While the Waukesha pump has long been known as the “Can-do” pump, at Triplex, we focus on applying the Waukesha line of positive displacement pumps so they’re the “can-do-better” pump. One of the applications we get questions about all the time is how do we pump products with entrained solids. So what’s different in pump selection when we do whole solids handling? Let us give you an overview.
Let’s start by looking at rotor type. By far, the most common rotor type for a Waukesha ECP Pump (Universal 1, Universal 2, or Universal 3) pump is the twin wing rotor. But for applications where we’re doing whole solids handling, we’ll want to consider a single wing rotor option. We to think about single wing any time we’re handling products we want to keep whole and minimize damage. Common applications for single wing rotors include large curd cottage cheeses, chili containing beans, fruit preservatives, and pie fillings.
The draw back to single wing rotors is that we can’t run them very fast. In fact, we only recommend running a single wing rotor at 150 RPM max and generally try to size for speeds of less than 100 RPM. Which is a nice segue to the next thing we want to keep in mind- speed.
Whether you’re running a single wing or double wing rotor, something you always want to keep in mind with whole solids handling is pump speed. Specifically, we want to make sure we’re running the pump slow enough. Why slow? What makes a Waukesha ECP pump a great pump for solids is the large annular space that product moves through. We want to give the our product as much time as possible to fill this space and minimize any contact with the pump rotor.
So if we’re running the pump slower, what else do we need to keep in mind? Well, if we’re typically running a U2 Model 60 at 350 RPM, and now we can only run at 150 RPM, we’re going to need a bigger pump- in this case, likely a U2 130 or U2 220.
As a general rule of thumb, we’ll always go “up” a size if we know it’s going to be a solids handling application just so we can keep the speed down and our product intact.
What does a bigger pump mean? Usually, it means bigger inlet ports. But even with the larger ports that come standard on larger pumps, we’ll want to consider the inlet port size. When pumping solids, we want to be sure product doesn’t bridge and starve the pump. So as a good rule of thumb, consider using a port size one size larger than your inlet piping.
We put seal type this towards the end of the post because it isn’t as important of a consideration for handling whole solids gently. Above all else, we just want to ensure good compatibility with our product. That being said, most of the solids applications we see are higher pressure applications so we tend to stick with single mechanical seals and flush ports drilled, just in case we need to add a flush down the road.
We spent the majority of this post talking about how to handle solids with a Waukesha ECP type pump (a Universal 1, Universal 2, or Universal 3 Pump). But it is important to know that there are other types of pumps that we can consider for solids handling applications.
Specifically, Waukesha’s line of Universal Twin Screw pumps are available with a range or rotor pitches for different sized products, volumes, and discharge pressures and are a great choice for sanitary solids handling applications.
We can also consider pumps like Air Operated Double Diaphragm Pumps (AODD). Graco, for example, makes a great AODD that is available with flapper instead of the standard check valves and is ideal for solids handling. Also worth considering are progressive cavity and even peristaltic pumps. At the end of the day, it’s about finding the right balance of cost, cleanliness, and performance.
To wrap this post up, when specifying a Waukesha ECP pump for a solids handling application, start by thinking about if a single wing rotor is a good fit for your application. You’ll also want to consider pump speed, running as slow as possible to give product time to get into the pump. And if you typically use a model 60, consider sizing up to a 130 or 220. And while ECP pumps are great for gentle solids transfer, there are other pumps like twin screw and air operated double diaphragm that may be a good fit for you application as well. As always, if you have any questions about your sanitary pumping application, contact a Triplex Sales Engineer today!