Whoa! I have no idea what a troll is, but I think I can guess. If you notice, I never asked for advice on my flow issues. That conversation was started by others and I only responded to questions that were asked of me. In fact, at one point (22 Feb 07 13:34) I tried to get everyone back on...
katmar- Do you ever sleep? I'm kidding!
I will try observing the startup for bubbles. We have not been able to shop test this pump. Our rebuilder does not have the facility to do this. We thought about setting something up to try that, but haven't gotten there yet. We have a few pumps acting...
Thanks for the image hosting site. I hope these help. While I certainly appreciate all of the free advice, my focus at this point is the possibility of entrapped air as shown. I also should have pointed out that all of the pipe is either buried under 10'-20' of dirt or encased in concrete...
The vertical pump intake bell is at 72' and the centerline of the discharge pipe is 93'. The sump water level is 82'. I know my NPSHa (~40') is marginal to my NPSHr (~34'). That's material for another post.
katmar- What calcs are you refering to? I assume it has to do with the self-venting vs...
We've gotten a little off track. I must have confused everyone. My total static head is only 19' (100'-81'). Add another 2' for dynamic losses and I'm up to 21' or so. I'm wondering if trapped air in the long horizontal pipe might be causing my reduction in flow (from 15500 according to the...
katmar- Thanks for all your input, but I'm confused. The BEP of my pump curve is around 31' and 13500 gpm. Is this what is refered to as "designed for" as others are indicating? My understanding is that the pump will operate at any point along the curve. In our case (with only ~21' of head) the...
The sump water level is 19' below the discharge level.
Elevations:
sump water level = 81'
120' horizontal @ pump discharge = 93'
60' horizontal run = 83'
discharge = 100'
katmar- Our pumps do not currently have gauges for pump discharge, but we are working on getting them installed next week...
rconner- I agree that an air release valve at the point where the horizontal run transitions into the down vertical run would be a good idea, but I need to have extreme confidence that there is air being trapped and reducing the flow. The cost of installing one now would be very significant and...
Does anyone have experience with this? Here's my situation:
Vertical pump sends 15500 gpm of water into an empty 30" diameter 120' long horizontal pipe that turns down 10' vertically, turns and runs another 60' horizontally and then turns up another 20' vertically. The 60' long "trap" holds...
Thanks ccfowler. Here's a FAQ from the HI website:
Q. Our plant is operating pumps on cooling tower service which are experiencing cavitation damage to the cast iron impellers. The pumps are operating close to the best efficiency point and the NPSH available is slightly higher than the NPSH...
I agree with Artisi. Excellent post, JJPellin. Thank you everyone for your expert input. I will look into these and report back with findings and fixes. Thanks again.
The sump is roughly a 100' square.
a
-------
| <-|
b| |d
|123 |
-------
c
The flow enters from side d (at the arrow) parallel to side a in a CCW flow. The pumps are lined up along side c in the corner by wall b. There is some natural circulation that we will be...
Thanks for the reply. The installation is about 10 years old and I'm told the reduced flow has there since the beginning.
There are vortices visable on the surface of the water and the pump currently being rebuilt shows cavitation wear on the impellor.
The pumps are generally rebuilt each...
