Flow to rotate impeller backwardly
Flow to rotate impeller backwardly
(OP)
How can I get the flow needed, from discharge to suction, to rotate pump backwardly?
(I am going to size a RO for pump warm up)
Thanks
(I am going to size a RO for pump warm up)
Thanks





RE: Flow to rotate impeller backwardly
Getting a (centrifugal) pump to run backwards is pretty easy; just pump stuff through it backwards.
Maybe you need to restate your question using a few more words.
Mike Halloran
Pembroke Pines, FL, USA
RE: Flow to rotate impeller backwardly
RE: Flow to rotate impeller backwardly
In addition to the problems it can cause for an electrically driven pump (not a fact in evidence so far), it can damage certain kinds of seals.
I have also associated it with an overheated bearing, but the bearing may have had other problems.
Anyway, centrifugal pumps are typically fitted with check valves and/or anti- reversing ratchets to prevent them from being driven backwards, so I too am really curious to hear why anyone would want to do it.
Mike Halloran
Pembroke Pines, FL, USA
RE: Flow to rotate impeller backwardly
Consult your pump vendor before you go backasswards.
"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein
RE: Flow to rotate impeller backwardly
RE: Flow to rotate impeller backwardly
I am not gonna back rotate impeller, I like to know what the max flow is for NOT having back rotation.
Thanks for your replies.
RE: Flow to rotate impeller backwardly
Pretty close to zero, unless there's friction in the shaft.
Best practice where backflow is a possibility is a backstop ratchet _and_ a check valve.
Mike Halloran
Pembroke Pines, FL, USA
RE: Flow to rotate impeller backwardly
Why not run the discharge from the online pump through the RO and to the suction of the offline pump. Then is is running forwards and there are no doubts.
StoneCold
RE: Flow to rotate impeller backwardly
RE: Flow to rotate impeller backwardly
Consult your pump vendor before you go backasswards. "
A pump running backwards form reverse flow will not unscrew the impeller from the shaft as the pump and motor rotate as a unit, if it were a diesel drive unit or similar where the drive unit cannot or is not permitted to rotate in reverse - there is not sufficient torque developed to "unscrew the impeller".
However, running backwards from reverse flow is an entirely different matter than from being driven backwards by starting the pump in the wrong direction with a screw on impeller, this usually ends up in a disaster.
Naresuan University
Phitsanulok
Thailand
RE: Flow to rotate impeller backwardly
I agree generally with the previous discussion of swing check valve seat bypass orifices for keeping warm an idle pump in a multipump flow system. We used a bypass orifice in the check valve body rather than through the disk for this purpose. The CPC data would not be useful for this kind of reverse flow since the CPC data would only apply to a stuck-open check valve where the reverse flowrate could be quite high like 60% of forward rated flow.
RE: Flow to rotate impeller backwardly
RE: Flow to rotate impeller backwardly
Just to let you know, I found a guideline for warm up line sizing. It is in Chemical Engineerig Magazine Nan 1995 Page 89.
RE: Flow to rotate impeller backwardly
= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
http://www.trent-tube.com/contact/Tech_Assist.cfm