I’ve made some progress with the design changes I detailed in post 1 of this series. I was able to implement the design, but in testing, it failed to give me the result I was hoping for. It has informed a revised design that I hold hope for working, however. This post won’t make any sense without reading the one linked above first.
When the loop was open to a significant degree (controlled by a butterfly valve), excessive pressure is not built within the loop – pressure sufficient to push liquid up to the mash tun return anyways. A check valve may be required on the mash tun output to prevent this, as with this design there is nothing stopping that loop pressure from being removed with just a bit of back flow. I don’t know enough about check valve internals and mechanisms to know whether it would be advisable to put one in this location. I do know that it would be a bit of an expense for me to get one to try it. My instinct is that a check valve isn’t a great idea as the involved pressures are pretty low and likely insufficient to trigger the most check valve mechanisms (whether closing a normally open check valve, or vice versa), and this may not even be the main issue.
The second issue, what I think is a larger issue, is that some kind of proportional valve, rather than a butterfly valve is necessary to control the loop flow rate. I think it’s possible that with sufficient throttling at this point that the idea works without a check valve on the mash tun outlet. In my initial testing, I did not have the granularity to test this using the butterfly valve. You would think this would be as easy as swapping one valve out – and it is, except the valve dimensions are different from one another, requiring a new plumbing layout. So, I’m in the process of testing a revise design with the butterfly valve swapped for a ball valve. Due to some decreased confidence in this idea, I am no longer determined to devise an entirely hard piped layout to test the second design revision. If I figure something out, great. Ironically, as my revised plumbing is almost identical to what I started with – I could’ve easily tested this without work on a new brewstand.
All in all, this has been a good lesson for me – test new ideas as rudimentary as possible and build from there. My next post will be testing the second design revision, hopefully with different results!