External, clamp on Flow measurement device

[pb2102sm]

Hi all,

Does anyone knows if there is any reliable external (clamp on)flow meter, capable of measuring gas and liquid flows and temperature? I've seen a couple of those on the internet, but was wondering at what extent they are reliable. Also, in case of insulated piping, can that device still making/getting a good reading?
Any input is much appreciated.

Thank you,
pb2102sm

 

[LittleInch]

The only clamp on ones I've used are ultrasonic so work on gas or liquid, but not 2 phase.

temperature clamp on is ok but you need to insulate over the top of it

You need to get a good bonding between the sensor and the metal pipe, so you would need to remove insulation in the bit where the sensors are.

They can be a little bit flaky if subject to vibration or just being hit as the sensor to pipe surface bond is key plus the alignment with the other sensor needs to be spot on.

when it comes to meters it's all about cost vs reliability and uncertainty. You pay the money, you get the results.

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

 

[EdStainless]

External temp can be very flakey.
You grind a bare metal spot, glue the sensor down with a thermally conductive epoxy, and then reinsulate over the top.
You will still have some offset.
And you cannot verify calibration of your sensor.
Ultrasonic flow meters can work well if you prep the surfaces and mount them carefully.

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P.E. Metallurgy, consulting work welcomed

 

[pb2102sm]

LittleInch and EdStainless,

Thank you so much for the inputs.

 

[danw2]

Transit time loves clean liquid but has trouble with any entrained gas in the liquid. Same with suspended solids.

The calculation for fluid velocity is based on sonic velocity of the medium. You might check to see if whatever meter you look at specs the sonic velocity of the medium in use at the temperature its flowing at because the sonic velocity changes with temperature. The top end meters have a database of fluids but it is what is.

Doppler: I used a transit time meter (that worked very well on clean fluids in transit time mode) that an optional set of doppler transducers with an algorithm for the doppler transducers. I installed it on a waste stream with lots of suspended solids. I found the doppler little more than a slow responding flow switch, it could barely distinguish between max flow and 1/3 max flow. When the flow was shutoff, it took over a minute to drop to about 10% of max flow reading. Pathetic.

Rusty steel pipe with scale will reduce the signal strength considerably. Treated boiler water was easy to get a reading on. 20 year old sch 40 pipe for untreated water was usually a no-go. Meter just wouldn't get a reading.

 

[EdStainless]

Anything that can reflect or scatter the signal, either in the fluid or on the pipe will destroy the readings.
Single phase flow and clean pipe are requirements.
If you are going to use an Ultrasonic gauge that you plan on moving, you need to have exact mounting points permanently marked.
If you don't mount it exactly the same way you will get different readings.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed