This sealing method is accomplished by a column bowl with relief ports mounted below the discharge head. Enclosed line-shaft construction is used above the column bowl, standard open lineshaft below. As fluid travels through the column bowl, a small amount of leakage occurs between the shaft and lower throttle bearing.
This leakage reaches the relief ports and drains back into the suction vessel. A shaft-mounted slinger aids in expelling the leakage. A second throttle bearing and internal relief port provide added deterrence against leakage. As a final precaution, a sensor can be attached to the discharge head in critical applications to detect any leakage before it can result in a surface spill.