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Dear experts,

We are using Barton (Model 7304) 4" turbine flow meters (6"flow line, Pressure 700PSI) to measure water injection. We are facing a problem in measurements at lower range, so our engineering consultant suggested we use 2" Turbine flow meters to get accurate flow measurement at lower ranges. My question is, if we use 2" flow meter on 6" flow line, what is the effect on flow rate? Does it maintain the same flow rate or will it decrease?

Thanks,
MK

Have you asked the manufacturer or their representative if the sensor can accommodate the expected maximum flow rates? Isn't that the key? More than likely, the smaller meter will restrict the flow, but will it accommodate the maximum expected flow-rates?

Also, you need to ask about piping inlets and outlets if the piping diameter will be reduced from 6" to 2" and back to 6" because of possible turbulence or other phenomena.

You also need to check the bearings and shafting for wear. Turbine meters have very large turn-downs, and they start losing their low end performance as a function of bearing and shaft wear.

You will have a significant pressure drop inserting a 2 inch meter body into a six inch line, calculate it as if it were a simple piece of pipe.

You will have a severe accuracy degradation unless you make the effort to mount the meter at least 10 diameters downstream of the flow constriction, and at least 5 diameters upstream of the change. You cannot just "reducer-in, reducer-out" to make this change.

You may very well have meter overrun at high flow rates. This will do anything from running the turbine off its shafts and down the pipe to increased bearing and shaft wear.

I strongly recommend that you don't do this, without a great deal more thought. You might want to engage the services of a flow measurement consultant like David Spitzer (disclosure--we are in partnership) or Dr. Richard Furness, or others.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
Mailto:wboyes@putman.net
Read my blog SoundOFF!! At www.controlglobal.com/soundoff

We need more details, e.g. flow range you want to measure.

Roy

Hi Roy,

Our required injection range is 3 to 70 cu m/hr,
Flow line pressure 700 psi and estimated flow line temperature is 55 Deg.C.

Consultant suggested we use Faurre Herman Heliflu, TZN50-70, having flow range of 7 to 70 cu m/hr.
If we use 2" flow meter in 6" line, does it affect the total flow rate/day? The existing flow meter is Barton 4" having linear range of 20-284 cu m/hr. I hope this information may be useful to you to help us.

Thanks,
MK

Dear MK,

In this situation the pressure in 2" line will increase if flow remains the same.

To keep the flow remaining the same you may have to add a pump to circulate the water.

Increased pressure at 2" pipeline will compel you to use thicker pipe, or technically you have to use a higher SCHEDULE # of 2" pipe.

You must involve a process engineer to establish new flow rate, use of pump to maintain older flow rate and pressure development at reduced diameter pipe.

And also a Mechanical Engineer who can exactly advise you regarding the required thickness or schedule # of the new pipe.

You must also mention your current flow rate. So that any of us may reply to you in detail.

PK

Check out ACCELABAR which can handle entire of your flow range with one single meter as the turn down is 65:1. Check out http://www.veris-inc.com

But at what accuracy, Rohit? You are talking about measuring at the very dirty end of the pressure transmitter you are using. Take the installation accuracy component, the device accuracy component and the transmitter accuracy component, and I bet you have pretty bad results at the bottom 20% of your scale.

A different flowmeter isn't this user's answer.

What he needs to do is re-design his piping so that he's got reasonable flow rates for the pipe size.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
Mailto:wboyes@putman.net
Read my blog SoundOFF!! At www.controlglobal.com/soundoff

7304 (4" meter) has a linear flow range of 95 - 1250 USGPM with a minimum repeatable flowrate of 63 USGPM.

7102 (2" meter) has a linear flowrange of 15 - 240 USGPM with a minimum repeatable flow rate of 9 USGPM.

A 2" meter will have a higher pressure drop at the same flow rate. For example, at 200 USGPM, a 7304 will have a DP of about 0.1 PSI, where the 7102 will drop about 3 PSI. The higher pressure drop will cause the flow rate to drop.

Gerry Corraini
Cameron Measurement Systems

Dear Mr.Gerry Corraini

Thanks for ur information.

Is there any procedure to calculate flow rate drop either practically or theoretically?

MK

A 2" turbine should work. I don't have any experience with those on water service.
I would prefer a 2" Mag 2 - 78 m3/h
or 3" Votrex 4 - 130 m3/h.
600# flanges are required.

Regards,

Roy