A new mechanical joining solution from Victaulic offers outstanding performance capabilities for high density polyethylene pipes
By David Sharkey, Victaulic VP-GM of South Asia Pacific
High density polyethylene (HDPE) is light-weight, corrosion-resistant, flexible, long-lasting and economical, so it’s an ideal material for underground buried and outdoor exposed pipelines.
While HDPE poly has been available for over 50 years, recent adoption of the piping material is quickly replacing steel, concrete and ductile iron piping. It is the fastest-growing piping material in mining, municipal, industrial and commercial applications, with a conversion rate to HDPE expected to increase by 5 per cent per year.
As the world’s leading producer of mechanical pipe joining solutions, Victaulic regularly communicates with contractors and engineers, gauging the requirements of the market and developing new technology to address the industry’s biggest challenges. In response to the growth of HDPE pipe across all markets, Victaulic has developed the Refuse-to-FuseTM system, a mechanical joint for HDPE piping. Strong and durable, the solution is starting to change the industry’s way of thinking about HDPE pipe joining. However, some misconceptions still persist about mechanical joining methods.
“For years, butt fusion and electrofusion have been considered the top joining methods for HDPE piping. People commonly overestimate the performance advantages of fusion; until now, it has been widely accepted as the easiest, most efficient method for joining HDPE pipe.
“The combination of fast and simple installation, integrity of design and structural reliability has seen mechanical joining become one of the most common joining methods for metallic pipe. The exciting news is these benefits are now available for HDPE,” said David Sharkey, Victaulic VP-GM of South Asia Pacific.
While mechanical joints are embraced in metallic piping applications, the market holds onto concerns about the performance and reliability of the technology for HDPE. This article uncovers the top myths about mechanical joining for HDPE.
Myth one: mechanical joints can’t be buried
The number one concern we hear is that mechanical joints may not perform as well as fused joints in buried applications. In actual fact, Victaulic mechanical joints for HDPE pipe have been specifically designed with buried services in mind, and are perfect for many underground environments.
Constructed of durable ductile iron housings and fluoropolymer-coated hardware, Refuse-to-Fuse couplings are protected from the most challenging underground environments. If there is an area where the engineer or property owner determines additional protection is required, a range of industry-accepted coating and wrap options are available.
Myth two: fusing provides stronger joints
While fusion has traditionally been seen as the “gold standard” in strength and reliability, empirical data may suggest otherwise. Historically assumed to be as strong as the pipe, the integrity of fused joints is at the mercy of many variables. A fused joint is only as good as the technician operating the machinery and tediously following a detailed process that leaves little room for fluctuations in environmental conditions. Surface contamination, windy
hot, or cold conditions, heating plate temperature control and fusion times can all impact the integrity of a fused joint – and there is no visual or effective non-destructive method to inspect the quality. The existing non-destructive testing methods, such as radiography and ultrasound “cannot reliably detect key issues that are known to affect HDPE joint quality such as fine particulate contamination, cold fusion in butt welds, or misalignment and contamination in electrofusion joints.1” Once completed, only time will tell how well the joint is fused.
To ensure the integrity of a fuse in the absence of any effective testing, equipment must be regularly inspected and properly maintained to record accurate temperatures and calculate appropriate heating and cooling times. A culture of continued training and professional development is crucial, limiting equipment operation to only those installers that have been trained and certified, and relying heavily on user competency to ensure that the processes are strictly followed.
Unlike fusion, Refuse-to-Fuse products use simple tools to install. The easy four-step process can be completed regardless of weather conditions and provides visual verification of correct installation – and joint integrity. By simply visually confirming metal to metal contact at the bolt pad, the installer can verify a leak-free seal. Ultimately, high-quality joints are not only easier to achieve using the Refuse-to-Fuse system, but also easier to verify than a fused joint.
For pipe sizes up to 225mm, Victaulic Refuse-to-Fuse mechanical joints install on plain-end HDPE pipe, with an internal stainless steel ring that bites into the pipe’s outer circumference. A common misconception is that the pipe will simply “pop out” of the joint, as the integral row of teeth might not provide a joint as strong as fusion. This is simply not true, as the
ring of teeth provides a fully restrained joint. In fact, Refuse-to-Fuse products have been proven to meet or exceed HDPE pipe pressure ratings, allowable tensile loads and bend radius recommendations of a fused joint. This means you can push, pull and drag2 your pipe like any fused solution.
Victaulic Refuse-to-Fuse is specifically designed with strength and durability in mind. In fact, under extreme pressure tests3, Victaulic mechanical joints have been shown to outlast HDPE pipes – meaning the pipe itself will fail under pressure before a properly installed Refuse-to-Fuse joint.
And for maintenance or expansion of the pipeline, the Refuse-to-Fuse system allows for quick and easy disassembly – without the need for expensive tools, specialist maintenance crews or lengthy downtimes. The components are completely reusable, so there’s no additional cost or downtime waiting for replacement parts.
Myth three: cut grooving the pipe creates a point of weakness
For sizes 250-900mm, the Refuse-to-Fuse system requires cut grooved pipe ends for the coupling to engage. It’s common for customers to ask whether cutting a groove into HDPE could impact the strength and structural integrity of the pipe.
The cut grooves for Refuse-to-Fuse couplings have been designed to a specific depth that allows the coupling keys to engage the groove, providing a fully restrained joint up to the working pressure of the pipe. Victaulic provides Refuse-to-Fuse grooving tools – and training on their operation – so the grooves are tightly controlled within the specifications for every pipe. The joint is designed so that the groove is filled with the keys on the coupling’s metal housing. Essentially, the reduced pipe wall thickness at the groove is reinforced by a restrained ring of iron – a much stronger material than HDPE to begin with. This design adds to the strength of the joint, rather than detracting from it.
The Refuse-to-Fuse system can be installed up to 10 times faster than fusing4. By using simple hand tools to tighten bolts and nuts, there is no need for expensive fusing equipment, power sources or certified fusion installers. Installation is weather independent, and can be completed rain or shine in any temperature. Since installation doesn’t rely on special equipment, multiple crews can work in parallel, and are not paced by availability of the fusing machines. This increases crew efficiency and cuts crew downtime on-site so you can finish projects ahead of schedule.
Finally, without the need for complex equipment, mechanical joints can be quickly installed in tighter spaces, difficult terrain and locations with limited accessibility that traditional fusing gear can’t reach. Fusing equipment is generally horizontally oriented, requiring pipe to be laying down in order to create the joint. Any vertical piping would need to be fabricated on the ground and lifted into position. Mechanical joints provide the ability for vertical spools to be constructed in-place, reducing the cost of construction with HDPE pipe materials.
Regal Engineering recently installed the solution at BHP’s Nickel West site, which has delivered strong productivity gains and cost efficiencies.
Michael Talbot, Maintenance Planning at BHP Billiton said, “Traditionally we have been limited to installing HDPE pipe using butt welds with stub flanges, but recently Regal’s piping division has introduced the 905 Victaulic coupling to us which has not only reduced the cost of repairs and installations, but has also reduced down time on site.
“We currently have couplings installed on our fresh water, process water and tailings lines and have been happy with the results so far and will be looking at further installations in the future.”
Myth five: mechanical solutions are expensive
While fusing may require hundreds of thousands of dollars-worth of equipment – depending on the size range of the project – the Refuse-to-Fuse solution eliminates the need for capital purchase and maintenance of these tools. Plus, because mechanical joining is faster and easier to install, projects can save on labour costs with fewer man hours required and no need for specially-certified workers. Overall, comparative studies of mechanical and fused projects have shown the Refuse-to-Fuse solution to be a competitively priced option.
“As leaders in the mechanical joining business, we are extremely proud of the Refuse-to-Fuse solution. At Victaulic, we’re passionate about educating the market about the benefits of our mechanical joints,” Mr. Sharkey said.
“Our solution exceeds HDPE pressure ratings, cuts down installation times, eliminates the need for expensive equipment and specialised workers and works in a range of underground buried and outdoor exposed conditions. What more could you want?”
1 https://www.pipeline-conference.com/sites/default/files/papers/ptc_2012_OConnor.pdf Page 4, Paragraph 2