Polyethylene pipe fusion explained: Part 2
In part one of our mini two-part series on polyethylene pipe fusion, we talked about the process behind ‘butt fusion’, and explained how it’s the main method used to connect PE pipes for gas connection – you can read it here.
In this blog, we’ve explained the basics of ‘electro-fusion’ – a method of fusion which the Squire contingent also experienced at the pipe fusion training course.*
This is another widely-used method of used to form joints and to install fittings, valves etc. on Polyethylene (PE) pipes. Electro-fusion still involves the bonding of PE through the application of heat, but unlike butt-fusion, it’s exclusively used for fusing fittings to pipes, (e.g. elbows, bends, connection fittings, tee-pieces, PE to steel transition pieces and suitable valves etc.), rather than only to joint one pipe to another. Although, PE pipe lengths are regularly jointed to another section of pipe by means of electro-fusion couplings when the pipe material, diameter and application is deemed suitable.
Pre-Joint Checks and Pipe Preparation
The preparation for electro-fusion is similar to butt-fusion, in the sense that the pipe needs to be free of contaminants, but the method of operation, bonding and the fusion process itself is very different. The area for fusion is marked out on the pipe wall and subsequently hand-scraped, using a device similar to a carpenter’s plane.
[‘marking area’ | ‘hand scraping’]
The operative must scrape away all evidence of the markings, as their removal will indicate that the surface has been adequately prepped and is clean. The preparation ensures that any oxidised polymers or other contaminants are removed as if present, these will have an adverse effect on the fusion process.
The electro-fusion process is again fully-automated by a fusion machine.
[‘Electro Fusion machine’]
Again, as with butt fusion, it requires considerable input from an experienced, trained operator, particularly with regard to pipe diameter, SDR, alignment, monitoring etc. For most pipes, the voltage used for electro fusion is 110v-39.5v, but for pipes >315mm dia, the voltage ranges rises to 110v-80v.
Fittings are located in situ on to the pipe and are then clamped in to position, to avoid any movement between the joint/fitting and the pipe. Cables from the electro-fusion machine are then attached to the points on the fitting.
[clamping the tee | clamping the elbow | attaching the fusion cables]
An electric current is then passed through the nodes which sit on the fitting and the automated fusion process begins. Fusion indicators on the fitting joint, (tiny little nodules), will pop up to show that a successful fusion operation has occurred,
[fusion indicator shown]
If these fusion indicators do not appear, then the integrity of the electro-fusion operation is deemed unsuccessful and the joint/fitting is cut out. Then the process is started over again. As with butt-fusion jointing, the results are scrutinised very carefully by our experienced operatives, looking for any indication of a joint failure. We allow no gas pipe into the ground until one of our competent engineers is 100% confident that the joint is correctly sealed and bonded and that it is fit for purpose.
Once the fusion operation is deemed successful, the operative will complete the works required. As with butt fusion technique, everything, from start to finish of the electro-fusion process, and every joint and fitting is checked and monitored by our experienced, trained operatives and once the appropriate works are completed, the pipe and fittings, including everything from the connection up to termination point is then tested for soundness, before being purged with gas. Then gas can flow, all is fit for purpose, `as laid` records are completed and reinstatement can be arranged.
With natural gas in the network travelling at velocities anywhere between 15m/s and 40m/s and at various pressures, it is vital that every single pipe connection that we undertake is competently carried out and correct. Our team of highly trained and experienced operatives, professional engineers, managers and support staff, monitor and control every part of the process – from quotations, design, procurement, installation, testing and handover. We ensure everything is carried out to the highest level of safety, quality and to industry procedures and recommendations.
Squire Energy invests heavily, both in time, recruitment, training and resources, particularly in these examples, in the science of pipe fusion, so that we can continue to install gas pipes and gas networks throughout the UK, safely, effectively and efficiently.
We hope that this guide has given you a helpful, albeit brief, insight into one of the fundamental processes of fusion pipe jointing, which underpins a significant proportion of the work that we undertake.
For anyone wishing to see general examples of the fusion operation underway, you may wish to access www.youtube.com as there are a number of examples available. Squire Energy does not however endorse any such content or examples.