Seal for a joint or juncture – Seal for well apparatus – For below ground apparatus
Reexamination Certificate
1999-05-26
2001-05-08
Browne, Lynne H. (Department: 3629)
Seal for a joint or juncture
Seal for well apparatus
For below ground apparatus
C277S422000, C277S401000
Reexamination Certificate
active
06227547
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to laterally translatable seal carrier mechanisms having rotary shaft seals. More particularly, the present invention is directed to an axially hydraulic force balanced laterally translatable seal carrier mechanism having a pressure staging system which divides a fluid pressure across two or more rotary shaft seals and also provides for active seal cooling and bearing cooling. In several embodiments, the axially hydraulic force balanced laterally translatable seal carrier system is substantially immune to pressure breathing. The invention also provides for enhanced rotary seal extrusion resistance, high operating pressure capability, and compatibility with rotary seal hydrodynamic lubrication.
2. Description of the Prior Art
A particularly difficult sealing situation occurs when a housing containing high pressure fluid is penetrated by a relatively rotatable shaft of large diameter. The difficulty is compounded when available axial space for the shaft sealing mechanism is limited. The energy industry, in particular, is currently in need of a compact high pressure rotary shaft sealing mechanism for sealing pressures in the range of 3,000-10,000 psi on shafts of approximately 8-24 inches in diameter which are subjected to severe mechanical loads and large resulting deflections.
Resilient rotary seals require a very small shaft to housing clearance and minimum runout for optimum high pressure extrusion resistance. If the shaft to housing clearance is too large, the pressure causes the seal to bulge or protrude into the shaft to housing clearance and suffer classic extrusion damage leading to early failure. The protrusion is a direct function of the pressure, the seal modulus of elasticity, and the size of the shaft to housing clearance. The larger the clearance, the more the protrusion. The inevitable dynamic runout of a large diameter shaft, in conjunction with “pressure breathing” of a large housing, efficiently destroys seal material which protrudes into the shaft to housing clearance. Cyclic strain causes the protruding material to break away from the seal, only to be replaced by more protruding material until the seal ultimately fails.
In practice, the shaft to housing clearance must be as small as possible to avoid seal extrusion damage, but it must also be sufficiently large to avoid shaft to housing contact. If shaft to housing contact occurs, the housing assumes part of the side load intended for other bearing locations, and the resulting friction and heat can damage the shaft and housing and destroy the rotary seal. Unfortunately, if the shaft to housing clearance for a large shaft is in a useful range for resilient rotary seals, it is virtually impossible to guide the shaft so precisely that it will not rub on the housing bore. It is therefore desirable to provide a laterally translatable rotary shaft sealing mechanism which provides efficient sealing at high operating pressures while minimizing the potential for seal extrusion and heat induced seal failure.
A number of factors prohibit a small shaft to housing clearance and precise shaft guidance in large machinery. Manufacturing tolerances are large, which directly affects the size of shaft to housing clearance, and also increases bearing mounting clearance and bearing internal clearance, which permits shaft runout and misalignment. Large components are often subject to significant elastic deformation when exposed to high pressure and large mechanical loads, and are often subject to significant dimensional variability from differential thermal expansion and contraction caused by seal and bearing heat. Such dimensional variability can have a dramatic effect on assembly clearances and bearing internal clearances, which can permit large dynamic runout and lateral offset of the shaft, and which can also cause large variations in shaft to housing clearance. It is desirable therefore to provide an efficient laterally translatable rotary shaft sealing mechanism which may be utilized effectively for large shaft diameters as well as high pressure conditions and is capable of accommodating conditions of enhanced dynamic runout and housing pressure breathing while effectively minimizing pressure responsive seal extrusion and thereby providing for extensive service life of the rotary shaft seals thereof.
SUMMARY OF THE INVENTION
It is a principal feature of the present invention to provide a laterally translatable rotary shaft sealing mechanism having efficient sealing capability at high operating pressures while minimizing the potential for seal extrusion and heat induced seal failure.
It is another feature of the present invention to provide a laterally translatable rotary shaft sealing mechanism having the capability for accommodating wide assembly clearances and bearing internal clearances in condition of large diameter rotary shaft sealing, which can permit large dynamic runout and lateral offset of the shaft, and which can also cause large variations in shaft to housing clearance.
It is an even further feature of the present invention to provide a laterally translatable rotary shaft sealing mechanism that is capable of accommodating conditions of enhanced dynamic runout and housing pressure breathing while effectively minimizing pressure responsive seal extrusion and thereby providing for extensive service life of the rotary shaft seals thereof.
Briefly, the present invention is a laterally translatable pressure staged rotary shaft sealing mechanism which is an improvement over the hydraulic force balanced, laterally translating rotary seal carrier assembly of commonly assigned U.S. Pat. No. 5,195,754. The invention provides laterally translatable seal annular carrier means which are laterally translatable relative to a housing having a shaft passage exposed to a pressure therein, and provides staging pressure means which divides a fluid pressure across two or more annular resilient rotary sealing elements by introducing a staging pressure into staging pressure chamber(s) located between the two or more annular resilient rotary sealing elements, and also incorporates a fluid circulation system to provide active seal cooling means and bearing cooling means. A force balancing system substantially balances the hydraulic forces acting axially on the laterally translatable seal annular carrier means, thereby assuring freedom of lateral translation. In several embodiments, the force balancing system establishes substantial balancing of radially acting hydraulic forces such that the axially hydraulic force balanced laterally translatable seal carrier means are made substantially immune to pressure breathing. The invention provides enhanced rotary seal extrusion resistance, higher pressure capability, and better compatibility with rotary seal hydrodynamic lubrication, compared to prior art.
The laterally translatable seal carrier means can take the form of a single annular seal carrier, or a plurality of two or more individual annular seal carriers; and each annular seal carrier may be formed in one piece, or may be formed from an assembly of two or more components, and may be deployed within pressure partitioning bulkhead means.
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patent: 4610319 (1986-09-01), Kalsi
patent: 5195754 (1993-03-01), Dietle
patent: 5199514 (1993-04-01), Titus
patent: 5230520 (1993-07-01), Dietle et al.
patent: 5527045 (1996-06-01), Pondelick et al.
patent: 5678829 (1997-10-01), Kalsi et al.
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patent: 5823541 (1998-10-01), Dietle et al.
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patent: WO 95/03504 (1995-02-01), None
M.S. Kalsi, W.T. Conroy, L.L. Dietle, and J.D. Gobeli, “Development of Composite Coiled Tubing For Oilfield Services”, Mar. 1997, Society of Petroleum Engineers Drilling Conference, Amsterdam, the Netherlands; SPE/IADS 37627 pp 469-477.
Dietle Lannie
Gobeli Jeffrey D.
Browne Lynne H.
Cottingham John R.
Jackson, Esq. James L.
Kalsi Engineering, Inc.
Mayor, Day, Caldwell & Keeton
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