HDPE Pipe – A Complete Guide
HDPE used to be the plan B pipe material for a project. But, HDPE pipe is now in its fourth generation of development and there has been a paradigm shift in its use worldwide. HDPE is no longer a secondary option for projects big and small, but a necessity. If you work with pipes, or just want to learn everything about HDPE pipes, this is the article for you.
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Many sectors have historically relied on concrete, metal, and clay for pipe products. However, because of the pressing need to keep production costs down and maintain quality, performance, and efficiency, HDPE pipes have become the preferred material of choice for nearly any project.
Today, HDPE pipes are a necessity as they are built to address modern-day challenges in contemporary development. As demand for water, gas and many more industries continue to soar, the use of HDPE is on the rise and is expected to keep growing.
Technical innovation and development are continually propelling HDPE as a superior material of choice in various applications.
Are Hdpe Pipes Worth It or Are We Biased to Their Use Due to Their Cost Effectiveness?
It wouldn’t be much of an article if the answer was yes. The costs are undoubtedly a significant plus, but what good would HDPE products be if they couldn’t stand the test of time?
HDPE pipes are a favourite for their ‘green’ attributes as they can safely convey potable water, wastewater, hazardous waste, chemicals and even compressed gases. We’ll look at the how the pipes are manufactured later in the article, but you can read more about HDPE material in its entirety:
To put it all in perspective let’s have a look at everything you need to know about HDPE pipes starting with a brief history.
1. Historic Development of HDPE Pipe
The first ever polyethylene (PE) pipe was produced in 1933. But, the manufacturing costs were extraordinarily high, and chemists had to find new and innovative ways of reducing costs while achieving better yields. After a staggering 20 years, they finally had a breakthrough.
In the 1950’s, the first HDPE pipe was created by chemists working at the Phillips Petroleum Co.
HDPE materials were first used to manufacture baby bottles since it was safe and didn’t break like glass bottles used at the time.
Here’s a short timeline of HDPE’s rise to fame:
In the late 1950’s, hard-wall HDPE pipe began taking over the functions of metal pipes in gas and oil gathering systems.
In the 1960’s PE started replacing iron pipes in nearly all distribution systems. Soon enough, HDPE took over the functions of clay pipes in agricultural drainage frameworks.
In the 1980’s, HDPE pipe made headway with advanced diameter width and was corrugated to become a better replacement for metal and concretes in the construction of stormwater culverts.
Today, HDPE is a thermoplastic resin that has continued to evolve throughout the centuries with constant developments in its performance capabilities. They are currently in the fourth generation stage of development. Its uses have diversified to replace glass in bottling and metal making of bails, gas tanks, and drums.
20 years into the future, HDPE pipes are expected to replace cast iron, concrete, and steel in all piping and conduit systems. Which promises a great future in a variety of sectors, including:
- Natural gas distribution
- Potable (drinking) water
- Industrial chemicals conveyance
- Oil and gas production
- Underfloor heating
- Mining (slurry and leachates)
- Road heating and cooling
A fairly quick rise to fame and it’s not slowing down anytime soon.
2. How Are HDPE Pipes Manufactured
HDPE, like many other thermoplastic materials, does not possess cross-linked molecular chains and therefore can be melted after application of the right amount of heat. Manufacturing an HDPE Pipe relies heavily on the melting point of PE – the temperature at which the plastic gets to an entirely amorphous state (between 120 to 180 °C (248 to 356 °F).
What Form is HDPE Before it’s Melted?
HDPE starts out as pellets, also known as thermoplastic resins. At this point, the first stage of quality control should take place. The raw material quality to be used to manufacture the pipes is the first essential (and necessary) step towards compliance with the specified requirements of a quality finished product.
Most companies use three different types of HDPE pellets which are well mixed before adding it to the hopper – plain, recycled and pellets with colorants for UV protection. The mix ratio depends on the specific application of the pipes. If the pipes are going to be buried or used as culverts the need for UV protection is limited, but not excluded as the pipes will still be exposed to UV during installation.
“Depending on the application of the pipe
the quality testing could be very in-depth,
or at least should be if the manufacturer
is worth their salt.”
Which means it would use less coloured pellets for productions. Typically, the process starts by feeding the thermoplastic resins into the extrusion machine using a hopper that feeds the pellets onto a rotating screw using gravity. The rotation of the screw moves the plastic along the heated barrel.
As the plastic runs along the channel depth decreases, forcing the plastic through a smaller area. The combination of compression and screw rotation causes friction and rotation, called sheer heating. This heat, with the heat of the barrel, melts the HDPE (at a temperature of about 230 degrees Celcius.) By the time it reaches the end of the line, the material is melted down and hot enough to go through the die.
The hot and melted HDPE is then forced through a die which then causes the solid particles to align in an extruding cavity. After which it can be molded, shaped, and extruded to be formed into a pipe. The hot liquid HDPE is then injected into the pipe mold while applying vacuum pressure for even distribution. An even flow is essential to maintaining the overall integrity of the final product. Any variations in the flow can produce weak areas.
The molten plastic then flows evenly around the mold to form and results in the diameter of the pipe being produced. A built-in cooling system hardens the plastic just enough to set the shape, enabling the pipe to be extracted from the mold. The pipe then passes through a cold shower to completely harden the plastic.
Random pipe samples are then selected for quality inspection. Depending on the application of the pipe the quality testing could be very in-depth, or at least should be if the manufacturer is worth their salt.
3. HDPE Pipe Quality Control
Resistance tests performed to determine impact strength. Test of tensile strength to test the reaction of the pipes to tension forces. Deflection temperature tests that ensure that the HDPE pipes conform to international standards by deforming under a specified temperature.
Other QC Tests Can Include:
- Visual Inspection
- Mechanical Inspection
- Compression Strength Test
- Density Test
- Material Traceability
- Dimensional Accuracy
- Hydrostatic Pressure
- Smoothness and finishing
- Tensile Test (basic tensile test video here)
Quality Assurance is based on PE 80 and PE 100 designations. This is essentially International ISO standards regulating the material design and Minimum Requirement Strength (MRS) of the materials. The PE 80 and PE100 regression tests according to ISO 9080 standards are particularly relevant to the manufacturer. These quality assurance tests tell the manufacturers if the HDPE pipes can offer 50 plus years of service under normal operating conditions. Further specifications can be found here: ISO 9080:2012 The regression analysis allows us to predict the minimum strength for a specific service lifetime accurately.
The data is extrapolated to ascertain the minimum strength at 20°C and at the specified 50 year lifetime. It’s rare to find a manufacturer that doesn’t comply with ISO standards, as a bare minimum! And it should be a major red flag if ISO standards are not in place. But, the standards adopted by each country differ. In the USA you’d need to comply with ASTM standards, but in Europe, you’d need to comply with EN and EN ISO, in the UK with BS and BS CP and so on.
This makes it essential for your manufacturer to know the difference and have all their certification in order! You can find a full breakdown of Polyethylene Pipe Standards here.
You can see the process in this nifty How it’s Made video:
4. What to Expect From A Good Supplier
Only the best of course! But, we’re not always that fortunate are we? Before choosing an HDPE pipe supplier, it’s prudent to know what you’re looking for.
Indicators That You’re Dealing With a Legit HDPE Supplier:
- The supplier should be well connected in the infrastructure industry. If they understand the market, they would know the best products to offer you. This can be quickly established with a single email with a few key questions or a quick phone call.
- The supplier provides bulk orders. This means they are used to high volume output, and you can rely on their lead times and your high-demand.
- A good service record. A company that prides itself on service has a slim chance of offering low-quality products.
- Go to a vendor that is hands-on in the development, research and production of HDPE and possibly similar plastic materials like PVC, PPR, PP, PEX etc. But, be careful of a supplier claiming to be a one-stop shop, often you’ll find that these are middlemen and don’t manufacture themselves.
- The supplier is somewhat flexible on cost. More quantity equals discounted pricing. Most people don’t like price hustling for a price, so a supplier that gets to the point is a good sign. It’s easy enough to promise drastically lower prices than the competition, but buying cheap for the sake of buying cheap has more risk than reward.
5. Why You Should Use HDPE Pipe
By now, you would have realised that we’re major proponents for HDPE, but here are a few unbiased reasons HDPE is as good as we say it is.
HDPE pipes are resistant to chemicals that could corrode the pipe. The pipe is chemically inert and doesn’t conduct heat or electricity. It, therefore, doesn’t provide an enabling environment for reactions to take place in the pipe. Thus preventing alterations that would affect its overall performance and longevity.
HDPE pipes can replace concrete pipes in sewer systems to save time and costs taken in repairing pipes that crack or burst. HDPE pipes are also the least costly option when compared to other piping materials concerning overall performance and installation costs. The pipes are light and easy to handle which cuts material handling and installation cost significantly.
Superb Flow Characteristics
HDPE is smoother than iron, concrete or steel. It has less drag (resistance) and a tendency for turbulence, especially at high flow rates. Its ‘non-stick’ feature makes it perfect for maintaining the fluids hydraulic characteristics. Even corrugated HDPE pipes are molded in two stages so the inside can be smooth.
Lightweight and Flexible
HDPE pipes are manufactured in either solid straight or flexible coiled lengths. It’s made from lightweight materials that are easy to transport and does not require heavy equipment for installation like heavy duty cranes. The combination of lightweight and flexible properties makes it perfect for earthquake-prone areas. The pipes are not brittle and can be easily installed in bendy terrain without additional couplings or welds.
6. HDPE Pipe Applications/Uses
HDPE pipes are used in water mains, service pipes, and sewer reticulation systems. They are also used for making conduits for cables in electrical installations.
HDPE pipes are used in cold water reticulation systems and house connections. They provide ducting for air-conditioning and refrigeration.
Due to the solid wall of HDPE pipes, they are used for irrigation in water supply schemes and suction lines. HDPE pipes are resistant to soil corrosion and salty water making it perfect for drainage and irrigation applications.
The HDPE pipes are used in domestic sewage systems for sewer effluent control and water purification in sanitary systems. In the petrochemical industry, HDPE pipes are used in the conveyance of most chemicals and the conveyance of potable water.
HDPE pipes are used extensively in both surface and underground operations and slurries. They are used in the transportation of fluids and chemicals, and pit and mine dewatering in open mine operations. HDPE sheets not discussed in this post are also used for linings in heap leach ponds for processing on gold mines, read more here.
HDPE pipes are used for supply lines and floats. They can withdraw a large amount of cold water from large water bodies. HDPE pipes also facilitate Trenchless technology that entails rehabilitation of existing pipelines with minimal disruption to the surface.
7. Ongoing Research
Research and Development is a major area of focus in HDPE, and a lot of experts are continuously working to further HDPE technology. Economic viability dictates that you can save more money in the future by spending more upfront, buying cheap is buying expensive. If you’ve ever seen someone tearing up concrete to fix a busted pipe you will certainly agree with us on that statement.
HDPE pipes are made to last for decades. But, how do you produce such a long-lasting piping solution without spending more on quality assurance and control? You spend more on the raw materials. You can request a certification stating the quality of the raw (pellets) HDPE before you even start manufacturing, something to keep in mind.
8. HDPE Pipe Size Chart
Click on the image above to redirect you to a comprehensive HDPE Pipe Specification chart, or simply follow This Link.
The bottom line is HDPE pipes that are manufactured according to standards are tough, durable, flexible and have enormous environmental stress crack resistance.
Be sure to look at the HDPE size charts to know which pipes fit your application for what they will be used for. Ensure that you get a reliable supplier/manufacturer for top-tier quality. Do not compromise on cost for quality and always go with someone who can guarantee you the pipes you ordered.
If you have anything to add regarding HDPE pipes why not leave a comment in the comments section below and get the conversation going?