Saturday, January 31, 2015

Waterjetting 29e - Back and Forth again

When the International Symposia on Waterjet Cutting (ISJCT) began (back in 1972) the uses of the tool were severely limited, both by the pressures available to customers, and by the limited knowledge of the capabilities of the system. Skip forward four decades and while the various tools available have widely broadened (the maximum pressure we have operated at runs well over a million psi) with cavitation, abrasive and polymer injection being just some of the more productive additions to the tool box, knowledge of system capabilities still lags in the general public.

The public wandering past a hydro-demolition site, where jets may be operating at 50,000 psi to remove damaged concrete – or by a civil construction site where hydro-excavation is digging a dry trench faster and safer than before, and the observer will likely have little clue as to the changes in technology that have taken place and the tool being used, since the jets are usually hidden by their surrounding shrouds.

Yet even in the industry that uses the tools – either for cutting aircraft parts, art pieces or for more mundane cleaning, the advanced technical capabilities of the tools they use are often a mystery to them.

Part of the reason for this, I suspect, is that the generation of scientists and engineers who pioneered the research that developed the industry have now, in most countries, retired. There has been a change in emphasis also for the research effort. There are many fewer opportunities for university teams to go out and demonstrate (as we did) that an abrasive waterjet system could be used to effectively cut a rock wall 20 feet deep within 50 ft of the Gateway Arch in St Louis, without any risk of the Arch crossing its legs. (Which was a major concern that the Park Service had when we did the work). In that project we also had to develop a 5,000 psi DIAjet drill to install rock bolts through 15 ft of dolomite, clay and chert to ensure that the walls remained stable (something not used much thereafter).

More of the research now (at a much smaller cadre of universities) is focused on enhancing the performance of jets in a much smaller range of applications, rather than finding and developing new markets in places where waterjets have not been used before. I will exclude the medical field from this restriction, since, particularly in Germany, new applications continue to appear.

What is also unfortunate is that the advent of the internet means that many of the earlier papers where, as with the case of hydro-demolition, the exploratory work was undertaken, are not easily accessible. And (writing as an academic who reviewed many theses and dissertations) few students go back much more than five years in assessing the previous state of the art.

As a result of this there is almost no effort to exploit some of the ideas that were developed over the early decades, where potential new applications were found, but which could not, at the time, be developed because of either technical constraints, or because (in our case) there were other more immediately rewarding paths to follow.

The movement at universities has seen high pressure waterjet systems move from the research laboratories into the machine shops of the support complex. As they thus become classified as “conventional systems” so there is less incentive to see them as places where innovation can bring the sort of rewards that can be found in developing other avenues of research.

This is a great pity since, although the industry has grown from being just a lab curiosity to an integral part of a number of industries (collectively doing billions of dollars of work a year), the range of applications for which it is uniquely suited have, as yet, only been tapped to a limited extent. As an example, the ability of waterjets to work in explosive environments to cut through different materials has yet to be fully recognized. Yes abrasive waterjets are used to cut the tops from oil and gas tanks, where remedial hydrocarbons pose a threat, but there are many other situations where – on a smaller scale – this ability could provide a number of benefits. (The coal mining industry comes to mind).

I remember watching an early demonstration of the use of a hand-held waterjet by a diver, as a way of cleaning barnacles and growths from an undersea platform. Previously the divers had to cling to the structure with their legs to give them support as they chiseled away at the growths with jackhammers. By putting a reverse jet on the lance, the diver could now float around the rig, removing growths without that sharp intrusion into his comfort zone. As I recall it took less than two years for the concept to sweep the industry, around the world, and I have mentioned before the reaction of one diver, who threw the jackhammer over the side of the rig with a profanity, after using a waterjet cleaning lance for the first time.

The above is another explanation for the focus that this site is going to have on some of the earlier papers in the technology over the next few months. It will try and provide a deeper explanation as to why certain things are done, based on the research of those earlier investigations, and also some pointers as to where we can expect the industry to move in the future. It should be fun!


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