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Graphic element Research > Growth > Research projects > Products & processes projects > Water jets at the cutting edge of technology
Graphic element Water jets at the cutting edge of technology
    04/02/2002
 

A cutting technology used to dismantle cold-war nuclear missile installations is now even better thanks to a CRAFT project. High-speed water jets can cut through many materials from steel to concrete but suffer from low efficiency. Research carried out under the BRITE-EURAM Industrial and Materials Technologies programme has shown how adding suitable polymers to the water can more than double efficiency.

The industrial use of water jets for cleaning and cutting began in the 1970s. More powerful abrasive water jets, which use water mixed with abrasive particles, arrived in the early 1980s but only became commercially important in the 1990s. The most powerful modern jets, known as abrasive water suspension jets, have jet speeds of hundreds of metres per second and can cut through 30 cm of steel or one metre of concrete.

"The major application for these jets is in dismantling and decommissioning redundant plant," explains project co-ordinator Christoph von Rad of the Institute of Materials Science (Institut für Werkstoffkunde or IW) at the University of Hanover. "These include, for example, offshore structures, demilitarisation, or the dismantling of nuclear power stations."

Polymers in the water
 

A few years ago a company known as ANT (formerly Alba Industries) approached Professor Hartmut Louis's research group at IW to see if they could help improve the efficiency of abrasive suspension water jets. "We have very close contacts with industry because our institute concentrates on research close to application," says Mr von Rad. "The question came up whether it was possible to increase the stability of abrasive water suspension jets by adding polymers to the water."

One problem with water jet cutting is that the narrow jet breaks up into droplets, drastically reducing the cutting efficiency. When pure water jets were first developed in the 1970s, researchers tried adding polymers - large organic molecules - to the water in the hope of preventing the stream breaking up. Polymers were considered again for abrasive water suspension jets in the early 1990s but not pursued since the jet technology itself was still immature.

Now, the time was ripe to try again, so the partners assembled a group of companies and research institutes to put together a CRAFT project. The project, led by IW and ANT, included two Italian research institutes: the University of Cagliari and the neighbouring laboratory of the Consiglio Nazionale delle Ricerche (National Research Council). Italian SMEs included FIP Industriale , a manufacturer of water jet machinery for civil engineering, Tecnocut , which makes water jet cutters for manufacturing industry, and Sonsub , a builder of remotely controlled underwater vehicles. PS Watercut, a Danish firm using abrasive water suspension jets, and French company Weber Lubrifiants , which supplied the polymers, completed the consortium.

 
Improved efficiency
 

After two years of research with different polymers, the partners have been able to improve cutting efficiency greatly, mainly because the jet holds together better. "The water becomes viscous because of the polymer and therefore the jet does not disintegrate into droplets so much and stays coherent for longer," Mr von Rad explains. "This is especially advantageous for deep cutting. The acceleration of the abrasive particles in the nozzle is also improved, but this effect is not as strong."

As a result, cutting efficiencies have been improved by as much as a factor of 2.6, depending on the polymer and the design of the jet nozzle.

The main remaining problem is that the polymers are normally supplied as powders or granulates, which are not directly usable in water-cutting machinery. If the chemical industry can be persuaded to supply them in the form of concentrated solutions or emulsions then the market for the improved technology should be considerable.

"There are many offshore structures which have to be dismantled and also nuclear power plants which will be taken out of use within the next few decades," Mr von Rad notes. ANT has even been using water jets to dismantle nuclear missile silos in the Ukraine, as part of the implementation of the START I disarmament agreement. This is not a huge market but will provide a lot of business for specialised firms working within it. And so far there seem to be no competitors supplying this technology, though that is likely to change as the market grows.

Meanwhile, IW is applying for EU funding for another project, this time to introduce polymer technology into another kind of abrasive water jet, the injection jet, used in the manufacture of products from very hard, brittle or heat-sensitive materials.

"The superiority of abrasive water jets is obvious when cutting materials such as ceramics, reinforced plastics and all kinds of composites, because they do not bring in any heat," explains Mr von Rad. "This is of even higher commercial interest. We did some small scale tests during this last project and got a very promising result of 20% increase in efficiency without any modification of the cutting heads, so we are hoping to get a lot more."

 
Polymers in the water
Improved efficiency
   

Key data

Improving efficiency of production technologies is an important element of the Innovative products, processes and organisation key action. This CRAFT project uses polymers to improve the effect of water jet cutting.

Projects

Improvement of efficiency, availability and quality of abrasive water suspension jets (BRST985261)

     

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