POSITIVE DISPLACEMENT PUMP REVERSE FLOW
POSITIVE DISPLACEMENT PUMP REVERSE FLOW
(OP)
hi all,
where can i find evidence/proof/article/etc. for the fact that reverse flow (from discharge to suction) can not occure in positive displacement pumps when it is stopped , because of the way it is constructed and nature of operation .
regards,
roker
where can i find evidence/proof/article/etc. for the fact that reverse flow (from discharge to suction) can not occure in positive displacement pumps when it is stopped , because of the way it is constructed and nature of operation .
regards,
roker





RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
If you have a leaky suction valve you may have reverse flow.
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
How many ideal PD pumps have you ever experienced?
Check valves leak, unless installed backwards by accident. That's another corrolary of Murphy's Law you can live by...
Back leakage through two check valves of the same construction in series is definitely possible, ie. the suction and discharge check valves of the pump itself. Add a third check valve at the point of injection of whatever stream this pump is generating, and make that check valve of different construction to those in the pump, and you'l reduce that likelihood considerably.
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
The usual over-looked hazard with PD pumps is an uncontrolled forward flow in cases where the discharge pressure (due to upset, process cycle, etc) falls below the suction- i.e. you shut the process down and find your chemical injection tank contents has flowed into the process if you didn't isolate the pump. The manufacturer can recommend a back-pressure valve at the discharge to guard against this scenario if needed.
best wishes,
sshep
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
Be especially careful of blow lines (air, N2, steam) the increased velocity can over-spin a PD. Bypass around the pump for blowing down.
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
If you are pumping something with solids, the check valves in diaphragm pumps can also hang up allowing back flow.
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: POSITIVE DISPLACEMENT PUMP REVERSE FLOW
Piston pumps/diaphragm pumps use check valves.
Gear pumps don't.
Check valves can leak. So can gear pumps-leaking thru the clearances. Plus gear pumps can be driven backwards by a reversed pressure gradient.