building a flow loop

[dftengineering]

I am building a simple flow loop to test flow capacity (water) thru valves. Is there a "building flow loops for dummies" book available? Is there a way to calibrate the system (flowmeter, pipes, pressure transducers) to ensure accuracy?

Specifically, I am having trouble getting the pressure transducers tuned in on the data acquisition system. There is way too much flutter or bounce in the pressure readings. How do I dampen the response of the transducers?

 

[btrueblood]

First figure out if the bounce is electrical noise or real pressure fluctuations. Hint: measure signal with various parts of system turned "off".

Try averaging a large number of samples from the ADC.

 

[NGiLuzzu]

dftengineering,
which is the ratio between the width of the "flutter or bounce" and the (average) pressure you are measuring?
And the frequency?
Do you think a double-check by means of a good-old-fashioned analog "clock" pressure gauge may be applicable?

Hope this helps, 'NGL

 

[JLSeagull]

A good response would require more information including the flow rate, existing system details including the flow measurement technique used, etc.

Most flow measurement needs a "fully developed flow profile", thus typically requires a straight run with the measurement upstream of the valve. What is the source of the noise? Perhaps you have a bad pump, flashing across an orifice plate, fluttering check valve, etc. Other likely problems include swirl that affects the flow meter. Consider eliminating the noise in the process system not only eliminating your measurement of the noise.

A liquid meter prover would integrate the flow rate measured over a period of time while pumping into a container. At the end of the run, check the flow totalizer against the calibrated volume.

Some of the industrial standards make nice flow measurement primers. One example is the API MPMS chapters 5 and 14.3. Many flow measurement technology specific standards exist too.

 

[amorrison]

1. Check out

http://www.swagelok.com/downloads/webcatalogs/EN/MS-06-84.PDF

2. If the piping loop is continuous (no openings) pressure surges from “turbulence” have no way of dampening so will continue to bounce around inside the piping loop causing difficulties in your readings.

The answer might be to have
a) the fluid discharge into a open tank (pail) to have these pressure reflections to dissipate or
b) a section of rubber hose to absorb the pressure fluctuations.

 

[zdas04]

Rather than a section of rubber hose (which can develop some pesky harmonic pulsations of its own) I'd use an air-filled pulsation dampener like you use on a plunger pump. They're relatively inexpensive and very effective.

David