1. A Training and Certification Standard for Fusion Welding of PE Pipes 4S Group Conference Stockholm Wednesday 15 th October 2014 Edward Ingham (Exova Utilities)

2. Introduction Failure statistics for PE joints in the UK Water Industry Causes of failure of PE joints Auditing of the welding process On site assessment of weld integrity Destructive testing Non- Destructive Testing (NDT) Training and Development of a UK National Training Standard

3. UK National Mains Failure Database (NMFD) Analysis of UK NMFD indicates 3.5 failures/100km/year for PE Rates possibly higher as repairs made without reporting Failures of service pipes not included in database Observed failures are not always correctly reported Reporting protocols often adapted from those for metal pipes

4. Polyethylene Materials Lessons learnt from problems with early low toughness materials Early PE materials (service pipes water) suffered from poor slow crack growth resistance Continuous development of PE 80 and PE 100 materials since 1960s Current PE materials have exceptional SCG and RCP resistance PE 100 materials tested to requirements in excess of current standards PE 100+ Association encourages high performance and consistency Exova research indicates PE 100 lifetime >200 years

5. Standardisation for PE Pipes and Fittings EN 12201 series of standards for PE pipe/fittings are satisfactory Some UK WIS requirements covered in National Foreword Certain areas are not adequately addressed Fusion lengths specified for electrofusion are minimum No tolerances for ovality of coiled pipes No contamination test for electrofusion fittings (WIS 4-32-08) Fittings >630mm (e.g. stub flanges not covered) Important tests (e.g. AREL) not covered in standards for mechanical fittings

6. UK National Mains Water Failure Database (<300mm)

7. UKWIR Report : Large PE Trunk Main Failures >300mm Diameter Extremely variable performance - How can this be improved?

8. Methods of Jointing of PE Pipe Systems Butt Fusion Welding (Above ground) Extremely reliable technique-historically extremely low number of failures Electrofusion Welding (In trench) More appropriate for installation in urban areas More sensitive to site conditions- disproportionate number of failures Failures due to misalignment, contamination, poor pipe surface preparation Jointing of coiled pipes significantly more difficult than straight lengths Mechanical Jointing (In trench) Reliable technique, but failures do occur due to poor assembly

9. UK National Mains Failure Database for Polyethylene

10. Butt Fusion Weld Failures Extremely reliable technique Failures extremely rare Contamination Pressure issues Insufficient heating

11. Heat Affected Zone in Weld Excessive pressure (single pressure) Typical weld bead

12. Failure of Mechanical Fittings Leakage A B C

13. Mechanical Fittings -Correct Assembly Good all round access to clamp bands

14. Suppliers’ ‘Vision’ of a typical trench On Site Welding Conditions The reality! Manchester in Summertime

15. Causes of Failure – Misalignment

16. Causes of Electrofusion Failures –Scraping of Pipe Poor scraping of pipe surface Hand scraping can leave areas of pipe surface intact Mechanical scraping ensure consistent/even removal of pipe surface

17. Causes of Electrofusion Failures -Contamination Particulate contamination due to poor site hygiene Incorrect use of welding wipes Correct use of welding wipes

18. Jointing of Coiled Pipes Large forces required to straighten pipe Pipe ovality causes gaps Two joints of potentially poor integrity

19. Solutions for Jointing of Coiled Pipes Reduce ovality at manufactureInserts to correct ovality Coil straightener to correct curvature

20. Assuring Good Workmanship Train Analyse Test Audit Continuous Improvement

21. Structured PE Competence Programme PE competence programme containing three elements that together address the root causes of poor joint quality

22. On-Site Joint Testing Demonstrate The implications of deviations from best practice (misalignment, poor scraping, etc) Give Immediate Feedback Provide advice on equipment and procedures to ensure joint quality Provide Positive Feedback Where correct equipment and procedure is used

23. WIS 4-32-08 ISO and Gas Geometry Destructive Testing of Butt Fusion Welds

24. Force / Deflection Data: Ductile & Brittle Welds Strength is equal, Energy (area under curve) is different Brittle Ductile

25. Assessment of Electrofusion Joints H P ‘encourage’ cracking P Cold Zone Starter Crack Side Grooves to P G Shear Test – full or part samples! F F Double Cantilever Beam (DCB) Hydrostatic Pressure Tests

26. Failure Modes of Electrofusion Couplers DCB Test DuctileMixed Brittle Voiding

27. Destructive Testing of Electrofusion Joints Site Audit Data All joints made specifically for audit purposes Welders were aware the joints would be tested

28. Destructive Testing of Electrofusion Joints Production Joint Data All joints taken at random from installed system prior to commissioning

29. NDT Testing of BF Welds (Very simple form) Twist bead an inspect for signs of splitting

30. NDT Testing- Microwave (MW) Imaging Material under inspection is bathed in microwave energy of an essentially constant frequency (≈ 25GHz) Energy is reflected from each interface of differing dielectric constants within specimen The reflected energy creates a resulting signal measured in volts The resulting voltage is sampled at discreet locations across sample to create an image Volumetric inspection technology: will view the entire thickness of the piece at once Channel A & B are a ¼ wavelength apart General Probe Configuration

31. NDT ( Microwave ) Evaluation of PE joints State of the art NDT methods available to inspect plastic joints in the field NDT techniques has been verified by mechanical testing Removes the need to cut out and destructively test joints. Immediate feed back regarding quality of joint. Testing can be done on new or in-service pipelines. The system can be used in conjunction with current site auditing practices to further improve the reliability and quality assurance of PE joints in the field. Fast assessment of joints

32. NDT microwave results of butt fusion joints PASS FAIL

33. Assessment of Weld Quality using Voltage Threshold

34. NDT Phased Array Results for Butt Fusion Joints PA-UT Field equipment Well fused region of EF joint Lack of fusion observed in EF joint

35. Issues with Current Training and Certification Some training courses based on UK WIS 4-32-08 Lack of National standard causes inconsistencies in training and hence competence Training is classroom based rather than under true site conditions All practical assessments use relatively small diameter pipes Practical assessments are on straight pipe and not coils Theory examinations too easy (everyone passes) No time limit before re-training/refresher training is required No system to address poor workmanship/or ensure corrective training is taken

36. Stakeholders Water UK Water Utilities PE pipe and fittings manufacturers Welding equipment suppliers Installation contractors of PE pipes Training companies Engineering Contractors

37. Administration of Standard and Qualification Expert group to be set up by Water UK Will review effectiveness of training and make change if necessary National database holding qualifications- held by UKAS accredited body Accreditation body to be appointed by Water UK

38. Structure of Specification Training Area EF 1 (20-180mm) EF 2 (200-315mm) EF 3 (≥355mm to 710mm) BF 1 (63-355mm) BF 2 (>355mm to 900mm) Electrofusion  -- Butt Fusion---  Service Pipes  ---- Distribution Pipes  Straight Pipe  Coiled Pipe  --  - Skinned Pipe Barrier Pipe  --  - Co-extruded Pipes  Branch Saddles  ---

39. Range of Qualification Standard will be for welding personnel and supervisors of welding personnel Aim to make personnel self supervising Supervisors retain status by continuous record of competency and on site welding every 6 months 3 Qualifications for electrofusion and 2 for butt Fusion Qualification will be modular (i.e. to gain EF 3 a welder must hold a current version of EF 1 and EF 2 ) For EF>710mm and BF >900mm specialist training from the fitting/equipment supplier and certificate of competence required Qualification valid for a period 3 years

40. Training for Electrofusion Welding

42. Training for Butt Fusion Welding

44. Theory Exam To ensure knowledge safe working/ production of high quality welds Separate exam for each qualification Exam will be 1 hour in duration with 20 multiple choice questions Failure to answer key questions will result in failure of whole exam Score of 80% required to proceed to the practical exam

45. Practical Test Carried out under site rather than classroom conditions Welding area set up in accordance with best safety and site practice Test to include welding of different pipe diameters Demonstrate ability to weld coils and handle long pipe lengths Welder and joints will be visually assessed Joints produced will be destructively tested

46. Welding Test Certificate Details of qualifications held on National database Welder provided with identity card containing qualification information Retention of qualification provided: Welding undertaken with regular frequency (no inactivity>1 year) No issue regarding knowledge or practical ability of the welder Employer shall establish the competency of the welder on an annual basis

47. Conclusions Draft specification well advanced. Publication hopefully in 2014 Strong basis on practical competency under site conditions Theoretical exam will be more demanding that at present Practical test ensures competency in joining coiled pipe Welders must show competency in welding large diameters before they are permitted to install these pipes on site Utilities can ensure competency of workforce by specifying the training standard in their procurement documents Standard will improve quality of installation and reduce leakage