is a small problem that can be a major problem, which is going to wear the ring of CIFA
it happens regularly during the pumping of water from the concrete get squeezed and compressed concrete in the process causing a blockage.
at the company where the pumi undergoing maintenance, they say there is little to do, say every time the wear ring against the wear plate in it somewhere and that is the pumi Otherwise there is at least 5mm clearance, in my opinion a thicker O-ring would be conclusive.
or someone has another alternative?

You could wonder if the company that does your mainenance has any idea what they are doing.. 5mm?? Sounds like you can't pump like that. But hey.. advantage is ... if you get your fingers between them you won't loose them.

cifa cutting ring is a hole new ball game,all you have is two little spacer rings that might be 1cm together,the cutting ring is supposed to be a floater that should turn magically by it self as long as you keep it clean.ha what ever.when its starting to show wear its time to replace it. you cant turn it because it will go right back to where it was .so you dont have that option.one thing that might help is to buy a new one and hardface it before installing. it has helped with schwing and putzs before they started selling them already hardfaced. GOOD LUCK