Sea Water 84" Carbon Steel Pipe flow meter


Thread Starter

Muhannad Mukhtar


we have two pipe lines, 84" and 72" Carbon Steel, both are equipped with Annubar flow meters. the 84" annubar is damaged and the 72" is inaccurate.

for more accurate and reliable options, I have looked up the retractable Annubar supplied by Rosemount, but it cannot work on a pipe larger than 48".

Now, I Need your help, I have contacted some ultrasonic flow meters suppliers but they haven't replied yet.

what do you recommend as a solution to maintain reliable operation and an accuracy in the range of 1% to 2%.

Thank you. and please contact me on my email if you have any info that would help me:

[email protected].
You didn't say whether you're talking about clamp-on ultrasonics or in-line. Given the large pipe diameters, I'll assume clamp-on, for financial reasons. The Siemens (former Controatron) ultrasonic works well on steel pipe if there is minimal internal scaling or corrosion. Steel transmits the ultrasonic energy, corrosion scale particles attenuate ultrasonic energy.

For reliability and accuracy

- use the high accuracy model transducers, not the universal models

- pay very careful attention to installation. The external mounting surface needs to be clean and smooth. A coat of paint is acceptable, multiple coats over flaking paint is not. The meter calculates the 'index' location for where the transducers are located. If this particular installation requires 'direct' mounting on opposite sides (not likely, but possible), careful marking of a large diameter pipe exactly 180° on the opposite side and at an exact axial distance is very doable, but can be botched by lazy installers. A transducer can not be mounted on a weld seam.

- for accuracy, the pipe wall thickness needs to be a known. If you don't wall thickness, get it measured with an ultrasonic gauge.

- If you've been using DP/averaging pitot tubes, then presumably you have sufficient straight pipe runs upstream and down stream to constitute a decent meter run. If you don't, then, make it so.

- Consider taking data out via Modbus (optional), rather than analog to avoid analog cal errors.

- The flow velocity has to be above the 0.3m/sec rate to stay with the accuracy curve limits. The meter will display lower flow rates, but the accuracy curve takes a sharp turn below 0.3m/sec

- If you're willing to research sonic velocity at whatever your salinity and temperature, the meter can be calibrated to a reference standard sonic velocity at your particular salinity/temp point.

- Keep the electronics at a reasonable temperature. I was at a site yesterday where the clamp-on flow meter was dysfunctional because the radiant heat from a rotary kiln 5m away baked it to death. I could not stand where the meter was because of the radiated heat. The plastic case was so hot I couldn't touch it. You're probably not running a rotary kiln, but you might be in a climate with high ambient temperatures.

Muhannad Mukhtar

Thank you very much for your prompt and in-depth reply.

I just want to clarify some points;

1. I am considering the clamp-on ultrasonic flow meter type. this is the reasonable and cheep solution

2. I have failed to give the flow data, we have a 40,000 T/Hr of continuous flow.

3. The pipe line thickness plus the cement lining will add up to 27.2 mm. is it going to affect the operability and the accuracy of the meter.

4. The ambient temperature might reach 50 C Deg, so what measures should we take in this case (Does it have to be covered??)

5. I have contacted GE for their ultrasonic meters, what is the difference between them and Siemens in terms of reliability and service.

Once again I appreciate your time and effort of sharing your knowledge and experiences.
2.  The flow rate is 3-4m/sec, easily in the accuracy zone.

3. I clamp to steel pipe and some plastic, but I've not done lined pipe.  We've run into old, corroded steel pipe where the Siemens meter will not provide a reading when the signal strength is too low due to internal corrosion.  My conclusion is that when the Siemens meter gives a (transit time) reading it's an accurate reading.  If it can't give an accurate reading, it gives no reading at all.  I'm very comfortable and prefer that measurement philosophy.

As to lined pipe, you'll have to query Siemens on suitability.  I've heard the flowmeter works on lined pipe, but it's outside my scope.

4. The spec sheet says it's rated to 60°C.   I'd make sure that it had a sunshield because ambient 
+ direct sun can be hotter than ambient.

5. I've only used Controlatron/Siemens.   I can't comment on GE.

John Accardo

Hello Muhannad

I am a Siemens Applications engineer and have been working for Controlotron prior to Siemens for 30+ years. Your application is perfectly suitable for the clamp-on meter, we have operated on many cement lined steel pipes over the years. The only question is the wall thickness of the steel itself which would determine the most suitable transducer. Please feel free to contact me at [email protected] so that i may address your concerns and put you in touch with your nearest Siemens representative.

Thank you.