Pump safety device

Details Pump safety device Pump safety device

1981-09-24

1983-07-26

Hornsby, Harvey C.

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

277 961, 415113, 415170A, F16J 1538

Patent

active

043950485

DESCRIPTION:

BRIEF SUMMARY
The present invention concerns a safety device insuring the longitudinal tightness of the shaft of a pump in the case of the rupture of the dynamic gasket separating the high pressure fluid chamber from the low pressure fluid chamber of the pump.
Such a device is particularly provided for application to the primary pumps of nuclear reactors.
In produce, primary pumps effect the circulation of cooling fluid in the reactor. This fluid is generally contaminated with radioactivity.
A set of three dynamic gaskets of the leakage type, placed successively, normally assure the longitudinal tightness of the shaft. However, in case of the failure of one of these gaskets, the downstream elements are exposed to a pressure for which they are not designed and, after the possible rupture of the gaskets located downstream, the contaminated fluid under pressure is released and fills the pressure vessel itself of the the reactor.


SUMMARY OF THE INVENTION

It is the object of the present invention to eliminate this disadvantage by means of a safety device that is readily applied to primary pumps in service.
The device according to the invention is intended to operate only in the case of the failure of one of the gaskets so that it cannot be used when it should perform its function.
According to the present invention, the device comprises a cylindrical hollow piston coaxially surrounding the shaft of the pump and is normally housed in a chamber provided for this purpose in the stationary housing of the dynamic gasket separating the high pressure chamber from the low pressure chamber and means to displace said piston coaxially so as to compress a toroidal safety seal between the shaft and the piston in the event of a failure of the dynamic gasket.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other objects, advantages and characteristics will become more apparent from the description hereinafter of two preferred embodiments presented in a nonlimiting manner, to which two sheets of drawings are attached.
FIG. 1 is a schematic axial cross section of a device according to a first embodiment of the invention; and
FIG. 2 is a schematic axial cross section of a device according to a second embodiment of the invention insuring.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referrring now to FIG. 1, the pump, the symmetry axis of which is shown by a dot-and-dash line, comprises a rotating shaft 1 and a casing 2 of the dynamic gasket fixed in rotation. The fluid circulating in the pump is at a high pressure in the chamber 4 and leaks past dynamic gasket 3 into the chamber 5, wherein a pressure lower than that of chamber 5 prevails. The leakage of the fluid is conducted along the shaft 1 and is evacuated through the conduit 6 in communication with the low prssure chamber 5.
In a known manner, the dynamic gasket 3 is integral with a floating bushing 7 which moves in translation and a compressed spring 8 maintains the gasket 3 in tight contact with the part 9 of the shaft so that only a fluid film escapes from the from the high pressure chamber 4 to the low pressure chamber 5 and insures the necessary relative sliding of the parts without heating.
A static toroidal gasket 10 is placed between the bushing 7 and the casing 2 to prevent any nonfunctional leakage of the fluid between the two chambers 4 and 5.
Without the device according to the invention, in case of the rupture of the gasket 3, the chamber 5 must support the high pressure of the chamber 4.
The evacuating conduit 6 becomes inoperative and the fluid under pressure, escaping through the narrowing 11, floods the enclosure of the reactor. To eliminate this difficulty, the safety device provided essentially comprises a piston 12 and means to displace this piston axially so that it is applied against the rim 33 provided for this purpose on the shaft 1, thereby compressing a toroidal gasket 14 to reduce and eliminate the escape of the fluid into the reactor enclosure. The preferred means to displace the piston 12 consist of an auxiliary sou

REFERENCES:
patent: 3096985 (1963-07-01), Biheller
patent: 3717352 (1973-02-01), Jansing et al.
patent: 4021254 (1978-01-01), Raimondi et al.
patent: 4174843 (1979-11-01), Arena et al.
patent: 4212475 (1980-07-01), Sedy
patent: 4230324 (1980-10-01), Derman

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