Question
Dear Professor,

I just installed an electromagnetic flowmeter on an 8 inch wastewater line. I am not familiar with flowmeters because we only purchase a few now and then. Today I had trouble with this meter -the readings are going crazy !! They seem to be going up and down all the time and don't reflect the actual flow rates. I have not read the installation instructions thoroughly but would be interested to have your opinion on what you think is wrong. I bolted the flowmeter in between two flanges and wired up the power line and analog output line correctly. Do you think I should be using another type of flowmeter ?? Please help!!!

Answer
Dear John,

It is always a good idea to thoroughly read instructions . If all else fails read your manual!! My experience tells me immediately that you have not grounded this flowmeter and that is why it is not working properly. There should be a connection on the flowmeter to run a cable to a ground rod. Please look for it. Do this and then go back and see what the display is reading .Electromagnetic meters should work fine on this application! Send me an email again if this does not solve the problem.

The Professor

Question
Hi Professor,

I have a 3" line coming off of a digester that I'm looking to measure the flow from. It is a flow rate between 250 and 1000 cubic meters per day, that averages around 800. The inlet pressure is quite low (approximately 11" w.c.). The gas is being piped over to a heat exchanger and a burner.

The gas is primarily methane (60-70%). I'm looking for a flow meter that is inexpensive, and that I can just install into the line and walk away from. The only necessary aspect is that it has to give a flow reading that the operator can read on a regular basis - but if it could eventually be connected to an electronic system (when the money comes in) then that would be ideal.

Thanks for any leads you can give me.

Ben

Answer
Dear Ben

Good to hear from you....

Try Weber sensor's model 3205.30/5, it is a stainless steel cased air flow meter that will output 4-20 mAdc for the rate of 0-2000 Cu/ft per day in a 3 inch line.

You could run this output to a display or digital meter (or analog) to read the output...the meter being scaled for 4-20 mA = 0-2,000. It could later be tied into a PLC or SCADA system.

Question
Dear Professor

I have to re-install several clamp on transit time ultrasonic flowmeters on carbon steel pipes 4, 6 and 8 inches on water applications in the next few weeks due to a factory relocation. I cannot find any good vendor data on where we should be installing the clamp on sensors in the new factory, as the piping is different from the original factory they were installed on. The only thing I have is drawings of the initial install from the consultant who designed the plant. Do you know anywhere I can get information on the best places to install the meters? Please help if you can !

Homer

Answer
Dear Homer,

There are certain guidelines you should follow when installing clamp on portable or fixed ultrasonic flowmeters . Please remember that these are only guidelines because there could be several factors involved in a process which could affect the flow regime such as velocity, temperature and other liquid properties . The important thing is that you should be measuring on a point where the flow regime is stable and well formed. Avoid pipe bends, reducers, expanders and pump outlets . You may want to take a look at the following set of guidelines produced by a particular manufacturer http://www.eesiflo.com/products/measuring_point_selection_01.html .
Hope this helps

The Professor

Question
Professor Flow,
I am an old racer who would like to fabricate a reasonably quick and dirty system to measure/calibrate different automotive mass air flow meters. I'd like to be able to do this in my workshop using the least amount of investment possible (of course!). The maximum amount of air mass would be in the range of 330 lbm/min with the minimum being almost zero. I can fab up the voltage input and output needs of the meter to be tested, but what I need is what is the test measurement device itself and the air pump size? Or? If you have any thoughts on this I would love to hear them...

Lawrence

Answer
You might want to consider one of the Coriolis, turbine, PD or other manufacturers we have here on the website. If your accuracy can be as low as +/- 5%, then I would go with a simple flow indicator type. However, if your work requires a high degree of accuracy, the go with a turbine or positive displacement meter, and have it flow calibrated to make sure it is correct and a meter factor is established for accuracy. If you are doing this for your business, be sure you have all the documentation needed, i.e. traceability to a national standard, as you will need that if there ever is a problem traced back to the airflow into the engine. In addition, re-calibrate the meter on at least an annual basis. Oops, there I go again, getting on that darn soap box. It sounds like you have all of the other (secondary) equipment figured out. You asked about what pressure to run this at, since your flow meters are at basically atmospheric pressure, then I would try and maintain that pressure when flow calibrating them. However, if you are dealing with just a mass flow, want some high accuracy mass measurement and can take a lager pressure drop, you may want to consider using a Coriolis meter. The American Gas Association is working on a Report describing the use of Coriolis meters in Natural Gas Service, and there is test data from a couple of manufacturers that show the meters work very well. The uncertainty of these meters are +/- 0.5%. With this meter, and they're not too cheap, you can be confident you are getting good measurement. Good luck, and I hope this has helped.

Best Regards,
The Professor

Question
Sir,
I am looking for a cost effective mass flow meter solution to sense FLEETCOL 9081 in a flow range between 2-10 gal/hour or 7-37 kg/hour. This is a defoamer additive used in pulp and paper delivered by a positive displacement pump. It has a viscosity of 2000 - 2700 cps at 25 C with a density of 8.2 lbs/gal. We would need 1/2" stainless pipe connections also. Our DCS requires a 4-20ma input signal. Appreciate your help. Thank you.

Brian

Answer
You mention cost effective in your email. Well, how cost effective do you want to get? Just remember, when you skimp in one area, you pay for it in another.

Now having said my soap box speech on that issue, I'll attempt to answer your question.

I would recommend a Coriolis meter in this application. There are several manufacturers of this type of meter. They almost all have 1/2" connections available in SS. They most all have transmitters that will give you a variety of outputs, including the 4-20 ma output that you require. In a previous question I listed several manufacturers of Coriolis meters. Here again is the list:

Emerson Process (Micro Motion)
Endress & Hauser (E+H)
FMC Measurement Solutions
Foxboro
Krohne
ABB
Schlumberger

Your application is critical in that you can ruin a whole batch by either under or over delivering the defoamer to the pulp. So, I would ask the question, how much does it cost to recycle or dispose of the batch? All of the costs, including loss of revenue? I would guess that it would not even take 1 time to pay for an expensive meter. Sorry, I got back up on my soap box.

Best of luck to you.

Regards,
Professor Flow

Question
Professer Flow:

I am interested in knowing what is considered accepted practice for 'revenue quality' metering for steam. Is a vortex flow meter which measures flow and then has either pressure or temperature compensation for density calculation and conversion to mass flow acceptable? or is an instrument such a coriolis type considered to be required for 'revenue quality' steam metering?

Fernando

Answer
With out knowing the actual process conditions it is hard to make a recommendation in a steam application.

Most applications use vortex metering. These will give you +/- 1% to 2% uncertainty depending on operating conditions. Another consideration here is to make sure that installation configurations are followed (I've seen and heard of several that are improperly installed).

Yet another excellent meter is the V-Cone meter. These meter work very well in steam applications. They are very accurate meters and are also in steam service.

Coriolis meters are used to measure steam. Since these meters are mass meters, there would not have to be any additional calculations done if you want a mass number. They typically have a +/-0.5% uncertainty, but are limited by temperature. A couple of the Coriolis manufacturers make some high temperature meters.

Best Regards,
The Professor

Question
Dr. Flow:

We need to measure a stream of 19% aqueous ammonia ranging from 15 to 35 lb/hr @ 60 to 70 PSIG through a 1/2" pipe. We need to send a 4-20 MA signal to a PLC. We currently use a honed orifice plate arrangement with a Honeywell Smart Trans., but are operating at the very bottom edge of the orifice and transmitter. We do not see consistency from unit to unit and have no faith in the output.

What do you recommend?

Joel

Answer
I would recommend that you look into using a 1/4" Coriolis meter, or a positive displacement (PD) meter with either a flow computer or a totalizer that will convert the pulse output of the meter into a 4-20 ma output that you need for the PLC.

My first preference would be to go with the Coriolis meter as it has no wearing parts that will need continued maintenance. Another advantage to the Coriolis meter is that most manufacturers have the electronics bundled as a complete meter with out having to get additional electronics attached, or buy additional modules for your PLC.

In either case, you should calibrate the meters on some frequency. Oops, here I go again, getting on my soap box. If your application is critical, you need to know with some degree of accuracy the volume of the fluid. With a PD meter, you would have to take the meter out of service and verify the meter factor has not changed (as the parts wear, the slippage of product will cause inaccurate measurement). A Coriolis meter would require a zero check, which is, in simple terms, blocking in the meter at operating conditions and checking to see if it reads, zero. If not, it is a simple thing to reset the zero. A word of caution here for all meters, is that if you see a constant shift in one direction over time, you might want to check the meter internals for wear or build-up of debris or some form of scale.

I hope this helps.

Best Regards,
The Professor

Question
Professor Flow,

Could you recommend a type of flow sensor for flue gas desulfurization slurrys? 10-50 wt% gypsum in water, 10-60 micron 20-40 wt% limestone in water, 10-100 micron I want accurate readings without bugging up the instrument with solids.

Thank you,

Answer
It would help to know pipe diameter and flow rates and temps but certainly Calorimetric sensors (try Weber for e.g) could handle this. Calorimetric flow sensors are ideal for slurry applications since there are no moving parts as with turbines or paddlewheels. You also might want to consider clamp on doppler ultrasonic flowmeters and depending on pipe size maybe transit time (time of flight) flowmeters that can handle this type of media but then again it would all be dependant on pipe size , temperatures and flow rates .

Professor Flow

Question
Dear Professor---

What type of meter would your recommend in terms of cost, maintenance, and relative accuracy (not custody transfer accuracy) for crude oil measurement service. The crude is typically about 20 API gravity. Pressure would be around 120psig, flow rate about 2000 to 3000 BPH in a 6 inch line at a temperature of about 60 F. Vortex, orifice, magnetic flow, or turbine?

Joe

Answer
For this application, of the options you listed, I would go with a turbine meter. Not the standard turbine, but a helical turbine. The helical will give you better performance at the cooler temperature. You may also want to consider a vortex meter, but my first choice is still a helical turbine. There are a few manufacturers of this type of meter for crude oil service that are well known.

Professor Flow

Question
Hi professor,
I am seeking advice on an economical flow meter. We have a resin core cleaning process that uses a vibrating unit with water and sometimes soap solution to clean mold release off the cores. The spent water is gravity flow to a holding tank with a stand tube. It flows out of this tank though a 1 1/2" pipe to another settling tank. The material runs from this second tank into the sanitary drain. It does this by means of a flex hose 1 1/2" diameter. the hose is about 3' long and makes one bend parallel to the floor before making another bend down into the drain. The slurry doesn't flow fast through this hose, about 1/2 gal. per minute average. The slurry is made up of 10-30% Crystalline Quartz, 1- 20 % Nepheline Syenite, 1 - 20% Talc, and 1-20 % Aluminum Oxide. I hope this information gives a good idea of what we are looking for. This monitoring is necessary for a Wastewater report we must do annually. Thanks.

Ted

Answer
Dear Ted,

If you are looking for economical this application looks like something that weber Sensors could do www.captor.com . I am sure there are others and I would be happy to add those companies in this reply if they are out there but this company comes to mind. They can monitor mediums that are water based, oil based, or other chemical based or mixtures. They also have no moving parts so there is no clogging or sticking as with paddlewheels or turbine meters. This particular application with .5 GPM on 1.5 inch pipe is a bit low for accurate metering, however if the pipe diameter could be reduced say to 3/4 or 1/2 inch from the holding tank to the settling tank for example, this would be a fine way to meter the flow.

Hope this helps!

The Professor