I think I was, but perhaps I wasn't clear enough in the beginning. The builder can only meet the time constraints with a 1% NPSH margin. Any increase in margin puts them outside the time they need to meet. I was interested in determining what the margin should be - only to put the pumps out...
Wishful thinking or looking for someone to say "yes you have enough NPSH margin"? I'm not sure I get that one.
I know they aren't calculating for enough margin, but how can you say they don't have enough NPSH margin if you can't say what that margin should be? Okay, how do I say that...
I'm working on contacts within Flowserve - the Houston number appears to be in the right direction. Thank you
http://turbolab.tamu.edu/pubs/Pump21/P21pg018.pdf is a good read. I'd found that before and was one of the indicators that we might have a problem.
What I've read indicates that...
The whole point is that the system operate well over the long haul. With enough margin the pumps will operate successfully, but won't make 9 hours. This doesn't met the performance spec and will necessitate their replacement. If the builder can come up with sufficient technical justification...
The system is built to a performance spec. 9 hours to pump out the volume of the tanks which by extension, requires 5000 gpm. There was no spec language regarding pump selection criteria although the system design must be technically supportable. It must function properly.
I don't think...
Further exacerbated by the increase in speed and that's just when the pumps are brand new. Wait until they start to get beat up.
I agree that it might not be clear exactly where the pumps will actually operate. Our SimSmart model indicates they will operate somewhere close to the end points...
The time constraints are fixed. 1770 rpm is the normal rating - 1950 is the increased speed. NPSH is a problem only because of trying to operate at the endpoint of the curve. We're at 150% of BEP with these pumps. With 55' of head we don't have problems initially, but as the level drops the...
I'm doing a design review for a seawater system using vertical turbine pumps in located in sumps within tanks. The system is to be designed to pump the capacity of the tanks in 9 hours. To do that requires 5000 gpm to be pumped. The BEP of the selected pumps is 3800 to 4000 gpm, but the...
I looked at the link from the last post and I understand now what is supposed to be happening. I certainly appreciate the help. The only thing I am left to wonder now, is how would the torque of the jam nut and then of the full size nut be determined? And lastly, how would you ever be able to...
I don't think compatibility is an issue. If the non-metallic insert could not withstand immersion in diesel oil, there are metallic versions available. While I haven't checked specifically for this application, Loctite has thread locking compounds for use in hydraulic systems. I don't think...
I've seen them used in situations where there is an adjustment to be made. That's not the situation here.
If I was at home, if I was working on my car, or if I was in the middle of the ocean and needed to lock a fastener and had no other choice available, I'd use two nuts. In a heartbeat...
That the use of double nuts is intended to prevent rotation of the fastener seems rather obvious. That should be a concern with any threaded fastener. Why jam nuts in particular would be chosen over the more widely used friction or chemical type locking devices is perhaps the better question...
I've never seen anything that I would consider official (pro or con) on the subject of using double nuts, but I've never been a fan for some reason. It just doesn't seem like a proper engineering approach to me; however, I wouldn't mind being able to make an educated decision. I'm not really...
