As the world moves toward more sustainable infrastructure, high-density polyethylene (HDPE) has become the material of choice for piping systems designed to last a lifetime while remaining reliable and leak-free.
Since the 1960s, HDPE piping systems have delivered leak-free, long-lasting water infrastructure worldwide, with a growing presence in many large- and small-diameter construction applications. It is cost-effective and can be installed in a number of environments, such as densely populated urban areas, that would prove difficult for traditional piping systems. In particular, HDPE’s corrosion resistance and longevity make it especially appealing for water applications.
“HDPE piping systems are superbly suited for potable water applications because their corrosion-resistant material and heat-fused, leak-free joints ensure that water quality remains uncompromised over decades of use,” said Jim Johnston, McElroy Vice President and Chief Technology Officer. “Their flexibility, durability, and ease of installation not only reduce maintenance costs but also provide a sustainable, cost-effective solution for modern water distribution networks.”
WORKING WITH WATER
The benefits of HDPE in water applications go beyond corrosion and longevity. When butt fused according to standard, the joint formed by the fusion becomes as strong – or stronger – than the pipe itself. Unlike PVC and ductile iron pipe, which have “allowable water leakage” rates of 10 to 20 percent, fused HDPE has a leakage rate of zero.
When properly fused, HDPE doesn’t leak, so the risk of contamination from outside forces is eliminated. In addition, thermoplastic pipe does not support biological growth like other piping materials, and its chemical resistance make it a popular choice in wastewater and mine tailings applications.
According to the Plastics Pipe Institute, the polyethylene pipe industry estimates a service life for HDPE pipe to conservatively be 50-100 years, providing a tremendous savings in maintenance, both in terms of time, replacement parts, and wasted water.
CONSTRUCTION ADVANTAGES
With thermoplastic pipe, installation methods go beyond traditional trench-digging. Eliminating the need for a trench not only reduces the amount of manpower needed for installation – it also minimizes the disruptions around the site, such as streets or waterways.
Some trenchless installation methods include:
- Horizontal Directional Drilling (HDD) – During HDD, a pilot hole is drilled and expanded using drilling fluid. The pipe is then pulled through the drilled tunnel.
- Pipe Bursting – A specialized “bursting head” is pulled through existing pipe. As the existing pipe breaks apart, the new pipe is pulled into the space.
- Slip-lining – Like pipe bursting, slip-lining involves replacing existing pipe. With slip-lining, a smaller pipe is inserted inside a larger pipe. When using HDPE, removing the external bead allows the new pipe to pass through the existing pipe more easily.
- Plow and Plant – Useful in large, open spaces, plow and plant requires a plow to dig a trench. Pipe is installed in the trench as the plow passes by, and the earth naturally falls back over the pipe once it’s in the ground.
- Submerged/Floating Pipe – For environments where the pipe will run through stretches of water, the pipe can be either submerged or floated.
IN THE FIELD
In the United Kingdom, butt-fused HDPE was the material of choice for an expansive wastewater project to increase capacity for a new housing development.
The project was split into two phases. The first involved installing 10 kilometers (6.2 miles) of 560mm SDR11 through SDR17 polyethylene to connect new housing to the existing wastewater works. In its UK debut, the Tritan™ 560 from McElroy was used to perform the fusions.
Once the first phase was completed, fusion work began on the second phase, which consisted of 160m of 560mm of SDR11 pipe slip-lined into a concrete ducting. To accomplish this, the machine itself was lowered into a pit that sat 10m below level ground.
The machine was put into the pit using an on-site crane and lowered down by the three lifting points on the machine.
“On this part of the project, the excavation and tunneling didn’t allow for a TracStar® to be placed into the pit,” said Gareth Coley, a pipefitter for project sub-contractor Thermofuse. “The depth of the pit also meant that an in-ditch system would not be able to work. The only machine that was able to butt fuse within the confined space was the Tritan.”
Fused HDPE also played a large role in a waterway improvement project in Launceston, Tasmania. Recently, the Launceston City Deal was established to improve the health of the Kanamaluka/Tamar Estuary. As part of that effort, initiatives were launched to deliver infrastructure upgrades and pathogen reduction.
It is one of the largest projects of its type in the southern hemisphere, the improvements included construction of a new sewer line, requiring two river crossings and a trenched section completed using 900mm and 1,000mm SDR11 HDPE pipe.
The first river crossing consisted of 700 meters (2,296.6 feet) of 900mm SDR11 pipe that was installed 40 meters (131 feet) below the riverbed using horizontal directional drilling (HDD).
An additional 400 meters (1,312 feet) of pipeline connecting the two river crossings was installed and backfilled in preparation for the second river crossing.
Two fusion machines – McElroy’s TracStar® 1200i – were on-site to perform the fusions for this project job, with a smaller TracStar® 900 Series 2 used by a second contractor to weld the 900mm pipe used in the river crossing.
“These projects are all about working together to create a place where we can live well and leave a healthy environment for our children and grandchildren,” said Michael Ferguson, Minister for Infrastructure and Transport Treasurer. “We can’t wait to see the positive impact of these projects on our community and the environment.”
THE McELROY CONNECTION
The benefits of HDPE when compared to traditional pipe materials are clear: lower costs, longer lifespan, and fewer leaks. But a pipeline is only as good as its installation, and McElroy equipment is designed to boost operator efficiency while also meeting the extreme demands of each specific job site.
In each of the projects above, operators and project managers praised their McElroy machinery for its rugged reliability, adding that their project timelines were met – or even beaten – thanks in part to the efficiency added by the equipment.
McElroy’s machine lineup spans a wide range of features, both for trenchless and in-ditch applications. TracStar machines are self-contained and self-propelled, allowing them to be driven directly to the job. In the case of these trenchless water projects, the TracStars® eliminated the need for additional heavy machinery to move the machines from one place to another.
In addition to its fusion machine lineup, McElroy’s DataLogger® 7 allows fusion technicians to log all parameters of each fusion, providing an added layer of accountability. That data is stored in the McElroy Vault™, a powerful cloud-based tool that allows for instant, credentialed access to the fusion information from anywhere in the world. That extra layer of oversight – and peace of mind that each joint was fused correctly – is an invaluable addition to infrastructure that serves thousands of people each day.
The world’s water systems are changing. Conservation and efficiency are becoming a top priority worldwide. Along with qualified operators, McElroy continues to lead the way in ensuring that the HDPE water lines installed today will last for generations to come.
