Coriolis flow meter, overview

[themroc]

We are running a test unit with vscous newtonion fluids.
In order to measure the flow rate in the moment we are using a "gear flow meter"
The accuracy of this device is not very good, in the future we are planning to switch to a more accurate device.

I am Investigating the use of a Coriolis flow meter.
Apparent advantage would be that we are measuring mass flow rates in which we are primarily interested in.

Because it is a test unit we are running a wide range of process, property conditions.

Flow rate: 2kg/min to 80kg/min

Viscosities: 1cP to 20000cP

Temperatures 20°C to 80°C

Questions:
Is there a huge pressure drop penalty to pay in order to use this instruments ?
Are they generally good devices to cover a wide operational range as described above ?
How is the acuracy effected?
Any idea for good suppliers?
thanks for your help

 

[Latexman]

Huge dP? No, but they are not low dP units.
I've used them for > 100/1 turndown.
Accuracy = f(flowrate)
Micromotion and Endress-Hauser can answer your questions.

Good luck,
Latexman

 

[JLSeagull]

The Coriolis sizing software that I use suggests a few choices in sizes and models with the pressure drop and accuracy listed for each meter at each flow condition. Coriolis meters are most practical in small sizes. A 4 NPS Coriolis meter is big and could cost nearly $25000. Some manufacturers publish sizes to about 10 NPS.

I assumed some density data for your application. At 33 lb/ft3 with 20000 cP, the drop is 8.5 psi at 4 NPS. The drop is 36 psi at 3 NPS and 4 psi at 6 NPS.

 

[DesignerMike]

I have used the E&H meters quite a bit. The high viscosity will affect the pressure drop (and restrict the sizes you can choose). The meters need a minimum velocity to maintain accuracy.

In order to maintain the velocity you will be forced to reduce the line size through the meters. This is what will generate the increased backpressure....If you are normally running a 4" line with the 20,000 Cps product to keep the backpressure down, you may have to reduce down to a 2" meter to have enough velocity for an accurate messurement.

Also look at the electromag meters (depending on your product). They are much shorter and will affect the pressure a little less PLUS they are less costly. The magmeter is approximately 35% the cost of the coriolis.

Give E&H and Micromotion a call to answer your questions and give you some data.

 

[themroc]

Thanks for your reply,
Only one Question for clarification:
JLSeagull, what kind of sizing software did you use, is this available online? And also can you just clarify what NPS means.

Thanks
tehmroc

 

[BigInch]

Nominal pipe size

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[Latexman]

One of the vendors makes a coriolis meter that also measures viscosity if that is an advantage. I *think* it is E&H.

Good luck,
Latexman

 

[JLSeagull]

My Emerson Process Management - Micro Motion sales person provided a customer version of their "Instrument Toolkit". It also calculates bore sizes for orifice plates, integral orifice meters and a few other flow element types.

I can be a standards nomeclature nut. I specify the line size and flange class using the nomenclature from the ASME standards. For example, 1/2 NPS pipe has no relationship to the dimension 1/2-inch either inside or outside. I specify Class 300 instead of 300 # RF. I also specify weld neck flanges as slip on flanges are rarely acceptable. Slip on flanges appear to be the Emerson standard for integral orifice assemblies if not clearly specified otherwise. I have written as RFWN and had questions from the Rosemount inside people as to this term. I may type out welding neck instead of WN to assure that inexperienced inside sales people can find the correct order entry selection.

 

[Ashereng]

Krohne makes a very straight single tube coriolis meter. The pressure drop in this is very small.

E&H makes a meter up to 10" in their Promass F series.

I have seen literature of 100:1 turndown for almost all the vendors. You need to check accuracy. A large turndown is good, if you can live with the accuracy.

Krohne and E&H both also make non-"U" non-"Z" type of meters. These configurations tend to have the higher pressure drop.

Also, at high viscosities, usually, the flowrate will be small - the pressure drop may be acceptable since the slow flow offsets the high viscosity somewhat.

One other note. Be careful about comparing meters based strictly on size. A 4" Micromotion will have a different range than a 4" Krohne, as well as different pressure drops and such.

The pricing has been fluctuating recently. I am comparing quotes we obtained 1Q this year versus now. The pricing has changed dramatically. Contact your nearest rep for the up to date price.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[legs]

you could try MicroMotion, they have lots of experience in this field.

 

[jmw]

http://www.smartmeasurement.com/en/home.asp

On this page you will find some meter sizing programs.
By the way, your gear meter, dependent on manufacturer and type, ought to give very good accuracy and modern PD meters can be calibrated over a range of temperatures and viscosities. If you know the viscosity there is no reason you should not get an accurate reading with a PD meter. Besdies, you will only have to worry about viscosity up to a given limit for the meter after which it should be fully positive i.e. no significant change in slip flow for all higher viscosities.
None the less, coriolis meters have some good advantages and you should compare various meter types.



JMW

http://www.ViscoAnalyser.com

 

[themroc]

Thanks so far all of you.
There seams to be a lot of new development on the coriolis measurment devices.
The Proline Promass which actually measures also viscosity seams to be the perfect candidate for our purposes.
All the info was quiet helpfull.
thanks

 

[JLSeagull]

Some measure liquid density.

 

[jmw]

Did you need to measure viscosity?
Your question was about flow measurement in a test rig.
I assumed you were flowing fluids of known viscosity since you didn't ask about how to measure viscosity.

If you need to measure viscosity, is this simply for operating temperature conditions or do you need reference temparature conditions?

What accuracy do you need?

I believe the Promass uses amplitude measurement for viscosity (an inverse square law relataionship between viscosity and signal amplitude at resonance).

That being said, be very sure to explore the accuracy of this measurement across your entire viscosity and temperature range.

The viscosity temperature relationship is loglog(v +0.7)= A+Blog.T where log is baes 10, V is kinematic viscosity and T is degrees absolute.
Take a look at the graphical solution at

http://www.viscoanalyser.com/xls.html

and note just how steep the curves are at lower temperatures, even at 500cst and 40egC.

Measuring viscosity can be a very demanding requirement. Perhaps you could explain your needs in more detail.



JMW

http://www.ViscoAnalyser.com

 

[moltenmetal]

I think what the OP meant to say is that they're dealing with viscous, non-Newtonian fluids.

Low flow coriolis meters all suffer from the same problem for your application: small diameter tubes are required to provide significant turn-down. This means high pressure drops when dealing with high viscosity fluids- if you size a meter based merely on the mass flow. The good news is that your flows, at 2-80 kg/min, are not really all that low as far as coriolis meters go. You will not require a tiny unit with 1/8" (or smaller) internal tubes, as you would if your flows were 2 kg/hr or so.

You have several choices amongst various coriolis meters, each with advantages and disadvantages that each vendor's competitor will only be too happy to inform you about.

Put your application to E&H, Emerson (Micromotion) etc. They will no doubt select for you a larger bore meter operating at significant turndown (i.e. 1/10th to 1/100th of the maximum mass flow which such a unit can measure) in order to reduce the pressure drop for your most viscous products. Make sure that your entire desired measurement range is handled at a reasonable accuracy- they can predict the accuracy based on the zero stability of the instruments which is a fixed number. Accuracy rapidly decays below a certain mass flow as it approaches the zero stability.