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Safe behind the Oosterscheldekering

Yunex Traffic replaces coders for gates for Rijkswaterstaat

After intensive maintenance on various Delta Works, the Netherlands entered the storm season with a safe feeling. The sensors on the Oosterscheldekering between Schouwen-Duiveland and Noord-Beverland have been renewed, among other things, which ensure that the gates lower evenly when the barrier is closed. Jos Maassen of Rijkswaterstaat (RWS) and Andy Kriek of Yunex Traffic talk about this project.
Jos Maassen was there when the Oosterscheldekering was symbolically closed for the first time in 1986 by the then Queen Beatrix. At the time, Maassen was a control technician at Rijkswaterstaat. 35 years later, as a contract manager, he is closely involved in the maintenance of the barrier. “The Delta Works are all about reliability and availability,” says Maassen. “The gates and moving parts of the Oosterscheldekering must be constantly preserved to prevent corrosion. After all, they are in a wet, saline environment.”

Also (electrical) technical parts are regularly maintained and replaced when they are end-of-life. An example are the so-called code generators of the gate height measurement. These sensors ensure that the 62 slides run straight into their rebates when the barrier is closed. There are three sensors on either side of each slide. This has to do with reliability requirements: if only two of the three sensors are working, the sliders still drop nicely level. All 372 sensors have been replaced since the opening of the barrier, but due to their age they had to be replaced again.

The tender was won by Yunex Traffic (spinoff of Siemens Mobility) based on price and quality criteria. Six sensors have been replaced for the 2020/2021 storm season. They were used during the winter period to test their reliability. After this successful pilot, Yunex Traffic was also allowed to replace all other sensors. This lasted until mid-October 2021. Site manager Andy Kriek of Yunex Traffic led the installation and commissioning of the sensors. He worked together with two technicians from Istimewa. Kriek came back from vacation early to install the last sensors in October: “You want to complete your work as well as possible and assist your colleagues in the final phase. We worked under strict conditions. For example, we had to test every gate immediately after the conversion.”

A well-secured working environment on the Oosterscheldekering is no superfluous luxury. Kriek: “Due to the strong current and the distance to land, you don’t stand a chance if you fall into the water. We worked behind railings and in closets out of the wind. We didn’t pick up cell phones while working. Every day we held a Last Minute Risk Analysis to check whether we could work safely. Our equipment hung from a springline construction so that it could not fall into the water. Mutual communication was via walkie-talkies. We always reported ourselves when a colleague received a call. So absolutely safe, just don’t be afraid of heights or water. Some sliders are very high. You have to be able to see into the depths through open grids, where very fast flowing water swirls around the concrete pillars.”

Yunex Traffic had to take into account the many other parties working on the barrier. This required good coordination. Maassen: “You can’t always get started on the same slide. For example, if we conserve a slide, it will be out of service and packed for a few weeks. Then you cannot replace and test sensors on that slide.” Kriek: “We were able to move our work relatively easily and have done so a few times. If you can help each other with that, don’t you just start working on a different slide?”

The new sensors are somewhat faster and more compact than the old ones. They are housed in an aluminum housing that is resistant to seawater. Their position can be read in different ways. Before installation, all sensors have undergone an endurance test of 720 hours. Yunex Traffic has built a test bench on which six sensors can be tested simultaneously. The test setup is full of PLC technology, software and other components. She will remain available for the next 20 years. During that period, Yunex Traffic is responsible for second-line maintenance. Kriek: “In principle, the sensors are maintenance-free, but they can of course break down. Then we have them repaired and they end up in the reserve stock. RWS continuously keeps 25 sensors in stock. The entire reserve is periodically tested by Yunex Traffic to see if the sensors still work.”

In the course of the project, Yunex Traffic was able to make a nice acceleration. Kriek: “Installing and adjusting the sensors is a difficult job. The first slide took us almost three days. We then optimized our working method, which made things much faster. Routine also played a role in this and the fact that we as a team were increasingly geared to each other.” Like other contractors, Yunex Traffic itself had to monitor the quality of its work. Kriek had a check-off form for each slide. Are cables fitted with ferrules? Do we meet all the other requirements that have been drawn up?” Maassen: “In the past we at RWS had the management of such a contract, but nowadays we assume that every contractor guarantees its own quality and monitors its processes. We no longer watch constantly, but carry out tests.”

Maassen is very satisfied with the quality of the work delivered and the cooperation. Kriek also looks back on a successful project. “As with previous projects for RWS, we experienced our interaction with each other as respectful and open. We are proud to have contributed to the optimal reliability and availability of this important Delta work.”

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