Surprise, we are having problems with our acid pump attached to a Delta V. 
It usually stops pumping at the beginning of a run.  I have made sure 1) the
ss inlet and outlet go thru the inner o-ring, 2) they dont go into the pump
housing and 3) the acid is not crystallizing.  

After opening the pump and watching it go thru a run, I observed the belt
slipping on the pump side.  When this happens if I try to turn the pump ring
manually in the same direction, there is a lot of resistance...so the belt
slips because the pump is seizing a bit.  If I turn the pump manually in the
opposite direction for a bit and then back in the original direction it
unseizes and turns fine.

Any ideas on what might be causing this resistance?  It's not acid viscosity
since once it is turning fine acid drops out without problem; but once it
seizes it just slips for the rest of the run.

Has anyone ever attempted to replace the wooden wheels and rubber belt with
anything different...like a set of cogs and small chain?

Thanks for any help.