초록 ▼

A centrifugal pump with hydraulic thrust balance and tandem axial seals. The centrifugal pump has an impeller with front and rear axial seals operating in unison to either reduce or increase the size of gaps therebetween. The gaps are of a minimal dimension to minimize leakage. The rear axial seal i

A centrifugal pump with hydraulic thrust balance and tandem axial seals. The centrifugal pump has an impeller with front and rear axial seals operating in unison to either reduce or increase the size of gaps therebetween. The gaps are of a minimal dimension to minimize leakage. The rear axial seal is located at the tip of the impeller with the front axial seat located either at the impeller eye or radially outwardly thereof. Hydraulic thrust balance is achieved and continuously maintained by axial movement of the impeller shaft and impeller to modulate the gap at the rear axial seal and, thus, control the value of an effective pressure acting on the back side of the impeller whereby an outward thrust force resulting therefrom counterbalances an inward thrust force resulting from pressure acting on the front shroud of the impeller. A clearance at the rear of the impeller communicates with suction pressure through a restricted passage. Impeller hydraulic thrust balance forces usually dwarf other thrust forces which are considered to be external thrusts without significant impact on overall thrust balance. Examples of external thrusts are those that arise from suction pressure acting over the process seal area and from helical gears in integral gear driven systems. A normally preferred thrust balance design is appropriate for the majority of pump applications, but design alternatives are offered for inordinate pump applications which provide maximum capacities to handle either outward or inward external thrust loads.

대표청구항 ▼

A centrifugal pump having an inlet and improved dynamic thrust balancing of an impeller having front and rear shrouds and provided by a pair of axial seals for the impeller relative to the pump case and wherein said axial seals are associated with the front and rear shrouds of the impeller, the fron

A centrifugal pump having an inlet and improved dynamic thrust balancing of an impeller having front and rear shrouds and provided by a pair of axial seals for the impeller relative to the pump case and wherein said axial seals are associated with the front and rear shrouds of the impeller, the front axial seal being defined by a pair of opposed axial seal surfaces with one seal surface on the pump case and the other seal surface on the front shroud, the rear axial seal being defined by a pair of opposed axial seal surfaces with one seal surface being on the pump case and the other seal surface on the rear shroud at the outer periphery thereof, said seal surfaces on the front and rear shrouds facing in the same direction whereby said axial seal surfaces move in tandem in either seal closing or opening directions, the pump impeller being mounted in said pump case to provide front and rear clearances between the pump case and the front and rear shrouds respectively, the rear shroud having an area exposed to fluid pressure in the rear clearance which is greater than the area of the front shroud exposed to the fluid pressure in the front clearance, and the seal surfaces on the front and rear shrouds facing in a direction opposite to the direction of fluid flow in said pump inlet whereby fluid pressure in the rear clearance controls the gap between the seal surfaces of the front and rear axial seals and an increase in said fluid pressure acts to urge said seal surfaces in a direction to reduce said gaps.