Clamp-on Ultrasonic Flow Measurement?

[tonyrgd]

Hello, I've searched the internet and the forums and I can't seem to find a lot of good information on this. I'm going to be purchasing a portable non-intrusive clamp-on flow meter for use in measuring water flow in chilled water and heating water hydronic systems. I'm just looking for product recommendations and general experiences with this type of flow meter.

My application will be analyzing existing hydronic systems used in HVAC applications, so chilled water temperatures will range from 40-54°F and heating water temperatures between 100 and 250°F (temperatures will be fairly constant during measurement). Water velocities should be below 10 fps in most applications, but I wouldn't be surprised if they exceed that in some circumstances. Pipe diameters should be under 10" in most applications, but capability for larger pipes would be nice. This will be used for taking quick field measurements and for doing some temporary datalogging to determine existing flow conditions.

I'd just like to know if anyone has had any good or bad experiences with certain brands or if there are any solid industry standards out there I should be looking at. I'm currently looking at Onicon's F-4400, and hopefully will be receiving one to demo before purchasing soon. I also plan on giving Siemens a call tomorrow about their SITRANS FUP1010. I'd also like to know if anyone has any general information on them based on experience.

Thanks.

 

[georgeverghese]

Clamp on ultrasonic FTs' are usually chosen for high turndown applications (in excess of 50:1 at least)with no loss in accuracy. From memory, the lower limit is a flowing Reynolds no of 2000 or so. On a recent project, the German Flexim FT was used for high temp hot oil service at 300degC in a stationary process control application - have had good operations feedback so far with this. These meters are popular with the oil and gas business people.

Dont know about the portable version on this - from memory, installing these on the pipe requires specialist skills.

 

[danw2]

Siemens used to be Controlatron. Long history. A couple different sets of transducers will handle all those pipe sizes. Great low flow capability, I've seen it show backflow through a stopped pump or dribble of thermal syphoning.

I heard a salesman recently say that the next gen electronics box for 1010 is due out this fall. As much as I'm impressed with this clamp-on, if it were me, I'd wait for the next gen, particularly for datalogging.

The only downside with ultrasonics is that it can not get a reading if the pipe really scaled up on the inside: insufficient signal strength. Works great on treated water, new and unscaled pipe, but on 35 year old CS pipes running untreated water? Toss of the coin as to whether you'll get a reading or not. But that's not just Siemens, that's any of 'em. Actually it's not a bad indicator of internal scaling, if anyone cared.

 

[LittleInch]

I've used clamp-on UT meters in the past and it was very successful.

However be aware of the issues of UT meters.

You need a good clean surface to clamp to, both inside and out, so any painted, coated or galvanized pipes can be difficult to get good readings.
You need 100% liquid, no bubbles or gas pockets
Set-up requires a certain length of straight pipe to get the signal return and avoid high turbulence areas
Set-up can take a while to get a reliable fixing and then accidentally nudging one of the clamps sends it off or leads to breaks in readings.
I don't know what difference temperatures make to the speed of sound in water, which is your key measurement issue - you would need to check to see how this variance, if any, is input into the machine to get a reliable reading.
Portable machines tend to be single path which are good, but need relatively stable flow. multi-path tends to reduce the impact of swirl and turbulence inside the pipe, but you won't often get that on a portable system.

If it was me I would hire one to get to grips with the issues or "try before you buy"

If you're going to do it yourself, you will need to factor in some training costs from the vendor otherwise you'll waste a lot of time figuring it all out.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Many people in the HVAC industry use the FUP1010. One of the best on the market.

https://www.youtube.com/watch?v=KRdoh2bBoYQ

 

[tonyrgd]

bimr, that is good to hear. I just spoke with my Siemens rep this morning and will be demoing the unit this week.

 

[danw2]

Good advice on factoring in 'training'.

The Siemens 1010 can tolerate some air and actually reports aeration as a unitless value.

The transit time transducer are super, but the doppler transducer set is merely an indication of flow, with no reasonable means of getting an absolute flow rate value and too slow in response to use as a flow switch. Save your money, skip the doppler option.

A 4" angle grinder with a wire brush does wonders for cleaning off the outside of the pipe.

Yes, temperature affects sonic velocity. The 1010 actually measures the sonic velocity of the medium at the start of a commissioning setup. I have no idea how.
The manual has a table with sonic velocities for water at 2°F intervals and a graph of ethylene glycol at various percentage concentrations.