What Makes a Great Craft Beer Pump? Part 2- C Series Seal Selection

In part 1 of our series on craft brew pumps, we provided a general overview of the pump technologies we see in the brewery. In this post, we will do a deeper dive on the workhorse of most breweries- the centrifugal pump, specifically, the C series line of pumps and the seal options available that can make the difference between smooth, consistent performance or loud, leaky operation.

The C Series Pumps- What is it?

The C Series pump is one of the first mass produced sanitary centrifugal pumps. Originally introduced in the 1960s to support the increasingly regulated dairy industry, the C series remains a staple in the portfolio of most sanitary pump companies. SPXFlow, Ampco, Alfa Laval, Q Pump, Topline, and several others each offer a version of the C Series pump. Pump and performance curves are identical, and parts are interchangeable regardless of manufacturer. What differentiates different C Series pumps are the options and aftermarket support available. Having the right seal, impeller type, and size combination is critical to ensure long pump life and optimal performance. In this post, we will do a deeper dive on each of the C Series seal types we see in the craft brewery.

Seal Options

Type D Seal

The most common type of seal we see used in C series pump applications is the type D seal. The Type D seal is a simple seal that uses just 4 parts- a spring, a seal cup, a seal o ring, and a carbon seal. The spring is pushed forward by the drive collar on the shaft until the pin on the drive collar engages with the slot in the cup. The pushes the carbon seal forward and onto the sealing surface on the backplate, creating a seal.

The type D seal is inexpensive to maintain and replace and works in about 85% or so of the applications we see in the brewery. Whether it is hot liquor pumping, brite tank transfer, or feeding a canning line, the Type D seal will work great.

Where we often see issues with the type D seal is applications where we are pumping wort (unfermented beer) at near boiling temperatures. When we do this, flashing is likely to occur, which leads to premature failure. Carbon vs. stainless is not an ideal combinations and while flush cooling options are available to dissipate heat, this failure of the D seal leads us to the second most common seal type we see in craft breweries- the CB+ internal seal.

CB+ Internal Seal

The CB+ internal seal, originally introduced by Ampco, was designed specifically to prevent leaking seals when pumping fluids near boiling. Because the seal is internal, it is submersed in product to promote cooling.

Additionally, the pressure within the pump casing creates a higher closing force on the seal faces, minimizing product build up. IN CB+ applications, we also run silicon carbide seal materials, which better handle abrasives that see the seal faces.

Finally, the internal spring agitates wort solids, further avoiding material build up on seal faces. So if you’re C series pump is screaming (literally), it may be time to consider converting to an internal seal. Triplex Sales is able to support conversion of any major manufacturers C series pump to an internal, CB+ seal.

While the CB+ seal option is great for these higher temperature kettle applications, there are some draw backs. For one, if the seal fails, where does it go? Because the seal is internal, it has nowhere to go but into the beer. Additionally, due to it’s more robust design, replacement kits are more expensive than standard D type kits. For these reasons, we typically only recommend the CB+ on more difficult kettle transfer applications.

Type DG Seal

The Type DG seal is another C Series seal option that is quite common in many dairy and industrial applications, but we see it less frequently in brewing applications. The DG seal starts with your standard D seal, but instead of having carbon on the stainless backplate, we bolt a ceramic station seal seat into the back plate for the carbon to ride on. The stationary seat is reversible for quick changeouts if one side is damaged.

We tend to see the DG less in breweries mostly due to cost. At a premium to the type D seal and comparable price to the CB+ seal, the DG, while great for highly abrasive applications, does not provide the performance at high temperatures that the CB+ does. Accordingly, we typically only recommend the DG seal in very abrasive applications.


After reading this post, you should have a better idea of the seal options available for your C series pump and what to keep in mind when selecting a pump or changing the seal type. If you feel like your brewery is constantly plagued by high pitched seal squealing or persistently leaky pumps, visit www.craftbeerpumps.com or contact a Triplex Sales Engineer today!

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