What type of flow meter would you choose? 1

[StoneCold]

I am working on an a flowmeter application and wonder what other users have chose. I want to measure the discharge rate from two centrifical pumps. The process fluid is 70wt% to 80wt% methanol with the balance being water. Pump number one flows close to 60 gpm through a 2" stainless pipe. Pump number two flows close to 120 gpm through a 3" copper pipe. The meters I chose were Endress + Hauser vortex shedding flow meters. They are sized one pipe size below line size to keep the velocities high enough to measure the flow rate when the pumps are in spill back mode (15 gpm and 20 gpm respectively). Have other users had good luck with vortex shedding flow meters? I have never used them before but I think I will be happier with them than with an orfice meter or a turbine meter.
Thanks for your comments

StoneCold

 

[CARF]

If the fluid is conductive I would choose electro magnetic flowmeters. E+H or ABB

If you are interested in density and temperature as extra signals and you have some money to spent you may choose Coriolis massflowmeters.

Vortex will do the trick, but are less accurate and also have an obstruction in the pipe (the bluff body).

There's this E+H software called "Applicator" which helps to make a good choice:

Applicator System requirements PC with Pentium® processor, 64 MB RAM (128 MB RAM recommended)Operating System Windows 95®, Windows 98®, Windows NT®, Windows 2000®, Windows XP®
SVGA graphics card, 600x800, 256 colours (1024x768, 65536 colours recommended)At least 100 MB free hard disk space
Internet Explorer 5.0 or higher, Netscape 4.5 or higher

Please find on the E+H site:

http://www.endress.com/

Good luck,
CARF

 

[StoneCold]

Carf
I am trying to stay in the $2000 USD range so I am not going to go with coriolis, though I agree they are the best.

I don't think that electromagnetic will work with changes in composition, am I right on that or does it just have to be somewhat conductive regardless of changes in fluid properties?

Thanks
StoneCold

 

[khan101]

For Magmeter fluid composition is not an issue as long as it is conductive and does not coat the electrodes. But I think vortex meter is a good choice. The only problem, there is a low flow cut off point with vortex. Depending upon manufacturer, it can be anywhere from 5 to 25% of the total flow. We had a Yokogawa vortex which had a cut off point at 25% so below that point it did not register anything. Check with E&H about thier vortex meter. One suggestion, If you have a continuous process or you can not shutdown the pump, install a bypass around the meter. This will allow you to safely remove your flowmeter for maintenance purpose without interrupting your process. Rosemount also offers integral orifice meters. Check them out as well.

 

[quark]

Generally vortex meters have better turndowns around 30:1.

E&H vortexes are very good and you need not have compensation for external pipe noises(vibration). Only problem with these meters, when compared to mags, is that they can't detect partial flow in the pipelines. If you ensure that your pipe is always full then they are the better bet.

Regards,

 

[CARF]

What you can do as well is have both Vortex and Mag on a rental base. Put them in series in the pipe and compare the performance (i.e. through a data logger).

Cheers,
CARF

 

[jsummerfield]

Stonecold said <i>"I am not going to go with coriolis, though I agree they are the best."</i>

Flow meter selection involves compromises. Coriolis meters may be ideal for this application but are not the best for all applications. The down side for coriolis meters include the pressure drop required and size limitations. Installation issues also exist. The pipe must be full and this is true for most flow meters. Coriolis meters are expensive.

Once operating, let us know how the vortex shedders work on this application. I think that they will be OK.

John

 

[hacksaw]

shedders are the way to go on this one.

forget magmeters on this one, methanol and water is not considered conductive fluid unless you have special electrodes

turbine meters are a no brainer, you'll lose them on pump startup if you have any surges.