Why AIM33 for EF joints of PE pipe?

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Polyethylene (PE) is good material for gas piping.

 M.Fujikake, M.Fukumura and K. Kitao, “ Analysis of the electrofusion joining process in polyethylene gas piping ” , Computer & Structures Vol. 64, No.5/6. Pp.939-948, 1997 – PE hardly corrodes and is very flexible, so it is safe from earthquakes and a ground subsidence. – It is also light and easily constructed.

 Many others agree!

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For the use of EF joint.

 M.Fujikake, M.Fukumura and K. Kitao, piping ” Pp.939-948, 1997 “ Analysis of the electrofusion joining process in polyethylene gas , Computer & Structures Vol. 64, No.5/6. – However, as for the large size PE pipes, there remains a fundamental barrier to the wide usage of the EF joining technique because of the absence of quantitative performance data and reliable computational models.

– The influences of power input, heating time and clearance size on the quality of the joints had been carried out by previous researchers.

– The quality will be heavily dependent on the temperature and the pressure at the interface region during the joining process.

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To make EF joints, we need

 To make EF joints, we need – a suitable range of heating time.

– a suitable range of interface temperature.

– a suitable range of interface pressure.

– a suitable cool-down time.

– a good preparation of the outer surface and inner surface of pipe.

– a good alignment.

– a welding equipment that can control heating time, interface temperature, and interface pressure.

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To improve joining process

 Jeremy Bowman (Fusion Group Plc), “ A review of the electrofusion joining process for polyethylene pipe system ” , Polymer Engineering and Science, April 1997, Vol.37, No.4

– User of EF fittings can gain guidance on the essential site practices from their fittings suppliers.

 Up to date, people focused to improve joining process to make good EF joints.

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Is the welding equipment intelligent enough?

 The present welding equipment indicate electric power supplied (fusion time).

 Can the present welding equipment indicate that – there are no flaws?

– the original PE piping and coupler are defect free?

– the EF coupler is made well?

– the interface pressure is good?

– there are no contamination at the fusion interface?

– the welding equipment itself is working properly?

– welding operators are not making mistake?

 We can not rely on the welding equipment ’ s performance for expected life time and safety.

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Is the pressure test assure joint quality?

Pressure test is an indirect method for leakage test.

Can the pressure test assure joint quality for expected life time of EF joints?

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We need direct inspection methods such as nondestructive testing (NDT).

Factors causing failure by EF joining process

    Factors on human errors; cleaning, clamping, cooling time, operation of welding equipment, gap between fitting and pipe Factors on equipment errors; equipment performance variation, degradation of equipment, frequency of electricity, input voltage, excessive length of electric cable, capacity of portable power generator at field, loose of connectors for fitting, contamination of connectors Factors on environment; temperature, rain, dust Factors on installation; bending www.kndt.co.kr

Factors causing failure by manufacturing process

   Factors on EF fitting; errors on implanting resistance heating wires, lamination between wire area and fitting, flaws such as void inclusion and cracks, size variation, contamination of terminal pin, inner surface contamination, geometrical deformation by environment, storage or/and transportation Factors on piping; flaws such as void inclusion and cracks, size variation, outer surface contamination, geometrical deformation by environment, storage or/and transportation Factors on material www.kndt.co.kr

Factors causing failure in service

 Internal gas pressure loading  Bending stress  Fatigue  Cracking  Ground movement such as earth quakes and a ground subsidence www.kndt.co.kr

Need to ensure integrity of EF joints

 Jeremy Bowman (Fusion Group Plc), polyethylene pipe system ” and Science, April 1997, Vol.37, No.4

“ A review of the electrofusion joining process for , Polymer Engineering – Significant loads are applied for extended periods of time. (PE pipe systems must sustain pipe hoop stresses of  8MPa for a typical design life of 50 years.) – The long term strength and integrity depends, in part, on the strength of the fusion joints.

– Since many of these system carry fuel gas, failure rates at joints must tend to zero.



It is essential to have direct inspection method such as nondestructive testing (NDT).

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The missing factor in EF joining system

 T.H. Striplin, (McElroy) Pipes ” “ Non-Destructive Testing of Electrofusion Joints and Large Diameter Gas – For years, the pipeline industry has had a means of non-destructive testing the welded joints that they installed. When plastics arrived on the scene, the rules changed. Since there was no valid means of inspecting fuse welded joints, the practice was discarded. …… Why not have the same tools available for PE pipe joints as are available for steel?

– At any rate, the missing factor in the EF joining system is the lack of a method for NDT.

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NDT needs for EF joints (1)

 T.H. Striplin, (McElroy) Pipes ” “ Non-Destructive Testing of Electrofusion Joints and Large Diameter Gas – Although the number of EF joint failures have dropped significantly, there is evidence that there is potential for EF joint failures as with any joining method. – While EF has been sold as an easier method of joining, it could be argued that it is as operator dependent and perhaps less trouble free than other methods.

– They were experiencing problems with failure primarily due to contamination.

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NDT needs for EF joints (2)

 T.Kitaoka and J.Furukawa, (Osaka Gas Co., Ltd.) “ Development of electrofusion interface ultrasonic inspection technique, contributing to construction of highly reliable PE piping ” – Strength of EF joint decreased when some foreign substances like water, mud, sand, and ect. was included on the fusion interface.

– Development has been awaited of a nondestructive joint inspection technique which can reliably detect any defective joint immediately after PE pipes are fusion-welded.

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NDT needs for PE piping system (1)

 G.J.P. ter Horst, F.G.E.B Weyn, R.J.M.Hermkens,(GASTEC N.V., The Netherlands) “ Ultrasonic inspection of butt-fused PE-joints ” (A project funded by EnergieNed, the Dutch branche organization for the energy distribution companies.) – For a long time the energy distribution companies in the Netherlands have expressed their need for ways of effectively assessing the quality of field-installed PE-pipe systems to prove integrity and reduce maintenance and repair costs. – This becomes especially important with the increased used of these PE-systems for higher pressures. (In these higher pressure systems, x-rays inspections are done as quality control on the steel pipe welds.) www.kndt.co.kr

NDT need for PE piping system (2)

 I.J.Munns and G.A.Georgiou, (TWI), polyethylene pipe ” “ Ultrasonic and Radiographic NDT of butt fusion welds in – As new polyethylene materials are introduced and increased demands are placed on existing polyethylene materials, there is an additional need to monitor quality through reliable non-destructive testing (NDT) methods.

– At one stage a guideline standard (ASTM F600-78) for the manual ultrasonic inspection of butt fusion welds in polyethylene pipe was introduced. Unfortunately, the results obtained using this standard were so heavily dependent upon the skill of the operator that it was withdrawn in 1991.

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Previous NDT study for butt joints

 Helge Petersen (Natugas Syd I/S, Denmark) and T.H. Striplin (McElroy), “ Examination of American and Danish butt fusion joints and test methods in thermoplastics material ” , Ref: 95612/HP/md/bd, August 1995 – Acoustic Resonance Technique method that was developed by Naturgas Syd in cooperation with the FORCE Institutes. (Basically, the idea of the method is to measure the attenuation of the transmitted signal as a function of time) – McElroy Test Procedures, /ULTRA-Mc/, (Pitch-catch and Pulse-echo with the S/W that goes through a decision tree and using the values from some of the 12 features) www.kndt.co.kr

PE system needs NDT !

 PE system needs NDT for both pre-service and in-service nondestructive testing  NDT is essential especially for fusion joints such as butt, EF, and saddle joints.

 Pipes with large diameter needs NDT.

 Ball valve need NDT.

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Nondestructive testing in PE system

    NDT will increase integrity and service life.

NDT will save money by reducing maintenance and repair cost.

NDT is strongly recommended to prevent man-made disaster by gas leakage.

NDT will help research for the development of the PE structures.

NDT should be included in the EF joining process to complete the quality control system for PE pipe installation.

NDT should be considered for the maintenance for the suspected positions of buried piping.

NDT should be considered to evaluate remaining life time estimation www.kndt.co.kr

Previous NDT studies for EF joints

 T.H. Striplin, (McElroy) --- Tradition A-scan method It is possible to detect some contaminations in EF joints. However, a more extensive project must be carried out to provide the true capability.

 T.Kitaoka and J.Furukawa, (Osaka Gas Co., Ltd.) -- Traditional B-scan www.kndt.co.kr

Innovative Nondestructive Evaluation System

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AIM33

 In 2003, new NDT methods for PE pipe system are developed by INDE System Co., Ltd in cooperation with Korea Gas Corporation.

 The unique capability of the AIM33 system allows for precise examination of the EF joint by obtaining real time ultrasonic images of the cross section of the EF joints.

 AIM33 overcome a lot of hinders that were introduced by previous NDT methods.

 AIM33 is easy to use in real field as well as lab.

 Normal fitter can operate AIM33 with a few hours of training.  Inspection results are provided by on-site real time images so that there are many functions available.

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