US 4,065,232 A · Liquid pump sealing system

Abstract

An improved system to eliminate a stuffing box or mechanical seal around the rotating shaft of a pump for liquids. The pump and its motor are hermetically sealed, and a pressurized gas pad maintains a liquid seal at the shaft entrance to the pump casing. A suction return line is provided from the seal liquid to the pump suction. A small flow of pumped liquid leaks past the shaft entrance into the seal liquid, then through the return line back to the pump suction. The gas pad and seal liquid are at slightly higher than pump suction pressure.

Drawings

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Drawings

Claims7

Dependent claims

In the combination of a motor, a pump having a discharge and a suction, a rotatable shaft extending vertically downward from said motor, said shaft being operatively connected to said pump at a shaft entrance, a liquid pump sealing system comprising the elements:

a reservoir tank hermetically sealed to said pump around said shaft entrance and to the interior of said motor, said reservoir tank being partially filled with pumped liquid, said reservoir tank having a normal inherently stable liquid level range,
a volume of gas in said reservoir tank above said liquid level, said gas being at the order of and slightly in excess of the suction pressure at said pump, said gas being displaced within said reservoir tank solely responsive to a differential pressure between said reservoir tank and said suction
a bearing gap between said shaft and said pump at said shaft entrance, one side of said gap communicating with said discharge of said pump and the other side of said gap communicating with the interior of said reservoir tank, a suction return bleed line communicating from said reservoir tank to said pump suction, to provide a continuous flow of liquid from said pump discharge through said bearing gap into said reservoir and a continuous flow from said reservoir through said suction return bleed line to said pump suction, said flow being controlled responsive to pressures of said gas within said reservoir tank, said continuous flows inherently tending to equal each other, and to provide a normal inherently stable liquid level range in said reservoir tank above said suction return bleed line and below the top of said reservoir tank, said elements being the sole necessary means to maintain said liquid level inherently stable within said range during normal pump operation, said reservoir tank including means to sense said liquid level,
a pressurized gas source controllably communicating with said reservoir tank through a pressurizing valve,
a vent controllably communicating with said reservoir tank through a venting valve,
said liquid level sensor being operatively connected to said valves to open said pressurizing valve when said liquid level rises above said normal range, and to open said venting valve when said liquid level falls below said normal range, and to close both said valves when said liquid level is within said normal range.

3 more elements

Dependencies are inferred from the claim text.

Description4,676 words

Summary1,147 words

#1. Field of the Invention

#This invention relates to hermitically sealed liquid pumps. Certain types of such pumps are known as "canned pumps". It has applicability particularly to those pumps which operate from a rotating shaft, such as turbine pumps and centrifugal pumps in particular. A feature of the pump permits the elimination of a stuffing box or mechanical seal at the point where the rotating shaft enters the pump casing. This type of structure has particular advantage when pumping corrosive, explosive, low boiling point, or toxic liquids, or when pumping refrigerants or any hazardous liquid or slurry. It is useful in the fields of cryogenics and in heat transfer applications. In general, this pump sealing system is useful in applications where it is desired to avoid any leakage of the liquid being pumped.

#Some advantages of this system include more stable and reliable operation than has been available before, better control of the liquid level over the pump and below the motor, the possibility of using much lighter gage and weight construction, better motor cooling, the possibility of using smaller frame size motors, and more protection against catastrophe.

Brief description of the drawings5 figures

#FIG. 1 is a vertical view, partly in cross-section, of the pump sealing system.

#FIG. 2 is a schematic diagram of a demonstration system illustrating the operation.

#FIG. 3 is a schematic, fragmentary vertical view, partially in cross-section, showing means for keeping noxious vapors away from the motor.

Detailed description3,432 words

#The invention is best initially understood in connection with FIG. 1. This is a vertical view, partly in cross-section, of a pump and motor provided with the sealing system. The vertical section is taken along the diametrical center line of the pump and its discharge and suction, in accord with conventional practice.

#The pump 1, here shown as a centrifugal pump, comprises a casing 2 and an impeller 3. It is provided as a vertical pump, that is, the impeller rotates in a horizontal plane, and the rotating shaft extends vertically to a motor provided above the impeller.

#The casing is provided with a suction 4 and a discharge 5. The detailed structure and operation of the pump itself are not within the scope of this invention.

Facts

Application

05/566,078Filed 8 Apr 1975

Granted

27 Dec 1977

Term ended

27 Dec 1994

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification8 codes

F04D 7/06
Of centrifugal type: the fluids being hot or corrosive, e.g. liquid metals
F04D 13/083
For submerged use: and protected by a gas-bell
F04D 29/086
Sealings: especially adapted for liquid pumps
F04D 29/106
Shaft sealings: especially adapted for liquid pumps

Description4,676 words

Summary1,147 words

#1. Field of the Invention

Brief description of the drawings5 figures

#FIG. 1 is a vertical view, partly in cross-section, of the pump sealing system.

#FIG. 2 is a schematic diagram of a demonstration system illustrating the operation.

#FIG. 3 is a schematic, fragmentary vertical view, partially in cross-section, showing means for keeping noxious vapors away from the motor.

Detailed description3,432 words

#The casing is provided with a suction 4 and a discharge 5. The detailed structure and operation of the pump itself are not within the scope of this invention.

Liquid pump sealing system

Life of this patent

Liquid pump sealing system

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims7

Description4,676 words

Drawings

Classification8 codes

Life of this patent

Description4,676 words