5 replies to this topic

[VIrendra20911]

We know that , We cannot run centrifugal pump longtime closing of dicharge valve.What happned when we do it?

 

[fallah]

Hi,

 

The liquid get vaporized due to excessive heat generation and pump will run dry; hence the mechanical seal, bearing and other parts of the pump will be damaged...leading to progressive leakage of liquid to pump around...

[breizh]

Hi,

 

A few tips about centrifugal pumps:

 

http://www.mcnallyin...6-html/6-7.html

 

Breizh

[samayaraj]

Hi,

 

If you see the pump curve, during shutoff condition, the minimum power supplied to the pump will keep accumulating in the pumping liquid and there by increasing the temperature of liquid. This I will show you in a example.

 

Pump power @ shutoff head (Q)= 1 KW

Mass of liquid present in pump casing + discharge piping upto discharge valve (m)= 15 kg

Initial temperature of liquid (t1) = 40 Deg. C

Specific heat cap of liq (Cp) = 4.18 kJ/Kg Deg. C

 

Q = mCp(t2-t1)

 

1000 (J/sec) = 15 x 4.18 x 1000 (J/Kg. Deg. C) x (t2 - 40) (Deg. C)

 

After one hour of operation, the temperature t2 will be nearly 97.5 Deg. C. By this you can visualize what is happening if centrifugal pump is operated without opening discharge valve. As Mr. Fallah stated above, as temperature increases gradually and it will start to boil and thereby makes damage to pump internals. Also look at the below link for further reference.

 

http://www.cheresour...ntrifugal-pump/

[VIrendra20911]

Thanks to all 

It will really help me

[breizh]

Hi ,

Some litterature about temperature rise and minimum flow rate.

 

Good luck.

 

Breizh