At a South American refi nery plant, failures occurred at regular intervals on the double-acting mechanical seals of two API 610 refi nery pumps used to pump crude oil. These not only led to repeated unscheduled maintenance visits, but also to costly production stops. These not only led to repeated unscheduled maintenance work, but also to costly production downtime. A pump monitoring system with integrated mechanical seal monitoring was used to identify and eliminate the causes of the faults.