gear pump 1

We are using Kawasaki make external gear pump for pressure boosting of polymer. In this pump suction pressure is hunting. Can anyone guide me a possible reasons.

The pump details are as follows.

Operation condition.

Name of liquid - Pet Polymer
viscosity - 2000-3000 poise
Specific gravity - 1.2
Inlet pressure - 10 kg/cm2
Outlet pressure - 200 kg/cm2
Theoretical disp. - 930 cc/rev

thank u
vijay

 

[abeltio]

quite a little hefty pump you have there...
trying to go from the easiest to the most complicated my first approach would be to:
1. check for air in the inlet piping.
check for high points without vents, any inverted U is a high point... an extremely common mistake is to vent the highest point in the system)... see the following diagram:
A B C
------ ------ ------
| | | | | |
__| |___| |___| |____

A, B and C are high points and need venting...hope the dwg makes any sense at all...but TTF's are tricky...

2. check the NPSHR and NPSHA conditions, positive displacement pumps do cavitate too.

HTH
Saludos.
a.

 

[hero123]

there is only one situation responsible for that and many reasons responsible for that situation:

Ur pump is somehow not getting the fully developed desired flow, that is the suction of the pump is deprived of the fluid temporarly in a periodic manner.

Reasons responsible for it:
a) the fluid to be pumped is highly viscous.
b) pipe internal surfaces may be very rough.
c) bends and other diversions in the suction piping is reducing the NPSH(R).
d) A strainer, if installed at all, might have got choked therby not allowing enough flow to pump suction.
e) Air locks in the piping.
f) the duty point of ur pump may be highly deviated from the best efficiency point of ur pump.
g) straight section prior to pump suction may not be enough to make the flow fully developed.
h) if u r using a reducer before the suction, make sure it's eccentric type.

hope u identify the correct problem. in case u can provide me the details of the storage tanks and the piping from the tank to the suction, i may help u even more.