International collaboration to detect disturbances in the mains with fibre-optic technologies

Two technologies were tested: DALI (with Evides, Fluves NV and Vigotec NV) and BLAST (from Aragón Photonics). This was the first time TUBES had been used for a larger study. “That was a success as well,” says KWR researcher Amitosh Dash. “TUBES turned out to be ideal for practical tests that you would rather not do in an operational drinking water mains, for example because of hygiene risks or the disruption of the water supply.”

Mariëlle van der Zouwen (deputy KWR director) officially opens the TUBES setup at the end of a successful week of international research collaboration.

Using fibre-optic technology to determine pipe condition

Drinking water companies need a clearer understanding of the condition of their infrastructure, particularly the underground pipes that make up the mains network. There are a range of techniques for monitoring or describing the condition of pipes. One method involves using optical fibres that are sensitive to disturbances such as strain, temperature and pressure changes. By inserting these glass fibres through the entire length of the pipes and then sending laser pulses through the glass fibres, it is possible to detect disruptions in the mains.

DAS and DTSS

This is because a change in strain, temperature, or pressure and sound waves alters the way the light pulses in the fibres are reflected and propagate. Equipment linked to the glass fibres converts the information from the fibres into measurements of factors such as temperature, sound or strain. Two of these fibre technologies are Distributed Acoustic Sensing or DAS (for sounds/vibrations) and Distributed Temperature & Strain Sensing or DTSS (for temperature/strain).

During the workshop, Stefan Knijnenburg of Evides talks about the role of fibre-optic sensors in setting up the “mains of the future”.

International pilot projects in the TUBES testing facility at KWR

To test these technologies, a major international pilot study was conducted from April 17-20 at KWR in the TUBES testing facility. The pilot study was a combination of collective research for the water utilities BTO and an Evides research alliance with two technology suppliers. TUBES was originally designed and built at the KWR site to test the limits of autonomous inspection robots but it can be used much more widely. This testing facility is a good representation of the Dutch drinking water mains. At first glance, it looks like a maze full of pipes of various materials and diameters and all sorts of valves, connections and fittings. It also incorporates features to simulate leaking, broken and displaced pipes. Most of the pipes are above ground, making it easier to conduct all kinds of tests and install technologies for research.

Pieter Sannen creates an artificial leak in TUBES to test the DALI technology from Fluves NV and Vigotec NV.

Three research questions

The study in April focused on three main research questions:

1. To what extent can DALI (a DAS technology from Fluves nv and Vigotec nv) be used to identify leaks and interventions by third parties, and to help water utilities to shape the mains network of the future? (This study was commissioned by Evides.)
2. To what extent can BLAST (a DTSS technology from Aragón Photonics) be used to measure temperature and strain in order to monitor pipe status and/or drinking-water quality in a mains network?
3. To what extent can the TUBES testing facility at KWR be successfully used as a low-threshold pilot setting for testing technologies?

The test was set up in mutual consultation with all the alliance partners, a range of technology suppliers, water utilities and KWR, with KWR contributing knowledge about TUBES and the technology suppliers contributing knowledge about the capabilities of their technologies. To conclude the week, a workshop was organised on Friday, 21 April. In the morning, experiences and results were shared between suppliers, KWR and experts from water utilities; in the afternoon, suppliers were given the opportunity to demonstrate their techniques. On 15 June, Fluves will be hosting a webinar to further explain the results from the DALI tests. The experiences acquired during the monitoring campaign will also be shared at the “19th Computing and Control for the Water Industry Conference” in September 2023.

Evides, Fluves and Vigotec: DALI and hygiene

“Evides is working on the Mains of the Future. That involves investigating digital techniques that will help to optimise our understanding of the mains network so that decisions can be made in a well-founded, targeted and cost-effective way,” says Stefan Knijnenburg (Innovation and Policy Advisor at Evides). “So we want to work with suppliers Fluves and Vigotec to see how we can use DALI technology in our mains system. However, we wanted to find out first whether and how it can also be used responsibly in a hygienic way. So we were happy that KWR and TUBES were on hand. And we have seen how the hygienic insertion of the glass fibres is possible and that DALI can detect leaks we simulated in TUBES above ground – even though we expect the picture with real leaks to be different because they are, of course, underground. This is a good start and we were pleased with the collaboration with KWR.”

Thijs Lanckriet (Fluves NV) demonstrates the DALI technology to experts from water utilities, other suppliers and KWR.

BLAST from Aragón Photonics

The Aragón Photonics experiments with BLAST also reduced good results, even though it was the first time the company had applied this technology in a drinking-water environment. Changes in temperature and angular displacement were detected well and simulated using simple tools, from a hot air gun or ice, to adjusting the angle of a connection. The simulation of subsidence was also relatively straightforward: it involved simply removing a bracket from the section of the pipe above the surface.

TUBES ideal for practical tests involving hygiene risks

Researcher Amitosh Dash (KWR), along with the thirty people who attended, looked back with satisfaction on an instructive week of experiments. “TUBES has now been applied in research for the first time and it has proven ideal for conducting practical tests that you would rather not do in an operational drinking-water network, for example because of hygienic risks or the possible disruption of the water supply,” says Dash. “And we have been able to conduct a wide range of tests. The fibre-optic technologies have been used to detect induced leaks, vibrations caused by a truck or by tapping, temperature changes, sagging and angular displacement. We also used the setup as an obstacle course for the DALI tests, which was also the original idea behind the labyrinth structure of the setup. And although we did not disinfect during the tests, we could see that disinfection at each step was entirely feasible. TUBES offers excellent prospects for future studies of the mains.”

Jairo Gascón (Aragón Photonics) heats an overhead TUBES pipe section with a hot air gun to test whether his company’s BLAST technology detects temperature changes effectively.