Over Replacement of Circulators

[mhphs]

Hi folks,
I have been asked to look at a job in which the pump/circulator has been changed apparently 4 times over the last 8 years!

This obviously cannot be right. Any ideas what to look for or what could be causing it from the outset. Its an external pump from the boiler, so I am assuming it is open vented, but I shall have to see.

Recon it is something to do with the circulator cavitating, due to draging air in from somewhere and gradually wearing the pump down? What can I do to prevent this from happening again? (If I remember college from a time ago) is it something to do with the open vent being just before the pump instead of after?

Thanks
Richard

 

[Deleted member 2053]

Do they fail because they sieze, or because they spin but stop circulating?
Latter could be crud in the system. Former could be that they are mounted so that the small bearing in the top is lower than the impeller. Could be that you are getting them from a supplier that throws them around and the ceramic shafts are pre-cracked for you! Take a failed one apart and have a look inside.

 

[fatoftheland]

The open vent is meant to be before the pump. The vent should be the very first thing before any take off. If it was air then there would air in the rads. If it was air from pumping over, after all there years the rads would be rotton. I think Grahamep is right in that the pump is at the wrong angle and the top bearing is running dry.