What is the Best Seal for my Waukesha Universal 3 Sanitary PD Pump?

Part 3 of our series on Waukesha Pump seals focuses on Waukesha’s newest addition to it’s external circumferential piston pump portfolio, the Waukesha Universal 3 Sanitary Positive Displacement pump. Unlike the Universal 1 and Universal 2, the Universal 3 features breakthrough front loading seal technology. We’ll spend the rest of this post reviewing the Universal 3 front loading seal and the available seal options.

Front Loading Seals

U3 Rotor. Note the stationary seal located in the rotor hub.

Before we take a look at the different types of seals available in the Universal 3, let’s talk for a moment about a cornerstone feature of the Waukesha Universal 3 Pump- the front-loading seal design. What does this mean and how is this different than the Universal 1 and Universal 2?

To start, in the Universal 1 and Universal 2, all seal types are considered “external” seals, located entirely outside of the product zone on the gear case side of the pump body.

In the Universal 3, however, for mechanical seal configurations, the rotary seal is located in the rotor hub and the stationary seal is located in the pump body. And for o-ring configurations, the seal sleeve is located by the rotor as well.

Why is this a big deal? Well, with the Universal 1 and Universal 2 Positive Displacement pumps, in order to service the seal, we would have to pull the entire pump body. This could be quite difficult if the pump was located under a tank or in a difficult to access place. The pump body, especially on models 60 and up, is also heavy and difficult to move.

With a front loading seal, we don’t have to worry about pulling the pump body for most routine maintenance. We simply need to remove the pump cover and rotors for direct access to the seal wear parts. If you’ve had to pull a pump body before, you know how much time, energy, and effort this saves us.

So front loading seals are great, but which one is best for my Universal 3 Sanitary PD pump? Let’s take a look at that now.

O-Ring Seal Options

Universal 3 O- Ring Seal Options
U3 O Ring Seal Sleeve

Like the Universal 1 pump, the Universal 3 pump is available with single and double o-ring seal options. O ring seal options are great for applications running at less than 100 PSI, especially when we’re running fluids with high lubricity. O ring seal parts are lower cost, but do tend to require more regular maintenance.

For these reasons, Triplex Sales Engineers recommend o-ring seals only for light duty applications. Think lotions or milk transfer applications. We also recommend using a double o-ring seal for chocolate applications. But remember- for double seal configurations in the Universal 3, we will need a flush medium, just as we do for the Universal 1 and Universal 2.

Single Mechanical Seal

Single and Double Mechanical Universal 3 Seal Options

This is the standard seal configuration for the Universal 3 (Silicon Carbide vs Carbon) and the seal configuration we see used most often. Available with either Silicon Carbide, Tungsten Carbide, Carbon, and both Silicon Carbide and Tungsten Carbide narrow face options for the stationary seal and either Silicon Carbide or Tungsten Carbide for the product side rotary seal seat, the single mechanical seal does not require a flush and is great for medium duty applications.

Double Mechanical Seal

The Universal 3 Sanitary Positive Displacement pump, like the Universal 1 and Universal 2 Positive displacement pumps are also available with double mechanical seals. The double mechanical seal features four total seal faces- a product side stationary and rotary seal, as well as a flush side stationary and rotary seal.

This robust seal design makes the double mechanical seal great for handling highly abrasive products, vacuum applications, and other severe duty pumping applications.


So which seal is the best for my Universal 3 Positive Displacement pump? Well if you’ve been reading our preceding posts on the Universal 1 and Universal 2 Positive Displacement pumps, you won’t be surprised to hear that it depends. For low pressure, light duty applications, single o ring options are inexpensive and easy to service. For most applications, we’ll stick with the single mechanical seal, and for severe duty applications, we’ll use a robust double mechanical seal with flush.

As always, if you have any questions about seal selection for your Waukesha Universal 3 Positive displacement pump, contact a Triplex Sales Engineer today!

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