Looking for Test Bench Design Help

[BrewKaiser]

Hello HBT members. Long time since I've posted to HBT and I hope you are all doing well during the COVID-19 crisis.

I am looking for help designing a closed loop, fluid control test bench to pre-calibrate flow meters for a customer. There are three different meters and supply hose diameters, and 27 different calibration points to record based on Low/Mid/High flow volumes. Flow volumes range from .20 GPM to 9 GPM. Maintaining temp and pressure in addition to flow rate is also a requirement. I am looking for a digital flow meter to be used on the bench that can accurately record flow rates at +/- .05 GPM or better.

I began working with an engineering firm but with recent events they are unable to help now. I thought many of you hold degrees in fluid dynamics and are experts in control systems.

If you are interested, please PM me and we can discuss.

 

[day_trippr]

Good luck with that meter flow requirement - especially the .05 GPM end.
That's a bit under 0.2 LPM and I haven't found a meter spec'd for that low a flow rate that can still handle up to 20 LPM (which is well under your 9 GPM). The SF800 meters I use are spec'd from 0.5 LPM to 20 LPM...

Cheers!

 

[BrunDog]

Agreed... might need different FM's for different ranges, and then then need to be calibrated next to each other.

Can you share any more details BK?

 

[BrewKaiser]

Thanks for the responses, gents.

Yes, already am thinking multiple flow meters will be required on three different flow lines. I'm also trying to wrap my head around how we set and control flow rates to each line and flow range. The closed loop will be run by a variable speed pump and controlled with a VFD.

We use 3 different Flow Meters in the ranges of: 0.2 to 2.5 GPM, 3 to 4.5 GPM, and 0.6 to 9 GPM. Below is a chart of the three meter ranges and the Max/Mid/Min Flow rates our customer wants each to be calibrated at. There are 9 different assemblies these are used on and we have to calibrate roughly 50 of each per month. So we intend to gang up 5 of each meter assembly in-line to calibrate in batches of 5. Doing this for 450 meter assemblies a month will be a chore!

Our customer is requesting that prior to delivering the manifold assemblies containing the flow meters that we record the scale and offset values for each meter at 3 different flow rates (in GPM). The formula is Frequency = (scale X flow rate) + offset.


You'll note that the highlighted sections show a meter the customer wants calibrated outside of its stated range. Still working with them to understand this.

The end machine these are mounted to use silicone hoses of varying lengths and sizes. I have concerns that flow rates are dependent on velocity and while the calibrated bench flow meter(s) are reading 1 GPM, the actual flow inside the FM being calibrated will be different on final installation. The FM manufacturer specifies that inlet length needs to be 10 times the orifice size. In some cases we are a bit under, in others the combination of a length of nipple pipe plus flare fitting gets us to the inline length requirement, but I'm unsure what the effect of the union of the nipple pipe to flare fitting has on the flow.

Basically, I want to avoid our customer returning a bunch of these because our calibration environment does not match their final installation environment.

Anyway, any advice and suggestions are welcome. I should have noted in my original post that I expect to compensate whoever can help with engineering and design help on this. NDA would be required before proceeding. I figure a few qualified folks may have extra time on their hands right now given current COVID-19 events...