A roller mill is one of the most important pieces of equipment in a brewery. The mill crushes and prepares the malt for the rest of the brewing process. This step determines efficiency, the final flavor and quality of the product, and ultimately, profits.
Purchasing the right mill is the first step, but brewers also need to use the right mill setting for the roller gaps. Making this simple adjustment correctly helps you achieve optimal efficiency. Here we talk to RMS’s Andy Bryan and Blake Sandnes to answer some of the most common questions we get from our brewery customers about roll gap.
What Does it Mean to “Set Roll Gap” on Your Mill?
Roller mills work by passing grain through a pair (or multiple pairs) of corrugated rollers. The rollers are set a certain distance apart from each other (the gap) to achieve the ideal crush on the grain.
The grain mill setting refers to the roll gap setting. The ideal spacing between the rolls optimizes efficiency. Says Andy, “We’re adjusting the gap between the two rolls to a certain setting that’s going to get us the maximum efficiency from our grain and get it cracked properly without damaging the grain too much.” Damage can result in grain husks or creating too many fines.
Why Is the Grain Mill Gap Setting Important?
Brewers need to maximize efficiency, to get the most out of every grain. You lose the starches vital to the brewing process if whole grains, or incompletely crushed grains, make it through the milling process.
On the other hand, if the crush is too fine, you end up with small particles that can result in “stuck mashes”. The ideal setting will leave mostly whole husks that can be filtered out quickly and efficiently. Adjusting the roll gap is all about maximizing efficiency and optimizing return on your investment in the malt.
What Happens if the Gap Setting Isn’t Correct?
There are two common ways to set the roll gap incorrectly: a gap that is too wide and a gap that is too narrow. When the gap is too wide, the grains are not getting crushed enough. You might even see whole grains pass through the machine. “If the gap’s too wide, and the grain’s going through, basically you’re wasting that grain,” says Andy.
If the setting is too tight or too narrow, you will overcrush the grains. This can lead to an excessive amount of fines, pulverized hulls, and a sludgy mess that sticks and is difficult to separate.
What Is a Typical Starting Gap Setting?
At RMS, we give brewers just installing our roller mills recommended starter settings. These recommendations are based on average needs. We expect our customers to run at these settings, perform sieve tests, and adjust the gap as needed.
We generally recommend starting out with these gap settings:
- Single pair roller mill: 0.050″ to 0.060″
- Double pair roller mill: 0.065″ on the top pair and 0.050″ on the bottom pair
How Much Can I Adjust the Gap?
RMS roller mill rolls can be completely opened up and tightened all the way down to touching, so there is a lot of room for making adjustments. According to Andy, “ideally, you’re not going to make a lot of adjustments, but you are going to fine tune to get the best results.”
The recommended settings are pretty close to ideal, but most breweries need to fine tune to account for grain type and size. You may need to open the gap all the way for cleaning. Tightening the rolls all the way is useful aligning them during the setup process.
Why Does the Gap Need Adjusting?
There is no single perfect setting for every brewery, recipe, or even season. In distilling the setting varies because of the use of different grains in making spirits. The grain mill setting for beer typically varies less for type of grain, as most recipes use malt. But, there are other reasons the setting needs adjusting from time to time:
- You might use different grain types in different recipes.
- Even when using the same type of grain from the same supplier, the size often varies from year to year, necessitating a change in settings to maintain optimal efficiency.
- The size of the same grain type can also vary by region or farm if you switch suppliers.
- Finally, being able to open the rolls all the way is essential for quick cleaning and removing anything that shouldn’t be in the mix. A rock or piece of metal might find its way into the bag of malt, which can damage the machine if not removed.
Contact us today to talk more about brewing equipment, roller mills, gap settings, and any issues you’re having in your brewing operations. We can help!
