If I'm doing this pump, you see there in the bottom of the page it says the service is some type of a reformate splitter reflux pump. If I was a betting man, I would probably say this pump is probably a tag off of something you would find at a refinery. That's probably going to be pumping some type of a refined petroleum product. It’s specific gravity is going to mess with that pressure setting, okay? So if we're trying to figure out exactly where that pressure lies, we're going to have to know what this reformate splitter fluid is that we're pumping, because now, as you see in the formula down below there, pressure equals head divided by 2.31, divided by specific gravity. So that would throw my pressure gauge to a different world. 

Excuse me. So, as we go along a little more breaking down the hydraulics of a pump, flow rate is the volume of fluid that passes per unit of time. Flow rate is given as how much water can be moved, and it's typically in gallons per minute. On every single pump, no matter how old it is or how new it is, flow rate and pump head are the two most important specs that you're going to get in there. Because if you get into that and start looking at it, that's really what the pump is doing. That's going to tell the end-user, it's going to tell the technician, it's going to tell the engineer, it's going to tell the designer exactly what this pump's capable of doing. So it's kind of important to understand the flow rate. "So is your pump working?" Good question. Yes. Great. Okay. No? Now what do I do? Is it really time to panic? Well, no, it's really not time to panic if you think about it. You still got something to salvage there in front of you. You just have to do a little more research. So I always tell people, one of the other things, pieces of information that are very valuable to the pump, it's going to be my pump curve.

And everybody goes, "Oh, yeah, you know, I heard about that mysterious little piece of paper, but I have no idea what it is or how to read it." So that's okay. There's a lot of people out there that don't understand the pump curve. I know a lot of engineers that can't understand a pump curve. They've seen them, they don't understand them. But as you're looking at this example on the right-hand side, this is a pump curve that I generated, took a picture of and said, "Hey, this looks pretty good." So I threw it into the program. I figured, "Oh, we could talk about this." Off the top of my head, I don't exactly remember whose pump this is, but I can tell you that the maximum pump impeller that fits this pump is 12.875 and the minimum impeller that fits this pump volute is 9.375. But my requirements in that system as how I asked for this pump was 120 feet of head at 800 gallons per minute. You see that little right angle red, right there in the picture? That little right angle red thing in the pump curve is what we call the um line [SP]. Don't ask me where that name came from. It's the one guy that taught me everything I needed to know about pump curves but was afraid to ask told me, "That's the um line. That's where your pump's supposed to operate at." 

I can also point out a few other things in this picture or this slide. You'll notice these little green isobars or whatever, you know. If you were looking at a weather map, a weather forecast, you say, "The isobars." Well, these are lines of efficiency, okay? And these lines of efficiency come into play when we're trying to diagnose problems of a pump. So, keeping that in mind, you'll notice there's a couple more things on this pump curve. You notice at the 200 gallons per minute line, I've got this big red line hanging out here. You don't ever want to operate your pump to the left of the big red line, okay? This pump could operate all the way over to here. I could get, oh, somewhere in the near neighborhood of about 140 or 135 gallons per feet of head at say maybe 350 gallons per minute, 300 gallons per minute.

So I would be way down here at this point of the curve if I ran the line up here. However, if I ran that pump at this point, you're probably going to find this pump's going to be a troublemaker, and when I talk about a troublemaker, you can poll these questions. It's really hilarious when you start listening to it. I've had people in the class tell me, "Well, you know, we've got all these pumps in a room. We're changing these seals every year, because they're always leaking. And then you'll see somebody else in that same room when we're talking about pumps, and they'll say, "Well, that's kind of funny. I've got a pump that's 30 years old, and we've never changed the seal on it." And so people start scratching their heads, and they say, "Well, why am I changing seals on this pump so often when this guy's got almost the same pump and almost the same application and not replacing seals?"

So the question comes in. This is where the pump curve will tell you what's going on. The pump curve is going to say, "Hey, if you operate too far to the right or too far to the left, you start throwing things at your pump that it's not designed to handle," and typically those are pressures that show up as vibration. And those vibrations will actually show up as something you can measure. So we'll talk about that in a little bit.


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