Thanks for the input,
We do have a level indicator in the pit which I didn’t mention. It’s an air bubbler type device that seems to work. Our level stays fairly constant at around 45%. We also have a flow meter at the degas tower that reads a combined flow from two separate pits, but it is also fairly steady. I don’t believe we are running the pit dry or cavitating the pumps.
You are correct in assuming I cannot bypass my degassing unit, at least not for long enough to make a difference. The pumps meet their hydraulic expectations, and have at times run for up to a year with no issues. On the opposite hand, we can have pit fires three days in a row that appear to be related to one particular pump at the time. I’m keeping an open mind as to other potential causes of pit fires/SO2 spikes, ie iron sulfides, static discharge, globs of sulfur fuzz hitting the incinerator, etc, but with the build up in the pump bearings it seems likely the pumps are the culprits. We’ve installed pumps with a 0.020″ clearance and taken them out with a 0.002″ clearance due to this “plating” in the bushings.
We have tried several bearing clearances. Opening the bearing up much beyond 0.020″ total clearance results in high vibration of the shaft. Closing them too much results in starving the upper bearing.
35# steam is the ideal temperature for pure sulfur. Granted our sulfur is far from pure, but we have seen problems with the pump tripping out when the jacket steam gets up around 50-55psig.