In Focus

A Masterpiece in the Oosterschelde Estuary

A Masterpiece in the Oosterschelde Estuary

For a quarter of a century, a storm surge barrier on the North Sea coast of the Netherlands has been protecting land and people from the sea – safely and reliably.

The building is still regarded a masterpiece nowadays because, with the planning as well as with the building, virtually every step was a step into unknown territory. A great example of a notable European cooperation.

Shortly before the 25th anniversary of the storm surge barrier on 4 October 2011, representatives of the companies involved as well as representatives of the relevant authority came together again: Piet Maljaars, Cluster Coordinator at the Rijkswaterstaat (Dutch Water Authority), Erik-Jan Driessen from Klüber Lubrication, as well as Ellis van den Hout from SKF Netherlands and Peter Schmehr from SKF Germany shared fascinating insights on the past cooperation, the present performance of the storm surge barrier and prospects for the future.

Oosterschelde - Klüber Lubrication Interview

Would you say now, 25 years after its opening, that the storm surge barrier has been an all-around success?

Piet Maljaars: At the Oosterschelde, the Deltawerken have indeed achieved what they stepped up to do after the flood disaster in 1953. Not only has a reliable protection been installed for the people, who have been able to live and work here safely ever since. Another goal was to protect the flora and fauna and maintain the ecological balance. Mussels, oysters and many other animals are here more plentiful now than ever. For the Netherlands, the storm surge barrier is of vital importance. Today, the structure and the surrounding nature reserve exist in harmonious symbiosis.

The main difference to the building of a dam, as had originally been planned, is that the Oosterschelde Estuary has not been turned into an inland body of water by the storm surge barrier and, therefore, the natural tidal action was not cut off. This means that mussels and oyster breeding have survived.

Piet Maljaars: Exactly - and as soon as a storm is coming on, we can close everything off. When the sea level rises more than 3 metres above the Amsterdam NAP level, which means above the mean sea level of the North Sea, then it's time to operate the sluice gates.

Building a storm surge barrier with gates was technically much more demanding than building a dam. Can you explain what makes the barrier so special?

Piet Maljaars: Well, building the storm surge barrier was a huge challenge for all companies involved. After all, it consists of 62 moving gates weighing between 250 and 400 tons each. That's enormous. Consequently, the requirements pertaining to the hydraulic system that moves these gates are extremely high. The same applies to the bearings which are an absolute necessity to move the gates at all. Not least, also the lubricant has to withstand extreme conditions inside the bearings. All those factors had to be taken into consideration during the planning and building. There were no real empirical values from earlier projects. So it is even more gratifying that up to the present day everything has been running so smoothly.

How many times have the gates had to be closed for safety reasons over the past 25 years?

Piet Maljaars: We have had to close the gates 26 times. 24 times because of a storm surge, and twice because it had rained so much. By closing the gates and pumping out the water from the polders into the Oosterschelde, the water level behind the barrier can be held low artificially.

What exactly happens in the event of an emergency? Do the gates close automatically?

Piet Maljaars: There are two operating modes. The first is the manual one. That's what we prefer, because, in the end, after taking all aspects into account, man can still make the best decisions. Then there is the fully automatic mode designed for the event that no-one can get to the control centre in time. The whole barrier can be closed in just one and a half hours - without any power from the electricity grid. This means we can operate the gates in a totally self-sufficient way in the event of an emergency. And to make sure that everything runs smoothly in the event of an emergency, we carry out a complete test run four times a year.

Weather forceasts have become more accurate over the years. Are their data useful for you, and how do you use them for your warning system?

Piet Maljaars: Rijkswaterstaat has its own meteorological services. Experts are constantly observing and analysing the technical data. The moment they have good reason to fear that the water will rise 2.75 metres above the Amsterdam level, they start making their calculations. Then the team has to decide whether to close the slides or not. But the director of the water authority here in Zeeland always gets the last word.

Oosterschelde - Klüber Lubrication Interview

How vital was the input of the companies that were given the opportunity to demonstrate their capabilities here - such as Klüber Lubrication, the German lubrication specialist, and SKF, the Swedish rolling bearing manufacturer - to the success of the project?

Piet Maljaars: Of course, the planning was done on many different levels, including the political one. Personally, I haven't been on board for so long, so I can't comment on it from my own experience. For me, it is an extraordinarily good sign that the professional cooperation and the good personal relationship between us and the companies still continue up to the present day.

Ellis Jan van den Hout: Such close cooperation is something out of the ordinary also for us. Here on site, for example, we still get involved in the maintenance work. Rijkswaterstaat, SKF, Klüber Lubrication and many others work hand in hand. A great example of good European cooperation. Special efforts had to be made for this special project and there had to be a huge degree of commitment towards the contracting authority on the part of the companies. If we hadn't given long guarantee periods, we couldn't have done any business. The openness everyone evinced towards each other led to synergies that no one would have thought possible beforehand. The enthusiasm with which everyone participated in the development of this big and totally new achievement was noticeable. Know-how from industry, authorities and the different interest groups all came together here.

So everyone had to enter unknown territory and actually get involved with a unique project.

Piet Maljaars: That was exactly what made it so special, so unique.

And what, in your opinion, were the biggest challenges?

Piet Maljaars: The compression of the seabed so that the piles could be firmly anchored was one thing. Then, of course, we had to deal with the specific local circumstances, such as the changing of the tides. And the size of the project required the delivery of gigantic volumes of concrete. The best steel bearings were needed for the gates as well as a speciality lubricant that was able to fulfil its lubrication purpose reliably and on a long-term basis and that was, furthermore, capable of preventing corrosion by the sea water. And then, of course, there was also the precision with which everything had to be performed. The gates had to be fitted to very fine tolerances. In the end, it was all the little details together that resulted in the impressive overall result. And the very best thing is that 25 years after its opening, the whole thing still works with the same precision as on the first day.

One element is of special importance: the lubricant that is used for the bearings of the gates has not had to be exchanged until today. The requirements were very high and it was a big challenge to find the perfect solution.

Ellis Jan van den Hout: The lubrication capacity of the grease was as crucial as its resistance to water. The bearings have to be protected in the best possible way, but protection from corrosion also has to be ensured. Salt water is extremely aggressive. If anything has a highly destructive influence on the lubrication, it's salt water. So the best precaution is absolutely essential.

Erik-Jan Driessen: The corrosion protection was crucial. I still know from the past - I have been working for Klüber Lubrication for more than 20 years now - that we have always attached great importance to fulfilling both functions: sealing and lubricating. Naturally, bearings can never be designed to be completely sealed if they are to work. After all, they have to be free to move. So the lubricant has to take over a sealing function as well.

How did you go about choosing the grease, and how come you decided to go for the German provider?

Peter Schmehr: Extensive and protracted examinations of the components were necessary. We had to gain a first-hand understanding of the contact of the grease with the other components. For example, how would the sliding material and the steel go with each other, likewise the seal that would enclose the bearing later?

Every single component had to be compatible with the grease. After all the tests there were just four types of grease left that we then investigated more closely. The Klüber product attained the best results. So we suggested Klüber Lubrication as the right partner. In further tests, at SKF and also at Klüber, we validated once again the best type of lubricant.

Erik-Jan Driessen: Keeping the balance between the requirements of protecting and lubricating was the most difficult task, but we managed it. The protective function had to keep going for many, many years and the lubrication function had to be available whenever needed.

It has always been our defined goal to find precisely the right solution for the customer. In this case, one of the big challenges was to warrant a service life of ten years. A lubricant that would have to be replaced after five years would have incurred much higher overall costs than the extra cost of our lubricant. The process of exchanging the lubricant alone is very pricey - and that doesn't even include the cost of the grease.

So, Klüber's specialty lubricant should not be considered a typical C-component but an actual design element?

Erik-Jan Driessen: Exactly. Even with 14,000 kilograms of lubricant the one-time cost of purchase isn't the critical factor but the additional value for the operating company over the whole operating period. I mean, we cannot just pump out the old grease and pump in the new one. Everything would have to be completely dismantled. The costs would probably be immense. But at the moment there are no signs that any exchange might be necessary. So the decision for Klüber Lubrication in terms of a long-term investment protection has proved to be right!

The lubrication at the Oosterschelde storm surge barrier is subject to regular sampling. Can you describe this process?

Erik-Jan Driessen: The free movement of the cardan suspensions is measured every year, and once every five years the amount of grease is checked. Grease samples have been taken from the bearings and analysed in the laboratory three times so far - without any cause for complaint.

The lubricant is simply too good.

Erik-Jan Driessen: In the Oosterschelde storm surge barrier project everything just worked out really well. This cannot simply be explained by the well-engineered technology of the individual components. I can only repeat: everything went together perfectly and was perfectly coordinated, too.

Has the lubricant been improved in the meantime? Or is the product offered today still the same as it was 25 years ago?

Erik-Jan Driessen: Both. The product that was used back then still exists. But of course a lot of new products have been developed in the meantime. The permanently increasing requirements from the different industries require specialty lubricants with a high functional and economical effectiveness. Therefore, at Klüber Lubrication, we attach utmost importance to innovation.

The Oosterschelde storm surge barrier became a prestige project for the companies involved. Is it still the same today? Are those who were and still are involved still proud to say: We were part of it?

Piet Maljaars: Yes, the Oosterschelde storm surge barrier is an excellent testimonial. The vast number of company brochures with pictures of the Deltawerken is proof of this.

Erik-Jan Driessen: For Klüber Lubrication I can say: we are proud that we got to be involved. An achievement and a result that carries weight.

Peter Schmehr: Also for SKF, it was and still is a highly prestigious project.

Finally a personal question: 4 October is the 25th anniversary of the storm surge barrier - is it a special date for you?

Piet Maljaars: The Oosterschelde storm surge barrier was a pioneering project 25 years ago. Because of that it is still something special today. So at the anniversary the international network for protective water weirs gathered here for a seminar. Apart from that, 4 October was a working day just like any other.

Further information: A symbiosis of technology and nature - the Dutch Oosterschelde Storm Surge Barrier celebrated its 25th anniversary