We talk about head as a measure of pressure, and it's expressed in feet. We saw that on that pump tag, that pump tag was 170 feet of head, okay? So at 170 feet of head, we got to figure out, "How do we do the calculation?" So 1 cubic foot of water contains exactly 7.48 gallons, weighing in at a hefty 62.3 pounds. Now, when I go through this part of the session, everybody kind of goes, "Well, you know, a foot of water is 8 pounds." No, a cubic foot of water is 12 by 12 by 12. So if you do your math, and you remember early math, we can take that and we can break that into 144 cubic inches. So what I get out that big cube is I get a 1-foot by 1 inch by 1 inch squared column. And if I take that 62.3 and I divide it by 144, I get that 0.432 pounds. And if I want to really know how this whole thing goes, I take that all together and I break it down. I know that 1 cubic inch of water weighs 0.432 pounds. And so if I do a little more science in there, and I get into it, and I go, "Well, I need to figure out how much I can get out of that," it takes exactly 2.31 pounds of this 1 by 1 stacked on top of it to give me 1 pound of pressure, okay? 

So one of the hard things to get through when you're trying to figure this out, as I remember, "Do I do divide, or do I multiply?" Well, if I got the pressure, then I'm going to multiply. If I've got the feet, I'm going to divide, okay? And if you can remember that, you're halfway through the ballgame on this. So if my pressure gauge in the pump reads 70 PSI roughly and the pump tag says 165 feet, oh by golly, that pump's got to be doing what it's supposed to be doing. 

I don't need to go find a flow meter to find out if it's working or not. I can tell by the pressure gauge that pump is doing exactly what it was designed to do, pump 165 feet of head. Hear where I'm going with this whole scenario? A lot of times people think the pump is the problem, but it's really not the pump, it might be the system. So what kind of valve was put in the wrong place? Was there a basket strainer that got plugged up? We'll get into that a little bit later on here so...okay? Now, let's say, for instance, I can't find that pump tag, but I want know if my pump's working right. Well, I could take that 70 PSI, and I can multiply it by 2.31, and that would give you that 165 feet of head. But I would have to go find out exactly what that pump was supposed to do, okay? So somewhere in your facility perhaps you've got a file on pump XYZ1234 that says, "Hey, you know what? This thing is supposed to be only doing 130 feet of head, but yet I've got 70 PSI on my gauge." So this is where you have to typically... On a good application of a pump installation, you're actually going to end up with a pressure gauge on the discharge side and a pressure gauge on the suction side. 

Yes you can have pressure on the suction side. So typically what I tell people is you can take the pressure on the suction side and either add or subtract it. If it's a negative number that's less than atmospheric, it's going to show up as a negative pressure, and then you got to subtract it. Or if it's being fed by another system, maybe perhaps I got five stories of water standing on top of that pipe, that's actually going to change the incoming pressure on the pumps. So you need to know what the outlet pressure is, and you need to know what the inlet pressure is. And, by the way, that needs to be measured right at the outlet of a pump and right at the inlet of the pump, because things in your system beyond that pump can cause the pressure to read erroneously, okay? And I'll explain that a little bit later on as we go along. So, to find my pressure, if you look at this pump tag here on the right-hand side of the picture with the pressure gauge sitting on top of it there, you see it's one of these nice pump tags that says "Flowserve" on it. And, not plugging Flowserve or anything, this just happened to be a really nice pump tag that I was able to pull out of there.

Hearing a lot of good information on this pump tag. Should you desire to have to figure out if you need parts for it, it tells you what the bearings are inside the pump. It tells you the customer item, the customer order number, which I have blanked out, the serial number, the type of pump, the size of pump. And you'll notice on the right-hand column, it says 307 gallons per minute at 184.7 PSI. Well, I don't get really nervous about the 0.7, because pumps will actually vary somewhat while they're operating based on temperature. So if the fluid temperature changes, it's going to kind of throw off your head a little bit, because the density of the water is going to change as we change the temperature.

But I always tell people, take that 184 feet of head, divide it by 2.21. You know, in an exact world I get 79.65 pounds per square inch. As you're looking at that number, I always tell people, "Don't get excited if that pressure gauge reads 75, 74, 83, 85. You're somewhere in the range of what that pump was designed to be operating on." Because if we're trying to figure out if there's something wrong with the pump, this will tell us that we're kind of like right there in the ballpark, okay? And, like I said, this is kind of old-fashioned science. In fact, this technology's been around forever. This feet of head dates way back to the 1800s. So, anyway, I wish I could throw out there and say any questions so far, but it'd be kind of crazy if all couple hundred of you decided to ask a question at once, so kind of think about this, and we'll see where we're going with this.


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