Hartley Kingon
Civil/Environmental
I have noticed multiple pump manufacturers do not provide NPSHr data for Jet Pumps.
Does anyone know why this is?
Kind Regards,
Hartley
Does anyone know why this is?
Kind Regards,
Hartley
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations JAE on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Jet Pump NPSHr Data 4
- Thread starter Hartley Kingon
- Start date
- Status
LittleInch
Petroleum
Well all the links on the OP state "self priming". I can't see why they wouldn't be?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
-
1
- #22
Just adding to Valvecrazy's comments.
Self prime is a misleading term.
Only vacuum assisted "self-priming" pumps will self prime, all other so called self-priming pumps need to be primed initially and will re-prime each time the pump is restarted, provided the system remains primed.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
Self prime is a misleading term.
Only vacuum assisted "self-priming" pumps will self prime, all other so called self-priming pumps need to be primed initially and will re-prime each time the pump is restarted, provided the system remains primed.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
If you look at the drawing in an earlier post you will se that normally a volume of water would be left in the pump house. So in that case i think that it would ne enough to get the ejector effect going had "suck" more water to the pump. Remember, this is a pump for domestic application so frequent start/stop but with relatively small volume.
--- Best regards, Morten Andersen
--- Best regards, Morten Andersen
LittleInch
Petroleum
In practice once the pump is filled it should stay more or less filled as the inlet and outlet are both at the top.
The operating manual does say that you need min 50% full for the self priming to work.
So yes, the pumps are not inherently self priming, but if the pump body is partly full of water then it effectively acts like a vacuum pump.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
The operating manual does say that you need min 50% full for the self priming to work.
So yes, the pumps are not inherently self priming, but if the pump body is partly full of water then it effectively acts like a vacuum pump.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Valvecrazy
Mechanical
On a domestic application a foot valve is mandatory and keeps the pump from losing prime. Even if/when a jet pump will self prime, it would take a minute or so. With frequent starts/stops of a domestic application, you don't want to be waiting for water as the pump re-primes after each start. Also, there are ways to keep a jet pump from cycling on and off so much on domestic applications. ![[bigsmile]](/data/assets/smilies/bigsmile.gif "[bigsmile] [bigsmile]")
- Status
