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Hi,

Good day!

I would like to seek for your opinion regarding the comparative study I am doing.

I am comparing the advantages and disadvantages of Ultrasonic and Magnetic Flowmeters in a landscape irrigation application.

I already have the process data. So far, both transmitters have met the ambient conditions and others factors. Pipe size is from 100-800mm and material is HDPE.

Can someone share ideas or give me more reference regarding this study?

Thank you in advance.

No irrigation experience here, but in general ultrasonic clamp-ons have had a break-through in the past several years so that the technology works fairly well on full pipe water flows at a fraction of the cost a decade ago. The technology's drawback is that the transducer contact point with the piping needs periodic renewal, a maintenance requirement. But one clamp-on fits all pipe sizes.

If the water carries suspended solids or has entrained air, transit time ultrasonic meters are likely to choke. If you can get a doppler measurement to work beyond the crude point of flow/no-flow, you should be selling your skills to the people who make those silly meters. Yeah, the factory guy can make them work if he dinks with them for a day, but is that feasible, cost-wise? It might be in a refinery on a high value process, but for irrigation water?

For magmeters, the tube price increases significantly as pipe size increases (electronic converter box [transmitter] stays the same).
There are different tube sizes for different pipe sizes (one size does not fit all).

Clamp-ons ship in a carton that UPS delivers. Large mag tubes ship on a pallet.

Either technology can be found in a model that can be configured from the converter keypad, without a HART handheld, which can be a factor.

There's the somewhat obvious feature that a clamp-on retrofits onto existing pipe without the cutting & welding needed to install a mag tube.

Mags are about the most reliable (full pipe) water flow technology out there, but if the site can maintain a clamp-on, clamp-ons have some advantages.

Thank you.

I would like to add a question. I haven't used an Ultrasonic flowmeter, Are the ultrasonic signals coming from this type of flowmeter has no problem with a HDPE pipe?

Thank you.

I would like to make a follow up question.

I haven't use any of those flowmeters I've mentioned especially Ultrasonic. Is ultrasonic flowmeter good with an HDPE pipe?

Again, thanks.

I can speak only for one brand, formerly Controlatron, now Siemens.

Their universal transducers are called 'universal' because they're supposed to work on any material pipe. I know they work on PVC pipe, I've done so, even used it on concrete lined steel pipe, but I haven't used a clamp-on on HPEC pipe.

The manufacturer will answer that for you, most will offer to demo a unit on your pipe to prove performance.

Dan

Some, but not all, clamp-on transit-time flowmeters can be used with HDPE pipe. It is best to contact one of the manufacturers or sales office to confirm their meter will. And to further confirm, request an on-line demonstration to be sure. While I am in sales and also perform installation assistance, I have to admit some will say their meter will perform when they know it could be questionable. I always like to show the user it will operate in their application. Since these clamp to the outside of the pipe, an online demonstration is not difficult to perform. They can also look at the application to see if there are any other conditions present that may cause the meter not to perform properly. Less than full pipe for instance. I agree with David, stay away from a doppler type meter. Transit-time meters, however, have improved significantly over the years and will now operate in conditions where suspended solids or air bubbles are present. For instance, they are now able to operate and are being used reliably on raw waste water flows entering a WWTP or pump stations.

Thank you to those who replied. You're inputs are really helping me with my study.

Still waiting for other opinions...

Thanks again!

Generally, who is more accurate of the two instruments?

Thank you.

As always, it depends. If you compare a spool piece magnetic flow meter with a high precision transit time spool piece flow meter, the installed accuracy will be very high, and the difference so close as not likely to be measurable _in situ_. If you compare either of those to a clamp on doppler flowmeter, the doppler flow meter will be significantly less accurate. A clamp on transit time meter, IF INSTALLED CORRECTLY will have an accuracy that compares favorably to a magnetic flowmeter. However, the transit time meter is significantly more application dependent than the magnetic flowmeter in applications where solids or entrained air are present.

Remember, flow applications are highly dependent on the individual conditions, and YMMV. If you really want an answer to this question in a specific application, you should consider contacting a flow expert like David W. Spitzer.

Walt Boyes
Editor in Chief
Control and ControlGlobal.com
555 W. Pierce Rd Suite 301
Itasca, IL 60143

wboyes [at] putman.net
www.controlglobal.com

NO clamp on flow meter will work accurately on HDPE pipe because the diameter "ovals" and changes with pressure pulsation, thus changing the Inside Diameter of the pipe-- and thus changing the diameter constant in the flow equation. You must use a spool piece type flow meter to preserve the diameter of the measurement zone.

Whether you use a doppler type or a transit time ultrasonic type flow meter is dependent on the solids and entrained air content of the fluid. Doppler flow meters work very well if the solids are of a specific gravity greater than about 3.0 g/cc with a particle size of greater than 75 microns, and if the solids content is between 80 parts per million and 30% solids. Higher than 30% solids causes attenuation of the signal and less than 80 ppm causes erratic readings.

Transit time flow meters do not do well in conditions of changing density or high levels of entrained air, because both of those conditions change the speed of sound in the fluid, and that changes the transit time equation.

They can be calibrated to work well in some viscous slurries and mixtures if the density of the fluid does not change.

Walt Boyes
Editor in Chief
Control and ControlGlobal.com
555 W. Pierce Rd Suite 301
Itasca, IL 60143

wboyes [at] putman.net
www.controlglobal.com

Hi,

Good day to all!

Thank you again for the replies.

However, I would like clarify if the periodic renewal of contact point of the ultrasonic flow meters means that the transmitting and receiving paths will be relocated? If that's the case, this somehow affects the reliability of the ultrasonic flow meter?

How about with magflowmeters? Does the lining material needs a frequent check also?

And based on your experiences, which is more reliable of the flowmeters?

Thank you in advance.

> periodic renewal of contact point of the ultrasonic flow meters means that the transmitting and receiving paths will be relocated? <

The ultrasonic energy is transmitted from the face of the transducer to (and through) the pipe to the liquid through the contact point where the transducer and pipe meet.

Historically, a sound conductive paste-like grease material is used to ensure contact between the two. Recently a strip of elastomer that looks like rubber is said to serve the same purpose.

It was always recommended that the contact point be examined and the paste renewed on a periodic basis, particularly for those units mounted outdoors where weather and temperature cycling could affect the contact point. That requires removing the transducer, renewing the paste/grease and then remounting the transducer.

Reliability, meaning ? ? ? ?

The electronics of both technologies is excellent, but if the clamp-on ultrasonics' contact point is not up to snuff then the readings aren't any good. Right up front, ultrasonics needs periodic servicing. It's like a radio can be functional, but if its antenna is knocked down, the signal doesn't get transmitted or received at its full strength. The radio is reliable, but its only a part of a system. The whole system has to work.

Magmeters electrodes can corrode or get covered with gunk in some types of service, but that's probably unlikely in irrigation water service.

Oh, my experience for mags is that in plastic pipe, grounding rings and their correct installation are essential. Some recent claims say "no grounding rings needed". Sure. Talk is cheap. The talkers don't come out and fix it when it doesn't work. It's cheap insurance.

And if you don't have a full pipe, all bets are off. You've got to pipe it so the mag tube is full. See the installation instructions for any brand magmeter, they're all very clear on this. But who reads the instructions?

Transit time ultrasonic flowmeters are subject to sensor fouling. This changes the apparent speed of sound and therefore the calibration. Magnetic flowmeter electrodes are also subject to fouling, which is why there are a variety of sensor cleaning strategies available. Magnetic flowmeters in highly corrosive or highly abrasive applications need re-lining sometimes as often as every two or three weeks... Which is the most reliable? Overall, I'd say magnetic flowmeters...I know of several that have been installed over 40 years. But that doesn't mean that delta-T sonic flowmeters are NOT reliable. They are reliable enough for use as custody transfer meters in oil and gas service.

Walt Boyes
Editor in Chief
Control and ControlGlobal.com
555 W. Pierce Rd Suite 301
Itasca, IL 60143

wboyes [at] putman.net
www.controlglobal.com

If we use clamp-on sensor, we do not have to clean it, because it does not contact the liquid directly. And if we use insertion or prover section sensor, we also do not have to clean it in many years.(I do not have the detailed time data). The top of the sensor is made of china, and it is not easy to be fouled.

We are manufacturer of ultrasonic instrument. Welcome you to visit our website to get more information. www.tuf-2000.com

Susan
email: tsonic_susan@163.com

I know that there are 3 types of optional transducers for ultrasonic flow meter.

1. clamp on type;
2. insertion type;
3. prover section type.

For the clamp on and insertion type, you do not need to cut the pipe but for the last one, you have to. The measuring pipe size is from DN20mm to DN 6000mm. There are portable ultrasonic flometer, handheld ultrasonic flow meter and fixed ultrasonic flowmeter.

I am sure that ultrasonic flow meter can be used on HDPE pipe. As long as you installed correctly, it will be very reliable. The linearity is better than 0.5% and accuracy is better than ±1%. Another advantage for ultrasonic flowmeter is that it can adot low voltage which the meg is not good at this.

I worked for a factory which specialized in manufacturing all kinds of ultrasonic flow/heat meters. If you need more information, I can send you a copy of user manual by email.
Hope this can be of your help.

Susan
Taosonics instrment co., Ltd
email: tsonic_susan@163.com
Website:www.tuf-2000.com

Hello,

Thank you guys for all the help and replies. I was able to generate the report.

Susan,

Thanks for the offer. May I have a copy of the manual?

Again, Thank you all.

Hi,

Electromagnetic flowmeters are any day a better solution than insertion Ultrasonic flowmeter for various reasons.

1)Insertion ultrasonic flowmeters working on transit time will work on treated water.These cant work if the liquid contains suspended solids.Electromagnetic flowmeters will work up to 40% suspended solids in liquid.

2)Insertion UFM is generally promoted by saying that you donot need to cut the pipeline and the sensors can be directly mounted on the pipeline.This is not true,sensor alignment at site is not possible and hence if sensor is installed at site it gives erratic reading.

3) Insertion UFM needs minimum of 10D and 20 D upstream and downstream straight run whereas the Magmeters need just 3D and 2D straight Run.

4) When you program the Insertion Ultrasonic UFM at site we need to enter various parameters of pipe line such as pipe OD , uncertainty of 1 mm in diameter of pipe will further introduce an error of 0.2%.

5)As per ISO7145 The best measuring accuracy is 3% of MV whereas magmeters offer an accuracy class of 0.3% of measured value.

Hope this helps.
Regards
Rakesh Mishra

Flow Measurement is highly dependent on application rather than technology. All flow meter are equally good & equally bad. Studying application is more important than debating on the technology. Simple application like water, there are over 50 technology that can work efficiently. Electromagnetic Flow Meter have been one of the front runner followed by Ultrasonic Flow Meter. Now Ultrasonic Water Meters are also available which can be of good choice for your application as it has defined spool piece with properly installed transducer to give accurate measurement. This can also work on battery (life is around 6 years) & do have GSM compatability. Clamp On Ultrasonic has different advantages over Electromagnetic Flow Meter, clamp on devices are the best monitoring devices but on difficult applications they can be a good choice too. For me application, practicality, accuracy requirement, price are key to decide on the technology to be used.

What Rohit said.

It is all about application, application, application!

Walt Boyes
Editor in Chief
Control and ControlGlobal.com
555 W. Pierce Rd Suite 301
Itasca, IL 60143

wboyes [at] putman.net
www.controlglobal.com

I used to do a lot of mine dewatering projects.

I found propeller type flowmeters to be the most cost effective in the line sizes you are using. You can get them with a simple non powered totalizer, rate-meter or with 4-20 mA and pulse outputs.

Ultrasonic transit time flowmeters work well with HDPE pipe provided the water doesn't have too many air bubbles entrained but for a fixed installation I would go Propeller for sure.

Roy

Based on your query, my assumption is that you will be using clean water for landscape irrigation.

Magnetic flowmeter is one of the best solutions for this application. However, for the large HDPE pipe sizes, you have some sizing issues to consider. Large HDPE pipes normally have thick walls, so you will need to choose a mag-flowmeter a few sizes smaller than the HDPE pipe size so that the inside diameters match each other. That means you will have to provide adapter spools. Adapter spools may have to be made of internal-coated carbon steel. You also need to provide isolating and bypass valves so you can remove the magflow tube for lab calibration if required.

If you use Ultrasonic flowmeter, consider using Clamp-on Transit-Time Flowmeter if you have clean bubble-free water. Clamp-on configuration eliminates the need for adapter spools and valves that mag-flowmeters need. The bigger the pipe size, the cheaper Ultrasonic becomes, compared to magnetic. For sensor probe selection, you have to check with the vendor the maximum thickness the Ultrasonic probe can handle and make sure it is within the thickness of your HDPE Pipe.

Magnetic Flowmeter product technology is more mature than Ultrasonic, and is generally more accurate at +/- 0.3% or better. Ultrasonic Accuracy is typically around +/-0.5% to 1.0%. If accuracy is not an issue, Clamp-on Ultrasonic flowmeter is well worth considering.

Magnetic and ultrasonic flowmeters are velocity flowmeters and can meet your request.

For the request, you need to consider the cost, and output, and power supply. Ultrasonic flowmeters have the clamp-on features which don't need to cut pipes, and almost low maintanance.

You can visit the website www.ultrasonic-flow.com for various kinds of ultrasonic flowmeters.

Hai,

I want to share my experience. it may help to you.
Ultra sonic flow meters are easy to use and are portable in nature. Like your projects these are suitable. But we must take care during measurement. It requires skill. Placing the measuring probes in tact and using the manufacturer recommended jelly/grease. enter the pipe dia. material of construction details,pipe wall thickness...enough it displays the flow rate.

Magnetic flow element as the size increases the minimum flow factor influences our measurement. Installation requires that the flow tube must be always in filled condition. It is not portable. If at all you are going with mag flow meters better buy an integrated model. It requires only power, both amplifier and flow element are integrated. This avoids signal cable related troubles. Hope this information helps you to some extent. Good luck

Hi,

I was watching the comparison. The electromagnetic flow meter requires high conductive process fluid to detect the change in flow and they are generally applicable for low temperature cases. We were preparing the specs for an non-intrusive flow measurement where the ultrasonic and em flow meter were competing. We opted ultrasonic since our process water was low conductive and process condition is high pressure and temperature.

Santanu

Hi,

First you need to check the budget of your project. As price remains same/similar for Ultrasonic Flow Meters for any line size. Whereas, EMFM it starts increasing significantly over the higher line sizes. Which further increases issues for handling and installations.

Advantages Ultrasonic over MAGs:

1. Ultrasonics (Clamp-on NOT Inline Ultrasonic) are easier to install.

2. No need to cut the pipe, so installation is possible on running process line.

3. Most of the Ultrasonic Meters comes with %age of Aeration monitoring in it. You can configure alarms based on these Aeration levels.

4. Easy to Handle as its size similar for almost all the line sizes.

5. Best to check whether there is leakage in the region due to quick installation and packing.

Disadvantages of Ultrasonic over MAGs:

1. Standard Accuracy starts from 0.5% to 1%. Whereas MAGs having 0.25%, 0.2% or 0.5% based on selection of each OEM.

2. Alignment of Transducer should be perfect else who will verify the reading? 1cm difference in transducer location can cause 1-2.5%loss of Ultrasonic Waves, this will lead to another deviation in its accuracy.

3. For Line sizes below 24inches it is going to be expensive technology as compared to Mags. from 24inches to 32 inches prices are comparable to Magflow meters. These Ultrasonics are best for bigger line sizes costwise.

As your application is for Normal Irrigation Water,hence you can proceed with ElectroMagnetic Flow Meters. It will give you better accuracies & prices for the line sizes mentioned by you.

Regards,
Davinder Singh

Thank you Davinder Sing,
vijay

100 - 800mm

In the larger sizes there is no question ultrasonic wins hands down.
32" flanged mag meters don't come cheap and even wafer style require pipe flanges.

I have used U/S time of flight meters on HDPE pipe with a wall thickness of nearly 2" and had good corelation to an adjacent mag.

The same Ultrasonic meter could be applied to the 100mm and the 800mm pipe.

I mentioned propeller type earlier for irrigation purposes because you can have a simple meter with totalizer not dependent on any power source. 4-20mA or pulse outputs to drive remote display.

Saddle type propeller meters for large pipe are a cost effective.

Cheers
Roy

Thanks, Roy. I was going to say the same thing. I caution about using transit time ultrasonics on HDPE. Unless it is thick enough to get rigid, under pressure the pipe sometimes ovals, changing the inside diameter and sometimes even loosening the mounting hardware and breaking signal.

A weld saddle propeller meter is the least expensive way to go, and will work extremely well.

Walt

Walt Boyes, FInstMC, Chartered Measurement and Control Technologist
Life Fellow, International Society of Automation
Editor in Chief, Control and ControlGlobal.com
wboyes@putman.net
office: +1-630-625-1132
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