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Overtime, a centrifugal pump's job may change. In some cases, the pump may be asked to do more than what it was originally designed to do, causing hydraulic issues where there were none before.
If this sounds familiar, check out this quick demonstration with one of our experts, Rick Ogle. Rick will show how adding additional demand on a centrifugal pump can present new maintenance challenges.
I'm back here at the glass-faced pump demonstration to go over another example for you. I call this one the "Washup Hose Work Order" . It's definitely one I've seen multiple times in the field and it's really good example of how you can take a happy pump and kill it pretty quickly.
Again, I've got a pump that theoretically is a very happy pump. I've got a nice clean suction line, no air entrainment, no cavitation, right now the discharge pressure gauge shows 15 psi, but let's just suppose that's times 10, for this example, 150 psi. Like a nice high pressure shower pump, with, again, very happy setup and a nice high 150 psi discharge pressure.
So let's use a paper machine example, and it's determined that operations needs a washup hose header to clean the machine during sheet breaks or in between grade changes or whatever. So somebody is innocently walking around and maybe sees a nice discharge pressure gauge on this pump that's been happy for years, and sees 150 psi.
The thought, and the good intention here is that I have a very nice pressure, out of this pump that I would love to give the operations folks to help wash up the machine. They should be able to wash the machine from the operator side all the way to the drive side without interacting with the machine or causing any issues.
So a work order is generated, and it's to add a washup hose header off the discharge side of this pump system to leverage this 150 psi to be able to properly wash the machine.
So the down day come, the work order is executed, and the header is installed and then the system is started back up, and this could represent after the work order is executed, the machine is running again. No one is using washup hoses so the system is very happy. Everything is just fine.
Now we're going to fast forward to the next outage and this pump that has never had a problem suddenly had a seal fail in it. So, ok, we'll put a work order in and we're going to order a seal and we're going to go ahead and replace that.
So we do that on that work order, and the next outage comes, and now we've got a bearing pick up, or now we've lost another seal. It's a little confusing to everybody because when everybody comes by the pump in its normal operation everything is fine. But we're starting to have reliability issues more and more frequently.
Maybe we have the seal provider come in and take a look at the issue to see if there's a better seal that could hold up longer. But really what's happened is we have ignored what the original problem was right from the beginning.
Again, all intentions being good, what we've done is modified the system intermittently without analyzing the pump itself to see if it could handle it. I should be able to demonstrate that for you guys.
So again, the work order has been executed, the washup hose header has been added, the pump is very happy, there's no signs of a problem.
But then let's say, two in the morning comes, it's the first sheet break or the first grade change, and you need to go ahead and wash up the machine. So then operators grab their brand new washup hoses and they start washing up the machine.
The pump starts cavitating almost immediately as soon as I put that extra load on this pump which was designed for the flow rate and head conditions that were original, but not the added washup hoses. But then they go ahead and they stop washing up the machine, and everything's just fine.
If the seal failed in that short instance, somebody might have come to the pump to try to figure out why the seal has failed and everything seems to be happy. So they replace the seal in the next work order. The next several washup hose cycles go on, and this is what we're doing to the pump. Every time we use the wash up hoses, shaft deflection, mechanical seal failures, bearing loading, possibly even a snapped shaft.
But every time we come and look at the pump in it's normal running conditions, we can't really understand what is happening. So this is a perfect example of not looking at the whole system before we make a system change. Every time we touch a system, we should go back to the beginning and start talking about the things we talked about in the beginning of the presentation. What are my process conditions? What is my fluid condition? So I understand that the pump that's existing is still set up properly for the change to the system downstream of it that I'm making.
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