Polyethylene potable water mains with an assumed minimum design life of 50 years have been in widespread use in the water industry for more than 30 years.
In the 1980s and 1990s Severn Trent Water in the UK buried two polyethylene pipe test beds in the Midlands. These two test beds near the pumping stations at Great Gates and Coopers Green, had all the pipe material analysed chemically and mechanically before installation. This was documented in several studies as well as the subsequent exhumations in the following years.
So Electrofusion.. it’s a mix of electricity and fusion but what does that mean?
Electrofusion, or EF for short, is a method of joining PE pipe in situations where butt fusion is not practicable, like where valves, elbows and tees need to be added.
Specialised electrofusion fittings have electrical heating coils imbedded into them. When current is applied to these EF fittings, heat is created which melts the plastic of both the fitting and the pipe.
The plastic from both are forced to mix together under pressure due to the design of the fitting. Once the mixed plastic cools, the pipe and fitting are fused together permanently.
How does EF welding work?
The parameters of each fitting, like the fusion time, are recorded in the barcode on each fitting. These details are entered into the welding control box via a barcode scanner or some control boxes automatically detect a fitting’s settings when it is connected to the machine’s leads.
An electrofusion control box sends electrical current through metal coils inside the fitting. The current causes the metal to heat up. The plastic around the coils begins to melt and forms an expanding pool of hot, molten plastic. The melt pool from the fitting comes into contact with the surface of the pipe. The continued application of current causes the pipe surface to also melt.
The pipe melt and fitting melt is forced to mix as pressure builds up in the coupler area, due to the design of the fitting, forcing the two plastics together. This is key to producing a good weld. Following the end of the weld cycle, the fitting and the pipe are left to cool and the melted material solidifies to form a permanent joint.
Hot and cold zones, sometimes called melt and freeze zones, are formed when the wire coils heat up. The length of these zones is key to achieving melt pressure. The precise positioning of the coils in the fitting is also important to ensure uniform heat distribution.
Fusion parameters: temperature, pressure and time, are controlled by the electrofusion control box and it is fed parameters from the barcode on each fitting, or from the fitting itself. The electrofusion control box also records a report of the procedure with all the settings and data from the weld.
PLASSON has developed the SmartFuse system, which includes specialist fittings, a range of EF weld control boxes and an mobile phone app which guides installation, to help simplify the whole electrofusion process. Using the SmartFuse system makes welding quicker and easier. The automated process helps reduce errors and prompts installers to complete and double check all steps. You can read more about SmartFuse and watch our demonstration videos here…
The non-brittle and flexible characteristics of polyethylene make it ideal for many pressure and non-pressure applications. Those useful characteristics also mean PE pipe can alter shape. Ovality generally known as ‘out of roundness’ is one of the most common issues found in PE pipe. One of the best tips to ensure a quality electrofusion weld is to ensure that polyethylene pipe is not out-of-round before attempting the electrofusion process.
To determine if out-of-round conditions exists measure the pipe diameter in numerous directions across the pipe end with a tape measure. If the measurements exceed the maximum tolerance, a re-rounding clamp or device must be used to bring the pipe back to a round condition.
HOW DOES POLYETHYLENE PIPE BECOME OUT-OF-ROUND?
Installers need to confirm that polyethylene pipe matches all dimensional requirements for the job and the fitting being installed and that the pipe does not exceed the allowed ovality. If ovality is greater than allowed you must take steps to re-round the pipe.
Polyethylene pipe that is warehoused for a period of time or stacked on top of each other can experience ovality issues (more pronounced with large diameter pipe).
Large Diameter Polyethylene pipe will tend to relax a little during storage due to a combination of its weight and its natural flexibility.
Mechanical forces experienced during some trenchless installation techniques such as Pipe Bursting or Directional Drilling can temporarily leave the polyethylene pipe elongated and out-of-round.
Polyethylene pipe that has been underground for awhile is subjected to earth loads. These earth loads can cause the pipe to sag and/or become out-of-round.
WHY IT IS KEY TO ADDRESS PIPE OVALITY FOR ELECTROFUSION INSTALLATIONS
One of the most critical functions of the electrofusion process is to seal the gap between the pipe and the fitting and to build up interfacial pressures for the fusion process to take place. If this gap is not sealed and interfacial pressures cannot build up, there is no way for the electrofusion joint to effectively achieve the high quality fusion it was designed for.
If a pipe is out-of-round the initial concern is that the surface area of the pipe may not adequately come in contact with the fusion zone of the electrofusion fitting. This could result in the electrofusion fittings cold zones, which are designed to contain the material generated in the melt pool, allowing the molten material to escape out of the fusion area without producing any melt penetration. This is a key concern when installing tapping and branch saddles since they do not fully encircle the pipe like an electrofusion coupling.
HOW TO CORRECT OUT-OF-ROUND PIPE
First, determine if out-of-round conditions exists. This can be done visually for extreme cases or by measuring the pipe diameter in numerous directions across the pipe end with a tape measure. If the measurements exceed the maximum tolerance, a re-rounding clamp or device must be used to bring the pipe back to a round condition.
The following table shows the approved dimensions for PE100 pipe:
The PLASSON range includes high quality tools to prepare pipe correctly for electrofusion, inlcuding re-rounding clamps.
Click here to see PLASSON’s tooling range….
PLASSON’s SmartFuse mobile app is designed to make electrofusion simpler and more efficient. And it is 100% free to use and always will be.
PLASSON’s SmartFuse offers a weld recording and reporting system. When using the app, installers are not only guided through systemised welds, the app ensures photos record each step. These visual records are stored along with details for the fitting being installed, the precise location, the installer’s ID, all control box weld stage times and data and even the temperature on the day!
This data can be saved on site via USB, which is handy in remote areas with limited internet access, or automatically in the cloud. This gives managers and asset owners a real-time comprehensive picture of what is happening on any job, anywhere, anytime
WATCH HOW THE SMARTFUSE APP SIMPLIFIES ELECTROFUSION
Why PE makes sense and cents!
This industry is pumped full of letters and numbers – like SDR11, HDPE, PE100 and PN16. There is handy information in those codes that explains exactly what amazing PE can do. And, when it comes to the different grades of PE, or polyethylene, the magic of what each one delivers is definitely in the detail.
You will find LDPE widely used in plastic packaging or plastic wrap. HDPE is often found in construction and plumbing. And UHMW PE, which is many times stronger than steel, is a high-performance plastic used in bulletproof vests!
The process that makes PE a success was developed in the 1950s by two scientists, Karl Ziegler of Germany and Giulio Natta of Italy. Polyethylene is now one of the most widely produced thermoplastics in the world. It’s light and strong – it’s cheap to transport, easy to handle and safe to store making it a smarter choice than most other materials – especially when it comes to PE pipe.
Polyethylene, like other plastics, starts with the distillation of hydrocarbon fuels into lighter groups called “fractions”. Some can be combined with other catalysts to produce plastics (typically via polymerization or polycondensation).
Low-Density Polyethylene (LDPE) is a very flexible material with unique flow properties that makes it particularly suitable for shopping bags and other plastic film applications. LDPE has high ductility but low tensile strength, which is why it stretches when strained.
Ultrahigh Molecular Weight Polyethylene (UHMW) is an extremely dense version of polyethylene. It is spun into threads with tensile strengths many times greater than steel and used in bulletproof vests and high-performance equipment.
High-Density Polyethylene (HDPE) is a robust, moderately stiff plastic with a highly crystalline structure. It is used to make all types of strong and tough containers. The HDPE used to produce corrosion-free, long-life pipelines for water, waste water and gas is called PE100. PLASSON’s range of poly pipe joiners are designed to easily and securely join PE100 pipelines.
PE is classified as a “thermoplastic” (as opposed to “thermoset”), based on the way the plastic responds to heat.
Thermoplastic vs thermoset
One of the benefits of thermoplastics is they can be heated to their melting point, cooled, and reheated again without degradation. By contrast, thermoset plastics can only be heated once. The first heating causes thermoset materials to set (a bit like a 2-part epoxy), resulting in a chemical change that cannot be reversed. These properties are what makes PE ideal for gas pipelines joined by electrofusion fittings like the PLASSON SmartFuse range.
PE is rugged, flexible, and durable. Both the pipe and PE pipe fittings have outstanding chemical and environmental stress crack resistance. PE pipelines have been successfully used in a wide variety of applications for over 50 years. Add to that strength and corrosion-resistance, and you get a life-span far in advance of other pipe materials.
Here’s a quick look at pipe colours and codes for those new to the game or keen to brush up:
Polyethylene pipes, or PE pipes, have been produced in Australia since the mid 1950’s. The industry started small with diameters like 20mm, 32mm and 63mm for industrial and agricultural applications but PE pipe and fittings are now available in diameters up to 2000mm.
PE pipe has grown rapidly in popularity and polyethylene pipe connected by compression or electrofusion fittings is now largely made from PE100. This is the third generation of PE and it delivers high performance, long-life PE pipes that will provide reliable service for 100 years or more.
PE100 pipe is used to convey all types of liquids and gases for above and below ground applications including:
- Urban water and gas supply
- Mine dewatering
- Irrigation supply
- Slurry pipelines
- Vacuum, pressure and gravity sewer systems
- Submarine pipelines and ocean outfalls
- Trenchless pipeline installation and rehabilitation
- Industrial process pipe work
- Compressed air services
- Electrical and telecommunication cable conduits
- Upstream coal seam gas and water pipelines
Polyethylene pipe has a coloured stripe extruded into the pipe wall as a permanent reminder of what it is inside. These are the main colour codes you are likely to come across when joining PE pipe with compression or electrofusion fittings:
BLUE = potable water
RED = fire mains
LILAC = recycled/grey water
YELLOW = gas
GREEN = rain water/raw water
CREAM = sewer
Polyethylene, or PE, pipe has been successfully used throughout the world for more than 50 years. The main benefits of PE pipes and fittings are corrosion resistance, high strength, toughness and flexibility, so it’s no wonder it is a popular choice worldwide.
Aside from the colour indicating what is being carried by the pipe, there is valuable detail printed on the pipe too.
What is PN?
PN is printed on the pipe. For blue stripe potable water pipe this is usually PN16. The acronym PN stands for Pressure Nominal. When a pipe has a rating of PN16, it is designed to handle 16 Bar internal pressure.
Poly pipe comes in a range of pressure ratings:
PN10 which has a maximum pressure rating of 1000kpa
PN12.5 which is for a maximum of 1250kpa
PN16 for a maximum of 1600kpa
What is OD?
The OD is also printed on the pipe. This is the Outside Diameter, or OD, of the pipe measured in ‘mm’.
Then there is also the acronym SDR, which stands for Standard Dimension Ratio.
When the outside diameter of the pipe is divided by the wall thickness, it gives the SDR of the pipe.
These are important measurements to know and understand when installing pipes that will carry anything under pressure.
Why choose PE100 pipe?
It has an optimum balance of three key properties: Minimum Required Strength (MRS) – this provides long-term strength and creep resistance. Stress crack resistance (sometimes referred to as slow crack growth resistance). Rapid crack propagation resistance.
Pipe that carries potable water in Australia is made from PE100 which is a type of plastic resin that has been proven to have a minimum required strength (MSR) of 10 MPa at 50 years and 20 degrees celcius. The operational service life of PE pipelines is dependent upon a number of factors that include: raw material quality, processing conditions, installation, the aggressiveness of the fluid transported, operating pressure and temperature.
PLASSON began over 50 years ago and has grown into a global family of over 2,000 people.
Our Australian team is based all over the country. From Kalgoorlie to Cairns, Toowoomba to Tassie, we have PLASSON people on hand to help.
PLASSON are constantly working on new things but we will never change our commitment to excellence, service and support.