C Series Sanitary Pump Seals- An Overview

January 17, 2017
The C Series Pumps has been a Workhorse in the Sanitary Process Industry for Years

The C Series Pumps has been a Workhorse in the Sanitary Process Industry for Years

The C series pump is possibly the longest running sanitary pump that has ever come to market. While new centrifugal pump technologies have emerged, the C series has endured. While newer designs offer efficiency gains, magnetic drives, or are better suited for ultra-high purity or CIP applications, the C series pump’s simplicity, ease of maintenance and ability to handle most clean, low viscosity fluids. While the simplicity of the C series pump has kept it around for over 50 years, largely unchanged, there have been new introductions that have allowed the pump to continue to appeal to a variety of markets. This post will focus on some of the seal variations and other modifications we’ve seen and attempt to highlight the differences.


Type D Seal- the type deal seal is the original and most common seal supplied with the C series pump. It is what we call an “external balanced seal”. What that means is we have a rotary seal (for the series that material is carbon), rotating against a stationary seat. In this case, the stationary seat is the stainless steel backplate of the C Series sanitary pump. While this seal configuration will struggle with slurries or exceptionally hot fluids, it is ideal for beverage, dairy, and even tomato juice applications. Service kits are inexpensive and easy to replace.

Type DG Seal/Seat- While the D seal is great, customers also needed a solution for applications where they may be handling abrasive, non-lubricating products. For these applications, we recommend the Type DG seal configuration. This seal assembly uses a modified back plate to enable us to affix a silicon carbide, ceramic, or tungsten carbide stationary back plate. The type D seal is then assembled so the carbon seal from the regular D seal rides on the stationary seal we’ve just installed. While the carbon vs. stainless configuration of the type D seal is great for most clean fluids, the carbon vs. silicon carbide arrangement provides maximum corrosion resistance for hard to handle products. The stationary seat is reversible and existing Type D pumps can be retrofitted to take a DG seal.

Type E Water Cooled Double Seal- the type E seal is the C series version of a double mechanical seal with flush. While we don’t see it often, it is out there and worth mentioning. The seal is locating within a stuffing box affixed to the pump back plate. The stuffing box is pressurized with a flush fluid, usually water and then taken to drain. This seal configuration should be considered for slurries or sticky and abrasive products where a double mechanical seal would typically be used. This is also the ideal choice for vacuum applications.

Internal Seal- One of the newest seal configurations used introduced for the C series sanitary pump is an internal seal design. Using a recessed back plate, this is the only C series pump seal that is an internal seal, meaning that the seal is located in the product zone. The internal seal (also sometimes known as a John Crane Type 21 industrial seal), has two silicon carbide seals. The stationary seat is pressed into the back plate. The pump impeller then pushes on a spring that is engaged with the rotating seal face to allow seal face contact between the two parts. This seal is great for hot fluid applications where a flush is not practical. It’s also works well in applications where the pump is going to be cleaned in place. That being said, the backplate does create a large sump that cannot fully drain (a no-no for a sanitary application) and what happens if/when the seal fails? Usually, it means seal components entering the product stream- or worse. That being said, we recommend this seal for many different applications and have found it to be an especially useful in brewery applications transferring for transferring hot wort out of the brew kettle.

So there you have a quick pass at the standard seal configurations available for the C series pump. If you have any questions about your C series pump or sanitary pump application, contact a Holland Sales Engineer today.