1 reply to this topic

[arpi]

Hi,
In plant some of the raw materials we have to charge through barrels and pump into reactor/vessel. In such cases there are provided some gear pump for charging of raw material viscosity varies from 100 cp to 1000 cp and also with season viscosity vary of similar raw materials.

so for the case there is some elevation of Gear pump is also available for charging through barrels but in most of the cases there is requirement of priming of Gear Pump.

I want to know that is there always requirement of priming in gear pump, because i didn't read about it in literature.
or any other reason for this type of priming.


thanks

Regards

[kkala]

Googling "gear pump priming" reveals a lot of information saying that gear pumps are self priming, such as http://www.liquiflo....Pump_Basics.pdf. This reference says in addition that this sort of pump has NPSHr that should be respected. Another reference looks into 4 sorts of gear pumps at http://www.pumpschoo...o/selection.htm.
Nevertheless self priming coused troubles in the fertilizer industry, where I worked in the past. I had not recognized the type of non centrifugal (self priming) pumps used, but dry priming was generally not easy; neither was wet priming for centrifugal pumps located above liquid level. Delayed priming after several efforts was attributed to leaking suction flanges or valves (introducing air), restriction of suction line due to scales or solids contained in liquid, probably to air ingression from the suction tank. It seems that a small quantity of air introduced through a loose flange can "silently" delay priming, or even neglect it.
I do not know whether other members have similar experience, or the troubles were peculiar to this specific industrial factory. Old pumps pulling water from earth by a hand lever had also problems of priming (mainly long delay) due to imperfect operation of check valves.
Probably some reservedness against self priming pumps is not bad. Which means generous margin on NPSHa and care on the whole suction line to reduce above mentioned problems, in case that a self priming pump has to be installed.

Edited by kkala, 24 August 2011 - 07:34 AM.