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flow rate measurement

flow rate measurement

flow rate measurement

(OP)
I have 110mm pipe that is receiving outlet wastewater from a treatment system. the flow is continuous but can be zero at times but mostly continuous, It varies constantly diurnal mainly and is very low. I am looking for an alternative way to measure the flow rate of water from the pipe without the use of a flow metre.

RE: flow rate measurement

Measure the flow without flow measurement? That is an interesting concept.

Is there a way to measure any other variable that is dependent on flow - e.g. the time required to fill/empty certain volume etc.?

Dejan IVANOVIC
Process Engineer, MSChE

RE: flow rate measurement

(OP)
Yes I was looking for a device maybe that can give me volume per specific time. is the use of the following feasible for a low flow rate pitot tube, vortex meter, pygmy meter, flume?

RE: flow rate measurement

But these are flow meters (pitot, vortex etc.). Pitot has low rangeability, vortex may be a good choice.

Dejan IVANOVIC
Process Engineer, MSChE

RE: flow rate measurement

(OP)
Oooo did not know, thank you how about venture flume is it applicable to low flow rates? I had also thought of using a positive displacement pump to measure volume per time

RE: flow rate measurement

Flumes are used for open channel (surface) flow, if I remember well. If that fits the description of your application, you might as well use V-notch or weir, which has 100:1 turndown.

Dejan IVANOVIC
Process Engineer, MSChE

RE: flow rate measurement

(OP)
No it does not fit well. I'm measuring flow rate from an waste treatment outlet

RE: flow rate measurement

Use ballistics to calculate velocity from the length and slope of the outlet stream. Multiply the velocity by the outlet pipe internal area for flow.

RE: flow rate measurement

ren,

The permutations and ideal systems are endless, but give us a bit more data here please:

What is your max / normal flowrate / velocity?
Is the pipe always full or sometimes / mostly partially full? - makes a huge difference in what works or doesn't work
Pressure?
lengt of pipe
Is pipe flat or sloping down?
Room to fit any device?

simple way is just a three way valve into a known volume and time how long it takes to fill said known volume or time it and then measure contents - then revert back to normal flow and drain volume back into the line.

Or just put a bucket under the end?

You tell us how sophisticated you want this be.

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

RE: flow rate measurement

(OP)
Thank you all for responses

The pipe is never full maybe a quarter way full, it is on a flat surface, a bucket cannot be used since the depth between the pipe and water surface is low as shown in the diagram. the flow rate is approximately 0.47m3/hour, worse case 0m/hour, minimum 0.06m3/hour highest 1.03m3/hour.

RE: flow rate measurement

(OP)
Penpipper, A flow meter was used before and it did not work well, so I'm tring to run away from a flow meter

RE: flow rate measurement

(OP)
bimr, would trapezium flumes fit with the pipe diameter i have and where exactly would i insert them?

sandcounter,i know ballistics for a projectile are they any for flow in a pipe? and since the height in the pipe is always varying would they work?

RE: flow rate measurement

In your chamber you probably need to create a weir and be able to measure depth of water over the weir.

Do a search on this site on "open channel flow measurement" and things like this crop up - http://www.eng-tips.com/viewthread.cfm?qid=400406

Try looking up V notch flow meters.

Look like they could be the right sort of thing, but again you will need a fairly accurate height measurement.

Something like this maybe? http://soil.co.uk/products/water-monitors-piezomet...

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

RE: flow rate measurement

(OP)
LittleInch, thank you let me look into that

RE: flow rate measurement

Ren, if this is for you float siphon, you know the volume of discharge water when it reaches draw down height. Measure the discharge time to deliver that volume of water. The result will be average flow rate.

The manufacturer publishes flow rates for various configurations.

Ted

RE: flow rate measurement

Really cheap and cheerful - Drop a couple of weighted buckets into your chamber. Lift water out until you get just below the outlet pipe. Then lift even more out quickly - measure the water you've now removed and then time how long it takes from when you start for the water to start flowing back down the outlet pipe again... Simples

For something online you would need some instruments like we-ve all just been discussing. You could build a small weir / V notch meter in that pit.

Bimr - that's a nice looking piece of kit. I'll have to remember that one.

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

RE: flow rate measurement

The other way maybe is to build a wall or insert a sealed plate and have a meter in a small bore pipe below water level which connects the two halfs together. A mag flow might be good there or something with no moving parts or things to get obstructed, but at least the meter would be fully submerged all the time.

e.g. http://www.omega.co.uk/prodinfo/magnetic-flow-mete...

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

RE: flow rate measurement

Install an on-off valve on the outlet. Close the valve, let the volume fill in whatever you call the container. Measure the level, open the valve at a fixed upper level.

The upper level defines a known volume. Count the number of 'empty' operations, multiply that number of empties by known volume to get total volume.

The error is the in-flow during an empty process, which is not part of the volume when the empty is initiated.

RE: flow rate measurement

(OP)
Guys thank you so much for all the responses, suggestions and chipping in, I appreciate all the effort it makes the load lighter

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