Coriolis is undoubtedly a great technology and receiving significant R&D investment to further improve it where possible.
I first got directly involved from in the late s with both the first single straight tube (not Khrone, whatever they claim) and a twin bent tube design.
But: I have also seen them come to be regarded as a sort panacea,
the solution to all flow measurement applications. I see people recommend coriolis for pretty well any flow or density application including where they are not in fact the best solution. Partly because they are perceived as a superior technology and as a safe choice but partly also because it saves having to rigorously evaluate the application to choose the best meter solution, something few can afford to do these days and where we rely on the suppliers to recommend the meter choice to us, trusting they can and will make the very best recommendation....
There are a variety of different formats and this is true also of MicroMotion. The very fact of the different formats informs that each has its own advantages and disadvantages and that there is no universal solution, even among coriolis meters.
So even though a fan of coriolis, I often have to say "take care you choose the right meter".
(see which links to an article I wrote for World Bunkering - there is a response in the Spring issue from an Emerson specialist and we do not seem to be that far apart, to my mind.
Here is what has been said on Linkedin:
The mass flow still has a long way to go as test are been carried out in Singapore. The problem here is test results are still not conclusive as yet. One area that needs to be look at is the recording by the meter during stripping time. If it is a normal supply without stripping the meter is very accurate. But when it comes to stripping time the figures does not correspond. So more studies will still be needed as we do not expect barges not to strip their tanks on completion. Cost is also another issue here, like what Hans mention the prices are squeezed from the buyer to the brokers, traders all the way down and by the time it reaches the suppliers the prices are so low they do not even cover cost. Anyway the Mass flow meter is good to have but it still need more study and testing. Presently in Singapore, Shell, ExxonMobile are testing it on 2 or 3 of the barges. Maresk Oil is testing on their barges and the results varies quite alot.
Stripping is where each compartment is pumped out of the last drop of fuel and necessarily introduces high volume fractions of air.
This is probably beyond the amounts lacajun mentions.
But see the multiphase triangle in Neftemer's paper....
A lot of MP technologies use a combination of volumetric measurement with various density measurements to determine the various volume fractions.
No doubt coriolis is great technology and no doubt it will continue to evolve over time but no technology has yet replaced every other technology and is unlikely ever to do so.
But the coriolis will be one solution amongst many for MP and the nature of the multi-phase will determine the appropriate technology. This is one reason why I have pointed to the Neftemer paper; because it shows the nature of the various fluids and some indication of the range for which the coriolis is capable.
It has been a while since I had any direct hands-on experience of coriolis meters so I cannot say exactly what the issues are. I can only speculate.
The flow stream enters the meter and divides between two parallel flow tubes. If we consider a single phase liquid then the density in each tube will be the same and, assuming the flow tubes have the same effective mass, and each tube will tend to vibrate at the same resonant frequency.
The flow splitter is a key design feature. It is designed to try and ensure that the flow splits equally between the flow tubes. If not then the mass rate of flow through each tube will be different and if significant then this may be a source of problems.
Now consider a two phase bubble flow. If we assume the gas volume fraction is relatively low and that the gas is finely and evenly dispersed in the liquid, then we can see that we should be able to achieve a similar outcome to that for a single phase flow, the same density in either tube and the same mass flow rates.
That isn't to say the meter will automatically be capable of handling bubble flow, there are some other issues to resolve. Vibrating elements sensors tend not to like bubbles on principle. Even a few bubbles can upset the sensor operation and measures have been taken to compensate.
For example, the Solartron density meters were notoriously sensitive to even a few bubbles. The evolution of the coriolis meter version caused some of these issues to be overcome by better signal processing but the key to the EGA density meter capable of handling 0-100% gas was to shift form driving in at one harmonic to another. The price paid was in accuracy. There may b something of this nature that would explain why entrained gas capability is only available on selected Micromotion meters but on the other hand, Foxboro have a signal processing solution which works on any coriolis meter format... but that only gets us as far as extreme bubble flow.
If we tend toward slug flow where the gas volume fraction is greater and where it is no longer finely divided nor evenly distributed, it is possible to have a situation where the mass flow rate varies significantly from one tube to the other and the density also.
It is at this point I'd probably want to suggest that the Exac meter would have been a better choice for Rosemount to keep when the acquired Fisher controls, instead of the Micromotion D-Type as many, myself included, thought it the superior design.
The Exac was a single tube coriolis meter which was formed into a two loop helical design where successive loops were vibrated against each other.
Hence, no flow splitter needed. So does this solve the problems?
No, on reflection, this design does not solve our problem because the density and mass flow rate will vary along the length of the tubes.
Hence with slug flow we might have one section of tube containing a slug of gas that will flow along the length of he tube first through one loop and then through the next. We now have different sections of the tube subjected to significantly different mass flow rates and densities compared to the next section.
It doesn't now matter if these are parallel flow sections or sequential. Once we get away from bubble flow we have to suspect we are in trouble, perhaps more trouble that complex signal processing can accommodate.
I suspect that this is where the problem may lie.
But my lack of hands-on over recent years means I may be seriously wrong.
This may be a difficult problem to overcome and if I had to suggest any coriolis format was better able to handle the problem than another I'd have to look at the single straight tube meters, the shorter the better. Perhaps the E&H promass has the best potential?
Meanwhile, volumetric flow measurement systems using volume fraction measurements are a viable way to reach the higher gas densities and flow regimes, though with many we still lack the sorts of accuracies we would prefer.
This is certainly one of those cases where coriolis is not the automatic response. It has its place as do other technologies.
JMW
The "Ping" is testing the tube stiffness and comparing to a baseline.
It is a valuable technique.
Another approach is based on taking a sample and measuring the density in the lab and comparing to the online measured value.
If they agree then the assumption is that the mass calibration is also good. (this evolves from or is similar to the Solartron air point tests which determine if the tube has corroded or been coated. easy enough to do air point tests on density meters, not so easy on mass meters so testing the density accuracy is an good alternative - the Solartron density meters are now Emerson Micromotion density meters).
No arguments with anything you say lacajun just some calrifications.
Except, actually, at the time Rosemount bought Fisher and dumped the Fisher Exac meter, the Exac was considered superior to the D type structurally and performance wise.
The structure was more flexible leading either to lower drive energy or better signal to noise (crude electronics in those days) but with far less stress on the welds as at the weld points you had some residual torsional stresses. The D types could suffer weld fatigue due to the geometry.
The Exac helical design, which for single phase liquids, (and that's all the D type did at the time), was superior because it didn't require a flow splitter. It also had a better headloss.
There are various factors that contribute to what makes one meter better than another, not just its accuracy. (Don't neglect what seem minor design points, quite a lot of work has gone into flow splitter designs especially in the early days when you didn't have such sophisticate signal processing to fall back on.)
Exac was an early victim and subject to a major patent war resolved only by the Rosemount purchase but later on a profusion of new mass meter manufacturers sprang up with different tube configurations.
Another new meter to show to advantage was the Schlumberger M Dot.
This also was a twin tube design but its tubes were again more flexible and with less stress on the welds.
No accident this, when setting out to design a competing meter you try and find solutions to the known problems with the entrenched technology.
I didn't like the electronics though (you may have seen my post about Ryvita) but the sensor was excellent.
For a while there, Micromotion seemed to be following the more common product cycle of introducing a new technology and then hanging on to the first generation design beyond the point where it was sensible i.e. when other manufacturers recognise its weaknesses and introduce
"me too but better" designs. Two ways to go, milk the product till the end of its days and bow out of the market or you invest in R&D and leapfrog back ahead again.
In terms of today's technologies, comparing back to the then Exac, undoubtedly the meters today perform very well. Doubtless, if the Exac had remained in production and undergone similar investment over a similar period, it would be much improved today compared to then.
What I was saying was that this historical view might have influenced me to think it would have been better but in reality, it just doesn't seem to offer any advantage when it comes to slug flows.... once you introduce a sizeable air pocket into the flow it replaces a like volume of liquid and makes a big difference to the mass flow rate at that point. Each pocket going through a meter tube represents a step change in the mass flow that may be different in each tube if the flow does not split equally (or, in an Exac, in successive sections of the flow tube). What you have to then contend with is the two tubes trying to operate at different frequencies and with differing mass flow rates steps changing through the tubes.
Signal processing has only gone so far at this time.
Foxboro developments for entrained air and
in situ vereifcation have been conducted at Oxford University; details can be found here: There are several papers on SEVA (self verification) on the site.
Most users will be extremely happy with their coriolis meters and for good reasons.
What happens though, is a variation of the Peter Principle. Sooner or later they will be pushed into applications where they initially fail.
This isn't a bad thing, on the contrary, it is a good thing where done purposefully.
Conservative companies stick to what they know, to the tried and tested and they stay away from "novel" applications.
They may do this because their product has become a bit of a cash cow and anything that adds to costs is to be avoided and novel applications have high cost of sales and after sales support.
In go ahead companies, what happens is that you keep pushing the envelope.
You try new applications.
You expect to see some extra costs at the outset but once you have gone through the learning curve and know how to make it work, you simple buffer sell into similar applications. In some cases you may need to invest in further R&D.
Every once in a while, you over-reach.
You may not know it till you fail, but if you don't try you never know what you can and cannot do.
But the more challenging the application, the more we move into an area of substantially increasing costs.
This means you start to look long and hard at the market and try to work out if the returns are there.
Failures are a sign that a company is trying to push the envelope. usually it will be because there is a significant market where the problems are anticipated and there is some confidence that the problems will be solved.
One such market is multiphase metering.
Look at the figures in the Neftemer paper; well head metering is a huge market.
Get it right and you can clean up.
However, whatever the technology, this is a market where total MP meter sales are very low and so far coriolis has only a portion of that market accessible.
There is a long road ahead.
What you then do is look for similar but simpler markets to try and recoup some of the costs - and maybe find the same sort of problems there as in the original market.
So when any technology fails at new and challenging applications it is not a negative.
It doesn't impact on the success of the technology in general applications. Failures are a sign the company is trying to push the boundaries and evolve even better technologies.
So there are two paths forward; the coriolis people will accept defeat and leave the application alone or they'll spend the money and solve the problems.
The reason to leave an application alone is if the returns do not promise to repay the costs.
Or if there is a better and simpler way to do it.
So no one says coriolis is not a good technology and getting better, but it is not axiomatic that it is always the best choice nor that it will not fail in some applications.
In MP metering it the size of the market and the installed base suggests the race is still wide open.
JMW
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