Very high turndown flow meter
Very high turndown flow meter
(OP)
I have an application where I need a flowmeter capable of a turndown ratio of almost 70 (0.3 L/min to 20 L/min)... So far I have not found a single flow meter that would do the trick. Also, this meter will be measuring a controlled variable on a PID control loop, so decent accuracy is needed. Any suggestions? Thank you very much.





RE: Very high turndown flow meter
John
RE: Very high turndown flow meter
1.5" line size, liquid flow, 0.3 L/min to 20 L/min variable flow rate depending on application, accuracy as good as we can get (ideally not more than 0.5% full scale). DP meters are out of the question, unless they can GUARANTEE accuracy over the ENTIRE range.
Thank you very much for your comments.
RE: Very high turndown flow meter
Dual Transmitters across an orifice (or maybe a single smart DP being recalibrated on the fly) might approach it, but at the lowest flow rates even 0.5% of full scale is 35% of actual flow.
But do you really need that turndown? Exactly what is the process?
RE: Very high turndown flow meter
RE: Very high turndown flow meter
I have been suggested a coriolis flowmeter... As a matter of fact, a special model could give 0.8% of measured value at the low end, but it's expensive.
I don't know if a mag meter could provide such a turndown ratio? Besides, I do not know if chemical additives would be conductive...
Turndown is needed because we are trying to design a "one size fits all" unit here... Different chemicals being added to another fluid flowing at various different rates.
Once again, thank you much for the valuable input.
RE: Very high turndown flow meter
RE: Very high turndown flow meter
KB
Quote: "Its not what you know, its who you know"
Everythings a learning experience-Everything
RE: Very high turndown flow meter
Sorry but you are wrong about the valve. The valve will not be the determining factor for accuracy, the flow meter will. The valve is just part of the controlled process.
The valve characteristics however will be a factor - the valve should have a high turndown too.
And yes,it looks suitable for a coriolis meter.
Francis
RE: Very high turndown flow meter
I hope this helps, and yes, I believe the best choice here would be the coriolis... I was just hoping someone would come up with a less expensive option.
RE: Very high turndown flow meter
The problem with this is that you require some amount of pipelength before and after, and space is a major constraint in our design.
RE: Very high turndown flow meter
RE: Very high turndown flow meter
Hydrae
RE: Very high turndown flow meter
In a pump the higher the pressure drop across it the greater the slip flow i.e. the fluid that slips through the working tolerances.
In a PD meter the pressure drop across the meter is usually very low so the slip flow will be much less and can be calibrated out (especially if you have a high resolution pulse output...)
But a PD meter could be a very good choice at this line size.
However, now we need to know the pressure.
If this is high pressure then you may need to select a twin case PD meter. For Coriolis meters high pressure caused more stiffness in the tubes and pulsating pressure, such as you can get from some pumps, can cause even more problems. You need to talk to the mass meter manufacturers to discover the current state of play. Of course, if the pressure is low, then you are fine.
JMW
www.ViscoAnalyser.com
RE: Very high turndown flow meter
RE: Very high turndown flow meter
John
RE: Very high turndown flow meter
What do you make of Foxboro's claim that their latest Coriolis meters handle mixed-phase flow without loss of accuracy? Some real-world experience is useful from time to time - cuts through the salesworm's spiel and reflects the truth instead. Micromotion seemed pretty adamant that their instrument wouldn't handle it.
----------------------------------
One day my ship will come in.
But with my luck, I'll be at the airport!