The ability to move mash, wash, and spirits around the production space is essential for any distiller. However, there are a wide variety of pumps on the market, and selecting the right tool for the right job can mean the difference between making a transfer quickly and efficiently or not—and, sometimes, between doing the job safely or not.
Here, we’ll consider the main types of pumps, as well as the jobs for which each tends to be the best fit.
Centrifugal
The most common pump type found in breweries is the centrifugal pump.
These pumps are very effective at moving pure liquids or media that contain low amounts of solids. While pump-head designs can vary cosmetically, all centrifugal pumps operate the same way: The liquid enters the center of the pump head, where a fast-spinning impeller drives it via centrifugal force—hence the name—to the outside of the pump head, where it exits on its way to its next destination.
In a distillery, these pumps are efficient and affordable for moving wash when running off a lauter or transferring fermented, grain-off wash. However, they are not as good at moving grain mash, thick fruit puree, or other high-solids media. They can be prone to cavitation and clogging when used in less-than-ideal situations.
When not paired with a pressurized source vessel, such as a closed fermentor with CO2 head pressure, these pumps tend to leave the outflow line—usually a hose with tri-clamp fittings—full of the transfer media. That’s because the force behind the transfer is the impeller in the pump head: Once the source vessel is empty, then so are the line into the pump and the pump head, and there’s no longer positive pressure on the line out to the destination vessel. That leaves the hose exiting the pump full of the stuff you’re trying to move.
When it’s just a couple gallons of fermented wash left in the line, that isn’t a significant expense, and it can go to the drain. On the other hand, the cost of losing a few gallons of higher-proof spirit at each transfer can add up quickly—especially for a small operation.
Above and beyond the financial concerns, though, there are also safety concerns when using centrifugal pumps in a distillery. By design, they rely on an electric motor to power the impeller, creating a potential flashpoint if used near distilling equipment that could leak flammable vapor or in other situations that can create a concentration of ethanol in the atmosphere. There may be areas in the distillery, such as a segregated space for mashing and lautering, that would be safe to operate a standard centrifugal pump. There are also explosion-proof models available, but these cost a premium compared to off-the-shelf brewery models.
Positive Displacement
The most common solution to address both safety and the ability to move solids is the air-operated positive-displacement pump—in particular, the diaphragm pump.
Rather than creating a flow that varies depending on the volume and head pressure of the source and destination vessels, positive-displacement pumps physically segregate a set portion of the media and mechanically move it from inflow to outflow.
Air-operated diaphragm pumps are self-priming, and they can run dry for short periods of time, creating suction on the supply line to overcome thick mash, molasses, or other high-viscosity media that might not be inclined to flow smoothly and easily. These pumps are designed with two lobes connected by a central piston that moves back and forth—as the piston oscillates, it compresses one lobe and opens the other, then vice-versa. That forces the media out of one side while priming the other side and creates negative (vacuum) pressure on the pump inflow, which allows the diaphragm pump to overcome the resistance of thick or viscous distilling feedstock.
There are other forms of positive-displacement pumps available in electric rather than air-powered, including rotary, diaphragm, peristaltic, and flexible-impeller units. These pumps can handle more viscous materials in an environment where there is no risk of ethanol vapor leaking or otherwise building up atmospherically—such as in a rickhouse or barrel warehouse.
Air-operated pumps do add a layer of infrastructure to the distillery’s plans, however, because they require compressed air. And, as with any soft materials in a distillery, you’ll need to ensure that pump diaphragms, gaskets, and any other seals are made of appropriate materials. Viton and PTFE (polytetrafluoroethylene, or Teflon) are effective gasket materials for high-ethanol, high-temperature environments. Buna-N gaskets, commonly found in breweries, are available with varying levels of quality. EPDM and some Buna-N formulations are not as solvent-resistant, leading to gaskets breaking down and potentially leaching into the spirit, though there are varieties of Buna-N rubber that are specifically designed for high-ethanol environments.
Regardless of the materials, you should have a plan in place to periodically check on seals and gaskets. Soft parts inevitably wear out, and a rigorous maintenance schedule can help to avoid unscheduled shutdowns. It’s best practice to keep a set of backup diaphragms, O-rings, gaskets, and other soft parts on-hand for these checks because a part can transition from “failing” to outright “failed” during a maintenance teardown. A set of backup seals is less expensive than having to shut down (when you’ll also need to pay for the parts to repair the pump).
Bottling lines, even the simplest varieties, often rely on a pump to bring spirits from the source vessel to the bottling reservoir. Some bottle fillers come with a pump pre-installed—these are generally self-priming and electric, so they need to be used in an area free of potential ethanol vapor leaks. A float switch in the reservoir is often connected to the pump, so that it switches on to refill the reservoir when the volume drops to a preset level.
Whether pre-installed or supplied by the manufacturer, small positive-displacement pumps are an effective tool for meeting the very moderate need of keeping the bottling reservoir filled. However, it’s best to communicate with your supplier to ensure that any soft parts on the pump—and the bottling line, for that matter—are appropriate for distillery use. Manufacturers may have different seal kits for distilleries versus lower-ethanol producers, such as wineries.
Gravity Sometimes, however, simplicity is the best solution.
Many small distilleries use gravity to feed product from one vessel to another. If your distillery has an elevated tank or one that can be forklifted on to a rack, or stacked onto another tank/tote, then gravity can work in your favor. This is a common solution in bottling with a filler that has a float valve: The tank can open to fill the bottling reservoir, and the float valve shuts off the gravity feed as necessary.
No matter the size of your distillery or its focus on different categories of spirits, pumps are ubiquitous in a production environment. Investing in the right types can make day-to-day operations more efficient, easier, and safer.