Video of this Episode
On the Road?
Listen to AUDIO ONLY
version of the Podcast
Follow the Process Chiller Pro podcast on these platforms.
Listening on your phone or mobile device? These great podcast platforms may require apps to be installed to access the podcast on your mobile devices.
Get an email alert when new episodes are posted.
In this episode, I will first share a real-life situation when I had a process fluid flow problem on a multi-million dollar MRI system I was doing a startup on. I figured out the problem by performing a field process chiller run-out test, really saving the day for my customer and myself.
Knowing how to perform a process chiller system pump run-out test can save you a LOT of time in ruling out the chillers system pump as the cause of the issue.
Without knowing how to perform a pump run-out test, you may have to tear down the pump and perform a visual inspection.
To access this episode in both video and audio-only versions, click on the link provided below to jump over to this episode’s page on the Process Chiller Academy website.
CLICK THIS LINK TO ACCESS THIS EPISODE
Important note: The topic I will cover in this episode of the Process Chiller Pro podcast falls under the “Technical excellence” or foundational component of my skilled trade’s success pyramid.
If you want to get more information on my skilled trades career success pyramid, pop into the Process Chiller Academy site, resource page, link below.
TO ACCESS THE PCA RESOURCE PAGE AND GET MORE INFORMATION ON THE SKILLED TRADES CAREER SUCCESS PYRAMID
This is Martin King process chiller Pro, I have a exciting video for you today. As I mentioned on my social post that we’ve got an interesting scenario here, that has to do with the hydronic side of a process chiller. And so I’m going to take a step away a little bit from the refrigeration side and talk about the fluid flow and how to solve a real life problem. This particular scenario covers the runout test. And this we’re not test is one of the things you put in your toolbox if you’re going to be servicing process chillers. It’s very, very helpful because it will circumvent hopefully, the need to tear down a pump in the field, which is super time consuming. And it makes it possible to figure out if I’ve got a problem inside my pump before you HAVE to do such a tear down. So this scenario was an engineered system, I was asked to come in and design a chiller system that was extraordinarily redundant for even for MRIs. This was a brand new out of the box, Mr. Ideal, and I had an opportunity to go down and assist on the startup because it was a high profile job in the Bay Area, I did not do the installation of it, it was the actual installation, the plumbing and all that stuff was done by a local contractor. And upon startup, we ran into some pretty significant pumping issues on the system side, the system pump side that was delivering the fluid to the MRI gradients, I wasn’t getting enough flow or pressure. And it was little pucker time in the beginning because I had a lot of union guys standing around, we’re literally getting ready to fire up this thing. And it was not performing as advertised. And then that’s just a just a stressful recipe for a stressful situation. Anyway, so I deployed a run out test. And I hope that you guys get a lot out of this. And let’s dig in here. So oh, by the way, if you’re watching this great if you’re listening on the podcast or audio only version, I’m going to do my best to not say things like well look at this or check this out. It’s it’s I’m going to try to explain myself. But if you get a chance to like what you hear, make sure you make some time to maybe pop in to the video version and see what I’m putting up on the screen. Because I think it’ll be even extra helpful to you the system that we’re dealing with a type of application is what we call a research system. So a research is very, very common in the mission critical side of the business. This is mission critical. Just to I covered this a little bit in one of my past episodes on, you know, what’s a process chiller if you get a chance to check that out. And what I’m doing is the this is a mission critical application because it’s an MRI and what mission critical means just to tell you quickly is if that system goes down, this customer is basically out of business, they they cannot use in this case, this particular MRI, which can cost a lot of money. And in the case of an MRI can turn into some life safety issues. So that’s what we’re dealing with here. So research system is typically the most common for mission critical applications in what it what it does. And again, sorry guys, I’m going to shoot over to my screen here, but I’ll try to explain this. We had a 500 gallon pressure rated tank and the tank pump package is separate from the chiller we had basically two boxes up on the roof. We had a chiller, very simple inlet outlet on it, it was a bleeder 60 ton chiller. And then on the tank side, we had the 500 gallon tank and then we had four pumps in this tank. The four pumps two of them are for what we call the research system. What I’m showing on the screen here is on the bottom of the tank, you’ll have the inlets to what we call evap pumps or restart pumps. Another way to do it, we go out we y off to these redundant pumps, we have valves for isolation, we go to the inlet of the pumps, the outlet of the pumps will have a check valve and that prevents backflow because we’re only using one pump at a time. So when one pumps running, the check valve prevents backflow from the other to the other pump right. And then out of the the pipes come back together and then it goes to a valve and then a strainer and then it goes out to the chiller to reject the tea right and then once it’s been cooled on the upper right hand side of what we’re looking at here is the return from the chiller. So that’s the research loop. So basically all that’s happening is fluids getting sucked out of the tank go through the children back. The chiller is out there watching the inlet temperature, which is basically the tank temperature, and it’s cycling the refrigeration system to try and maintain tank temperature. So that’s that whole research loop. The benefit of that is it the chiller really doesn’t care about what’s happening on the process side as far as the thermal goes, All it cares about is maintaining that tank temperature. So hopefully that makes sense to you in question here is the system side. So on the system side, we have two more pumps, same kind of setup, they’re redundant, you’re only running one pump at a time and their plumbing is configured exactly the same. The only difference on the system side is we have VFDs on each one of these pumps, which will come into play when we do this test. I’m going to talk about this in a minute. All right. So that is the configuration. And the lead pump that we were having an issue on is it as I mentioned earlier, was not able to provide enough flow or pressure downstairs, so the fluid was going down to the gradients. And the system was not happy that the Siemens MRI application was saying, Hey, man, I don’t have enough flow, I’m overheating, boom shuts off. So there was not a good scenario here. So what I had to figure out real quickly is do we have an issue with a pump? Or is there something goofy going on with a plumbing system, and the ladder does happen more often than you think now this particular contractor they had been a plumbing contractor for decades, I think over 100 years actually. And looking to what I could see, it was a pretty clean job. And these guys obviously knew what they were doing. But I’ve had it happen where you know, it starts out on the roof at three inch. And somewhere somehow somebody read the the drawings wrong, and dropped a section of pipe down two inch and a half, right. So that can cause us pretty significant pressure drop, which can cause a lot of havoc. I didn’t think that was a scenario here. Well, I suspected that I had a pumping issue. But what I wanted to do is I needed to come up with a way to figure out if this is a pumping issue or something external that has nothing to do with me, there’s a couple things that you need to set up a run out test. I’m going to go off on a tangent here a little bit on pumps, pumps, in general hydraulic pumps, in general, they actually do not pump water. I know that sounds weird. But all a pump really does is it creates a pressure differential between the inlet and the outlet. So I’m going to frame that out that way. Because it’s it’s germane to the conversation that we’re having, right, you have to do run out tests, we got to figure out what our inlet pressure is, and how much pump pressure this pump can do on the outlet. So that’s the difference, we have to be able to generate the pressure differential that this pump can generate. Now, if you’re lucky enough, you’ll have a gauge somewhere close to your chiller on the discharge of your pump. Not all the time. Sometimes, you know contractors want to do you know it’s a budget job, so they don’t put any more gauges in and they absolutely have to. So in that case, you’re going to need to come up with a way to measure pressure on the discharge of the pump on the inlet of the pump, which is generally inside your equipment somehow. That’s a hard one. Sometimes you because you don’t factories, most of them anyway, do not install pressure gauges on the inlet of their pump. So in this case, the 500 gallon tank had a pressure it was a pressure rated tank and they had hose bibs on it to either drain or fill. Right. So that helped that worked out really well. So what we needed on that side of the system was a little pressure gauge. Now, this is something you could get at Home Depot, it has a little brass fitting in here, that’s a hose bib size, and this particular 102 100 psi, typically you don’t need that that’s the most you need on the return side. Right? So this would be screwed directly into the hose bib on the on the tank, right. So that gives us tank pressure on the pump. In this particular scenario, we did have a valve or excuse me a gauge on the discharge of the the tank cabinet. So it was very close. As long as it’s within a few feet. You’re You’re pretty good, right? So what you if you don’t have a gauge, then you have to have something like this. And what this is is a This particular one is zero to 60 psi. There’s a little piece of hose here right? And what we did here is we have a barbed fitting with a three eighths male bracket regular thread, right. And I’m going to show you when I switch the screens over here, how you’re going to connect this to your pump. So those are the things you need as far as tools. And what I would suggest that you do is get yourself a little toolbox tool bag that equips you with all your hydronic stuff, and we can get in other episodes on things you should have in your kit. But having these pressure gauges to be able to measure pressure on both sides of a pump is critical, you got to have that. Alright, so as promised, we’re going to shoot over here to the pump. Okay, and I’m going to show you again, I’m sorry, I gotta do this, because if you’re listening in this is going to be tough, but I’m going to try to explain. So all centrifugal pumps will have two distinct parts to them, you’ll have a you’ll have a motor, which is pretty obvious to identify, and then you’ll have a pump head. So what we want to do is we want to zero in on two components or two parts of the pump head. On this particular pump. This is a Gould’s pump. And most pumps will have these for drain down. If you want to drain the pump head. Sometimes you have to do that for servicing, sometimes you have to definitely winterization you’ll have a vent on the top of the pump. In this case, it’s a three eighths plug. And then on the bottom of the pump head, you’ll have another three it’s plug for your drain, right. So what we’re going to do here, if we didn’t have a a gauge mounted close to the pumps discharge, we’re going to screw that little fitting on there with that gauge I just showed you, we’re going to we’re going to screw that into the pump head. Now you don’t have to get this super sealed, I just get a little Teflon tape in put it around the three eighths or whatever size fitting in is screwed into the pump head good enough, even if it drifts a little bit, not a big deal, right. But you want to make sure that you get it threaded in there good. One thing I want to mention to you before you pull that plug and you go to put that gauge on there, you want to isolate that that pump. So hopefully you have valves on both sides of the pump, you got to do that somehow, if you if you don’t have those valves, it’s going to be tough because you’re going to get a bath, you can be quick about it. But you’re going to lose water water glycol over the roof if you don’t have the ISO valves, but you want to try to isolate it as best you can. Or you’re going to have to drain the system down in order to do your run out test. Bummer, but some sometimes that’s the case. So isolate pull plug connect your gauge, and you’re good to go. So what we’re going to do now is we’re going to take a jump over to the pump curve, we’re going to take a look at what a pump curve is. And you guys have may have seen this before. But this is super important to be able to perform your run out test we’re gonna do a little bit of math I’m going to do it for you. So you can you can figure this out I’m sure on your own once you see how I do this
This episode is brought to you by GMD chillers. If you find yourself in need of a process chiller, check out GND at GE D chillers.com. Or better yet, give Andy or Paul a call over there. 805 50973 ne and Paul are my go to guys over at GND whenever I get approached by resellers and users even OEMs looking for a quality chiller to be designed and built for him. So check them out. If you do call them make sure you use promo code chiller pro so they know how you find out about them. Jean de chiller I love their tagline it goes big enough to produce and small enough to care and that’s definitely the truth out there for sure. So again, called G and D chillers, ask for Andy or Paul 800-555-0973 or check them out online at GD chillers.com.
So what you’re looking at here is the actual pump curve for the pump in question. What we have is a 10 horsepower seven inch impeller. And it’s represented on the curve as C as in Charlie. Now, before I get into this, these curves, every manufacturer produces a curve. So it doesn’t matter if it’s a manufactured pump, at least in the US here. You will have a pump curve available for it. So if you don’t In other words, if you’re on a startup and you go through the envelope there usually there’s some type of a startup document the manufacturer ships with the chiller there should be a pump curve in there if there’s not. What you’re going to have to do is go online and you want to get the the nomenclature off the pump and you’ll have to do a little bit of sleep thing to find out where that curve is because you cannot do a run out test without the pump curve. If you look at this curve, there’s a lot of complicated stuff. And I could actually spend an hour going over all the different nuances of this particular pump curve. But I’m only going to point out the stuff that we have to pay attention to right now. So all pump curves are going to be very similar to this. There’s a lot of manufacturers that try to make this even more complicated looking, believe it or not, but they’re going to have all these basic components on it. So on the left hand side, there’s going to be a scale range here. Now, this particular one, this is a bit this is cool, two pumps, and this is you know, they sell pumps all over the planet. So they’re giving you both in us as well as metric. What I care about here is the feet, okay, feet is a unit of pressure. And again, I can get a new long diatribe what that means, but it’ll be referred to as feet, feet of head or head feet, that’s on this left hand column here. Alright, this particular pump goes zero to 275 feet. And then on the bottom here, we’ll have flow, right, so you’ll have zero to 250 to 75 gallons per minute. Again, they’re also giving you in metric, but that doesn’t matter to me right now. Now, what I’ve done here is I’ve identified my design flow rate for this particular pump is in red here. But I don’t really care about that what I care about for the run out test is zero flow. Now, one of the things just a sort of a side note here, this addresses questions that I get about pumps all the time, pumps will as you increase the flow rate, you’ll notice that the curve slants downward, right, so all pumps, centrifugal pumps anyway, as you increase the flow rate, the pressure that that pump can generate will also will drop, lower flow rate, the pressure, it goes up. So that’s just how it works. And the other thing that I get questions about from time to time is amp draw. So on a centrifugal pump, your lowest amp draw that you will see is at zero flow rate. I’ve gotten into arguments with technicians about this, your your amtrol will always follow your flow rate. So the higher your flow rate, the higher amp draw, the lower the flow rate, the lower the amp draw. In another episode, I’m going to be going over how to how to get a pump to behave correctly, especially on a startup. It’s over ramping, so we’re gonna address that in another video. But that’s just sort of a side note, you might want to know what I care about, as I said is what the C pump can do at zero flow rate. So fortunately, this pump ends up right at about 200 feet. Okay, now I mentioned earlier, those gauges that we installed, are in pounds per square inch psi, right, so you got to get yourself a calculator. Or if you’re high tech, you probably have one of these on your on your smartphone. But what you have to do is in order to convert your feet or head feet to psi, you have to divide by 2.31. That is the value you’re going to use for water. That’s there’s other there’s other formulas, but we’re just going to plan on water today. All right, so 200 feet divided by 2.31 comes to 86.58. So we’ll just call this 86 pounds just because it’s not going to be an exact reading. So let’s just say 86 pounds is what our
pressure should be at zero flow rate. What we’re going to do now we’ve got our gauges installed. And let’s just for argument’s sake, say that our tank pressure is that atmospheric or zero gauge, and so we have zero on our inlet of our pump. Again, I apologize for you guys listening in. But the inlet is going to be in the center of the centrifugal pump heads. So on the inlet we’re reading zero psi. And what we’re expecting is 86 psi there abouts on the discharge when it’s running full steam ahead. Now I mentioned earlier, this particular site that I’m using for my sample here has a VFD. So this is super important. Because if you don’t if you don’t remember this, it’s going to really mess you up. If you have a variable frequency drive on a pump in order to get a accurate run out test that pump drive has to be running at 60 hertz full on. If you start dropping if it’s not at full hertz, you might as well just throw your pump curve out the window though, so it’s super important to make sure that you have your driver running at 100%. If you have just a standard on off pump, not a deal, not a problem, you just gonna be running it 3500 RPMs, it’s running full, full out, what you’re gonna do is you’re gonna measure that pressure in if you’re reading at six psi, or there abouts on this particular pump scenario, then you’re golden. In the case I was in the scenario I was telling you about, I did not, I only had about 35 psi coming out of that pump. So what did I find out? I found out that there was something wrong inside my pump, right? So I knew that I’m not performing on its curve. So that is, that was my answer on that scenario. So I was wondering, okay, well, what’s going on here, and I know at least that I know my pump is a contributor to the problem downstairs. But I got to figure out what the deal is. Because I ran my my run out test, I disconnected the unions, and we got the pump in a position where we could get into it. We popped off all the the bolts off of it on the drawing I’m showing you on the screen here. Number 347 Is the impeller, what we found out was the impeller had been installed backwards. And I gotta tell you 30 years doing this, I can count on one hand on a new pump. It’s extraordinarily rare because most of the major manufacturers are going to do a run out test when they’re shipping it or just before they ship this thing that is a major problem. We recognize what the problem was, we flipped the impeller around, put the pump back together again, slapped it in. And we did rerun our run out test. And lo and behold, we had around 86 psi run out so we knew that pump was working good. And it solved all of our problems. We had good flow downstairs and that kind of stuff. As I said, this is a rare scenario. However, there are scenarios quite a bit actually that you would want to be able to do a run out test in the field. I’ll give you an example. Which is probably the most common is you go out on a either a new install, or you go out on one that’s been a while been in a while. And the first thing you should look for is the in the path of flow to my pump, is there a way to filter or strain the fluid. So that’s a big one to think about. If there’s not, then there’s commonly a problem with the impeller, you may have some debris that’s built up over time or maybe part of a new install. And that has caused some type of a dynamic change to the impeller. And that will cause a problem it won’t be able to run its curve if the impeller vanes are not properly exposed, right. So now usually if you’ve got something stuck in like one vein, since that thing’s spinning at 3500 RPMs, you may get some vibration. So if you if you send some vibration, when you put your hand on the pump, that’s another indicator that you’ve got something going on with your impeller filtration is a is really a big, big issue in in process duty chillers. And if you’ve got a filtration problem, you may also have situations where you have excessive pressure drop across your evaporator. And sometimes the evaporator needs to be back flush, which we can cover in another episode, I hope that was helpful to you run out test is very, very helpful. And if you run out test is okay. In other words, you’re running at your design pressure psi, then you’re confident that that pump is going to be pumping the way it was designed to pump so then you have to start looking external to the process. So that’s it for this episode. Thanks for stopping into the process chiller Pro, Hey, before you go, make sure that you sign up for our alerts. You’ll notice on if you’re on the landing page for this episode, be scroll down just a little bit, you’ll see that there’s a place to sign up for email alerts. So if you want to get an email, when the new episodes drop, you can do that you can unsubscribe at any time. The other thing I’d like you to do is check out our resource page. And we have a resource page for our technicians. And if you jump over there, there’s a five day email course and mini course that we’re putting out soon that covers the skilled trades success pyramid process, which this type of video is a foundational video for what we call technical excellence. So I hope you check that out. Thanks again for stopping in. Let’s
keep the conversation going. I’m on LinkedIn. And you can also put comments on in one of the social posts if you want to pop that back over. If you do go over the social post. So where you see these episodes announced, make sure you click like it helps out a lot. Alright guys, have a great day. Thanks again for stopping in
Transcribed by https://otter.ai