How do glycol draft beer systems work?
Learn the equipment, how it works and why glycol systems are the most popular choice in hotels, bars and restaurants.
HOW DO GLYCOL DRAFT BEER SYSTEMS WORK?
Glycol draft beer systems operate through a process which is accomplished through three components:
- Trunk line
- Draft beer tower
The power pack, a commercial refrigeration unit, is the heart of the glycol system. The power pack is rather compact, as seen in the photo above, right. Don’t let this small package fool you. An individual power pack can have from one-three pumps and motors. The end-result is that a single, properly-sized power pack can manage up to three trunk lines, each up to 750’ in length and each capable of handling up to 24 beer products. In this plan, we’re showing the possibilities for three different opportunities for trunk lines in this particular building.
A typical trunk line is shown in the photo below: here you’ll see the cross section of a typical eight-product draft beer trunk line. If we zoom-in a little closer, you’ll notice a total of eight narrow-diameter product lines around the perimeter, sandwiched around a pair of glycol refrigeration lines. One glycol line is outbound, extending from the power pack to the beer tower, while the other returns from the beer tower back to the power pack. Each product line of the trunk line is connected to a unique barrel of beer in the walk-in cooler and each barrel of beer is connected to CO2 and Nitrogen cylinders through a series of gas blenders and pressure regulators. A more simplistic explanation is that the trunk line provides a conduit of beer product lines, connecting barrels of beer in the walk-in cooler to each respective faucet of the draft beer tower, while also housing sealed refrigerant lines from the power pack to the tower in a continuous loop. The assembly of product lines and glycol lines is wrapped in a shield and foam and encased in a plastic waterproof jacket that is fairly flexible.
DRAFT BEER TOWER
HOW ARE GLYCOL DRAFT BEER TRUNK LINES INSTALLED?
How are glycol draft beer lines installed? Trunk lines are typically installed overhead or under-floor. If installed overhead, the exposed downward trunk lines would generally be housed in a combination of PVC tubing and a decorative finish. Heavy pipe is another popular approach, as shown in the photo, above, right. When installing under concrete, you would run these product lines through a section of PVC tubing. This particular line that we’re showing here, which is eight products, is two-and-three-quarters inches in diameter and would typically be installed inside a six-inch schedule 40 PVC conduit.
HOW DO GLYCOL DRAFT BEER SYSTEMS OPERATE?
The way the system works is that the power pack pushes refrigeration through the center of the trunk line. The trunk line contains an outbound glycol line which runs from the power pack to the tower, over here, and return glycol line, which enables the refrigerant to complete the cycle and become re-chilled. The job of the refrigerant lines is to keep all of the surrounding beer lines temperature-controlled from the point of origin to the point where they’re dispensed. The fundamental challenge of glycol draft beer systems is to transport the beer from the walk-in cooler, over here, whose temperature is 36 to 38 degrees Fahrenheit, over significant distance, and dispense the beer over here at this tower at 36-38 degrees Fahrenheit. This (temperature) is mandated by the brewers and has been deemed to be the ideal temperature range for draft beer to maintain its intended characteristics.
THE NUMBER 1 GOAL IN DRAFT BEER SYSTEMS: MAINTAINING THE TEMPERATURE OF THE DRAFT BEER
As the beer travels along its journey, it tends to increase in temperature due to the gas that’s pushing it and the resulting drag of the plastic product lines that resist. Therefore, heat accumulates inside the product lines. The beauty of the glycol system is that the refrigerant lines, through the principles of thermodynamics, dissipate the temperature gains of the product lines as they get warmer. So, the idea is, even though the refrigerant and the glycol line is between 29 to 32 degrees Fahrenheit, it’s there by design — it’s there because it will ultimately offset the rising temperature of the surrounding product lines, so as to deliver the beer products at the recommended temperature by the time they get to each respective faucet.
THE INNER-WORKING OF THE DRAFT BEER TOWER
Once the beer product approaches the tower, however, the job still isn’t over, because the beer can still experience temperature gain over the last segment of its journey. In other words, a lot could still go awry inside the beer tower. Therefore, a bit of additional engineering is designed into the tower in order to complete the mission of delivering cold beer right up to the end of each faucet. The way this is achieved is that each of the beer faucets inside the tower, shown right here in these black circles, has a stainless steel shank that extends inside the tower head. A copper assembly known as the “cold block,” as shown here in this eight-faucet Micro-Matic Metro T glycol tower (above is a sketch of a cross section) — provides the rest of the magic. The inbound glycol refrigerant line, shown above in blue, enters the beer tower through a copper line that travels vertically inside the tower and creates a complete loop for the refrigerant to return to the power pack. So it travels around a large loop and returns back to the power pack. Along its path, however, a critical engineering detail is completed. Along the return path of the glycol refrigerant, its copper loop contacts the shank of each faucet and also branches into each respective faucet. This branch is known as the “cold block.” The end-result is that the temperature of each beer product is controlled all the way to the point of dispensing. Upon leaving the tower, the return-side of the glycol loop returns to the power pack so the refrigeration cycle can be repeated and repeated again. Even on its way back to the power pack, the return leg of the glycol line still helps to stabilize the temperature of the beer products on their way to the tower. This is the engineering of how glycol draft beer systems work.
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