We aren't really having a problem, but someone noticed there were no wear rings and started questioning if the plan 11 would work since he assumed the same thing of the stuffing box seeing full discharge pressure.
This pump was sent out for repair and from the pictures looks like it didn't have a back wear ring even back then in 2006. They just had the pump apart in the shop and there is definitely no back wear ring and no balancing holes, pump out vanes, or anything. It's a completely closed impeller...
I was hoping to get some help on calculating seal chamber pressure on a single stage overhung Union HHS8. It has a closed impeller with no balance holes and no back wear ring. I have found estimations for closed impellers, but I think they are assuming there is a back wear ring: stuffing box...