moltenmetal,
We use both the Milton Roy and B+L pumps in the same service and had just the opposite performance that you state. I should state that we inherited the MR pumps so any teething pains had long passed while the B+L we our own doing to increase throughput. We had some very expensive teething problems with the B+L pumps both on the mechanical end and pump heads. These were 3 and 5 high pumps. Right out of the box we had a problem with the B+L pumps as there was no way to drain the oil sump so we loss production while we modified the bases by adding a drain.
As stated we inherited the legacy MR pumps and not to say we didn't have any trouble with them would be a little white lie. Our original in service pump list was 33 MR and 4 B+L and now has changed to 18 MR and 18 B+L. This is because process changes allowed us to manifold part of our process feed. As our process is continuous the MR pumps have 3 in parallel so if one fails the other two can take up the slack. On most of our lines that use B+L there are two pumps in parallel and one can carry the load at 75% throughput.
We do all our pump maintenance in house. If a process line comes down for overhaul we also overhaul each pump whether it needs it or not.
Some of the MR pump frames and major components have been in use 24/7/365 since 1952. The only changes made on these pumps is adding cooling system to the packing gland and a piston material change(s).
All PD pumps will do the job if properly selected and sized and then maintained.
Addenda:
At the present all of the aforementioned pumps are idle as production demands are Zero. This is the first time that all have been down since startup in 1952. The plant has went from making 800,000,000+ pounds of polymer per year three months ago to making less than 7,000,000 lbs today by batch processes.
