Getting to Grips with Electrofusion Jointing

7 August 2015

electrofusion fitting

Our technical support engineer, Bob Warren, discusses some of the frequently asked questions we receive about electrofusion jointing.

Polyethylene (PE) plastic pipes are widely installed throughout the water and wastewater treatment industry as the material of choice for conveying water, yet the electrofusion method of jointing the pipelines are beginning to develop a poor reputation. Bob Warren answers some of the FAQ questions we receive on the subject.

Why have some water companies banned the use of these fittings?

 There has been a lot of publicity surrounding the integrity of electrofusion fittings, due to a report published by UKWIR, which the industry focused on the headline stating that 1 in 5 electrofusion joints would fail before their expected lifetime. Despite later publishing a statement that confirmed its report had been misinterpreted and reinforcing the message that “PE pipes have the lowest failure rate among different materials used in the construction of water mains” and identifying “poorly constructed electrofusion joints” as the problem, the damage had already been done.

The initial report cast doubts over the integrity of this method of jointing and has led to some water companies banning the use of these fittings without properly understanding the real issues. In contrast to industry beliefs, analysis of products that have been returned, reveals that less than 1 in 10,000 fittings are returned to manufacturers due to product failure.

How does electrofusion jointing work?

Electrofusion is a method of joining plastic pipes by using fittings with built-in electric heating elements, which are used to weld the joint together. The pipes to be joined are cleaned, inserted into the electrofusion fitting and a voltage, of typically 40V, is applied for a fixed time depending on the size of the pipe and fitting being installed. The built in heater coils then melt the inside of the fitting and the outside of the pipe wall, which melts together to produce a very strong homogeneous joint.

What applications can electrofusion fittings be used for?

Electrofusion jointing can be used to join new pipelines, which are conveying water, gas and sewage along with various other applications. The exception is with projects in which plastic pipe is inserted into existing iron pipes as a cost effective way for water companies to upgrade their pipe networks. For insertion applications, butt fusion welding is preferred as this method of jointing results in one continuous pipe, offering easier maintenance.

How long will an electrofustion joint last?

If the pipe has been prepared in accordance with guidelines and the jointing process has been carried out correctly, by a competent installer, the fitting is expected to last as long as the lifetime of the pipe system and a minimum of 50 years.  

What can be done to ensure joints don’t fail?

The majority of fittings that leak do so because of poor quality workmanship or incorrect installation practices of the fitting. The three main causes of joint failure when using electrofusion fittings are:

-        Poor joint preparation

-        Contamination of the joint caused during the jointing process

-        Misalignment of the pipe within the fitting

These failings occur due to poor site practice and poorly skilled installers of the pipe systems. In order to reduce the number of joint failures, and subsequent water leakage, the whole industry needs to adopt a cultural change to work together to address the issues of installation best practice and electrofusion skills.

There are three areas of improvement that need to be addressed:

Site Practice - with support from manufacturers, contractors and installers need to be ensuring the highest standards of installation. Manufacturer guidance on the installation of their systems needs to be to be enforced, while pipelines should only be fitted by knowledgeable, skilled and qualified professionals.  

Robust equipment - from torque spanners and hot plates, to pipe alignment clamps, the installation equipment must be robust, reliable and fit for purpose. It is also imperative that the correct equipment is used and not bypassed with the aim of completing the installation more quickly.  

Quality control - confirming that a genuine, leak-free joint has been made is critical and so a clear quality control procedure needs to be implemented, including on-site pressure testing and regular auditing and feedback to facilitate improvement.

What other jointing methods can be used?

The other commonly used method of jointing PE pipe in the UK is Butt Fusion welding, which involves heating two planed surfaces against a heated surface, after a specified amount of time the heating plate is removed and the two pieces are pressed together and allowed to cool under pressure, forming the desired joint.

As with electrofusion jointing, it creates a homogenous joint and is comparable in terms of cost and speed of installation so it often comes down to application. Butt Fusion jointing requires more equipment so can sometimes be more costly on smaller pipe diameters, but can work out more economical on sizes above 90mm. The semi-automated process of Butt Fusion welding also reduces the risk of human error and as such failure rates are significantly lower.

The other jointing technique that can be used is socket fusion, which uses custom-shaped and sized heating plates rather than a basic flat surface. These heads allow for more surface contact, reducing the time needed to heat and fuse the pipe. Socket fusion requires less pressure than butt-welding and is more commonly used on smaller sizes of pipe 90mm or less.

Other European countries seem to have strict regulation controlling pipeline joints, what is in place in the UK?

Water utilities in countries across Europe take far greater responsibility for the jointing of pipelines, compared with those in the UK, with many requiring welders to be trained and third party certified before they are allowed to undertake such work.

In the UK, there has been a relevant training and certification standard available since 2003; ‘BS EN 13067: 2012 – Plastics welding personnel: Qualification testing of welders and thermoplastic welded assemblies.’ However, this standard has not been adopted by the UK water industry, which has led to poor workmanship and ongoing problems with the quality of electrofusion jointing.

The UK water industry also has its own standard for product specification; WIS 4-32-08 ‘Fusion Jointing of Polyethylene Pressure Pipeline Systems’. Yet this standard is just advisory not mandatory.

European countries have adopted a different set of standards to the UK and training bodies provide certification in accordance with DVS standards, with DVS 2207-1 and DVS 2212-1 being the relevant standards that are used. Both of these standards cover electrofusion, Butt Fusion and Socket Fusion jointing methods.

The process descriptions of these standards are no different to those available in the UK, but they include some specific requirements in relation to quality and training including ‘every trainer has to be trained and in possession of a valid qualification certificate’ and ‘the welding work must be monitored’.

These standards, along with the existing WIS guidance, need to be adopted and made mandatory in the UK. The entire water industry needs to take responsibility and work together towards achieving zero leakage by 2050.

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