Portable clamp on flow meter

Looking for recommendation for a portable clamp on flow meter to check water flow in steel pipes and compare it to other flow meters as a double check
Water temp is between 140 – 190 F.


Thanks,

We are doing that now as well. We have an E&H and a Flexim.

Look into Keyence. they have some really nice options for what you are looking for.

Thank you.
The Keyence FD-R looks nice and simple to install. Anyone use one?


PDF appears to be too large to attach.


Thanks,
Bob

You need an ultrasonic clamp-on flow meter. I would recommend FLexim.It is compact and very easy to use.

It has been about 10 years since I used a portable ultrasonic and I don't recall the brand (someone else bought it, I just had to make it work). I recall having to know the inside diameter of the pipe. In order for the velocity to be converted to flow, that is a requirement of any velocity based flow meter. That turned out to be some trouble for my application since it was an unusual size of stainless steel pipe. I got an educated guess to get me close, then had to do some tweaking.

The other requirement when we used it in another spot was that the paint had to be stripped off the pipe. That was not a big deal. Another issue is if you are using it on ductile iron pipe that has a cement liner. On those types of pipe, especially if they're old, the ultrasonic waves tend to reflect off the liner and make it hard to find a good spot to apply the sensors.

A model that has gotten some praise from one of our preset customers is made by Fuji. Theirs are permanently installed, but I think there is a portable version.
https://americas.fujielectric.com/fecoa_products/flow-meters/#productinformation

Ultrasonic transit time flow calc is based on medium’s (water’s) sonic velocity which is temperature dependent. Check whether meter has selection of medium (water) temp range.


Every ultrasonic needs to know pipe ID to do a flow rate calc.



Interior condition of pipe determines available ultrasonic signal strength. Scale, corrosion pitting and deposits, or a liner, as OkiePC mentioned, can absorb or distort the ultrasonic signal. Unless you’ve got x-ray vision, interior condition is an unknown. Beware of older carbon steel pipe.

GE Panametric are very good but $ to buy new.

Bob O said:

Thank you.
The Keyence FD-R looks nice and simple to install. Anyone use one?


PDF appears to be too large to attach.


Thanks,
Bob

Click to expand...

Bob, call your local Keyence rep. They will be more than happy to bring one in for a free demo.

I've contacted Keyence but I can't meet the install upstream [DN] requirements at my original planned location after a pump according to their docs. I asked what kind of difference there would be and didn't get a solid ans which I can understand.
I can get ~15 DN on a straight vertical pipe off the pump discharge but not the 50 shown with other flow disturbances.


Hope that made some sense.

Are you saying you don't have the straight pipe lengths to meet the instrument specs?

You'll get a reading, but the swirling turbulence is likely to affect the accuracy of the reading.

danw,
If you were to guess/estimate, what would the difference be? Searching the web I've seen 1% but this is the info I was after from the manufacturer and I can live with a difference.

Thanks,

The most common problem with flow measurement is inadequate straight pipe for the meter installation. The amount of error varies with the type of meter and the type of disturbance. A flow nozzle downstream from a single 90° elbow will not be as bad as a single point device like a pitot tube downstream of a close-coupled tee and elbow. In any case, a 1% error is, in my opinion, very optimistic.

The problem is a result of obstructions and fittings creating an asymmetric velocity profile across the pipe. Depending on the fluid being pumped there are flow straighteners that can minimize the swirling and velocity disturbances. ( https://www.instrumentationtoolbox.com/2016/01/how-flow-conditioner-works-flow.html ) These will create some pressure drop. The recommendations in this source are for custody transfer type accuracy - most suppliers will suggest more like ten diameters upstream and five downstream.

You can start with the flow meter supplier, but here are some other sources:

https://www.onicon.com/wp-content/uploads/0497-7-Flow-Straightener-Catalog-Sheet-03-18.pdf

https://mattech.cz/en/produkty/uklidnovac-proudeni-se-svazkem-19-trubek-263/

https://www.fluidcomponents.com/products/flow-conditioners/vortab-products/vip-flow-conditioner

Bob O said:

danw,
If you were to guess/estimate, what would the difference be? Searching the web I've seen 1% but this is the info I was after from the manufacturer and I can live with a difference.

Click to expand...

Bob,

If I knew, I'd tell you. But the magnitude of error in flow measurement is largely undocumented. In 30 years of reading, I've only encountered two cases where the potential error is documented/reported.

1. I found several references that documented that orifice plates installed backwards always read low on the order of 10-35% from actual flow rate.

2. Siemens actually tested one model magmeter flow tube on a flow stand to prove it could qualify for the European standard for potable water distribution with an error less than ±2% from the reference flow rate. The test involved multiple non-allowable piping configurations - a Tee close coupled, two in-line 90° elbows with 2 Tees, Four 90° elbows. Highest error was actually less than 1%.

When I saw the report I was astounded because I had never seen any report of the magnitude of potential error for any magmeter when the minimum upstream/downstream rule was violated. I had no idea if the error was 5%, 10%, or 50%. To think that it was a mere ±2% or thereabouts.

Siemens tested only one flow tube model and would not state that other flow tube models would perform similarly. But given that 95% of all magmeters are pulsed DC excitation and use Faraday's law, I suspect that almost any magmeter would have close to the same performance. By the way, Toshiba announced their "Mount Anywhere" magmeter meaning there is no restriction on upstream/downstream piping (can't have a valve upstream) about the same time as Siemens made their announcement.

Clamp-on
I can tell you that the Siemens clamp-on ultrasonic transit time flow meter (doppler is a joke) has a selectable (blind) correction factor for several piping anomalies that are not considered "fully developed flow" (1 elbow, 2 elbows in-line, 2 elbows out-of-phase, expander, reducer, header inlet upstream; no correction for a valve or intrusions).





The amount of correction is undocumented, one just enables or disables any one of the selections. "Trust me, I'll still love you in the morning."

I tend to go with Tom Jenkins in that 1% is probably too little error from a close upstream pump, but it's my gut feeling, without any documentation. I've had three instances of confirming a magmeter reading within a fraction of a percent with sufficient upstream/downstream with a Siemens clamp-on. But clamp-on ultrasonics recommends 'multi-path', that is, multiple sets of transducers (installed at 90° radially) to correct for flow profile pertubations. Multi-path gets expensive and it wouldn't be an option if there were a better way to do it. There is, sort of, trust the flow profile correction factor if it's a piping anomaly.

But for a pump? I've never mounted one real close to a pump so I just do not know.