Municipality Minimizes Disruption Using Flexible Metal Piping

Problem

In order to control energy costs, a municipal building was to be connected to an existing district heating system prior to the building starting construction.

To complete the connection, the local utility company would have to run two 6-inch district heating pipes underneath a busy downtown road to the location where the building would be built.

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To avoid interfering with the infrastructure already in place beneath the road, conventional rigid pipe would have to be installed at a depth of 18 feet. This would require the road to be heavily trenched, for a welder to work well below the surface, and for local traffic to be disrupted for an extended period of time. Upon review, the city declined a construction permit for the project.

Solution

After the construction permit was rejected, the utility company began to explore horizontal directional drilling (HDD) using flexible piping as a potential solution. Swiss-based Brugg Pipe Systems is the only pipe manufacturer to offer flexible piping for HDD applications. Brugg's product FLEXWELL piping for district heating has a double-walled steel construction that can withstand the loads caused by using the HDD method.

Unlike rigid pipe, FLEXWELL piping can be installed in one continuous length and around obstacles without the use of trenches, elbows, or expansion loops, reducing the number of welds and labour requirements. FLEXWELL pipe is delivered on reels to facilitate it being safely and easily uncoiled and pulled through the tunnel in a controlled manner.

Once the HDD tunnel has been dug and is ready for the pipes to be pulled, the FLEXWELL pipes are attached to the end of the drill with a pulling head and pulled through the tunnel to the other side where the connections can then be completed above ground.

The pipe can be pulled on it’s own or in a bundle with other pipes and cables. This would allow crews to pull all required connections from the location of the new building at once, eliminating the need to dig deep trenches, send workers to weld below the surface, or disrupt traffic.

Once the project shifted towards an HDD approach, the construction permit was approved to move forward.

Brugg’s patented FLEXWELL pre-insulated pipe is a double walled stainless steel design with integrated leak monitoring specifically designed for use in district heating.

Impact

This project marked the first installation of FLEXWELL pipe in Canada. It was important to ensure that construction crews were trained in proper installation methods. Armour Valve worked with Brugg and the construction crew on-site to prepare the team to install the FLEXWELL safely and effectively.

Armour Valve has three factory-trained and certified technicians who provide on-site supervision and training to ensure that Brugg pipe installations move forward as quickly, safely, and efficiently as possible.

The ability to pull a large section of pipe through the horizontal tunnel allowed for significant time savings during installation. The drilling and set-up of the FLEXWELL and additional cabling took approximately one week while the time to pull the pipe through the tunnel was less than a day (~7 hours). The bundle of pipes pulled included the two 6-inch FLEXWELL supply and return lines, fibre optic cables, and two 10-inch HDPE pipes.

Not only did the cost of using HDD and FLEXWELL compare favourably with the cost of installation of rigid pipe in this project; the combined benefits of the FLEXWELL pipe design and HDD solution enabled the project to move forward with city approval.

The connection of the new municipal building to the existing district heating system and resulting energy savings would not have been possible using conventional piping and installation methods.

Brugg FLEXWELL pipe on spools ready for installation
The length of each spool of FLEXWELL pipe depends on the width of the pipe. Smaller pipe diameters allow for longer spool lengths. The maximum length of a reel of 6” pipe is 230 metres. Seen here are the 2 spools used in this installation.

Impressed with the FLEXWELL product and speed of installation, the utility company is currently working with Armour Valve to complete a second installation of Brugg pre-insulated piping solutions using a combination of their rigid PREMANT and flexible CASASFLEX pre-insulated piping.