Split face mechanical seal system

Details Split face mechanical seal system Split face mechanical seal system

2000-05-26

2002-07-02

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

C277S405000, C277S406000, C277S407000, C277S937000, C277S938000

Reexamination Certificate

active

06412784

ABSTRACT:

STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
BACKGROUND OF THE INVENTION
The present invention relates to methods and apparatuses for sealing machinery, more particularly to mechanical seal systems for rotary shafting mechanisms such as used in propulsors, pumps and compressors.
Current mechanical seal systems for the main propulsion shaft apparatus of marine vessels typically comprise either circumferential-type seals or face seals.
A known kind of circumferential seal includes packing which seals by being hydrostatically compressed from the axial clamping force of bolts acting on a stuffing box and packing gland arrangement. Other conventional methodologies of circumferential sealing include lip seals (or variations thereof) which make use of a spring to radially load an elastomer around the rotating shaft. Circumferential seals are inexpensive, but the failure mode involves leakage and shaft wear, with concomitant repairs entailing a new shaft sleeve or new shaft.
Face seals, on the other hand, have replaceable wearing elements which wear on their axial faces (i.e., perpendicular to the radial direction). These seals are easy to maintain once installed, since there is usually no or minimal leakage and there are no adjustments required. Generally, the failure mode for a face seal is leakage over time, which leads to replacement or seal face refurbishment.
A notable type of failure mechanism for propulsion shaft seals involves dirt and contamination which will wear at the sealing interface. An ideal seal behavior is one that exhibits recovery from leakage attributable to the ingestion of wear debris. The present invention has basis in the recognition that the design of the seal, including the design of the materials, plays an important role in promoting seal recovery.
Currently, the U.S. Navy almost exclusively uses face seals on its large surface ship combatants and submarines; its small combatants and commercial boats, however, most often implement circumferential seals. As compared with a circumferential seal, it is more desirable to use a face seal in smaller water craft (e.g., smaller naval combatants) because of the relative lack of attention required as well as the minimization of bilge leakage. In terms of commercial availability, there is an apparent dearth of completely split face seal designs such as would be suitable for the U.S. Navy's smaller marine vessels. Although small unsplit face seal designs are commercially available, these do not appear to be rugged enough for the naval marine environment. Moreover, the U.S. Navy lacks knowledge and experience with the design and materials used in the commercially available “off-the-shelf” products. The present invention appreciates that the design and materials for a small split face seal can be improved or optimized to suit U.S. Navy and other applications.
Incorporated herein by reference are the following pertinent United States patents: Reagan U.S. Pat. No. 5,820,129 issued Nov. 13, 1998; Clark et al. U.S. Pat. No. 5,725,220 issued Mar. 10, 1998; Duffee et al. U.S. Pat. No. 5,716,054 issued Feb. 10, 1998; Clark et al. U.S. Pat. No. 5,711,532 issued Jan. 27, 1998; Bessette et al. U.S. Pat. No. 5,662,340 issued Sep. 2, 1997; Reagan U.S. Pat. No. 5,615,893 issued Apr. 1, 1997; Azibert U.S. Pat. No. 5,571,268 issued Nov. 5, 1996; Borino et al. U.S. Pat. No. 5,529,315 issued Jun. 25, 1996; Radosav et al. U.S. Pat. No. 5,490,682 issued Feb. 13, 1996; Bowers U.S. Pat. No. 5,409,241 issued Apr. 25, 1995; Carmody U.S. Pat. No. 5,354,070 issued Oct. 11, 1994; Glynn et al. U.S. Pat. No. 5,292,138 issued Mar. 8, 1994; Pecht et al. U.S. Pat. No. 5,217,233 issued Jun. 8, 1993; Radosav et al. U.S. Pat. No. 5,199,720 issued Apr. 6, 1993; McOnie U.S. Pat. No. 5,192,085 issued Mar. 9, 1993; Radosav U.S. Pat. No. 5,114,163 issued May 19, 1992; Nagai et al. U.S. Pat. No. 5,067,733 issued Nov. 26, 1991; Mullaney U.S. Pat. No. 5,020,809 issued Jun. 4, 1991; Lowe et al. U.S. Pat. No. 4,795,169 issued Jan. 3, 1989; Azibert U.S. Pat. No. 4,576,384 issued Mar. 18, 1986; Copes U.S. Pat. No. 4,410,188 issued Oct. 18, 1983; Wilkinson U.S. Pat. No. 4,239,240 issued Dec. 16, 1980; Adams U.S. Pat. No. 3,773,337 issued Nov. 20, 1973.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a reliable face sealing system for a rotary shafting mechanism, such as a ship's main propulsion shafting mechanism.
It is another object of the present invention to provide such a sealing system which will remain leak-free for a significant period of time, such as throughout the life cycle of a ship.
It is a further object of the present invention to provide such a sealing system which is easily maintainable.
Another object of the present invention is to provide such a sealing system which may be used in certain applications, such as in association with small naval vessels, wherein circumferential sealing systems are customarily used.
In accordance with the present invention, a mechanical face seal combination is suitable for use in connection with machinery of the type wherein an axially rotative shaft passes through an immobile housing. The inventive combination comprises a first annulus, a second annulus and support apparatus. The first annulus has a first annular face which is at least substantially planar. The second annulus has a second annular face which is at least substantially planar. The support apparatus includes biasing means. The first annulus, the second annulus and the support apparatus are adaptable to arrangement wherein: the first annulus is attached to the housing; the support apparatus is attached to the shaft; the first annular face and the second annular face coaxially abut; and, the support apparatus holds the second annulus in position with respect to the shaft whereby the biasing means contactingly presses the second annulus so as to approximately axially bias the second annular face against the first annular face.
Notable among the features of the present invention is the robust, integral construction of the rotational structure inclusive of the face (surface) designed for dynamic abutting contact with the face (surface) of the non-rotational structure. This rotational structure, viz., the second annulus, is able to directly bear, in the absence of any intermediary structure, the loading imposed by the support apparatus which holds the second annulus in place with respect to the rotational shaft. Similarly featured is the robust, integral construction of the non-rotational structure inclusive of the face (surface) designed for dynamic abutting contact with the face (surface) of the rotational structure. This rotational structure, viz., the first annulus, is able to be directly coupled with the housing—e.g., directly fastened to the flanged (radially annularly projecting) end portion of a ship's stern tube.
A resultant advantage of the superior material strength and unitary construction of both the first annulus and the second annulus is the reduction of parts needed for the overall seal configuration, with the concomitant advantage of a simplified design. In particular, obviated is the functional or structural need for additional or auxiliary structure—whether it be of an intermediary, intervening, interpositional, dampening, buffering, holding and/or containing nature—used in association with: (i) the first (stationary) annulus in relation to the stationary housing; and, (ii) the second (rotational) annulus in relation to the support apparatus which holds the second annulus in place with respect to the rotational shaft.
According to many inventive embodiments, the second (rotational) annulus includes (e.g., is at least substantially made of a polymeric matrix composite characterized by sufficient structural integrity (e.g., in terms of strength, rigidity and elastic deformation) for endu

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