We've been having a bit of an internal debate at work lately over the use of sealed/shielded vs open bearings. A bit of history: We have 2 compressors we rely on that are driven by electric motors. The electric motors in question are 30 HP a piece and run (24/7 3600 rpm) in a rotation of 5 days on, 5 days off. They were installed in 2003 and had the original bearings in place until 2 weeks ago. The bearings that came out were a greaseable bearing while the bearings that were installed were ordered as a sealed bearing. The tech that was installing the bearings pulled the shield off of the bearing to make it greasable since that was the way the originals were and he felt we would be better off with a greaseable bearing given the speed/load those motors run at. I guess my question is, is a sealed bearing designed to run at that speed and last 11 years? It is my feeling that the tech did the right thing in making the bearings greaseable and others feel that he may have been in the wrong since one (of 4) of the bearings failed over the weekend. But I may be way off base and completely wrong. Look forward to hearing a response on this. TIA!