isolaing or regulaing valve separaing he wo secions. This should be close o he boundary of he indusrial sie, bu may be inside or ouside he boundary. Operaing emperaure up o 75 C. NOTE For higher emperaures reference should be made o EN A1:010, bu i should be kep in mind, ha CEN/TC 107 only deals wih pre-insulaed piping wih emperaures up o 140 C and diameers up o 800 mm, which is sae of he ar for hese producs. Normaive references The following documens, in whole or in par, are normaively referenced in his documen and are indispensable for is applicaion. For daed references, only he ediion cied applies. For undaed references, he laes ediion of he referenced documen (including any amendmens) applies. EN :01, Meallic indusrial piping Par 1: General EN :01, Meallic indusrial piping Par : Maerials EN :01, Meallic indusrial piping Par 3: Design and calculaion EN :01, Meallic indusrial piping Par 5: Inspecion and esing 3 General 3.1 Safey a) Buried piping wihin an indusrial sie presens a poenial hazard o sie personal, equipmen and environmen. The secions se ou in his documen provide guidance as o how he hazard presened by he piping may be assessed, and he inegriy of he piping sysem mainained. NOTE 1 Aenion is drawn o appropriae Naional or Local regulaions. b) The main facors o be considered are: Design including Rouing, Layou, Ineracion wih connecing sysems; Maerials and Consrucion Specificaion and Qualiy Conrol; Operaing Procedures and Conrol; Corrosion proecion; Exernal Impac Proecion and Miigaion. 5

8 All of hese facors inerac. NOTE NOTE 3 I is recommended ha all buried piping be subjeced o a formal hazard analysis procedure. Aenion is drawn o appropriae Naional or Local regulaions. c) Addiional safey requiremens may be specified for group 1 fluids according o EN :01, including auomaed means of isolaing buried secions of piping. 3. Roues All roues for buried piping shall be agreed wih he owner and operaor of he sie. The sie owner shall be required o furnish deails of all oher acual or planned buried services (including cables) and all roadways or oher surface loads wihin he consrucion working widh or zone of he proposed pipe. Piping in caegory III according o EN :01 shall be separaed from any oher pipe or service by a minimum disance of 0,5 m unless i can be demonsraed ha a smaller disance is accepable. 3.3 Deph of insallaion In he absence of special proecion (e.g. concree slabs) buried piping shall be provided wih a minimum cover of 0,8 m. The designer shall consider increasing he exen of cover above he minimum where peneraing cold or fros heave of he ground is likely, or where damage from excavaion aciviies is a possibiliy. 3.4 Pipes marking and recording Buried pipes shall be marked by a coninuous ape or oher agreed means placed direcly above he pipe and no closer han 0,3 m. All buried pipes shall be idenified on as-insalled drawings which accuraely locae he roue relaive o srucures or oher permanen feaures. The sie owner may require he roue o be physically marked by he use of idenificaion poss or cover slabs a appropriae inervals. 3.5 Inernal inspecion provisions Where periodic inernal inspecion of buried piping is anicipaed, and he specificaion idenifies he mehod proposed, he designer shall incorporae appropriae means of inroducing and removing he inspecion devices. Such closures, and openings for inspecion shall be designed in accordance wih EN : Conens removal The design of he piping sysem shall make allowance for he safe filling and removal of he conens. This shall include ven and drain poins or falls as required, and he selecion of appropriae bends and fiings. 6

9 3.7 Trench drainage The designer shall recognize ha pipe renches for buried piping can ac as channels for ground waer. Appropriae means shall be employed o ensure ha he boom of he rench has sufficien slope o soakaways or sumps o preven accumulaion of waer around he piping. Where such measures are no possible, he designer shall include he possibiliy of floaion in he design calculaions. In addiion, he drainage arrangemens shall dispose of he hydrosaic es waer. Care shall be exercised during his operaion o ensure ha washou of bedding maerial does no occur. 4 Maerials Maerials shall conform o he requiremens of EN :01 excep ha he value for he specified minimum elongaion afer fracure for he longiudinal direcion (see EN :01, ) shall be 0 %. Maerials wih elongaion values less han 0 % shall be avoided, and shall only be used subjec o agreemen beween he purchaser and he designer. 5 Design and calculaion 5.1 Minimum wall hickness for buried piping Unless he pressure design calculaions lead o a greaer hickness, he wall hickness of he pipe shall no be lower han he value given in Table Design Table 1 Minimum wall hickness for buried piping Nominal size (DN) Minimum hickness mm DN 80 3, 80 < DN 150 4,7 150 < DN 450 6, < DN 600 7,9 600 < DN 950 9,5 950 < DN 1 % DN 5..1 A simple single dimensional model linking buried pipes and he surrounding ground may be sufficien for piping designed in accordance wih EN :01. More complex analysis of pipe o soil ineracion may be used where sufficien accurae geo-mechanical daa is available, or where he condiions of his annex canno be me. NOTE I is assumed ha he loads imposed by he piping on he soil do no exceed is load bearing capaciy. 7

10 5.. The designer shall include in he calculaions he weigh of soil or backfill above he pipe and he maximum prediced value of raffic or oher saic and dynamic loads imposed on he ground above he pipe. Wih a minimum immediae (firs) cover o he pipe of 150 mm of sand, or similar free-flowing maerial, he forces may be considered as acing over he enire 180 of he upper pipe surface In addiion o calculaions a he design pressure, he loadings on he unpressurized sysem shall be calculaed Pipe movemen will be significanly resrained by he fricional force a he inerface wih he surrounding soil, and may be effecively prevened a buried bends and large branches. Unless specific measures are incorporaed o permi relaive movemen, buried pipes shall be considered as fully resrained axially for calculaion purposes. The axial sress due o combined pressure and emperaure change effecs shall be calculaed as follows: S L S p E ( T ) (1) where S L S p T is he longiudinal sress 0,90 x yield srengh a design emperaure; is he circumferenial sress due o pressure alone; is he maximum emperaure range; is Poisson s raio Where no deailed analysis is underaken, he maximum emperaure range (including he insallaion emperaure) shall no exceed 35 C, and resraining feaures such as buried bends and ees shall have a separaion of no less han 5 DN. Where deailed analysis is underaken, i shall be in accordance wih EN :01 supplemened by Annex A (normaive) Where seismic evens are o be considered, he pipe shall be reaed as if rigidly conneced o he ground and following he imposed displacemens. Dynamic amplificaion may be ignored. NOTE The surrounding soil can be considered o effecively dampen all harmonic exciaions of he pipe The designer shall consider he inerface beween buried and above ground secions of he piping for all design condiions. For he saic analysis, he buried par shall be considered as clamped for hermal expansion, and i shall be ensured ha he flexibiliy of he above ground par is sufficien in order o limi he loads a he connecion of he wo pars o accepable values. The designer shall analyse he effecs of any anicipaed selemen of he buried piping relaive o he conneced piping overground or in ducs, and shall ensure compliance wih he requiremens of his documen. NOTE When gaseous fluids are carried by he piping, he designer should noe he likely rise in emperaure in he discharge lines of a compressor and corresponding reducion a he ouflow from pressure reducing equipmen. 8

11 Where such in-line iems are close o a buried secion, he designer shall consider he effecs of he emperaure change. 6 Insallaion 6.1 Trenches The normal mehod of insallaion shall be by he excavaion of renches. Alernaively, secions of underground pipe insalled by hrus boring or similar renchless mehods shall be se in casings The boom of he rench shall be consolidaed and free from sharp objecs, rocks or sones. The rench shall be made wih sufficien slope o provide drainage for he pipe o minimise floaion and corrosion. Where necessary, soak-aways or sumps shall be provided. The piping shall be laid on an even bed of sand or similar maerial and consequenly he longiudinal bending sress due o weigh may be discouned A bedding base of free-flowing maerial such as rounded sand or fine gravel shall be provided wih sufficien deph o suppor he pipe and assis drainage. 6. Pipe laying 6..1 The rench shall be subsanially free of waer before he pipe is placed in posiion. 6.. Provision shall be made for sufficien access o joins o permi proper examinaion during hydrosaic or oher esing operaions, and o wrap or oherwise proec pipe joins in he rench. Adequae means shall be provided for removing he hydrosaic es waer from he pipe and rench The bore of he piping shall be clean o he required sandard before laying in he rench All pracical means shall be aken o preven damage o he pipe and is coaings in sorage and during pipe laying. Wire ropes and chains shall no be used for lifing. Proecive pipe coaings shall be visual examined or high volage esed afer he pipe is laid and prior o back filling he excavaion. 6.3 Back filling All ie and examinaion operaions shall be compleed before backfilling The firs cover of he piping shall be made using free-flowing maerials o a minimum deph of 150 mm, ensuring ha he whole circumference of he pipe is in conac wih he filling The remaining backfilling shall be he same maerial ha was excavaed o form he rench or of similar characerisics. No vegeable or wase maer shall be incorporaed. Compacing shall no commence before a cover of 0,3 m has been achieved. 9

12 7 Sleeves or casings Where buried piping is subjeced o frequen overhead raffic or occasional heavy loads, consideraion shall be given o providing he pipe wih an exernal proecive sleeve or casing. These shall also be employed for secions insalled by hrus boring or similar means. Casings shall be of seel, concree or plasic composiion wih a diameer providing a minimum of 100 mm clearance from he carrier pipe. They shall be consruced o carry all likely exernal loads, wihou consideraion of he carrier pipe and any inernal suppors. The hicknesses of seel ubing shall no be less han he values required by EN :01 according o he loads applied (wih a minimum of 9,5 mm). No less han 3 supporing cenralising spacers shall be insalled around he pipe a inervals no exceeding he span requiremens wih a maximum of 4 m. Casings shall be sealed a heir ends o preven he ingress of waer or oher foreign maer. If he annulus beween carrier and sleeve pipes is o be filled wih a fluid, he seal need only be sufficien o wihsand he pressure of he filler unless, oherwise specified by he purchaser. 8 Corrosion proecion 8.1 General Buried piping shall be proeced from exernal corrosion which can arise from waer and ground conaminans, and he effecs of sray earh elecrical currens. Proecion shall be provided by a combinaion of coaing he pipe surface and cahodic elecrical proecion. I is normal for he piping specificaion o idenify he necessary requiremens for corrosion proecion of buried pipes. These shall be in he form of preparaion, coaing and cahodic proecion specificaions. All appropriae informaion in respec of he corrosion hazards likely o be encounered on sie shall be provided. 8. Coaings All coaings shall be suiable for he underground environmen and have mechanical and elecrical properies o sui he specified condiions. In he absence of any oher specificaion, he manufacurer shall consider he relevan European Sandards for he selecion of suiable coaings. Coaings shall bond srongly o he pipe surface and be resisan o loss of bonding a geomerical disconinuiies and damaged sies areas exposed o exernal impac. Offsie coaing shall be maximised o ensure applicaion under he mos favourable condiions. Sie coaing may use alernaive mehods o achieve he requisie proecion, e.g. ape wrapping of joins or similar small areas. Care shall be aken o selec a mehod which will bond adequaely wih he coaing of he main pipe body and is appropriae for he insallaion condiions. 10

13 8.3 Cahodic proecion Cahodic proecion of buried piping shall be applied o reduce he risk of aggressive localised corrosion a poins where he proecive coaing is or could become defecive. Proecion shall be eiher by he connecion of sacrificial anodes or he use of an impressed curren. Proecion shall be applied as soon as pracicable afer insallaion. Aenion shall be given o he risks of pick up from sray earh currens in complex indusrial sies, and he designer of he proecion sysem shall consider he possible ineracion wih oher local elecrical neworks. The designer shall ensure ha elecrical coninuiy is in place for all buried piping. NOTE Flanges and oher in line componens may require specific coninuiy connecions. Elecrical connecions o piping shall be hrough he use of fully welded pads compaible wih he maerial of he pressure shell. Direc connecion o he pipe wall shall no be permied. Buried piping shall be elecrically isolaed from above ground secions hrough he use of isolaing flanges or similar arrangemens. 9 Examinaion and esing Buried piping shall be examined and esed in accordance wih EN :01. Wherever pracical, buried secions of piping shall be pressure esed prior o laying in he rench, and all final connecions subjeced o leak es or oher recognized non-desrucive esing mehods. 11

14 Annex A (normaive) Calculaions for buried piping A.1 General This annex describes he applicable requiremens for buried piping, supplemening hose of EN :01 and EN :01. Thus, i is proposed o deal wih he calculaions for buried piping aking accoun of he following: weigh of he soil or backfill above he pipe according o he differen ypes of insallaion; saic and dynamic loads imposed on he ground above he pipe (e.g. raffic loads); flexibiliy and sabiliy of he piping subjeced o combined pressure and emperaure change effecs. A. Maerials The requiremens specified in EN :01 apply wihou any resricion. owever, one shall remind ha he corrosion phenomena occurring in he case of buried piping may be significanly differen from hose o which piping above-ground, in ducs or unnels are subjeced. A.3 Design and calculaion A.3.1 Calculaion procedure a) Deerminaion of he required hicknesses from he equaions given in EN :01 when he piping is subjeced only o inernal pressure; b) deerminaion of he loads due o backfill (A.3.) and o live loads (A.3.3); c) checking of he hicknesses defined in a) for he differen operaing condiions under which he loads defined in b) are applicable (A.3.4); d) checking of he global sabiliy of he buried piping sysem. A.3. Deerminaion of he loads due o backfill A.3..1 General The insallaion mehods for buried piping covered are as follows: 1

15 piping in narrow rench; piping in wide rench or in posiive projecing embankmen condiion. A.3.. Noaions For he purposes of his annex he following noaions shall apply: C ass Selemen raio (see A b)); C dyn Coefficien for aking ino accoun he dynamic effec of he live loads; D o Exernal piping diameer. For sandardized ubes, D o is he heoreical exernal diameer, olerances excluded; e ord Ordered wall hickness; E Backfill maerial modulus; E Modulus of elasiciy for he piping maerial (see EN :01); Toal heigh from he op of he piping o naural ground surface (cover); e Disance from he plane of equal selemen o he op of pipe; k Raio of laeral pressure o verical pressure for he backfill maerial (Rankine coefficien): k an 4 L Widh of he rench in he horizonal plane conaining he op of he piping; Uni weigh of backfill maerial; Angle of inernal fricion for he maerial used o fill he rench; Coefficien of inernal fricion of backfill maerial; ' Coefficien of sliding fricion beween he backfill maerial and he rench walls; ' is always less han or equal o and ' may be aken as provided ha backfilling maerial of proper qualiy (homogeneiy) is used; F Load per uni lengh. A.3..3 Soil properies In he absence of specific daa, he values given in he able hereafer may be used for he design and calculaion of buried piping. 13

16 Table A.3..3 Soil properies and backfill maerial Type of soil Densiy = an () k ' = an (') k k ' dan/m 3 Topsoil a ,404 0,184 0,184 Parially compaced ,330 0,500 0,165 (mois) opsoil b Sauraed opsoil b ,370 0,400 0,150 Sandy clay c 5 0,406 Clay c Sily clay a ,364 0,178 0,178 Plasic clay a ,49 0,15 0,15 Sandy clay Mois clay a ,13 0,139 0,139 Yellow clay, mois and parially ,330 0,400 0,130 compaced b Sauraed yellow b 080 0,370 0,300 0,110 clay or loam Coarse gravely sand c 43 Medium sand c 40 Fine sand c 38 Sily sand c 36 Uncompaced a ,601 0,19 0,19 sand Sand - Gravel a ,649 0,191 0,191 Clayey sand a ,404 0,184 0,184 Sauraed clayey b 110 0,350 0,400 0,140 sand Dry sand b ,330 0,500 0,165 Mois sand b ,330 0,500 0,165 Sludge c 18 Marshy ground a ,13 0,139 0,139 Pea (Coninued) 14

17 Table A.3..3 (concluded) Type of soil Densiy = an () k ' = an (') k k ' dan/m 3 Loamy loess (alluvial deposis) a ,35 0,17 0,17 Loam Marl a 100 0,404 0,184 0,184 poor clay Sandy sil a ,466 0,189 0,189 Gravel Pebbles a ,754 0,187 0,187 Loose gravelly backfilling ,330 0,580 0,19 maerial b Sony-sandy backfilling ,330 0,500 0,165 maerial b Mois-loamy backfilling 000 0,330 0,450 0,150 maerial b a Calcul des solliciaions exérieures agissan sur les conduies enerrées (Calculaion of exernal loadings acing on buried pipings) - CERIB b The heory of exernal loads on closed conduis in he ligh of he laes experimens - MARSTON c Sabilié des canalisaions enerrées (Sabiliy of buried pipelines) - E.M.YASSINE e V.I. TCERNIKINE - Moscow A.3..4 A Soil properies Definiion A piping is considered as piping in narrow-rench condiion (Figures A o A ) if one of he following condiions is saisfied: L D 0 and 1,5 L or L D 0 3 and 3,5 L If neiher of hese condiions is saisfied, he piping is considered as piping in wide-rench condiion. A Calculaion of he load due o backfill The load per uni lengh he piping is subjeced o is given by he Equaions A and -: F 1 C 1 L (A ) 15

18 L C1 1 e ' k ' k L (A ) The value of C 1 may be derived direcly from Figure A as a funcion of he raio / L and of he produc k'. Figure A Figure A Figure A Figure A

19 Figure A Deerminaion of C 1 17

20 A.3..5 A Piping in wide-rench condiions or posiive projecing embankmen condiions Definiion a) Projecion raio. The projecion raio, q r, is defined in Figures A and A and he mos commonly used values are given in Table A Table A Values for he projecion raio q r Angle q r , , , ,75 Figure A Figure A

21 b) selemen raio. The selemen raio, C ass, is defined as follows: C ass S1 S T1 T (A ) S 1 where (see Figure A ) S 1 S T 1 T NOTE selemen of he backfill adjacen o he piping, measured beween he naural ground plane and he horizonal plane conaining he op of he piping; selemen of he naural ground under he backfill adjacen o he piping; selemen of he piping ino he naural ground; deflecion of verical heigh of he pipe. Two cases may be envisaged afer back-filling: The backfill above he piping seles less han he res of he backfill. In his case, which corresponds o a «rigid» piping, (see NOTE ), he shearing forces a he boundaries will end o increase he load on he piping and he selemen raio will be posiive. The backfill above he piping seles more han he res of he backfill. In his case, which corresponds o a «semi-rigid» or «flexible» piping (see NOTE ), he shearing forces a he boundaries will end o lower he load on he piping and he selemen raio will be negaive. Figure A

22 Table A gives a se of values recommended for his selemen coefficien for he mos curren cases: Table A Selemen coefficien C ass «Rigid» piping on rock or firm soil 1,0 «Rigid» piping on ordinary soil 0,8 o 0,5 «Rigid» piping on unconsolidaed soil 0,5 o 0 «Flexible» piping wih non-compaced backfill on each side «Flexible» piping wih slighly compaced backfill on each side «Flexible» piping wih well compaced backfill on each side «Flexible» piping wih opimally compaced backfill on each side NOTE 1 E E A piping may be considered as a «rigid» piping if: e D ord o 3 1 0,4 o 0, 0, o 0 0 o 0,4 0,4 o 0,8 NOTE In he case of a «rigid» piping which does no undergo any deformaion and if he foundaion soil is incompressible, he selemen coefficien is equal o 1. c) plane of equal selemen. The plane of equal selemen is defined as he plane above which he selemen of he backfill above he piping and ha of he backfill adjacen o he piping are idenical. The disance, e, from he plane of equal selemen o he op of he pipe may be deermined from he following equaions: C ass 0 e k e Do C ass 0 k D o e k q r C ass 1 (A ) e k e Do k D o e k q r C ass 1 (A ) NOTE The value of e may be derived direcly from Figure A

23 Figure A Plane of equal selemen Deerminaion of e 1

24 A Calculaion of he load due o backfill The load per uni lengh he piping is subjeced o is given by Equaion A F C D e (A ) The coefficien C is given by he following equaions: a) e : virual plane of equal selemen C ass 0 o o e D k C D k 1 (A ) C ass 0 o o e D k C D k 1 (A ) b) e : real plane of equal selemen C ass 0 o e o e e e e o ' D k D k D k C 1 1 (A ) C ass 0 o e o e e e e o D k D k D k C 1 1 (A ) The value of C may be derived direcly from Figure A for differen values of k.

25 Figure A

26 A.3.3 Deerminaion of he loads due o live loads A Concenraed live load In he case of a concenraed live load F c in Newon, he load per uni lengh he piping is subjeced o is given by Equaion A : Fc F7 C7 C (A ) dyn L C 7 C 71 C 7 B C71 arcan A A B A Rr A B Rr Rr A R r A Rr C B 7 B The coefficien C 7 may be obained direcly from Figures A and - wih: A L/ B D o / C dyn 0,3 1 Srees and roads 0,6 1 Railways and airpors 1 Saic concenraed loads L Piping lengh, loaded by F c (equal o 1 if he acual lengh of he piping under consideraion exceeds 1) F c Concenraed live load R r A B 4

27 A.3.3. Disribued live load For an area load of p r in N/m², he load per uni lengh he piping is subjeced o is given by Equaion A : F 8 C 8 p r D o C dyn (A ) C 8 C 81 C 8 B C81 arcan B B A A B A Rr A B Rr Rr A R r A Rr C8 The coefficien C 8 may be derived direcly from Figures A and - wih: A L B D o Dimensions of he projecion area affeced by he area load C dyn 0,3 1 Srees and roads 0,6 1 Railways and airpors 1 Saic loads p r Surface pressure due o disribued live load R r A B Area load 5

28 Figure A

29 Figure A

30 A.3.4 Deerminaion of he momens acing upon he piping A General The equaions given hereafer permi he deerminaion of he momens a any poin of he piping wall for differen loading cases. The superposiion of hese differen cases make i possible o accoun for he behaviour of his piping. The sresses () may be derived from he values of he resulan momens M () using he following equaion: A.3.4. ( ) A M ( ) I / v Momens due o backfill and live loads Load per uni lengh Figure A sin Dm M ( ) Q π (A ) where D m is he mean diameer; Q is he oal load per uni lengh wih Q F 1 F 7 (where A is applicable) F 8 (where A.3.3. is applicable), if A.3..4 is applicable; or Q F F 7 (where A is applicable) F 8 (where A.3.3. is applicable), if A.3..5 is applicable. 8

31 A Disribued load In order o ake accoun of backfill and live loads, a less conservaive mehod is given hereafer. Figure A where 0 / Dm 1 3 cos M ( ) q sin (A ) π 8 3 π / D m 1 1 sin cos M ( ) q (A ) π 8 3 π q is he load per uni lengh, relaed o he mean diameer Q q ; D m D m is he mean diameer. A Dead load of he pipe D m cos M ( ) pcw π sin 1 (A ) where p cw is he weigh of he pipe per circumferenial uni lengh. 9

32 A ydrosaic pressure 3 pw D cos M ( ) m 1 π sin (A ) where p w is he uni weigh. A Taking accoun of he bedding condiion (e.g. coninuous supporing on sand bed) Figure A qoal Dm M ( ) U K cos π sin cos cos (A ) π qoal Dm M ( ) U K cos π (A ) wih U sin (cos 1) K sin cos (A ) (A ) where q oal is he disribued oal load (backfill load, dead load and hydrosaic pressure). A.3.5 Global sabiliy of a buried piping sysem A General The procedure oulined hereafer allow o check he sabiliy of a buried piping affeced by operaing pressure and operaing emperaure changes, for service emperaure above 35 C. 30

33 A.3.5. Noaions For he purpose of he following paragraphs he noaions hereafer shall apply in addiion o hose in A.3..: S Cross-secion of a pipe Thermal expansion facor Change in emperaure beween mouning emperaure (backfilling) and operaing emperaure c Circumferenial sress in a pipe caused by inernal posiive pressure D m Mean diameer of he pipe W p Weigh per uni lengh of he pipe I Ineria of he pipe S Cross secion of he pipe E Young modulus of he maerial of he pipe Rulim Allowable deformaion facor of he soil A Load due o pressure and emperaure on a sraigh par of a piping F a S (E 0, c ) (A.3.5.3) A Reacion of he soil R Dm an 45 Dm (A.3.5.4) A Deerminaion of he effecive lengh The effecive lengh of a sraigh par of a piping is given by he following equaion: Leff Fa Q Feff (A ) where F eff '' ( D m W p ) (A ) wih 0,5 Sludge - Clay 0,4 Sand 0,3 Gravel 31

34 A Resrained pipe For a sraigh par of a piping, when he sum of he effecive lenghs deermined a each end of his par where relevan is less han he acual lengh he following checks shall apply. A Sabiliy of he resrained par Criical load F 4, p q E I S (A ) c 09 where p μ" q q a a 0 8 Dm 0, 9, W p Dm q 0, 9 Wp 0, 8 an 45 an Dm and 0,8 and 0,9 are safey coefficiens. Allowable load Fc Fall (A ) 11, The design is accepable if: F a F all (A ) This verificaion shall be performed wih or wihou pressure in he pipe and wih or wihou backfilling. A Longiudinal compressive sress in he resrained par L E 0,3 c (A ) where L is he circumferenial sress due o pressure. The design is accepable if: L 0,9 R e (A ) wih R e as defined in EN :01, Table

35 A Sabiliy of he effecive lengh of he pipe Criical load for a radius elbow/bend 1,5 D F 3, p q E I S (A ) c 5 Allowable load Fc Fall (A ) 11, The design shall be accepable if: F a F all (A ) A Sress in he effecive lengh of he pipe Facor K K m (A ) R ulim R D D m Elongaion of he effecive lengh aking accoun of fricion (for informaion) Y 1 1 F a R (A a) S E or Y 1 1 Fa RLeff (A b) S E Facor, c, R 1 4 K 4 β (A a) E I c F β S E F K eff a (A b) R' c c Fa (A c) Toal elongaion (for informaion) Y R' β K (A ) --```,,`,,`,`,,,``,`,`` 33

36 Bending momen M R' β f (A ) The design is accepable if: A M I v 0 R f f, 9 (A ) e Unresrained pipe For a sraigh par of a piping when he sum of he effecive lenghs is greaer han he acual lengh he procedure given in A shall apply using Equaion (A b) and for L f he calculaed value or L if L f L. 34

37 Annex Y (informaive) isory of EN Y.1 Differences beween EN :004 and EN :01 The 01 ediion of EN conains he 004 ediion of he sandard and he Amendmen(s) and/or correcion(s) issued in he meanime. Significan echnical changes include: Revision of 5. relaed o he design of he buried piping. Addiion of he new Annex A relaed o he calculaions for buried piping. NOTE The changes referred include he significan echnical changes bu is no an exhausive lis of all modificaions. 35

38 Annex ZA (informaive) Relaionship beween his European sandard and he essenial requiremens of EU Direcive 97/3/EC This European Sandard has been prepared under a mandae given o CEN by he European Commission o provide a means of conforming o Essenial Requiremens of he New Approach Direcive 97/3/EC. Once his European Sandard is cied in he Official Journal of he European Communiies under ha Direcive and has been implemened as a naional sandard in a leas one Member Sae, compliance wih he clauses of his European Sandard given in Table ZA.1 confers, wihin he limis of he scope of his European Sandard, a presumpion of conformiy wih he corresponding Essenial Requiremens of ha Direcive and associaed EFTA regulaions. Table ZA.1 Correspondence beween his European Sandard and Direcive 97/3/EC Clause(s)/subclause(s) of his EN Essenial Requiremens (ERs) of Direcive 97/3/EC, Annex I Qualifying remarks/noes 3.1 b) and 7 6 (a) and 6 (g) Piping as referred o in aricle 3, secion Design for adequae srengh b) Calculaion mehod 8.1 o Corrosion Annex A..3 Calculaion mehod WARNING Oher requiremens and oher EU Direcives may be applicable o he produc(s) falling wihin he scope of his sandard. 36

39 Bibliography [1] EN 13941:009+A1:010, Design and insallaion of preinsulaed bonded pipe sysems for disric heaing 37

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