70% of installed meters arethe wrong technology or the wrong size. 1

[jmw]

This is the interesting statement in an article in Control Engineering:

http://www.controleng.com/index.php?id=483&cHash=081010&tx_ttnews

[tt_news]=6047
I was initially surprised by this figure and then, once I realised that it was not about meters that simply didn't work but about not choosing the optimal meter (and I'd suggest this is probably true of most instruments) it made sense.

I like these big numbers... 70% sounds really alarming. I remember a presentation on Condition Based Maintenance that quoted someone like Boeing saying that 80% (or some similar high number, I don't recall the exact figure now) of all failures were due to maintenance.....

They get your attention.

My suggestion is that 70% being not the optimum choice is simply the cost of doing business the way we now do.

Any other thoughts?

JMW

http://www.ViscoAnalyser.com

 

[zdas04]

JMW,
Your link didn't work, it got me to Control Engineering page, but has the message "no news_id given". A search of their site for "Flowmeter selection: Right size, right design" got me to the article (the url is exactly what you posted). The article is limited to flow measurement within plants. I would contend that the problem extends far outside of plant fences.

Thinking about Natural Gas, a single molecule tends to be measured when produced, when transferred from a gatherer to a mid-stream transporter, when transferred into a plant, several times inside the plant, when transferred to a transporter, when transferred to a utility, and when transferred to a consumer. Each of those categories would have a different number. I can buy that well over 70% of the production meters are wrong in so many ways. The count of bad meters into midstream should be lower, but not a lot lower. Bad meters into plants should be a bit lower than into mid-stream. Bad meters inside the plant was the topic of the article. Bad meters into transport should be pretty rare. Bad meters into utilities should be rare. Bad meters into final consumers could easily be back to above the 70%. The article is talking about a simple count, 70% bad is plausible. If they had been talking about the measured volume being bad, the number is much lower.

In my measurement classes, I emphasize that all meter technologies always give us numbers but the numbers may not really have much to do with flow and you can't tell the difference from the office. I recently evaluated a meter station for a customer and found that the volume numbers reported were no better than +/-40% and that the decisions they were making based on these random-number generators were only slightly better than a blind guess. That station was designed by someone at a huge engineering firm with world-wide scope, and no particular measurement expertise.

Thanks for posting that.

David

 

[JLSeagull]

Try

http://www.controleng.com/index.php?id=483&cHash=081010&tx_ttnews

[tt_news]=6047

... "When people are sizing flowmeters in general, they tend to use some legacy information and not the most up-to-date data for making decisions," he notes. "You might end up with the wrong size meter because you haven't looked at the latest innovations."

Using legacy information may assure that something actually works without the newest and neatest devices.

These [Control Engineering] articles lack any real information beyond suggesting that more flow measurement technologies exist. The points raised have been published numerous times over the last few decades.

 

[jmw]

And how much is due to a lack of instrument technicians at the end user?
How much is due to single source contracts, strategic alliances etc.
Once upon a time lots of "single product" companies had sales engineers who would compete with other sales engineers and all would talk to the plant engineer.

Today we have the majors with just about every product in their portfolio.
So today the few plant engineers left can write a spec and submit to purchasing and purchasing will send it to their strategic alliances partner who will source within their own product range.
The supplier now has a set of sales engineers responsible for thousands of products and reliant on selection software and sizing programs to do the grunt work.

This is today's business model and I am not surprised that 70% is the figure.
Of course, that isn't to say that 70% of meters are a disaster. It may mean that if it is the right technology it may not be the best nor the cheapest, in fact it may be both inferior to and more expensive than a competitor product.

This is before we even ask if it is the right technology or the right size.

But while this may be the case, I suspect the system works, and this is the cost of that system, because few of these "choices" are actually totally useless.

If this is the case and this is why, will it get better or worse or stay the same?
Is there a major catastrophe in waiting somewhere? Or is it no more of a problem than the conventional/historical approach?

I guess part of the reason it works is the influence of modern smart technologies and the more forgiving instruments.

JMW

http://www.ViscoAnalyser.com

 

[jmw]

PS sorry about the link.... I copied from my post in Linked in...

JMW

http://www.ViscoAnalyser.com

 

[zdas04]

I blame "Supply Chain Management" by both the purchaser and the seller. I have a client whose gas is measured by a third-party gathering company. A few years ago the gathering company fired most of their measurement staffs (non-core activity!) and put the measurement function in the hands of purchasing clerks "where it belonged" since meters are built to AGA and API standards that are pretty rigorous. Then the "continuous improvement" process kicked in and they standardized on 4-inch Square-Edged Orifice meters (AGA3). Next step was to spec 1.25-inch orifice plates and 0-250 inH2O transducers with 0.25% uncertainty (+/-0.625 inH2O) for all stations. This is in a field where the wells vary from 50 MCF/d (0.25 inH20 at 100 psia) and 200 MCF/d (4.7 inH20 at 100 psia). At 72 MCF/d (0.625 inH2O) you know that your volume is somewhere between zero and 100 MCF/d. When I've explained this to the purchasing clerks they point to the special award that the got for saving money. When I ask about their material balance they say that they allocate system losses back to the individual meters so they don't matter. Sometimes these "losses" can be a 5% gain--the gatherer then takes ownership of the 5%, then deducts 3% of the reduced total for contractual system losses.

When I talk to the big engineering firms about this, they don't seem to have any measurement engineers at all any more (we've all retired). It just isn't a priority with anyone.

David

 

[hacksaw]

70% is a bit high by a factor of ten to twenty. In detailed meter surveys, the majority of meters are correctly selected and installed. Most of the uncertainty is the result of changed process conditions, or mixups in the shop records.

Where custody transfer is involved, the error rate is much lower, and most of the disagreements are contractual in nature.

 

[zdas04]

Hacksaw,
Do you have any data to support the number you are putting forth? I work with upstream gas producers (custody transfer) and find that more meters are wrong than are right.

David

 

[IRstuff]

Hardly a solid statistic:

At a recent industry event, an expert suggested that 70% of installed flowmeters are either the wrong technology or the wrong size (generally too large) for the application.

the article link should work, but it doesn't for some reason; it's the fourth hit on my search for it:
wrong meter

It may also be that you need to have the website already open

TTFN

FAQ731-376

 

[jmw]

And admittedly, the "expert" is not named but it is implied that this is an article based on informed comments by flow professionals.

Given that the supplier will offer the best match from their range and that the client may not have the option, these days, to canvas the market even if he had the time and skills, it is not at all surprising the figure is large but in a significant number of such cases I am not sure how critical or concerning it is.

It has to depend on what is meant by "wrong".

Some of us might think wrong is if the meter fails in a short time or is grossly inaccurate.

Others may decide a meter should be sized in a particular area of the flow rate range and that to do otherwise is poor practise. They may think one meter is better than another because of its cost of ownership rather than its cost of sale.

I would be much more interested to know the proportion of meters where it is a serious issue and not to be shrugged off with a "so what?"
Maybe not quite in the "supply a mag meter for a non-conductive fluid" bracket maybe but a step further away.

What really concerns me is where I suspect a company's offerings are biased toward promoting its flagship technology over other better and more appropriate technologies in its range for that application.
Again, the meter may do the job or measuring so is not "wrong" in that sense, but it may not be the best choice for the client if all the clients considerations were taken into account.

JMW

http://www.ViscoAnalyser.com

 

[dcasto]

My experience is that a lot of meters the author surveyed where not needed anyway. They could have well just have been digital, flow yes, flow no. We also tend to get the wrong meters because we want new and flashy ones. How can an orifice meter be to big or too small??? Change the plate, and forget about doing the calculations and installing a 2.6238563895904 diameter hole, we have flow computers now.

zdas, there had better be better measurement on the wellheads today, the lawsuits over mismeasurement by the royality owners is running rapid.

 

[zdas04]

No, there is not. I saw a new installation just last week that should have been a 2-inch tube that was a 4-inch because of "policy".

David

 

[dcasto]

since there is no flow data for a 2" meter in the database used the create the flow equations, how can you say a 2" tube is better?

 

[zdas04]

I think you may have that one wrong. There are a large number of (tens of thousands) of 2-inch orifice meters in the world. Daniel makes a 2-inch Senior fitting. They also make a simplex fitting and an OFU in 2-inch.

API 14.3 (AGA 3) part 1 (section 1.2.2) says

This standard provides design, construction, and installation specifications for flangetapped, concentric, square-edged orifice meters of nomina1 2-inch Schedule 160 and larger pipe diameters.

It also says (section 1.9.1)

To assure the accuracy of such flow measurements, the user may wish to calibrate the meter in situ. This is particularly suggested for orifice meters under 2 inches (50 millimeters) nominal pipe size. In situ is defined as being under nominl operating conditions, with the actual approach piping configuration, using the actual fluid with the actual orifice plate and recording system in place.

(I cut an pasted the above from the standard, the misspellings are theirs) Seems to be pretty decisive proof that the database includes 2-inch.

David

 

[ccfowler]

I am not surprised by any seemingly large proportion of flow meters being a wrong or poor choice. That seems to be a chronic problem going back in history. I've seen many, if not most, flowmeters being at least misunderstood if not outright poor choices. As digital displays became more common, the misunderstanding of accuracy has only been augmented. The fact that a 6 or 8 digit display is presented is commonly misperceived as an indication of great accuracy--pay no mind that the overall installation is at best +/- 2% to 4% (only the 2 or 3 most significant digits have any meaning).

I've seen vortex flow meters used to cover way too wide a range, and much of the operating time, the actual flow is below the minimum so that no flow is actually indicated. Some of these have been in custody transfer service with a very happy customer, and a supplier trying to understand where the missing product has gone.

I've seen several cases where orifice plates have been installed backward. From the outside, all seemed to be in order since the orifice "pan-handles" were all stamped on the same side. After being in service for many years, it was found that some of the orifice plates had been stamped on the wrong side of the pan-handle. This revelation then explained why operating data from some process trains made no sense by comparison. Process trains that were thought to be performing poorly had, in fact, been performing very well, but their flows had been drastically understated from the time of original installation.

The great improvement in the availability of computing equipment to better compensate for orifice meter performance characteristics over wider flow condition ranges has been most helpful for accuracy of these well-documented (and relatively inexpensive) devices. I've seen many cases where the application of more elegant computation capabilities to long-serving orifice meter installations has resulted in far more accurate measurments over very wide flow rate ranges with results that have startled operating personnel--especially during periods of reduced flow where the older, simpler instruments greatly understated the actual flow rates.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[KiwiMace]

My experience in this matter, is that at design time, no-one really knows what the flow is going to be because the client could not justify the budget on, and therefore face, reality; but all have a good handle on the max theoretical limit.

The engineer in charge of speccing the flowmeter may have a feeling for the likely range, and will comment on this at some meeting, check the minutes the following week to make sure it was written down, and then spec the max conceivable limit to cover his or her derriere.

 

[JLSeagull]

Typically a control systems or instrument engineer receives the maximum, normal and minimum flow rate for valves and flow elements from a process engineer. My observation is that most process engineers use the material balance normal rate and include a factor for minimum and maximum without any real thought about startup or unusual conditions. Also the recalibration process is complicated by the management of change process. However the rangeability of many modern instruments can ofte accommodate startup changes.

 

[dcasto]

The databases used to do the linear regression to create the flow equations are lacking in data from lines smaller than 2".

 

[zdas04]

I can buy "smaller than 2-inch", not "lacking 2-inch and smaller". When I was working as a measurement engineer in the early 1990's a guy from my company was on several of the API/GPA measurement committees and he kept pulling me into committee meetings to address specific questions. Some of those questions required access to "The Database" and I clearly remember a large number of S40 and S80 2-inch stations included. There were some thicker wall 2-inch, but I can't remember if there were a lot of them or not.

2-inch is very well represented in the statistical analysis.

David

 

[dcasto]

I spent plenty of time with Upp, Jerry Arbour, Kientz and Hickle on measurement. 2 inch meters were not added until 1990.

http://www2.emersonprocess.com/site...ent-of-Orifice-Meter-Standards-techWPaper.pdf

What counts is beta ratio and unless you have less than a .625 inch orifice, the 4" meter is fine at 50 mcfd at 100 psig.