BrewMonitor® offers your brewing team access to insight that has never been available before: high-resolution data from inside your fermentation tank, allowing you to track the progress of your fermentation, analyze results, benchmark future batches, and much more. The resulting graphs for each completed fermentation – dissolved oxygen, pH, gravity, pressure, temperature and conductivity – provide extremely clear views into the events that transpired and techniques that were employed. This series of articles shows examples of data curves from specific parameters, as they were recorded from the fermentation of various styles in different scenarios. These graphs are from actual fermentations, and offered as a look into how these conditions express themselves as measured data trends.

In this installment, we step through some examples of fermenter failures. Process or system malfunctions can come in many forms, including equipment failure and operator error. Detecting and solving these issues as early as possible can mitigate the impact they have on your final product, your production time, and your mental health!

See our earlier post on typical gravity curves »
See our earlier post on typical pH curves »
See our earlier post on typical conductivity curves »

 
 
 

Failure Curves: Glycol System Solenoid Issue
Figure 1: In this graph, the fluid temperature (gray) took a steep downturn about 40 hours into fermentation. This was caused by a solenoid in the glycol system getting stuck open in the middle of the night. The rapid unplanned cooling of the fermenter caused yeast metabolism to slow, and the rate of sugar consumption to drop (green). The drop in fluid temperature was detected and an alert was sent out so the error could be corrected. The fermenter was warmed by the exothermic process of fermentation and the product was fermented as normal, once the issue was caught.

Failure Curves: Glycol Jacket System Failure
Figure 2: On temperature feedback systems like those found in most commercial breweries, an in-tank temperature probe reports the fluid temperature to an electronic controller. When the fluid temperature goes over a set point, the controller opens a solenoid valve allowing glycol to flow into the tank jackets. A system with as much thermal mass as a fermenter is subject to a certain amount of hysteresis due to the time it takes for the system to cool to its set point. The temperature rises with the heat generated from fermentation, and then drops rapidly when the cooling system turns on, causing the “sawtooth” pattern seen between the start of fermentation and hour 48.

However, in this case, the glycol jacket cooling system for this fermenter failed slowly over time. This can be seen in the fluid temperature graph; the “sawtooth” pattern begins to degrade as the glycol chiller fails to cool the tank back down to its set point every time the controller sends the signal. Ultimately, the cooling system failed completely and the tank experienced temperature free rise, along with three other active fermentations.

Failure Curves: Blowoff Valve Left Closed
Figure 3: Some processes may be overlooked in a brewery setting, yet operator error can cause irreparable damage to the final product. In this case, the fermenter was filled and pitched with yeast, but the blowoff valve was left closed. Fermentation began as expected, but the carbon dioxide produced had no escape route. Pressure (green) built up in the fermenter and was released when the cellar operators realized the pressure release valve (PRV) was open and releasing gas.

High pressures like this can cause multiple issues with the fermentation process. First, many fermenters are not designed to handle more than 29psi (2 bar). Even with a PRV in place to protect the fermenter, the speed at which CO2 is produced will outpace the rate of blowoff through the PRV. Second, yeast are particularly sensitive to large pressure swings. This can be seen in the pH (gray), as the sudden increase and subsequent release of pressure caused rapid changes in the metabolism of the yeast due to their stress response.

Thoughts about these data curve examples? Post your comments below.

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