Close Accuracy Batch Fill Method

I think coriolis and ultrasonic flowmeters will be unable by far to attain this accuracy, and I even wonder about various positive displacement types. Instead, I would look at a positive displacement pump driven by a stepper motor. Once this is calibrated, accurate volumes can be achieved by operating the motor a specific number of steps.

A paint mixing station might almost be an off-the-shelf way to do this.

And, no, the customer is not always right.

Have you considered weighing the vessel with load cells, rather than flow metering?

If you have to CIP the process piping, the metering part doesn't get heat/acid/caustic treated.

Weighing has the resolution to provide you those accuracies. Typically you need a main flow to some high percentage (like 97% of batch size) and a 'dribble' line at a fraction of the main flow that runs until the batch size is reached. And weighing can confirm solids batching (salts, powders) at low levels, too.

I've used Sartorius industrial load cells because of their incredibly fast response and their ability to hold up to wash down. Due to some unique property, they don't need or use the signal filtering that other load cells do. Filtering stretches out or averages out the response from the load cells, which is not what you want when you're approaching the batch limit value. Fast response is needed for batching control.

On a coriolis meter batchers, we've had to experiment with shut off values to get the right one for any given flow rate. It isn't adjusting the value that's time consuming, it's running the batch and then checking it, then running it again, until we hit the right value.

I know Hoffer has a sanitary turbine meter. I'm not sure whether vortex meters meter sanitary requirements or whether they're just available with triclamp fittings. You might get by with vortex meter because of the requirement for flow/no flow, where your system would never modulate down into the the low flow cutoff level inherent to vortex.

Yeah - load cells or a scale, as the tank is on casters - that was my first choice - the customer does not want them.

Sooner or later the customer is going to have to accept something!

Yes, and on the last project we had a simple turbine flow meter and a ball valve on top of the tank for flow start/stop. Accuracy was at best ±1L. Price drove us to this simple arrangement, as they kept asking for lower costs each bid we submitted. They are using this system now, but the complaints over filling repeatibility rang out for 3 months. This time, they have asked for the flow meter and valve again, but have included the ±0.01L specification. As I said, I immediately asked about load cells and got an emphatic "NO". This is what they want - flow meter and valve. I am trying to optimize this combination as best as possible. Cost seems to have become a non-issue.

No load cells? I don't blame them. I was "no load cells", too, until I discovered Sartorius.

It isn't clear how they do it, but they do not drift, period. No drift.

No summing box.

There is no iterative tweaking for calibration, whether at startup or over time. The load cells come precalibrated, each and every one at exactly the same output 2.000mV/V and they stay that way, no drift.

Startup takes about 10 minutes to get the tagged data from each cell entered. Done.

The response time is phenomenal. Lay a clip board on top of the vessel and the response is an instantaneous step change. Or a pencil.

You almost have to see it to believe it, if you've lived in the world of drifting, averaged-over-time, need-to-be tweaked-and-tweaked-and-tweaked bonded load cells. German know how, I guess.

I'll keep that in mind - I often wondered how the load cell systems were ever used in the "real world" (I design/build controls for process skids - not use them) when the darn things drift so much. We have customers get concerned about the readout on a temperature transmitter being 0.1 off from the PLC at times, as they drift around a point a couple hundredth above the reading. But, they have no problem accepting the drifty load cell readout. (????)

1 part in 10⁴. OK. At what temperature?

60°C

Use a positive displacement pump and limit no of strokes etc v acurrate

Alfa Laval (formily Triclover before that G&H) has a sanitary flow meter a PD340 Very expensive. Need a PLV. Shut-off calve would be fine. Would need a PLC, oops, I see no mag meter

I see its a low volume what is the flow rate, did you have you considered load cells

p911

Flow rate will be as low as I can convince them to keep it in 1/2" 0.040" wall tubing. Slower is better for control. I hope they can allow a 1/2 hour to fill, but suspect we will get full flow from a 1/2" tube at 60 psi. (haven't calculated that yet) I doubt they will consider any pressure dropping or flow restricting devices before the tank. More later after a phone meeting tomorrow.

See my reply #11 for the load cells.