Using Butt Fusion to Join Piping Systems

The science of butt fusion results in leak-free joints for today’s modern thermoplastic piping systems replacing conventional piping systems that are failing across the country. A crucial part of any new installation is the selection of a fusion machine that will cater to your jobsite’s specific needs.

Wheeled fusion machines are towed with another piece of equipment.The science of butt fusion results in leak-free joints for today’s modern thermoplastic piping systems replacing conventional piping systems that are failing across the country. A crucial part of any new installation is the selection of a fusion machine that will cater to your jobsite’s specific needs.

The Theory of Butt Fusion

The principal of heat or butt fusion is to heat two pipe ends to a designated temperature and fuse them together by application of force. This pressure causes flow and mix of the melted materials resulting in fusion. As the joint cools, the two pipes become one homogeneous pipe. The fusion joint is as strong as or stronger than the pipe itself. Here are a few tips to get you going on machine selection.

Pipe Size

What size range of pipe and wall thickness will you be working with? This determines which size carriage or combination of carriages you may need. Fusion machines are available for pipe as small as 1/2-in. copper tube size (CTS) to as large as 2,000-mm outer diameter (OD).

The pipe size range, dimensional ratio (DR) and the particular fusion standard being followed will dictate whether a low-, medium- or high-force fusion machine should be used on your job. Typically, when fusing pipe with high interfacial pressures, a medium- or high-force cylinder
is required.

Magnitude of the Job

How much fusing will you be doing and where will you be doing it? If you are fusing smaller-diameter pipe in the confines of a ditch, a manual butt fusion machine may be all you need. These compact machines will fit in tight work spaces more easily. They are lightweight and can be physically carried from joint to joint yet they are rugged enough to perform fusions all day long.

But if you are fusing a very long pipeline with medium- and large-diameter pipe, you will want to consider the portability of the machine and how much accompanying equipment — such as generators and hydraulic power units (HPUs) — you are willing to haul around. Fusion units mounted on a wheeled chassis or track systems are good options because they allow for greater mobility.

The wheeled fusion machines are towed with another piece of equipment to the fusion area and remain stationary as sticks of pipe are fused and pulled through. Many are self-contained as well, generating their own electricity and hydraulic power, so you don’t have to transport those items separately.

The tracked machines are not only self-contained, but they are self-propelled which offers greater freedom of movement even across rugged terrain. They can remain stationary at your fusion site or easily move between fusion locations. Whether a rolling or track machine, the fusion unit can be easily removed for in-ditch fusion. In tight installations, the outer fixed jaw and skid can be removed for an even more compact fusion unit.

If there are many fusions on schedule for the day, opting for the hydraulic clamping feature should be strongly considered. Operators using manual fusion machines rely on their own strength to apply fusion pressure and can become fatigued. A lot of time and effort can be saved when the necessary muscle is hydraulically-powered. On the other hand, the most powerful machine may not make sense if only a few fusions are being done. A more lightweight and economical machine in the line of fusion products may be a better option.

Deadlines

What is your deadline? Time is of the essence on most jobsites. Taking advantage of productivity tools to expedite your fusion process can help you turn out long runs of fused pipe each day saving time and money.
Powered pipe-handling systems can hold a day’s worth of pipe at the jobsite. A series of adjustable racks lift and feed pipe into the fusion machine which increases productivity by 150 percent and eliminates costs for the extra manpower and heavy machinery that would be needed otherwise.

Pipe stands hold the fused pipe lengths level with the machine which helps maintain the alignment for ongoing fusion processes. Pipe rollers work well to pull long lengths of fused pipe long distances. These kinds of productivity tools allow the fusion to be staged in one area.

Installing coiled pipe is also performed more quickly with equipment designed to straighten and re-round an entire coil of pipe with a minimum of two fusion joints. 

Data Collection Requirements

The advantage of choosing machines with hydraulic power, even for pipe as small as 2 in., is the built-in data logging capability which keeps a record of each fusion joint.

Data collection is being required on more and more jobsites today so that joint integrity can be verified. A consistent routine of data collection can provide assurance that fusion joints are safe and sound before they go in the ground, potentially avoiding costly expenses to extricate and repair questionable joints.

This is especially important to contractors, pipeline owners and engineers as new regulations continue to emerge that require better record keeping and increased accountability for those creating and managing pipeline infrastructures.

Data logging tools are becoming more and more advanced in an effort to capture information in a variety of ways. GPS tagging targets fusion locations, built-in 5MP cameras capture fusion alignment and barcode scanning is used to input data from pipe and fittings. Easy-to-interpret graphics record the key parameters of the pipe fusion process such as heat and cool times and fusion pressures which help determine if the operator performed the fusion correctly.

There are also devices that will physically determine the ductile and tensile strength of fusion joints by destructively testing a fusion joint coupon. Laboratory testing along with side bend and tensile testing in the field can be used in the development of new materials, qualifying operators, quality assurance for existing materials or in fusion compatibility to determine lot uniformity, strength and fusibility of pipe and fittings.

Maintenance and Operator Training

In addition to machine selection, two other factors must be strongly considered for a successful fusion operation: maintenance of fusion equipment and well-trained operators. Both are achieved by taking advantage of on-the-job, hands-on and classroom training that is available which helps promote efficiency, productivity and safety.

Equipment that is properly maintained can last for decades and not only saves the contractor time on the job but also ensures that the proper fusion parameters are achievable. A properly trained operator is more productive and attentive to the step-by-step procedures recommended to make quality butt fusion joints. A qualified work crew will enhance the bottom line on any construction project.  

Susan Hylton is a Public Relations Specialist at McElroy.

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