I once got a kick out of seeing a spec written to include both a "no more than 95% of max impeller diameter" and also, "will operate on a VFD.
The most reasonable way to specify the pump is to simply list what you want the pump to be capable of in the future and let the manufacturer determine...
A sealless solution works best when the precipitation is because of the seal. With the solids in this application, there would need to be some provision to keep solids out of the recirculating/lubricating flowpath.
Mjpetrag, I"m not sure the fluid needs to be "self lubricating" but it does...
waterpipe, does ISO 9906 correspond to the Hydraulic Institute Standards, are are they completely separate. I've run across HI standards much more than ISO 9906 but that might just be my location(USA).
Most pumps I have seen have some fudge factor in their sizing(how often do you see a pump sized within a foot of head of where it's supposed to be?) and taking account for the small variance in RPM is probably part of that.
I've seen something similar with the suction piping. Low pressure in the suction piping(from the running pump) was actually drawing small amounts of air into the suction line at one of the connections, it caused a few performance headaches and the visual of small bubbles going through the flow...
For the bearings, the number I always hear floated is to rotate the shafts every three months but I don't know how much of a safety factor is built into that number. . For convenience, I would have it coincide with checking lubrication in bearing frames.
I don't do a lot of low temp stuff myself but the one project I did work on had an Innomag pump(www.innomag.com) do some odd temperature cycling application that went down to -90 F. Other than the casing frosting up on the outside it was fine.
@PKEngineer: best thing to do would set a small, 1-2 second delay when programming and to make sure that it works, dead head the pump and make sure that motor trips off. Dead heading will use more power than dry running so if your lower limit excludes dead head, it will also exclude(prevent)...
NPSHr is the net positive suction head required and a functon of the pump, impeller size, and speed it is running at.
the required is not something that can be easilycalculated. It might be possible to calculate it analytically using computerized fluid flow software however even then, you...
First: my apologies for the length of this post.
To me, for centrifugal pumps, they work exactly as intended( don't have a lot of experience with using them on mixers and other equipment). The only time I've ever seen them not work is if they're not wired correctly, not programmed correctly...
There are several manufacturers who do not supply curves to pump-flo.
And I would have to strongly agree with CC and Tenpenny, without proper knowledge, pump flo could be less friend and more foe.
oxtox,
I cannot comment on piston diaphragm reliability but the pitot tube pumps generally have great reliability for clean services. The only things to take care of would be the bearings(standard PM) and the seal. On the pitot tubes I've seen, it's kind of an odd situation because the seal...
If there's a suction lift involved, the pump will either have to be self-priming or there will have to be a way to prime the pump. I don't know of any vertical self-primers out there.
How do you plan to prime the pump initially?
I believe it's a safety precaution in the event of a fire. If the ductile iron gets really hot and then hit with water, it could crack and give the fire one more fuel source.
If you have a hydrocarbon processing facility with a serious enough fire to really heat up that pump, I'd tend to think...
-30 C is about -22 F. Ductile if I recall is rated to -20 F, after which it begins to lose it's "ductility". I don't have a tremendous amount of experience with cast, but I've seen ductile used in services going down to -90 F. I would never recommend it but I've seen it done and at that low...
