R.I.M.S = Ricirculating Infusion Mash System
RIMS stands for recirculating infusion mash system: you recirculate the wort from the mash tun until it’s is at temperature and is clear (no particulates). If you did a good job mashing, then your grain bed will be set in a way that it is it’s own filter for you when you begin sparging. There are several variants of RIMS using flame, electric or a variant – the HERMS system. HERMS requires another vessel to perform the heat exchange though.
Direct Fire RIMS
The direct fire method is my current setup. When it’s time to raise the temp in the grain bed for a step mash or mash-out, I apply gentle heat to the bottom of the mash-tun. Then turn the pump on to recirculate via a sparge arm. You can normally have this going full-bore ensuring that no grain will be ‘scorched’ as the pump is pulling the hotter water from the bottom of the grain bed (it’s sitting on a false bottom anyways).
*Note, I have scorched before. Using adjuncts (rice, oatmeal) in a higher percentage tends to make RIMS more difficult and you can get a stuck RIMS. As long as you are paying attention, you can turn the burner off before any scorching occurs and then reset your grain bed. This recently happened to me on an oatmeal stout.
**I switched to this direct-fire RIMS as our previous system, using an indirect system to heat the wort in a separate grant during RIMS showed me that I could recirculate with the pump fully open.
Here is the direct fire RIMS setup:
Indirect Fire RIMS
Our older method used the same 3-tier system with the boil kettle at the top, followed by the mash/lauter tun then followed by the grant.
My initial designs had the very bottom tank as a hot liquor tank, but after shelving the design for a decade, upon resurrecting the project, I did not want my pump to be drawing directly from the mash-tun grain bed – I did not want grain compaction leading to a stuck sparge. So to ensure I maintained a gravity feed, the hot liquor tank doubles as a grant. Of course this meant that I had to ‘elongate’ my stand as the 3 teir system coudn’t have any overlap since I also gravity drained from the boil kettle.
The grant is meant to be a ‘holding tank.’ When I recirculate at mash-out, I let it gravity drain into the grant to minimize bed compaction. The grant is pumpside so I pump it out from there back to the mash tun to achieve RIMS.
In mashing this way, I have never had a stuck bed (never say never!). The 1/2 bbl system is filled up with nearly 30lb of grain and I sparge with ease.
The specifics of mashout and recirculation is to drain enough wort into the grant (about 4 inches) so that the pump can start without any priming. The pump is throttled-back by the ball valve on the grant. The mash-tun drain valve is also partially shut so a nice, easy gravity flow is attained.
Note, I am currently not using this method of RIMS. I am using the direct method as I can open the pump full bore for recirculation. There is no need for an intermediary grant tank to heat the wort.
ALSO, using the grant to heat the wort, you have a delicate balance between the mash-tuns ‘out’ valve’ and the grants ‘out’ valve which I found to require more diligence (can’t walk away) or the grant could dry up….or the mash tun could drain.