Waterjetting 36c - Cutting walls

This is just a short video from back in the days when 1/2-inch tapes were still our way of recording, but before we reached the higher quality resolution of today.

We had a problem in that the basement of our building was partially covered with dirt, and concrete window wells held that back from the windows used to light light into the rooms. It would have been prohibitively expensive for us to pay to remove the concrete conventionally, but it turned out that with the construction of a set of simple tools (there were no really good high-pressure swivels available at the time - hence the orbiting action of the nozzle as it moved over the slot) we were able to cut the walls relatively simply and quickly.

Figure 1. Cutting the window well protecting the wall. (Over 30 years ago)

In this first video segment I mis-spoke when I spoke of the nozzle as rotating, it was actually being moved over the wall in an oval pattern, as will be more evident in the second segment (below the fold).

As noted in the video the support platform for the rig is a simple platform shop lifter and the rig is held on the platform with a couple of G-clamps. There is relatively little reaction force and so the rig can be made very simply out of available tools. The lesson we learned very early on was that the rebounding water carried the removed cement and aggregate particles, so that PPE was important, and keeping folk back even more so.

After the window wells were removed we had to cut an entrance through the main wall of the building - about 14-inches thick.

Figure 2. Cutting the main wall behind the window well.

Note that it was not necessary to remove the glass in the window until after the walls had been cut, and it was time to remove both window and wall.

Tech Talk - Closing a coal-fired power plant

Much is made of large schemes to alter the way in which energy is produced in the United States. Large scale wind farms, and great arrays of solar panels attract large interest and funding, yet it is often in the smaller projects, from the individual solar panels to the change in energy sources for individual factories, or in this case a university, that there is at least as much progress, though with less fanfare.

I wrote, some eighteen months ago about the geothermal plans at Missouri University of Science and Technology (MS&T) previously the University of Missouri-Rolla and my academic home for 42 years. At that time the campus was beginning a process that would see the different parking lots and other open areas around campus disrupted while a series of vertical wells and horizontal pipes was laid beneath the ground, prior to its restoration.

Figure 1. The MS&T Geothermal plan, showing the zoning of the wells and the connection pipe network.

Time has moved on since the initial plans were set in place, the trenches have been dug:

Figure 2. Geothermal trenches on campus, with walkways re-routed around them

Within the lots wells were then drilled roughly 430 ft deep, through which the system fluid will flow, and as these were drilled they were lined and connected by a secondary network.

Figure 3. Drilling the wells in the parking lots at the top right of Figure 1.

The network of wells is connected through plastic pipes that carry the water out to the wells, down and back up and then return to the central heat exchanger systems of the different circuits.

Figure 4. The heat exchange between the water and the ground (inhabitant )

Figure 5. The initial connections to the wells

Larger pipes are required to carry the water to and from the different fields to the processing plants where it is used to heat/chill water in a secondary circuit that is then distributed (depending on season to either warm or cool) through the network to the campus buildings.

Figure 6. The main pipe connections.

The parking lots have since been regraded, tarmac applied, and have, for some time been functioning as before.

Now the project is entering into the final days of installation, as a significant milestone has been reached. This week the coal and wood fired boiler #5 will shut down and all steam production at the campus power plant will permanently cease. Chillers are now operating for the summer to cool the buildings served by three of the regional plantsm which covers most of the air conditioning needs of the campus, and heat is being sent to six of the campus buildings.

Given the age, and change in the nature of the heating and air conditioning service to the buildings some still remain to have their systems upgraded, but most will now be completed while the students are away this summer.

Estimates of the savings that this will bring to the campus are in various forms. The coal and wood that have provided the energy source in the past will no longer be needed (and in time the plant will be removed). As well as the plant itself this will also free up the space where the coal was stored, and will improve the local aesthetic considerably along that side of the campus.

Figure 7. The campus power plant

The change in fuel will also see the overall amount of fuel required reduced, and it is anticipated that the energy use will be cut by 50%. Carbon dioxide emissions will be dropped by 25,000 tons a year (the system will still use significant amounts of natural gas) and water use will be cut by eight million gallons a year.

It is anticipated that the $32 million project will initially yield the campus a saving of around $1 million a year which will rise to more than $3 million a year as energy costs increase, while the system should not need significant maintenance for decades. There is a video of the project here). When completed, sometime next year the system will be serving 15 buildings with around a million square feet of floor space.

As the Missouri system was beginning, the initial phase of a similar system at Ball State was being completed . This will ultimately supply around 5.5 million square feet of campus space, and is expected to yield some $2 million a year in energy cost savings. Following the successful completion of Phase 1 of that project in March 2012, the Phase 2 project, requiring an additional 1,000 boreholes, was started in June of 2013, and is expected to be completed by some time next year. The four coal fired boilers at the plant (which consumed some 36,000 tons of coal a year,) were shut down in March of this year. Power will continue to be supplied from three natural gas boilers on campus. The $80 million project will have drilled a total of around 3,600 wells at the time of completion of Phase 2.

Oregon Tech has a 1.75 MW geothermal power plant, which combined with a solar electric array of panels on a 9-acre site off campus to produce most of the power needs of the campus. The dedication ceremony was on April 18th of this year. It is expected that the plant, which operates on a more conventional use of high-temperature water from the underlying host rock, will save the campus around $400,000 a year in energy. Water is brought up from 5,300 ft below the surface at a temperature of 200 degrees F, and used to spin two turbines, and as source of building heat, before being re-injected.

As the dates suggest this is a very new venture for universities and, as yet, there are not a lot of players in the game. Yet if the savings pan out to be at the level or greater than currently estimated it may well be more popular in the future as overall energy costs continue to rise. (Although in the short term natural gas prices may well rise a little, while coal prices are expected to fall a little).

OGPSS - More on the MS&T Geothermal Project

Ah, the election is over! Those outside the United States might not understand the relief, but as a minor example we had 6 different phone calls urging us to support Todd Akin for the Senate, in the 24-hours before our polling station closed. I am not sure that there will be much in the way of new information on Energy Policies out of Washington for a while, as they debate the fiscal cliff, but one does wonder whether we might get a new Secretary of Energy. And so, with Iranian oil production very much a function of how effective sanctions remain, and with the new OPEC Monthly Oil Market Report due, I am going to return for a second week to discuss the geothermal operations at MS&T, with a little more detail than last time, since some of the numbers might be of interest. (And I am grateful to Jim Packard at MS&T for providing the information). Universities move generally very slowly. However they are, on occasion, willing to accept new ideas that resolve a problem quite quickly. (We once had to build a small plant to recover explosive and repackage it – not something that was possible on the surface, but by driving a new set of tunnels underground at the Experimental Mine we could create space for the plant and then operate it for the required demonstration without needing any of the permissions that would have been required had we tried to build a facility on the surface. (This was about 20-years ago, and we would likely still be moving the paperwork seeking permission). (Perhaps another argument for the accelerated use of underground space). The case for a change in thinking, and, perhaps, a hint of its urgency, can be seen by looking at the energy balance, before the new system is installed.

Figure 1. Comparison of the useful energy (upper circled numbers) to the input energy at the MST Power Plant. (MST) Given that fuel costs will likely only continue to rise, but that, while a new boiler was needed, there was no obvious source of funds to pay for it, a number of options were considered. It is interesting to note, in the following table, the costs of the current coal:wood system. (60% coal), relative to those of the proposed water to water (WTW) heat pumps that are being proposed.

Figure 2. Comparative Energy costs relative to the current system. (MST) To digress a little, for their part in addressing a similar problem, the University of Missouri at the Columbia campus is installing a bubbling fluidized bed boiler. The boiler will use biomass to be to displace about 25% of the coal use on campus. The $75 million project has just been completed. However, as I noted in an earlier post, there may be unrecognized processing costs for the biomass which may eat into the campus savings. And while MS&T are looking for ways of handling the now unnecessary smoke stacks, the biomass facility in Columbia has just added three 110-ft tall silos to handle the feed.

The new boiler, which was retrofitted to the university’s existing heating duct system, is expected to produce 150,000 pounds of steam per hour, increasing the 67-year-old power plant’s steam output by 30,000 pounds per hour, and use an estimated 100,000 tons of in-state renewable energy sources such as chipped hardwoods and wood waste.

Back at MS&T the number for the heat pump came in part from a WTW heat recovery chiller that the campus had installed in October 2007, and which was saving the campus some $1,500 a day by allowing some of the recovered heat to be produced in useful form. When the campus first looked at the potential they were also able to look at the experience of places such as the Richard Stockton College of New Jersey, which installed a system in 1996. Their installation pioneered many of the decisions made in subsequent operations.

The wells are located on a grid and spaced roughly 15 feet apart. Within each four inch borehole, the installers placed two 1.25 inch diameter high density polyethylene pipes with a U-shaped coupling at the bottom. After the pipes were installed, the boreholes were backfilled with clay slurry to seal them and to enhance heat exchange. In total, the loop system includes 64 miles of heat exchange pipe. In addition, 18 observation wells were located in and around the well field for long-term observation of ground water conditions. The individual wells are connected to 20 four inch diameter lateral supply and return pipes. The laterals, in turn, run to a building at the edge of the field where they are combined into 16 inch primary supply and return lines. These lines are connected to the heat pumps which serve Stockton’s buildings. In the heating mode, the loop serves as a heat source and, in the cooling mode, as a heat sink. The heat pumps range in size from 10 to 35 tons. All are equipped for with air economizers. The equipment is controlled by a building management system using 3,500 data points. This allows the College to take advantage of energy saving options such as duty cycling, night setback and time of day scheduling. The building management system also identifies maintenance needs in the system. . . . . . The system immediately demonstrated that it could carry the entire planned heating load. In the first few years of operation, the average temperature of the well field has drifted upward by several degrees. This occurred because the buildings use more air conditioning than heating. . . . . . Because of the constant changes to the system, and other energy conservation steps, it was difficult to verify energy savings exactly. Based on extensive monitoring, the predictions turned out to be quite accurate.

Figure 3. The polyethylene tubing and the metal end fixtures for insertion into the MS&T boreholes. (MST) With this encouragement there was an initial discussion of the system in Mid-September 2010, the scheme was approved by the Board of Curators in November 2010, and 2011 was spent in bidding and awarding the contracts and pre-ordering materials. The first day of drilling was on June 4, 2012, just after the Spring Semester. In order to complete the parking lots – to the degree possible – several drill rigs were used at once:

Figure 4. The use of multiple rigs to speed operations (how many?) (MST) Once a well had been drilled, and the pipes installed, the holes were backfilled with a grout that included significant quantities of sand, to improve the heat transfer. And the two pipes were all that were left protruding.

Figure 5. After pipe installation (MST) Trenches were then cut across the lot to allow the distribution and collection network of pipes to be installed. Once the field connections were fused together, the lines were connected to larger transport pipes at the end of the field, and set into a deeper trench.

Figure 6. The connections between the wells and the distribution network. (MST) The larger pipes were used to carry the water from each field to the heat exchanger/chiller plant, with three plants being located around the campus. All that then remained was to backfill the trenches, tarmac the lots again, and the campus began to return to normal. The last well did not get drilled until half-way through this semester, but the lots are now coming back into use.

Figure 7. Overall layout of the three circuits being used on campus (MST) With most of the work done on the fields, the remaining work involves the integration of the system into the existing infrastructure, and the necessary changes to the hardware in the various buildings to handle the different ways in which energy is used within them. Much of this change is required since the heating has been, in the past, using steam lines, and these have now to be replaced with the hot water circuit.

OGPSS - The quiet steps of a Geothermal movement

The election is now less than a week away, with two entirely different paths possible for our future as we move past the election into next year. The two approaches to energy are particularly different, but it is pointless to do any further comparison, since the airwaves have (on the rare occasion that these differences are explored) discussed these from all points on the spectrum. But nevertheless it gives an occasion to step aside from Iran, for a week, and to draw your attention to something you may have missed in all this debate, and yet is starting to happen on University campuses that are scrambling to meet that ever rising fuel bill. In the current debate both sides seem to anticipate that the energy future is rosy. As an illustration, I was struck by a comment just this last week:

"Peak oilers have become almost extinct, destroyed by the arrival of new technologies with the U.S. leading the oil supply change," said David Hufton of oil brokerage PVM.

And yet, in the same week I received another newsletter from Go Haynesville Shale predicting (from Seeking Alpha) that 2013 will see the decline in Hanesville production.

Figure 1. Production from the Haynesville Shale in Louisiana (Go Haynesville Shale ) Now there are a variety of reasons for the decline, a significant one being that the number of wells being drilled has fallen dramatically, as the article recognizes. But that is itself, in part, a recognition of the current economics of the business. I had a discussion, just this past week, with the daughter of an investor who had “lost his shirt” over a natural gas well investment. The difference between the hype and the reality is disturbing, and does not bode well for a stable future. Which poses the question as to what the reality of that future might be? I live in Missouri, and a number of years ago colleagues of mine evaluated the potential benefits of renewable energy and were left severely unimpressed with the potential for wind and solar in this state. At the time I was not sure what the answer for our state was. The campus where I worked until I retired, (Missouri University of Science and Technology – the new UMR) had been quite revolutionary some decades ago in starting to burn wood with coal, both as a way of controlling emissions and costs. Now those benefits were disappearing and the campus faced the prospect of finding about $25 million for a new boiler, at a time when state funds are not likely to be available, and which philanthropist wants to fund a boiler? So the campus had to be creative. And it was!

Figure 2. Old Campus Power Plant - the question of what to do with the stacks is unresolved. Starting in the summer of 2010 the campus proposed the use of a ground-source heat pump system as a method of using the Geothermal potential under the campus to lower the overall operating costs of generating power, while at the same time addressing issues regarding the generation of carbon dioxide, and the use of large volumes of water that are one of the costs of conventional coal-fired boiler use. The initial proposal was approved in remarkable time and over the past summer drilling crews moved in for the initial drilling of the wells. Unfortunately (but realistically) the greatest amount of open space around campus that can be used are the parking lots. And so s number of drilling rigs appeared as the students left for the summer, and proceeded to drill a series of roughly 600 wells, each around 400 ft deep. The last was completed last month, and the wells were then lined with piping and are currently being connected into a triad of networks.

Figure 3. Simplified illustration of the geothermal circuit. Basically the system works on the idea that the ground, in depth, is at a relatively constant temperature. (For those of us who have mined in depth the old rule of thumb in the Northern UK was 60 deg at 60 ft and 1 degree rise per 60 ft thereafter – but the geothermal gradient varies around the world). Given this relatively consistent temperature, in winter the cool water (the blue line) can be pumped underground, heated and returned through the red line, from which it passes through a heat exchanger system that provides heat to the campus, while then being returned via the blue line to repeat the process. In the summer the flow is reversed. The hot water from the heat exchanger/chiller is returned to the wells through the red lines, releasing the heat into the ground and cooling before it returns back to the surface through the blue line, and into the chiller/heat exchanger to provide a cooling source for the campus. Current estimates are that the initial costs (paid for with a bond issue) will be no more than the cost of that boiler (which wasn’t going to be funded, yet was needed), but that the campus will save, in the beginning, some $1 million in energy costs (the remaining energy will be supplied with natural gas and the boilers will be retired in 2014) and this will service the bond. The funds only allow some 60% of the campus to be initially served, through three separate plants that are set around the campus. In time, as savings mount, it is likely that other buildings will be brought into the loop (though some have sufficiently antiquated heating and cooling systems that the entire building will need renovation first. Over the lifetime of the system (and there is not a lot of fragile equipment in the loop, so this may be more than 50-years) energy savings are likely to rise to more than $3 million a year, as the energy crisis that we are currently pretending isn’t coming finally comes to pass. Given the benefits that the system will develop it is not surprising that MS&T are not alone in this approach. In fact they learned of the concept at the time that Ball State was beginning their project. That project has just been dedicated and anticipates, being larger than ours, that it will save that campus around $2 million a year. It also includes some 3,600 wells by the time that the second phase of the program is completed. The idea is beginning to catch on, and there are a small but growing number of campuses now that are in the throes of the same type of effort, though in each case tailored to the individual needs of the different campuses. Hampton University in Virginia is heating their Multi-Purpose Building, Indiana Tech has restored and powered a Civil War era building, Montana Tech will use the heat from mine waters underneath the campus. In Boise, ID the ground water temperature is a little higher (around 170 degrees) and the city has used geothermal energy since 1983, and now Boise State is joining in with its own plant. As with the Montana project, so the program at New Mexico Tech has also been funded as part of the Recovery Act. Some of the potential benefits of that program have been described by the Department of Energy. However that presentation also illustrates the transience of the funding opportunity.

Figure 4. The budget for the Geothermal Technologies Program (DOE) Given that drop in funding, it is yet still possible, given the savings projected not only here but elsewhere, that this technology may still catch on and become more widely adopted. I’ll keep you posted (among other things with more technical details).

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.