By arriving at my webpage, chances are that you already know what RIMS means because you were searching the web for RIMS or you were linked here from another RIMS webpage. But just in case you got here from some other brewing links or got here by accident I'll try to give a quick and dirty description of what RIMS is.
First off, RIMS is an acronym for a particular type of brewing system. It stands for Recirculation Infusion Mash System. Let's take these words a piece at a time and try to come up with what it means.
Starting at the back end we have the word "system". This is a system of components that when working in conjunction with one another will produce beer. (duh)
The "infusion mash" part means that water is infused into the grains to perform a function called mashing. Basically it's just soaking some grain in hot water to cause the natural enzymatic activity to cause the starches contained within the grain to be converted to sugars. And the sugars are what we are after, of course, so that the yeast has something to work on. Near as I can tell there is only one kind of mashing, really, infusion mashing. If you didn't infuse water into the grain you'd just have, well, grain. I have no idea as to why the word infusion has hung on but, it makes the acronym easier to pronounce by adding a vowel to a bunch of consonants. J By the way, there is another acronym, that I've never really taken a liking to, that some people use to describe a type of RIMS . It's called HERMS. I'll mention that acronym again in a moment. (But it did manage to drop the word infusion from the description.)
The "recirculation" part is what really defines this type of brewing equipment. A pump is pretty much required for this. Without it you would have just an IMS type system or maybe what you could call CIMS. With no "re" in front of the "circulation" all your hot water would just be "once through". That would practically limit you to doing single temperature infusion mashes (or perhaps decoctions but, that's something else). The hot water you infused your grain with is recirculated through the grain bed of your mash.
Hmmm.... You're thinking to yourself. "Since I'm recirculating all this water through the mash, why don't I do something useful with it." There ya go. You can add heat to this liquid before putting it back in the mash.
Why would you want to do that? Well, one thing you can do is compensate for heat lost during a 60 or 90 minute (or even longer) mash. You can insulate your mashtun to minimize your heat loss but, recirculating through a heat source will surely help in maintaining that target temperature. Another thing you can do is called step infusion mashing where you heat your mash to a given temperature and hold it for a period of time and then raise the temperature and rest again. This is done generally to compensate for different types of grain that benefit from these rests or to get characteristics in your end product that are characteristics of a given style of beer.
Ok, so those are just a couple of "WHYS" you would want to brew with a RIMS but, HOW are you going to go about adding this heat to the mash. This is where (I think) some of the beauty of each persons individually constructed system really shows. Some folks like to use electric heating elements (like those from electric water heaters) contained within a tube or pipe to heat the recirculating liquid. The amount of heat added can be controlled by either cycling the heating element on and off or regulating the power to the element. And, I suppose, controlling the flow rate of the liquid over the element. Using an electric element is probably the most conventional method of applying heat in a RIMS. Conventional in that it is the way a fellow named Rodney Morris, the godfather of RIMS, envisioned RIMS.
Another way of heating this liquid is to grab some heat from a tank of hot water with a heat exchanger (or coil). This where the HERMS I mentioned earlier comes in. It stands for Heat Exchanged Recirculation Mash System. This was my choice in system design. The amount of heat added can be varied by cycling the flow through the heat exchanger, regulating the flow through the heat exchanger or controlling the difference in temperature across the heat exchanger. (The difference in temperature between the heating liquid and the heated liquid.) How one goes about heating the liquid is a personal choice made by the person building the system. I've heard of someone trying to use fire directly on a recirculation line as a means of adding heat.
That brings up another way of adding heat. Directly heating the bottom of the mashtun with fire or a stovetop type burner. The way of controlling the heat adition here is by controlling the intensity of the fire. This may sound like the simplest way of heating the mash (and probably is) but there are trade-offs for this simplicity. There is an increased risk of scorching the bottom of the grainbed and adding a burnt taste to your beer. This is generally alleviated by stirring the mash while heating. This can be done by a mechanical stirring paddle device or the "armstrong" method. I recently did a mash with 46 lbs of grain and there is no way I'd be able to stir the mash for 90 minutes if I had to do it manually. You can see that there are quite a few different options that each have their own pros and cons.
One thing is certain, the real work of a RIMS-type system (or any all-grain brewing system) is done in the mashtun. The number of "tiers" and the number of vessels added to the system is rather arbitrary. Or at least as arbitrary as ones way of thinking. You can put all the vessels on the same level or they can be stacked one atop another or any way you want. How do YOU think the ideal system should be designed? When you decide you want to build your own RIMS system you should really put a lot of thought into it. I plotted and schemed and drew sketches for 2 or 3 months before I really bought anything or cut into anything. Use the internet to your best advantage by looking at as many different systems as you can and asking questions of the owners. You can start by going to my Credits and Links page to help direct you to some of the greatest RIMS pages out there. You may just decide in the end that RIMS systems are just too damned much work to mess with at all.