Overcoming Engineering Challenges in Riser Design

How grooved solutions have been making contractors and engineers reimagine the way they construct risers in vertical buildings.

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Enter into the right pub or head to a city’s museum or town hall, and you can often find a picture of how the surrounding area used to look. An image from 20 years ago and the difference isn’t too vast. 50 years back and there’s a definite change. A picture from over 100 years ago and it’s practically unrecognisable. And what’s the common theme running through these images? Cities are getting taller.

As more people migrated to urban areas, developers saw the need to go higher. But with this comes its own unique set of challenges. How can the safety of the ground floor be transferred to, in the most extreme case, level 163? To find out how grooved mechanical pipe joining solutions are helping developers and engineers go higher, FC&A spoke to Matthew Strohm, Director of Product Development Piping System Design at Victaulic.

When it comes to high-rise buildings, there are a number of potential challenges a piping engineer will need to take into consideration, most of which relate to thermal movement and the resulting forces on the building. Other issues such as seismic activity and building creep (the natural movement of a building due to settlement) also need to be taken into account.

Specifically related to piping systems – and subsequently, pipe joining solutions – is the unique problem of having to compensate for thermal expansion and contraction while at the same time accommodating for higher pressure. Change in pipe diameter is not an uncommon concern for engineers; however, providing a solution which could operate at a pressure gauge of 25 bars, or the fluctuating temperature of water, presents its own challenges.

It’s with these issues in mind that engineers choose their joining solutions, which is why these are the very criteria we set our Victaulic pipe joining solutions against.

Grooved vs traditional pipe joining

For decades, the traditional solutions for joining pipes have been either welding, threading or flanging. These are good solutions to choose from, but there is a distinct lack of flexibility in a solution which fuses or flanges system components together. This is where flexible grooved couplings come in: a best-in-class solution that allows controlled linear and angular movement at each joint to accommodate not only for thermal expansion and contraction but also building sway and creep.

So how do flexible grooved couplings manage this? It’s essentially down to the design of their components. The dimensions of the pipe coupling housing key are narrower than the pipe groove, allowing room for movement. Furthermore, the width of the pipe coupling housing allows for pipe end separation, which, in turn, allows the grooved pipe joint to accommodate movement.

There are many benefits of grooved couplings, with space-saving being a key advantage on projects both large and small. As many project managers and engineers know, saving on space can be the key to unlocking extra value above initial planning. Additionally, grooved couplings are perfectly placed to accommodate for piping movement whereas welded joints, which in their very nature are designed to be fixed in place, need to have an area of space to allow for a welded expansion loop or alternatively, enough space to allow the star-pattern tightening of a flanged flex connector.

Besides the savings on space, grooved connections offer contractors savings in three key areas: time, money and labour. The installation-ready design of Victaulic’s grooved couplings allows for easier installation, meaning a process which might take 30 minutes through a welded solution, for instance, can now take five. As any contractor will testify to, this is valuable time which can be used for other parts of the project.

With a reduction in time comes savings in cost and labour. Naturally, less labour is used for the same job and, in the case of grooved couplings, less skilled labour is required (in comparison to the high skill level needed for welded joints). It’s these aspects which will ultimately deliver contractors with valuable project savings.

Mechanical riser solutions

There are three ways to accommodate thermal movement within risers using a grooved mechanical system.

The first method is called the top of riser free floating method and involves installing rigid couplings on the riser and two flexible couplings on the adjacent horizontal piping at the top of the riser, which can reduce the need for riser clamps or other structural elements during installation and allows the system to move freely within the design tolerances.

The second method involves working with grooved expansion loops which help to save up as much as 2/3 of the size of welded U-shaped expansion loops and avoids forced welded pipe deflection. While welded expansion loops require eight welded joints to assemble, the forces exerted on the joint are far greater than those applied on a grooved expansion loop and generate greater stress, which ultimately requires larger anchors and guides in order to direct the movement.

The third method is working with grooved expansion joints instead of traditional in-line expansion joints, which typically have wear parts and manufacturer–recommended maintenance cycles of five years, which also poses problems due to riser accessibility once the construction is complete. Grooved expansion joints like the Victaulic Style 155 are maintenance-free for the life of the system.

Importance of anchors

In a system using only flexible joints, risers are installed with anchors at the top and bottom and the piping guided every other length to prevent angular deflection at the joints within the piping run. Anchors distribute the movement forces across the structure and also provide the important task of directing pipe movement. At the pipe anchor location, there will be no differential movement between the piping and the building structure, which forces the pipe to thermally expand or contract from that location. This allows the design engineer to control how and where the movement in a system occurs and to provide the best solution to accommodate that movement.

A good manufacturer will always listen to customer demand, especially in an evolving market, and off the back of strong feedback from contractors, Victaulic recently upgraded its A10 grooved riser anchors to a standard product. With the primary functions of carrying the weights and forces which act downward to the base of the riser and connecting the riser to the rest of the structure, the anchor has been providing sturdy support for some of the tallest buildings around the world.

Future trends for high-rise buildings

One trend already taking place, and I expect to continue, is contractors bringing riser experts into the project at an earlier stage. It just seems to make logistical sense to operate in this fashion; it’s a more efficient use of time to collaborate early in the process. I believe contractors and engineers will seek assistance from companies such as ourselves to help design blueprints together, working in tandem to produce the right solution.

Vertical buildings are on the rise. For generations, people have been moving to urban areas, putting greater demand on housing residents and employees. Through the use of grooved coupling solutions as an alternative to traditional methods, contractors can benefit from greater flexibility, reliability, ease of installation and ultimately and most importantly, speed of the installation process.

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