Why AIM33 for EF joints of PE pipe?

1
Why AIM33 for EF joints of PE pipe?
2
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!

3
For the use of EF joint.

• 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
• 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.

4
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.

5
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.

6
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 equipments
  performance for expected life time and safety.

7
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?

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

8
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

9
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

10
Factors causing failure in service

• Internal gas pressure loading
• Bending stress
• Fatigue
• Cracking
• Ground movement such as earth quakes and a ground
  subsidence

11
Need to ensure integrity of EF joints

• 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
• 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) Non-Destructive Testing
  of Electrofusion Joints and Large Diameter Gas
  Pipes
• 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) Non-Destructive Testing
  of Electrofusion Joints and Large Diameter Gas
  Pipes
• 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.

14
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.

15
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.)

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NDT need for PE piping system (2)

• I.J.Munns and G.A.Georgiou, (TWI), Ultrasonic
  and Radiographic NDT of butt fusion welds in
  polyethylene pipe
• 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.

17
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)

18
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

20
Previous NDT studies for EF joints

• T.H. Striplin, (McElroy) --- Tradition A-scan
  methodIt 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

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Innovative Nondestructive Evaluation System
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.