measuring flow velocity and pressure in a pipe

[Jon9]

Hi,

I am having some issues measuring the flow velocity and pressure in a 100mm pipe that is a couple of meters long. The issue that I have is that the pressure and velocity are very low at 1.5 bar and 1ms^-1 respectively and I could certainly use some help here. I have few holes drilled onto the pipe and I was thinking of sticking a pitot tube in there and use a manometer as well but I am not sure if that actually works in practice? or if there is perhaps a more sensible way of measure the flow velocity given how low it is? would an ultrasonic flow meter be better? I should probably mention that the pipe is 1m underwater.

I am curious if anyone here has any ideas of how to approach this problem?

 

[LittleInch]

A few things spring to mind.

1.5 bar and 1 m/sec isn't very low,

Is this gas or liquid?

What accuracy level are you using?

How much money do you have?

Do you have power?

A standard pressure transmitter will get you pressure. Flow rate can be many ooptions.

Can you add a full size meter on the end or are you looking for an insertion type device?

Give us something to go on here.

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

 

[Compositepro]

Measure the pressure drop across the pipe length. Calibrate the pressure drop versus flow rate with a bucket and stop watch.

Or use a commercial flow meter anywhere in the flow path before or after your pipe.

 

[mk3223]

There are several types of flow meters can be selected, depending on the process and condition, gas or liquid, clean or dirty service, required accuracy, flow range (max & min), etc. See a reference link of the flow meter selection, besides the pitot tube, as below.

https://www.google.com/url?sa=t&rct...election.pdf&usg=AOvVaw20xJ5uJ7kqp0tgZBA3-tfO

BTW, is the whole pipe underwater? And, why?

 

[Jon9]

Thank you all very much for your replies and apologies for the vague post.

The pipe contains clean water and the budget is reasonably good so I can spend anything from $100-$10000 to get the measurements (would of course prefer to spend less if possible).
I could potentially add add a full size meter at the end but I would prefer an insertion. The pdf attached looks very useful so I'll give a read.

 

[Jon9]

Is anyone aware of any insertion based flow meter? something like a pitot tube which can be inserted into a hole in the pipe but which also works underwater? Or can a pitot tube, in principle, work underwater too?

 

[LittleInch]

There's lots, just google insertion flow meters, e.g.

https://www.omega.com/en-us/sensors-and-sensing-equipment/flow/c/electromagnetic-flow-meters

There are also mini turbine and paddle wheel, heated wire and no doublt other options.

Pitot tubes are not common in liquid flow meters, but no doubt exists somewhere.


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

 

[Jon9]

Thanks! That's a great starting point I will do more googling and hopefully I will find something suitable from one of your suggestions. Also thanks for pitot tube clarification, it seemed like a convenient and relatively cheap way but it will possibly not going to work.

 

[danw2]

Be aware that the vast majority of flow meters are NOT designed to operate 'submerged' or 'submersed'. I know that Siemens' magnetic flowmeters has an option for the flow tube to be submersed at some spec'd depth with the use a potting kit used to seal the junction box for the needed wires/cables (the tube has some extra seals as well). But the flow tube would need to be installed under dry conditions, tested, then potted. You don't want to pot before you know it works because potting is a one-time deal. The electronics box (transmitter/converter with signal output, display, etc ) can be NEMA 4 for wet areas, but not submersed.