Microbrewery Draws Big Benefits from PLC Control

It's no secret that microbrewed beers are all the rage.

Companies Mentioned
Posted on Nov 03, 2006

FOOD & BEVERAGE It's no secret that microbrewed beers are all the rage. Two years ago, an average of one brew pub opened each week in the U.S. In 1996, that number grew to nearly four each week, bringing the total number of brew pubs and microbreweries in the U.S. to roughly 800. What may be ending, however, is the public's willingness to try (and, more importantly, to keep drinking) anything that's made by a small brewer. As the novelty of drinking microbrewed beers wears off and Americans have had the opportunity to sample a variety of small-brewery beers, they are becoming more discriminating, demanding beer that tastes good on a consistent basis. In order to attain the quality and consistency these beer drinkers demand, small brewers will need to monitor and control their brewing processes as carefully and reliably as their larger counterparts. However, while the world boasts many gifted brewers, there are many more "technophobes" among them than engineers. And, finding a reliable, cost-effective control system for the small brewing industry is next to impossible-or it was, until now. Glen Sprouse, brewmaster at Phoenix Brewing Co. (Atlanta, GA), is a mechanical engineer who got involved in home brewing about eight years ago. "Something I realized early on," Sprouse says, "was that one of the biggest curses to small brewers is that you really don't know what's going on in your brewing process." When Sprouse made the decision several years ago to open his own brew pub, he knew that one of the most important steps in assuring his brew pub's long-term success was attaining a high level of control over the brewing process. Drawing on his engineering background, Sprouse developed a cost-effective miniature distributed control system (DCS) that allows him to brew high-quality beer that tastes good consistently. As a result, Phoenix Brewing Co. has benefited from its consistently repeatable beer recipes. Phoenix customers know that the ale they are drinking today will taste the same when they order it from another batch made six months from now. The brewing process is more efficient, which saves time and money and decreases waste. It is also easier to track trends and pinpoint problem areas in the brewing process so they can be corrected quickly. Phoenix, which projects it will produce around 1,700 barrels of beer in its first year of business, is one of the most highly automated brew pubs in the U.S. The heart of Phoenix's distributed control system is a C200HS PLC from Omron Electronics Inc. (Schaumburg, IL) communicating with a Power Station Touchscreen from CTC (Cincinnati, OH) via RS-232 one-on-one communications. Based on recipes for each type of beer and other commands entered into the system using Interact software, the PLC, in turn, controls a series of Omron E5EJ temperature controllers in the brewhouse, fermentation room, and beer cellar. The PLC also controls three G3 variable frequency drives from Saftronics Corp. (Fort Myers, FL). Providing Precision Control Beer is produced from malted barley stored outside the brew pub in an enclosed grain silo. To begin the 8- to 10-hour brewing process, pale malted barley is brought from the silo to the grain mill through an enclosed, auger-type grain conveyor system. Grain is dumped into the mill in 10 lb. increments. An Omron H7CR counter, pre-set to shut off the feed auger once the proper amount of grain has been fed into the mill, records the number of dumps made into the mill. Monitoring the grinding process precisely is very important since grinding grain too finely affects taste and quality. Small quantities of specialty grains are then added by hand, lending additional flavor and texture to each recipe. Once the barley has been cracked and prepared for brewing, it's referred to as "grist." Grist is automatically moved from the mill via another enclosed auger-type conveyor to a temporary storage bin called a grist case. Grist is held here until the milling process is finished and has produced enough grist for a batch of beer. After the milling process is complete, a small gate in the bottom of the grist case opens. The grist falls through a chamber, where it is mixed very rapidly with hot water for about 10 minutes. The grist lands in a dual-purpose vessel known as the Mash Mixer/Brew Kettle, where the thick barley/hot water mixture is held at precise temperatures for pre-determined lengths of time. As the grist is heated, starches are converted into sugars. Three types of sugars are produced-fermentable, unfermentable, and partially fermentable. The time the grist spends at each temperature determines the balance of these different sugars, which, in turn, helps determine how the beer will taste. Recipes can have as many as eight different temperature rests or "soaks." Therefore, precise temperature monitoring and control-the rate at which temperature is ramped up as well as final holding temperature-is extremely crucial at this stage of the brewing process. The PLC sends the new setpoints to the temperature controllers to create the appropriate ramp/soak profiles. In order to attain the necessary precision, Sprouse enters mass and energy calculations into each beer recipe. These calculations determine the necessary water temperature at each phase based on the amount of grain present. Mixing the Mash Based on these calculations, heat from steam jackets in the insulated kettle walls is added to the mash. Three Saftronics variable-frequency drives control agitators used to spread heat uniformly throughout the mash during the mixing process. Based on the recipe, the PLC tells the drives at what speed to start up, what speed to ramp up to and how long to hold that speed, and when to slow down. After mashing, the grains and liquid are pumped to a lauter vessel, where sweet liquids are separated from the grain, "just like you'd separate coffee from the grounds in a drip coffee maker," Sprouse says. A straining gate at the bottom of the kettle allows the sweet liquid to run off slowly while the "spent grains" remain behind. Maintaining temperature within precise parameters is important at this stage because, if the mash gets too hot, bad tasting substances like tannins are extracted from the grain. If the temperature falls below about 156°F, the grain starts to harden, producing, in a worst-case scenario, a "set mash," in which runoff stops and the grains are bunched into a hard mass that is nearly impossible to scrape off the lauter vessel. So, Sprouse has written a piece of logic, based on a mass calculation, into each recipe that prevents the temperature from exceeding 180°F (while keeping it as low as possible, between 165° and 170°F). The temperature controllers monitor the mash temperature to ensure that it is maintained within these parameters. Sprouse also designed rakes into the system to help distribute temperature evenly throughout the mash. Rakes, which are run by the Saftronics drives, can be run so slowly at full torque that drain paths are cut through the grains without disturbing the bottom of the bed. "This way, we don't defeat our purpose, which is to have a nice filtration system set up here," Sprouse comments. This raking method allows brewers to attain more yield per pound of grain and a better, more repeatable beer quality. After runoff is finished, the mash should ideally contain 10% more total liquid than that in a finished batch (about 465 gallons). The mash is measured and the values entered into the computer to determine the "brewhouse yield" or "brewhouse efficiency." Based on the specific gravity of the liquid, the brewmaster can determine how efficiently the system worked for this batch. These findings are then entered into the recipe so the system works more efficiently the next time that type of beer is brewed. After the sweet liquids (now called "sweet wort") are drained from the lauter vessel, they are automatically pumped back to the Mash Mixer/Brew Kettle, where they will be boiled for one-and-a-half hours or more. The sweet wort is boiled for several reasons: to sterilize it, to concentrate the sugars, to cause non-desirable proteins to coagulate and drop out of the beer, to caramelize the beer for additional color and flavor and, most importantly, to add hops and extract their bitterness, distinctive flavor, and aroma. Based on the rate of temperature rise in the kettle bottom, the PLC knows when the boiling process has begun. Once the rise hits a certain temperature and ceases to move for a pre-determined time, the program knows when to add the hops and in what quantities. After the hops are added, the operator hits an "acknowledge" button. "This process allows us to record when we were supposed to add hops and when they actually were added," Sprouse says. "So, if someone is off having lunch, doesn't hear the prompt, and adds the hops five minutes late, and I notice my beer doesn't have enough bitterness, I'll be able to trace it back to this cause." At the end of the boil, the kettle is turned off and the hot wort settles so the hop and protein particles settle out. This "hot break" lasts for 15 to 45 minutes. On its way to the fermentation vessel, the hot wort is then pumped through a heat exchanger known as the Wort Chiller. Wort's Worth In the Wort Chiller, the hot wort is cooled to fermentation temperature, which is approximately 58°F. Most breweries use two tanks, a hot liquor tank and a cold liquor tank, to accomplish this. To decrease costs and to retain more control over this crucial and time-sensitive process, Sprouse dispensed with the $15,000 cold liquor tank, opting instead for one hot liquor tank. He built in an extra stage through the heat exchanger so that, instead of using chilled water to cool the beer, ambient filtered water is used to knock the beer's temperature down from about 212° to about 80° to 90°F. Glycol is used in the remaining stage to take the beer from 80° to 90° down to the 58°F fermentation temperature. To avoid the necessity of having to look at a thermometer and manually adjust valves during the wort chilling process, Sprouse installed control valves and temperature sensors that feed information to a temperature controller. "The wonderful thing about these temperature controllers is that, with fuzzy logic adaptive tuning, if the barometric pressure or some other environmental factor is a little different each time a batch is brewed, the Omron E5EJs adapt to these situations very quickly," Sprouse says. "With auto-tuning PID alone, the controller would never get it quite right because the brewing process is never identical. The fuzzy logic helps us considerably in attaining precise temperature control." Just before beer is pumped from the Wort Chiller to the Fermentation Room, 20 to 30 liters of pure yeast is added. The beer then moves in stainless steel piping to one of five 15-barrel (single-batch) fermenters or two 30-barrel (double-batch) fermenters. Depending on the recipe, beer ferments for three to six weeks. Fermenting takes place when the yeast feeds on sugars in the wort and reproduces. Known as "primary fermentation," the initial stage of yeast permutation is written into each recipe and controlled automatically. The temperature controllers control the flow of a chilled water/glycol mixture through an external insulated jacket on the tank. Each batch is sampled once every minute and information is stored in the computer. From this information, trending charts are developed and personnel can then view the trend charts for each of the seven batches in the fermenting room. To determine the final stages of yeast permutation, which are less predictable than the initial stages, the beer's specific gravity readings are taken and keyed into the touch screen. Based on these levels, the PLC controls heating of the fermenters. To remove the remaining yeast in suspension after fermentation, yeast is pumped through a sterile filtration media on the way to its final destination, the serving tanks in the cellar. Serving the Perfect Brew Phoenix has six sanitized serving tanks, one for each type of beer being served downstairs in the bar. When it enters the serving tank, beer is chilled to a temperature of approximately 36°F with a pH of about 4.2 to 4.5, making it a harder target for any stray bacteria to attack. Beer flows directly from the serving tank to the beer taps in the restaurant through sanitary, food-grade tap lines that are kept chilled by a glycol jacket. Beer carbonation is kept at an optimum serving level by maintaining a precise CO2 pressure in the tank. This pressure is attained by keeping the serving tanks at specific temperatures, monitored by E5EJ temperature controllers. "While you don't strictly need such a high-level controller for this application, we want all our parts to be as interchangeable as possible for easy re-ordering and to minimize downtime," Sprouse says. After the entire brewing process is complete, data from each batch of beer is stored into a permanent data file for future access. It's used both to alter recipes in future and to ensure accuracy when filling out the "tons of government paperwork" that must be completed each month. "Since we opened in March, we haven't lost a single batch of beer and, hopefully, we never will," Sprouse says. "The one way to prevent losing batches is to know exactly what you need to do and to have the ability to monitor and control each step of the process." While automation and precise control over all the stages of the brewing process is standard at large breweries, it is unusual at brew pubs and microbreweries due to lack of technical expertise and cost factors. That's why Sprouse is working with two manufacturers of micro brewing equipment to develop and market his control system. "There's nobody in the equipment market who addresses the needs of the small brewery. The small brewer cannot afford a multimillion dollar DCS," he says. "We are doing what the big multimillion dollar DCSs are doing at Anheuser-Busch, only we're doing it with a more cost-effective combination of Omron PLCs and temperature controllers, Yaskawa or Saftronics or Magnetek drives, and either Omron or CTC touchscreens." He anticipates selling the entire package-the main control panel, the grain milling panel, fermenting room panel, and cellar panel-for between $50,000 and $60,000. "Basically, we're going to use the knowledge we've gained here at Phoenix to develop a control package that will perform effectively at the small brewing level everything that the big brewers are doing," he comments. " This package will be offered at a cost range that small brewers can afford and that will enable them to produce a consistency of beer that large brewers are able to attain. And, with a typical microbrewery costing about $1 million to set up, a $50,000 control system is not an unreasonable investment." MA

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