The primary concerns that I have experienced have to do with selecting the proper materials of construction for the seawater itself, i.e. corrosion due to the chlorides and electrolysis (particularly the presence of dissimilar metals). Any manufacturer with experience in the application should...
Temperature, abrasion and pressure may be playing a part in the premature failure of the existing progressing cavity type pumps. Abrasives such as sand, sludge or metal fines in the tar combined with a high discharge pressure would have a dramatic effect on pump life, if it was not selected...