No problem at all if this turns into a general HERMS discussion. Sharing your experience will only help me build mine.
I plan to show off the brewery in its entirety 1-2 weeks, but here is a sneak preview to keep the discussion going.
Instead of a filter bottom, I am going to use a LauterHelix. It is a German invention by Matthias Hoßfeld. See:
The idea is to use a stainless steel spring to filter your mash. If you bend the spring, you create tiny slots in the bends. If the spring is bent with a diamter of 20cm, the slits are 0.5mm.
This way you create a flexible and very easy to clean manifold. And the end of brew day, you just unscrew it from the T-piece and clean in in the sink.
We used it once now and are quite happy with it. If you have a very thick mash, you just have to take care that you do not stir in a way that exposes the spring to air, which will let air go to the pump. Once we knew that, it was easy going.
Matthias only tested it with gravity fed sparging so far, but pumping through it seemed to work okay.
I cannot say much about efficiency yet, because there were other factors that were sub-optimal. When the rest of my setup is ready, and my temp profiles are completely reproducible, it will be a nice experiment to lay a false bottom on top of the spring to see if it makes a difference.
We are also going to use such a spring as a hop filter in the kettle.
We didn't like the simple plumbing tee that originally shipped with the LauterHelix, so we designed and CNC'd our own, with an integrated O-ring.
Here are the 3 kettles when we had just assembled them. The spring in the kettle (right) is too tight. Flow stopped during CFC cooling, but was resolved by bending the spring bit more. I will just shorten the spring to resolve this.
Another custom is our heating element enclosure, made from aluminum.
More pics on twitter:
And finally we have our custom fitting that is mounted on our inlets, outlets and HERMS coils:
It has an integrated O-ring groove and seals on the inside of the kettle. The O-ring groove is completely hidden behind stainless steel when a locknut on the outside is tightened.
This is our second version and it works well. We did some last design changes (round face with a hex behind it) and I will start production of the third version soon.
More updates soon
The brewery is a mess of tools and parts now.