I am changing one of our compounding processes. Currently we use a K-tron solids feeder to feed a rather tacky material. We have constant issue with bridging of the material and inconsistent material feed rates. The material has a rather low melt point ~60 deg C and is thermally stable. So we have agreed to look at the possibility of pre-melting the material and feeding as a liquid.

My question is what type of testing should I perform on the liquid pump to ensure that it is calibrated correctly and that the equipment provides a consistent flow.

The simplest idea is pump the liquid into a bucket and measure weight vs. time. But I am struggling with the specifics of how long, how often to repeat the test etc.

More specifics so that you can help confirm that I am setting this up correctly. (I hope.)
Require that the feed rate is 7 lbs per hour. This material is compounded into a compound produced at a rate of 100 lbs per hour. The specification of the loading for this material is +- 1% of the compound (6% - 8% of total compound.) I think that I need to confirm that the pump can generate a flow of 7 lbs hour average with a standard deviation of ~1/3 lbs/hr.

To confirm that the pump can accomplish this I plan on setting up the melting unit and the pump. Setting the flow to the desired rate (7lbs/hr) and running into a bucket on a scale. I would record the weight every min. for 1 hour and calculate 30 (2 min.) flows. These flows could be used to calculate a mean and SD.

Does that make sense?
Do you have a different suggestion?

Is this within the field of expertise of anyone here?

davis007,

Looks like we don't have any experts here to help you. Any luck resolving your issues?

davis007,

Looks like we don't have any experts here to help you. Any luck resolving your issues?

I think I would try and get in touch with the pump manufacturer's engineering people (not sales engineers, if they can be avoided). This type of study might have already been done.

Jim and CarolX;

Thanks for trying to follow up. I have spoken with the pump manufacturers and the performance of the pump can be determined. What I am trying to ensure is that from a quality stand point the pump performance meets my need. My first pass is that the specs are +/-1 lb/hr with a target of 7 lbs/hr, and I want 6 sigma performance so the pump needs to be centered on the 7 lbs/hr with a standard deviation of 1/3. The main issue is that since this is a continuous process I can measure the flow over any time period I want. As you increase the time period the standard deviation of the flow rate decreases. So what I am really stuck on is how do I determine the proper time period over which to measure the flow. It seems that it should have something to do with my process, which is a continuous mixer, perhaps 1/10 the residence time of the mixer?

Anyways thanks for the help.
davis007