process feature | Trenchless pipe installation
pipe pressure testing is then recommended. Pfirrmann said the system allowed fast and easy
installation, with just a single operator. “The full pressure rating of the saddle, combined
with the precision of the tooling, maintains total pipeline integrity,” he said.
Testing time for tees Pedrom Tayefi, a research engineer at Sheffield University in the UK, has studied the effect of contami- nation on the performance of electrofusion tapping tees. “Premature electrofusion failures are predominantly
Wavin’s TS DOQ pipe relies on Total’s XSC50 material
Africa – where leaking metal pipes were replaced with Wavin TS DOQ pipes. “The PE100-RC concept was developed in partner-
ship between our companies and we have used it extensively in our Wavin TS DOQ pipes,” said Glanert. “In this project, the PE100-RC pipes were welded seamlessly into one long section and were ideally suited to be pulled below ground through the existing pipe.” The slow crack growth resistance of the material
helps to ensure that surface damage during the burst lining and long time point loads are covered by the TS DOQ pipe.
On the saddle Georg Fischer Piping Systems presented details of a way to streamline the electrofusion (EF) process that is used to join large sections of pipe together. Ingo Pfirrmann, head of global products and services
utility, told delegates that tee joints are conventionally installed by way of a coupler – either by EF or butt- fusion (BF) welding. But he said there were downsides to these methods: the potential for axial misalignment; and the time taken for handling. He said that using an electrofusion ‘branch saddle’
reduced the number of joints needed: rather than needing a coupler and two butt fusion joints, or three couplers, this method uses a single EF joint and one saddle that sits on the surface of the pipe. A tapping device secures the saddle to the pipe wall. “There is flexibility for saddle positioning along the
length and around the circumference of the pipe,” he said. “Only the butt fusion jointings for the pipe sticks are necessary.”
Pipes should ideally have very low ovality, but this
can be assessed and corrected using special pipe ‘re-rounding’ tools, he said. After saddle installation,
34 PIPE & PROFILE EXTRUSION | October 2014
due to poor workmanship,” he said. “This can be categorised as: misalignments; poor scraping; and contamination.” He cited figures from UK Water Industry Research, which said there were three or four failures per 100km of PE pipe every year in the UK – and enough leakage to supply 40% of consumers. Tayefi built a rig to test EF tapping tees. It was capable of short- and long-term static and dynamic pressure tests. It also carried out a long-term dynamic (fatigue) loading experiment, based on WIS 4-32-08’s talc test. WIS 4-32-08 is a specification for jointing PE
pressure pipeline systems using PE80 and PE100 materials. The pipe was subjected to a ramp in pressure of 25 bar/minute. Initial results suggested: fatigue failure is possible
for contaminated parts; fatigue life decreases with increased pressure; and the predictability of failure decreases as pressure does the same. A second round of testing used ultrasonic post-fail-
ure analysis, in an attempt to observe the leakpaths of failed joints. – and identify potential trends. Tayefi said there were limitations to the results: only
a single product from one manufacturer was tested, and there were difficulties in linking fatigue failures with burst history. And while no trends for leakpaths could be found,
with respect to pressure range, he said that the ultrasonic technique showed promise for post-failure leakpath observation. “The rig is currently being redesigned,” he said.
On stony ground Omani pipe extruder Muna Noor has commissioned an extrusion line from Tecnomatic, to make multi-layer PE pipe – which it says is the first in the Middle East. Multilayer pipe offers a practical solution to
problems in the installation and jointing of PE systems, providing high security at little extra cost. By combining the best materials for specific loading conditions, they provide protection and long-time durability. The new
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