NPSHR for Grainger pump 4RU77 1

[TheRyno]

Hi All,

I have called grainger about getting the technical data for their DAYTON 4RU77 pump, i.e. I wanted a pump curve and NPSHR. They faxed me basically a maintenance and repair guide. The only useful piece of info I got from it was that for swimming pool application the Suction head can be no more than 6" below the pump inlet. This implies that the NPSHR is -.5 ft? Do you guys have any ballpark guesses or rules of thumb for NPSHR of this pump. I'm using this pump in a lab application which requires steady state flow across a filter where differential pressure is measured. It's a closed loop system with a bypass control valve and a main control valve.
Here's the data:

GPM of Water @ 20 Ft. of Head 46
GPM of Water @ 30 Ft. of Head 43
GPM of Water @ 40 Ft. of Head 40
GPM of Water @ 50 Ft. of Head 35
GPM of Water @ 60 Ft. of Head 31
GPM of Water @ 70 Ft. of Head 26
GPM of Water @ 80 Ft. of Head 21
GPM of Water @ 90 Ft. of Head 14
Max. Head (Ft.) 100
Min. GPM @ Head (Ft.) 4 @ 90
Max. GPM @ Head (Ft.) 43 @ 20
Best Efficiency GPM @ Head (Ft.) 28 @ 65
Best Efficiency Range GPM @ Head (Ft.) 16-38 GPM @ 85-58 Ft.

THANK YOU GREATLY FOR YOUR HELP!

 

[DubMac]

NPSHR is a function of the impeller design and flow rate; if you want to be exact, you will need to get curve from actual manufacturer (Dayton?). As the flow increases so does the NPSHR; it is not constant as their 6" value suggests.

These pumps are not made to excruciatingly high standards of manufacturing / repeatability; therefore curve could be off compared to the pump you have. Also, you can get into trouble trying to compare with a "similar" size pump of another brand, since impeller designs won't be the same.

Just wondering why is the NPSHR so important?? Are you experiencing troubles of some sort??

 

[bimr]

Teel / Dayton Pumps are manufactured by other manufacturers and then have a Teel label put on them. Teel changed their name to Dayton and changed the sourcing for many to China or India.

Teel is WW Graingers trade name for pumps and water handling supplies. Graingers should be able to supply you with all the info you need based on the part number.

The NPSH is probably in the range of 17 to 22 feet.

Zoeller has a similar pump with the pump curve:

http://www.zoellerpumps.com/ProductOtherPartInfo.aspx?ProductID=66#79983

https://app.qleapahead.com/rtp/libraryget.aspx?asset=79983,63

 

[TheRyno]

Dubmac: I'm worried about NPSHR because I'm getting vacuum readings on the suction side of the pump while running the system (about -.6 psi max). I'm trying to figure out why I'm getting unusually high differential pressure drop across a filter thats being testing in a closed loop with this pump.

bimr: thanks very much for that info and link.

Bottom line is I'm testing a range of filters with water in this test loop which is a closed system. There's a bypass line back to a reservoir and the main line which goes through the filter and the back to the reservoir, which supplies the pump inlet. I'm getting too high of pressure drops across the filters I've been testing.

 

[btrueblood]

Are you monitoring the temperature of the fluid? It will rise in a closed system. If it rises high enough, you may cavitate at the inlet.

"I'm trying to figure out why I'm getting unusually high differential pressure drop across a filter thats being testing in a closed loop with this pump. "

Not sure if what I wrote above (which is still true) will help you. Not sure why you are worried about NPSH, or a slight vacuum condition at the inlet (which seems pretty normal) if the filter is apparently clogging; if the filter is restricting flow, the pump should drop to a less severe operating condition in terms of NPSHr.

 

[TheRyno]

Yes, the temp is rising, its water and it starts at about room temp and gets up to 100 F max. Really I'm trying to get the pressure drop to match the data we already have, so I'm just trying to leave every stone unturned and control and check as much as possible to figure out this pressure drop. And the filters are fresh. However the water gets rusty a decent amount so I'm not sure how much it is affecting the pressure drop.