Reverse flow in vertical shaft pumps
Reverse flow in vertical shaft pumps
(OP)
Hi everybody
I've to dewater a reservoir to sea by using a wet pit mounted vertical shaft pump (axial flow), for watering the same reservoir i want to eliminate the extra pipe way and channel as there is positive head over the reservoir (sea level is 2.5 meter avove the reservoir)i am planning to use the dischrge flnge of the pump as the suction from sea to reservoir without runing the pump, Does anybody know what will happen to pump bearing wise?? Anyhow is it practible?? Please let me know about any remedies or cautions!!
Thanking you in advance.
I've to dewater a reservoir to sea by using a wet pit mounted vertical shaft pump (axial flow), for watering the same reservoir i want to eliminate the extra pipe way and channel as there is positive head over the reservoir (sea level is 2.5 meter avove the reservoir)i am planning to use the dischrge flnge of the pump as the suction from sea to reservoir without runing the pump, Does anybody know what will happen to pump bearing wise?? Anyhow is it practible?? Please let me know about any remedies or cautions!!
Thanking you in advance.





RE: Reverse flow in vertical shaft pumps
Normally the pumps have a check valve on the discharge side if it is so you must take it off.
BUT
The first to be aware is than when the water goes back the pump , the shaft will rotate in counter wise from original and the threaded parts could disassembly.
If you want to use the same pipe , use a check valve upward the pump and do a tee branch where to put valve , so when the pump is off you open this valve and can fill again your reservoir.
Dont worry about your english , mine is not better.
You can reach me at k281969@hotmail.com
but keep your post here for mutual benefits.
Pardal
RE: Reverse flow in vertical shaft pumps
Check with pump manufacturer.
Discharge check valves could be replaced with an actuated valve so flow could be stopped in reverse if required.
RE: Reverse flow in vertical shaft pumps
All VHS motors has non reverse rachets. motor will not rotate backwards and impellers will not come loose.
Regards
A. Ozden Ertoz
RE: Reverse flow in vertical shaft pumps
Having the motors drive the pump in reverse WILL unscrew the couplings. Reverse rotation due to back flow WILL NOT!!!!
NRR's are an option, and they keep pump frop overspeeding. There are thousands of pumps installed without NRR's which go into reverse rotation evertime they stop.
When you reverse rotate, the force is applied at the impeller. As such, the toque direction on the shaft does not change. The couplings are still being tightened!
RE: Reverse flow in vertical shaft pumps
I hope I helped somewhat.....
RE: Reverse flow in vertical shaft pumps
We do not have threads on the shaft, but I agree with Slagathor that it makes no difference. In the same sense, the axial force in reverse flow, caused by the water flow, will act downward, like in the forward flow.
The major force on the shaft is due to the water column in the pump. In reverse flow, this force remain the same.
So, I see no problem to the thrust bearing of the motor in reverse flow.
But! Vibrations can occur and cause damage, so you should be near the pump and inspect this.
RE: Reverse flow in vertical shaft pumps
RE: Reverse flow in vertical shaft pumps
the only problem i would expect from using the pump for discharging your reservoir would be overspeeding, which could cause excesive vibration. the speed on the pump could be up to twice nominal speed (if i remember well. it is called "velocidad de embalamiento" -sorry, i dont know the english word for it).
this wont happen if your motor has non-reverse ratchet. to keep speed within acceptable limits you would have to throttle the valve you have in the line (supposed you have one).
RE: Reverse flow in vertical shaft pumps
RE: Reverse flow in vertical shaft pumps