There's a lot of different types of sealless pumps, including diaphragm pumps, peristaltic hose pumps, mag-drive centrifugal pumps and canned pumps. Very different pumps for very different services, but I've used all but the peristaltic hose pumps in different services before, including petrochemical (a polyethylene plant, actually). What are you looking for specifically, to narrow it down a bit?