Waterjetting 1d - Not quite that simple!

When I first began the research on the applications of high-pressure water that was be one of the major parts of my professional life I must confess to a certain naïve innocence in regard to other folk’s work. One assumed that other folk had made similar mistakes to mine, and then corrected them, so that when different systems were compared that the early, obvious, mistakes had not been made.

One of the first times I found that this wasn’t the case was when we were asked to go and demonstrate that high-pressure waterjets could economically cut granite, in quarries located in the heart of the Granite industry, in Elberton, Georgia. We were working with Georgia Institute of Technology (Georgia Tech) at the time and were asked if we could, at very short notice, go down to a couple of quarries and run a demonstration.

Back during my graduate studies I had found that Russian claims were true that said that it was possible, with a 10,000 psi jet pressure to cut through a rock with a compressive strength of 30,000 psi. (I'll tell you how later)

Figure 1. 9-inch thick block of granite drilled through by a 10,000 psi waterjet at Leeds University. It took over 30 minutes. (Summers, D.A., Disintegration of Rock by High Pressure Jets, Ph.D. Thesis, Mining Engineering, University of Leeds, U.K., 1968.)

Knowing this, and having a suitable pump at Rolla, our group ran some tests at the RMERC to get the angles right between the two jets that we were to use, and then, about a week later, we went down to Elberton and set up a system in the quarry.

Figure 2. Starting to cut a 1-inch wide slot in granite, pressure 14,000 psi, 90 rpm, linear cutting speed around 9 ft/min, areal cutting rate around 20 sq. ft./hour.( Raether, R.J., Robison, R.G., Summers, D.A., "Use of High Pressure Water Jets for Cutting Granite," 2nd US Water Jet Conference, Rolla, MO., April, 1983, pp. 203 - 209.)

The trials demonstrated that high-pressure water could cut granite at commercial rates, we cut a slot some 11 ft long and about 2-ft deep, and, after a couple of days of work, we went home. Georgia Tech then went to one of our competitors who set up to run a similar test. We had been done in 2 days, it took them two weeks to cut a slot about 2 ft long and 6-ft deep. They were running a jet system at 45,000 psi, roughly 3 times the pressure of our system. Why did they do so badly?

Well it turned out that they connected their pumps to the nozzle through a very narrow length of high-pressure tubing, and we calculated (as later did they) that of the 45,000 psi being supplied at the pump, some 35,000 psi had been lost in overcoming friction between the pump and the nozzle, As a result they were trying to cut the granite with jets at a pressure of 10,000 psi effective pressure, and it was much slower than our system which retained most of the 14,000 psi from the pump to the nozzle. (Hilaris, J.A., Bortz, S.A., "Quarrying Granite and Marble using High Pressure Water Jet," paper D3, 5th International Symposium on Jet Cutting Technology, Hanover, FRG, June, 1980, pp. 229 - 236.)

Now you may note that I said something about mistakes – it turns out that we had made an identical mistake a few years earlier and had added a second 10-ft length of narrow diameter tubing to the nozzle, and suddenly a system that had cut adequately with 10-ft of tubing did not work with 20-ft. The reason was the pressure loss in the tubing was too great at the longer length, and the pressure fell below that required to cut into the rock. (But at the shorter length we were drilling the hard sandstone at 12-ft/minute).

It is a very simple mistake, and many folk have made it over the years. The system has to be designed from one end to the other to ensure that all the parts are properly sized for the systems that are to be used. (And I will refer to other cases such as that above as we go through this series.)

It is not just the diameter of the feed lines that is important. In 1972 it took, on average, 150 man-hours and about $2,000 for the U.S. Navy to clean a single ship boiler using chemicals and mechanical scrubbing and cleaning. An enterprising company showed the Navy that it was possible to use waterjet lances to clean the tubes. In the demonstration they cleaned a boiler in 10 hours, and it cost around $700. This being Government work, the Navy then arranged a competition to find the most effective contractor. Based on the performance of the system that had been used in the first demonstration they asked 5 companies to compete in cleaning boilers. The operating equipment was designated as having to operate at 20 gpm, at a pressure of 10,000 psi. The results were not even close, even with systems nominally the same.

Figure 3. Relative cleaning efficiency in areal percentage cleaned, of five competing systems in cleaning heat exchanger tubes in Navy boilers. (Tursi, T.P. Jr., & Deleece, R.J. Jr, (1975) Development of Very High Pressure Waterjet for Cleaning Naval Boiler Tubes, Naval Ship Engineering Center, Philadelphia Division, Philadelphia, PA., 1975, pp. 18.)

One of the differences between the competing systems, you won’t be surprised to hear, was that some had smaller feed hoses than others.

There are many different reasons that the various systems performed as they did. One of the aims of this series is to ensure that, should you be asked to engage in such a competition, you will know enough to follow the path of company A, rather than company E.

As systems have become more sophisticated the different factors that control the performance of the jets have increased in number. As a simple example, when abrasive particles are mixed with high-pressure water in streams of abrasive-laden waterjets at pressures that can run up to 90,000 psi in pressure, for high precision cutting of material, the factors controlling performance now include not only the delivery system for the water, but also that for the abrasive, the type of abrasive and the configuration of the nozzle through which that final cutting jet is created.

Again, when we were asked to compare the performance of these different systems we set up nominally identical test conditions under which to determine which nozzle system would perform better. If I were honest I would tell you that before the tests began I expected that the variation in performance of the systems would vary by perhaps 10% between the best and the worst. We were quite surprised by the result.

Figure 4. Comparative performance between 12 nominally similar abrasive waterjet cutting nozzles in cutting through steel at a standard speed, pump pressure, and abrasive concentration.

I use these last two figures to show that all the details of a high-pressure waterjet system are important, when it comes to optimizing performance. One of the reasons to write this series is to ensure that folk that use these systems in the future do not make the mistakes that we made, as we learned how to tune the systems from getting poor performance to the commercially viable rates that are achieved today.

Unfortunately much of the early research and tests that are the basis for this knowledge were performed before the Internet existed. As a result I will have to use references to books and papers (as above) rather than using the electronic references that are the more common habit now.

This concludes the basic introduction to the series, which will now focus on more specific subjects.

Rationalizing University courses U-Va and Mining

As the turmoil at the University of Virginia over the firing of their President continues, some of the underlying philosophical divides that drove the action are becoming more apparent. A piece in the Washington Post suggests that alumni of the Darden Business School at U-VA had some major impact on the decision, and that there was some feeling that departments who were not “paying their way” should be discontinued. The article suggests that the cuts would be in liberal arts programs and the classics, and there is a strong defense for continuing such programs.
 I am not going to go into all the reasons why we still need liberal arts programs, they do very nicely at defending themselves and sustaining their presence on campus. However it becomes something a little different when science and technical programs are concerned. My own alma mater, the University of Leeds was provided with a building by the Mining Industry and the last time I went it was occupied by the Art Department, while no-one was quite sure where the last remaining Mining faculty member could be found. (He apparently no longer even has a phone number).
Mining is still a valid occupation, there are vast sectors of the world’s industrial might that would disappear without the material that mining produces from the earth. But that is society’s secret shame, and thus the technology is not defended with the passion that comes from those who seek to retain the classics on campus. (Even though Mining was often one of the founding disciplines of many such a campus).
 With the globe vitally dependant on coal, for example, how many universities in the UK teach mining? How many in the USA? Have these numbers grown or shrunk in the last decade?
  A little personal information – I retired as a senior faculty member in Mining from a mid-Western University a couple of years ago, and had given a year’s notice before I left. So far they have been unable to find someone of adequate qualification to fill the position I left. In fact, due to a similar shortage of faculty who know about taking the ore after it is mined and transform it into the metal used in factories, a discipline known as Mineral Processing, the position will likely now be filled in another group. 
 The discipline that I was fortunate to focus in, that of making holes in things and then stabilizing them led into the use of high pressure water as a tool for excavation. And not just in coal, where I began, but also for tunnels and underground excavations. It is now a multi-billion dollar growth industry with an increasing range of applications. (I was at Logan airport recently and two surgeons were discussing its new use in a medical application, one of the more fascinating areas I found myself in – it can be used, for example, to discriminately remove cancer cells from skin, a technology for which I share a patent).
 Much is made of the fact that continued extraction of fossil fuels at a reasonable cost depends on new technologies as the resources become less concentrated and more expensive to produce. Whether it is the rare earths needed for modern “sustainable” energy producers, the components for advanced batteries or even that mundane black stuff that powers most of the world’s economy it has to be extracted from the ground to be of value. But to create new technologies, you have to some understanding of the current ones. And that requires both knowledge and experience, and within the universities of the country this is becoming a much rarer commodity in the fields that deal with fossil fuels. Do they teach this at U-VA? Well, no – you have to go to Blacksburg and Virginia Tech to find a program in the state (admittedly a good one) but the community is small enough that there is no clout in State or Federal legislatures to sustain a larger program. It is not as though the profession is not in demand, a couple of years ago the average graduate with a bachelor’s degree was starting at a salary of $48,351 petroleum engineers were starting at $86,220 while mining engineers average $64,552. 
Here’s the table:
 
Table 1. Average starting salaries for those with bachelor’s degrees in 2010. (Top 10). 
 The reality is that politics are much more important at the University level is controlling what courses are taught or sustained on campus. At U-Va it is rumored that Dr. Michael Mann – he of the Hockey Stick story on recent temperature rises - (convincingly refuted by A.W. Montford) was to be offered the Kington Chair at U-VA - though with Kington now resigned as vice rector the fate of the chair may now be more in doubt. Makes it sort of unlikely that they will have a fond spot for mining, I suspect. 
 Ah, well nothing much will change, so why get upset – time to find a more interesting topic.

Deepwater Oil Spill - a longer term problem, personnel

The recent take-up of oil through the cap and the LMRP to the Drillship Enterprise has reached a daily rate of 15,800 bd.

For the first 12 hours on June 9th (midnight to noon), approximately 7,920 barrels of oil were collected and 15.7 million cubic feet of natural gas were flared.

On June 8th, a total of approximately 15,000 barrels of oil were collected and 29.4 million cubic feet of natural gas were flared. The Massachusetts began lightering this morning and should finish early morning on the 10th (lightering is a process of transferring crude oil between vessels, in this case, Enterprise to Massachusetts).

The Loch Rannoch is on its way, as, possibly, is the Toisa Pisces. This latter is a Well Testing Service Vessel (WTSV) Dynamic Positioning ship, which has systems for the reception and processing of fluids from well completion, stimulation and repair. For those interested in well flow rates, that measuring capability is among its capabilities.

• Reception of the products from the well via flexible hoses connecting the well to the production system installed on the ship.
• Process and separate water, wasted and un-wasted chemicals, gas, crude oil and solids. The water will be stored in the WTSV’s tanks and later re-injected into industrial waste well or offloaded to a processing facility onshore.
• The crude and gas will be measured in quantity and quality. The combination may be returned to the export line, or if this last is not available, the gas will be flared and the crude stored in the WTSV’s tanks to later be exported to an onshore or an offshore offloading terminal.
• The solids are stored in containers to be disposed to shore.
• Crude ranges are from low to high (12 to 43O) API. Pressures up to 10,000 psi at the well head.

It has been suggested that it might arrive on site on the 19th June. The Loch Rannoch should arrive a few days earlier, releasing the Drillship Enterprise, which, I suspect, has other things that it might now be doing.


The Toisa Pisces was formerly a cable-laying vessel, and is not a FPSO.

Toisa Pisces

My main topic for this post, however, is not the possible change is the fleet over the well, but rather some thoughts on how to avoid this happening again. There were likely a cascade of several errors, each of which alone would not have led to the disaster, but cumulatively they did. So how do we stop it happening again?

In some ways the problem is similar to that the Mining Industry faces after more than twice the number of deaths (29) at the Upper Big Branch Mine in West Virginia in April. In both cases there were safety concerns reflected in the numbers of citations that the companies had received relative to other companies. So how does one install a different attitude in those who work to produce the fuel that we all need? To a degree it has to be done through the imposition of regulations that enforce the concept of safety in daily working life. Including in those regulations should be the appropriate recommended practices for carrying out different tasks in the operation.

But even with those regulations in place, they are only as good as the enforcement of them. If my memory serves, you could not become an Inspector of Mines in Britain during the National Coal Board years, unless you had a First Class Certificate of Competency (which is the examination that allows you to manage a mine). The standards of education and training for inspectors must be high, and they need to require a reputable image.

The problems, in part, for both industries, are that the fossil industry historically has been cyclic in nature. Often driven by the price of oil, when that price is high, there are lots of jobs, and both coal and oil boom. The price falls, times get tight, and lots of folk get laid off. It has happened more than once in my career, as we have students go from having many job offers, to students coming back for graduate degrees because there was no work in the industry. The employees that are laid off go find work in other, less cyclic industries. And so when the next boom comes around they are no longer available. Further the teaching departments at the Universities have closed. It is as a result of this boom and bust cycle that there is a dearth of middle management in many companies that work in the fossil fuel business. For many years they were not hiring, and the folk that they now need as long-time trained and experienced individuals do not exist in large numbers.

The number of both mining and petroleum engineering schools have fallen, and student enrollments, until the recent rise in the price of oil (the $140 one) were bring other departments closer to that action. At one time, for example, Leeds University in the UK was one of the largest mining departments. At that time it was housed in a building that was funded by those in the Industry in 1928. That building is now occupied by the Art Department and somewhere – not quite sure where (this from the alumni office and the secretary in the building that houses the remaining odd faculty member) – there is still someone that teaches the odd course (he was out). There is only one other Mining School in the UK, and it studies hard rock mining at Exeter (used to be Cambourne School of Mines).

The Old Mining Building at Leeds

The commemorative plaque

It is hard to criticize University leaders, who must look to where the students are, and which faculty hire will bring the best return to the University. In recent years that has not been within the ability of the fossil fuel departments, and so they are closing – though the demand for their product is now rising again.

It is one of those interesting items to note that the latest reviews of world oil supply are beginning to suggest, increasingly, that the world is approaching if not past the point of peak global oil production. That will require more mining and petroleum engineers, though at places like Leeds (my alma mater) they will likely only be able to produce the modern version of Thomas Hair, to record the modern version of his “Art of Mining,” rather than the subjects of that art.

So what does all this have to do with regulation and responsibility? Well it is very difficult to maintain high quality folk in industries that go through severe manpower cycles. When regulations are severely enforced under one administration and then almost neglected in another, either because the industry is in disfavor, or the apple of the administration’s eye it is hard to keep the regulatory inspectorate that is a vital part of running a safe industry. The regulations should be fair, be strict, and must be enforced by individuals that have been properly trained to a high level of understanding as to both the technology that they are reviewing and the consequences of error. The historical evidence is clear that Universities cannot be left alone to provide that education, and supply those individuals. The National Mine Health and Safety Academy at Beckley is a start in the right direction for the mining industry, but there are other changes that must be made, in the investment in research into new technology, in the general attitude to those who work to provide the fuels that we need (and will continue to do so).

Treating the industries and those who work in them as pariahs is not the way to solve this problem.