As petroleum prices spiral higher, new technologies are being developed to help keep prices down. The balanced flow meter, technology originally developed by NASA for the space shuttle, promises to ease pain at the pump by being more precise and consuming less power than current metering devices. Leading the project is NASA engineer Anthony Kelly.

NASA Tech Briefs:

What is the balanced flow meter, and how does it work?

Anthony Kelley: The balanced flow meter is a replacement for standard orifice plates. It’s a thin plate that goes into a flow stream of any shape, usually a round channel, normally a pipe, and instead of a single hole in the middle, it has multiple holes that are drilled and spaced per special sets of equations to balance energy across the face of the plate. And what this results in is very rapid return to fully-developed flow downstream of the plate. The fluid flows through the plate, and as it flows through, it creates a pressure differential across the plate; it’s called a differential head flow meter. So, that pressure difference across correlates to flow rate in the plate, through the plate, through the pipe. And that lets you calculate flow in systems, and the trick to this thing is that it is extremely accurate and gets you back to fully-developed flow very rapidly.

NTB: Why was it developed?

Kelley: We started off looking for something that would be a flow meter compatible in LOx (liquid oxygen). Liquid oxygen is a pretty severe fluid to operate in; if you have moving parts or any kind of part-friction, you can start a fire that consumes everything. Even metal will burn in the presence of LOx. And so we were looking for some kind of flow meter for rocket engine systems that would be LOx safe, LOx compatible. And this thing has no moving parts; it’s very compatible with LOx.

And that fills a need that is kind of unique. We have in the past put turbines in place of a LOx flow meter, and we had one fail and wiped out a test stand. I mean, literally torched it. You have to be very aware of that, and as a result, we typically don’t fly with LOx flow meters. This device is meant to go in there and be a replacement and be able to actually be used in flight applications.

NTB: How is it superior to a single orifice flow meter?

Kelley: To compare and contrast, they both cost about the same amount to make. They both fit the same profile — like in industrial applications, they’ll build welded-pipe systems to accommodate a quarter-inch or half-inch plate. We can be a direct, drop-in replacement to an orifice meter.

Single-hole orifice meters are used world-wide, and they are the number-one, most common flow meter technology ever purchased. I mean, there are billions of these things used around the world. So this is a direct replacement for all of those devices, and when you drop it in into the same pipe system, with the same instrumentation, you usually get about a ten-times improvement in accuracy. You get what is called a “permanent pressure loss” — any time you restrict the fluid, you loose fluid energy, and you never recover that. If you have a 100 PSI upstream and you go through a restrictive orifice or a plate like it, you may have 90 PSI downstream. Well, a standard orifice will have 70 PSI downstream. Our plate will have you almost back up to 100 PSI downstream. It’ll have like 95. That’s permanent pressure loss, and it does not have near the loss.

It also does not need to have straight pipe runs. With the single-hole orifice, if you put it downstream of an elbow or pipe bends or things like that, you get non-uniform flow distribution. That changes the accuracy of the meter and can mess things up and make it inaccurate. With the balanced flow meter, you don’t have that problem, because it actually conditions flow at the same time it is metering flow. And with just a very small Delta-P across the plate, it doesn’t care if you’re right downstream of double elbows or anything like that. We’ve actually tested it in those configurations, with no degradations in accuracy.

We actually did a 1-to-1 comparison with the single-hole orifice and the balanced flow meter, and one of the other things that popped out was the noise generation. If you are taking less energy out of the fluid, that is, the energy that leaves the fluid goes into the piping system, and goes into the surrounding environment. And if you are taking less of that energy out of the fluid, then you are putting less energy into your system, and as a result, you get much less vibration in the system and much lower acoustic energy. We did some tests as well, where we measured acoustic energy generated by these new plates and found there was about a 15-times reduction in the amount of noise energy generated. And that’s under identical flow conditions; everything is 1-for-1 except the plate itself, being a balanced plate versus a single-hole orifice.

NTB: This technology was originally designed for the space shuttle; is it in the shuttle now?

Kelley: It is not in the shuttle right now. The integration cost of these things — changing an existing flight system is very difficult. Putting it into a new flight system is relatively easy. So I would anticipate that it would be used in future flight programs, but I doubt that we will ever get it integrated into a shuttle engine. Any time you make modifications to an existing flight-certified platform, you invalidate 10 years worth of tests. You come, you put a new piece of hardware into the system, you change the system — well, now are all those tests you have run still valid or do they change? Often times, they change. And if that is the case, you have to re-verify things, so you go into an extensive test program in order to do it, and that is very expensive.

But in a new system, it is easy to design it in and have it in on the ground floor and have it run through preliminary testing.

NTB: How does it help reduce gas prices?

Kelley: Custody transfer. There is a very special class of flow meters that are called “custody transfer flow meters.” And in order to be a custody transfer flow meter, it has to be very accurate, it has to have very low permanent pressure losses. And the balanced flow meter fits in that realm. We’re actually in the process of doing a bunch of API and ASME testing, which are the American Petroleum Institute and American Society of Mechanical Engineers. They have some testing protocols for custody transfer differential pressure flow meters. We’re following their protocols, and we have access to a unique Marshall calibration facility that is a NIST primary standard — National Institute of Standards and Tests — that’s a primary standard that rated at about 0.27%. Custody transfer meters need to be below 0.5%, and the closer you get to 0 in total system error, the better you are. With the totally non-optimized design, we’re looking at 0.6%, and within the next two test rounds, we expect to be between 0.1 and 0.2% error, total system error, on these flow meters. So what that means is, custody transfer is kind of like the electric meter on your house. It’s got to be certified. They have to know it is really accurate so they know they are charging you at the same rate they are charging your neighbors down the street. Any losses, any errors they have, go across millions of customers and cost a lot more money. There is a lot more loss there.

Also, are you sensitive enough to detect leaks? Some backwoods person out there goes and taps your power line, and creates this independent system without a meter — are other meters sensitive enough to detect that? In a gas system, like natural gas, you have a huge gas pipeline network that runs across the US. They use big flow meters and they have to be very accurate. And in companies specifically, they will usually operate two or three meters in parallel, or in series, rather, that they can evaluate how much they are being charged, and verify that they are being charged the right amount of money from the power company. Say they use natural gas in their process to run a furnace. Well, they will double-check the power company, because if the power company is wrong, it can literally cost millions of dollars a month. That’s with even a very small error. So they typically have two or three different independent meters, and they’re all sitting there in series monitoring the same thing so they can keep an eye on each other and know whether or not they are being charged the right amount. The nice thing about the balanced flow meter is no moving parts, so it doesn’t degrade with time; if there is particulate flow in the pipe, that is, if you have a single-hole orifice and you have particles, say, sand going through air or something, it piles up in front of the meter. That’s not a problem for ours; it blows through the holes because they are spread throughout the pipe. So you don’t get degradation over time in a natural gas-type system.

You get the high accuracy and low permanent pressure loss, so it makes an ideal custody transfer meter. Orifices have been used in the past, but they tend to go with high-end turbines and things that are much more complex. They do a lot of ultrasonics and a lot of vortex shutters. Those devices, you’re talking $30,000 to $80,000 a piece, to be able to go into custody transfer, whereas in one of these plates, you’re probably talking about $3,000 or $4,000 with comparable accuracy.

So you put these in the gas pipelines, you put them in the oil pipelines, and you use them as custody transfer meters to make sure that the right amounts of fuels are going to the right places, and that you really verify and now how to bill across the US, and also to detect leaks in the system.

NTB: Of what is it made?

Kelley: It can be made out of anything. Anything that makes your pipe system. If you have a really erosive acid that is going to eat away metal, and you are using plastic, we can build it out of special plastic. Any fluid, any type of system — there is really no limit. The only limitation is whether nor not you have pressure transducers and temperature transducers that can survive the environment. Most places have worked those problems and have such devices that work in their systems. So we can make it out of steel, we can make it out of aluminum, we can make it out of stainless, we can make it out of ceramic, we can make it out of plastic, PVC — we’ve made it out of five different materials already. Materials really aren’t that big a deal.

NTB: It is in use right now?

Kelley: It is being used right now. There are several oil companies that are using it, and they are very pleased with the results. The largest one we’ve put in the field is 22 inches, and so, for a 22-inch steel pipe, that’s a pretty big flow rate. There is no limit on the upper end; we’ve got probably on the order of 80 to 100 plates in commercial industry right now that are being used in different places. And they are being used in liquid flows, gas flows, some slurries, even. We’re able to operate in some slurry flow, which is a multi-phase flow problem, and we’re able to get some pretty good results out of that.

To give you an idea of the accuracies we’re talking about, at 0.2% or so, you’re talking about a fraction of a teaspoon out of a gallon. So you’re talking literally about a few drops out of a gallon, and that’s what you have to have for custody transfer. If the gas pump meter that you use to pump your fuel is wrong, that, for you, may only add up to a couple of cents, but when several thousand of customers come through there, it adds up to be several hundreds of thousands of dollars. Multiply that across a huge gas industry and you’re talking about lots and lots of revenue that’s based on accuracy of custody transfer meters. So what we are after right now making this unit a custody transfer meter, and it’s well on its way to that.

The other place where we are getting some interest, some good application, are the shipping industries. There are several places where ships use large-scale flow meters and have to monitor their processes. And so there is a very good chance they’re going to be showing up on some shipping systems pretty soon.

As a standard, it’s based on the old orifice flow standard technology. I guarantee there is a standard orifice plate in every chemical plant; every plant that manufactures anything uses flow meters. Just about any of them will have an orifice plate flow meter that we could be a drop-in replacement for. And the nice thing is, they are here operating on that standard orifice, and they are getting somewhere between a half and 3% accuracy, usually closer to 3% on most applications. If they just come and change that plate and drop in our plate, they instantly drop their accuracy below 1%. And that makes a huge difference when you are mixing chemicals, mixing compounds in very exact ratios. It has a huge market potential.

For more information, contact Anthony Kelley at the Marshall Space Flight Center at This email address is being protected from spambots. You need JavaScript enabled to view it. .


NASA Tech Briefs Magazine

This article first appeared in the September, 2006 issue of NASA Tech Briefs Magazine.

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