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Spinning Our Gears

Pumps are fundamental to just about everything we do, in one way or another. Even the big trucks mostly exist to mix and pump things, in the broadest sense. It's why we have a dedicated pump shop on site - without pumps working at their peak, the nicest skid that the fab shop can assemble won't really be worth a whole lot.

So I figured it was high time that we talk about pumps on here... we've obviously touched on them throughout the life of this blog, whenever they've come up, but they haven't received a dedicated post, until now. First thing's first, huge shoutout to our guy Sir Isaac Newton here.

Newton wasn't perfect, he believed in alchemy and flew off the deep end late in his life, likely from mercury poisoning. But before that, he accomplished something pretty important: the discovery of centrifugal force, or force away from the center of a body moving uniformly in a circular path. It's important enough that we named centrifugal pumps after it, as centrifugal force is the essentially what makes them work. Obviously a lot of Newton's work is evident in a lot of this stuff - particularly his second law of motion - but we don't call them Second Law Pumps, do we? No.

But where better to start than with our reliable and often-overlooked friend, those centrifugal pumps? While the plunger pumps get a lot of the downhole glory, the c-pumps are the ones getting things between points A and B prior to that. Obviously a lot depends on the specifics of what you're doing, but they can accomplish anything from intake and discharge, mixing, recirculation - basically, most of the grunt work that makes the fun part at the end possible.

How do they work? Sort of why we're here I suppose, so let's start with a video that explains exactly that. It's seven minutes long, a little more that I'd usually want for something like this, but it's engaging seven minutes in my opinion. Either way, I'm going to reiterate a lot of what it says below, don't worry.

One quick addendum to the video: while volute casing is definitely a thing, we often go with concentric casing which, as the name implies, is concentric with/equidistant from the impeller at all points. Some manufacturers believe concentric casing tends to offer a smoother flow and longer pump life. Here's one of those.

I had to lift that thing to get decent lighting, and you might recall that I'm a desk jockey who's mostly worked in regulatory compliance and graphic design, so if you need me, I'll be dead.

The impeller, in a couple ways, is sort of the centerpiece of the operation. In fact, it was basically the jumping off point for this post, which was supposed to be mostly about them... but you can't really talk about impellers without giving the larger context, right? Anyway, here's an impeller that happens to live in our warehouse, literally a shelf above where the casing goes.

It's a little hard to make out, but you might be able to see "4 x 3 x 13" written on what's actually called a vane, but I still want to call a blade. Suction hole, discharge hole, impeller diameter - that's generally how we refer to the sizes of these things, in inches, because that's what we do in America. 4 x 3 x 13 is a pretty common one.

Going deep on the wheres and whys of that stuff is beyond the scope of this post, but trust me when I say there's a lot of engineering behind it. A lot. I mean, if it was easy to understand, I wouldn't have just linked to someone who has a four-year degree in manufacturing engineering and a decade of professional experience, right? The overview of all of it is that your specific requirements will vary based on what you're pumping, the flow rate you're pursuing, the competing pressures in the system, and the horsepower required to meet that goal. The good news for you is that we have smart people who can help you out with that one. Hey, I have to mention it once.

The impeller is rotated by a motor, which does two things. First, it creates suction through the intake, because obviously stuff has to get in there somehow. Then it converts the rest of the mechanical energy from the motor into centrifugal force that drives the fluid around the casing and out.

I didn't ask around, but I'm guessing that's a misconception about impellers - even though they kind of look like they could drive a paddle boat, that's not actually what they're doing. Put water in a glass, stir it vigorously in a circle for a little bit, stop, and notice that the water keeps going for a little bit until the centrifugal force you've created dissipates. Same idea. The impeller is needed to create the force, but it's not directly pushing anything. Their shape, with the vanes/blades, is largely to allow fluid to get from the center to the outside.

You could very literally do a whole second part to this just on the rest of the pump beyond the casing, but I'll broad stroke that one a little here.

Obviously, the primary thing going on is that the drive shaft is running from the motor to the impeller through that frame (like many things, there are several different types of "overall" setups, I picked this one because it's nice and shiny, and also because it offers a decent look at what's going on).

A lot of it, particularly towards the top end (as the photo above is sitting) involves bearings, for the obvious reason that we're dealing with rotational movement, and accomplishing that movement that with a maximum amount of stability and a minimum amount of friction is ideal as things approach the motor.

But, to be honest, my favorite parts of this whole area are the stuffing box and packing, which are towards the base of that whole assembly. Their function, essentially, is to seal off the casing (leakage there would be bad, obviously) while still allowing free movement to the drive shaft running into that casing to meet the impeller (because restricting the drive shaft is also bad). Google disappointed me on the quality of diagrams available, but here's one that hits the basics, with the different rings and the parts that keep them in place.

Why is that my favorite thing? Okay let's close with some self-depreciating humor, why not. This isn't easy to admit, but when I first started I thought that "packing supplies" referred to stuff to help transport pumps from one place to another like, you know, packing a suitcase. In fact, this page on our website still gives that away a little with "even packing supplies," like "wow, we really do offer everything, we'll even help you tie it down in the back of your pickup truck." I've kept it like that even after knowing better as sort of an inside joke with myself. Now you're in on that too, congrats.

Newton, one of the smartest people who ever lived, would certainly be proud of me.

As always, hope you learned something, but if not, hope you were at least entertained!

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