Flow Restricter for Mud Lubricated Earth Drilling Motors

The present invention relates to a flow restricter for lubricated earth drilling motors.

A number of downhole motors used in the oil or mining industries for drilling through earth formations are mud lubricated. These earth drilling motors have an outer housing, an inner tubular member concentrically disposed within the outer housing, and a plurality of bearings disposed between the outer housing and the inner tubular member to facilitate the rotation of the inner tubular member. Mud lubrication is passed through a passage in the tool firstly, to provide some lubrication for the bearings and secondly, to dissipate heat which builds up within the tool.

Each mud lubricated tool requires a flow restricter to control the rate of mud flow. This is particularly critical at pressures in excess of 500 pounds per square inch. If the flow is too great it will "wash away" portions of the tool until the tool is destroyed. Conversely, if the flow is substantially cut off the heat will not be effectively dissipated and the tool will be destroyed by the resulting heat build up.

Mechanical seals have previously been used for the flow restricter, due to their ability to function at the pressure levels required. Mechanical seals work effectively when the tool is newly constructed, however, as wear occurs in the tool these flow restricters lose their effectiveness. It is common knowledge in the art that a critical factor in having effective sealing with mechanical seals is controlling the pressure on the seal faces. When wear occurs in bearings axial movement occurs which effects the pressure on the seal faces.

What is required is a flow restricter using mechanical seals which is self-adjusting to maintain its effectiveness in the face of tool wear.

According to the present invention there is provided a Flow Restricter for a mud lubricated earth drilling motor, having an outer housing, an inner tubular member with an interior drilling mud flow passage concentrically disposed within the outer housing, and a plurality of bearings disposed between the outer housing and the inner tubular member facilitating the rotation of the inner tubular member. The Flow Restricter is comprised of a first seal support having a first seal face and a second seal support having a second seal face. Means is provided for non-rotatably coupling the first seal support within an interior bore of an outer housing while permitting the first seal support to be axially movable in relation to the outer housing. Means is provided for non-rotatably coupling the second seal face to an exterior surface of an inner tubular member while permitting the second seal support to be axially movable in relation to the inner tubular member. The second seal face is in axial alignment with the first seal face. Biasing means exert a biasing force axially upon the first seal support thereby bringing the first seal face into sealing engagement with the second seal face to form a mechanical seal, having a first side adjacent the outer housing and a second side adjacent the inner tubular member. Stop means limit the movement of the second seal support. A first fluid flow passage extends from the interior drilling mud flow passage of the inner tubular member to one of the first side and the second side of the mechanical seal. A second fluid flow passage extends from the other of the first side and the second side of the mechanical seal to exterior of the outer housing. At least one groove is provided in one of the first seal face and the second seal face, extending from the first side to the second side of the mechanical seal, such that a continuous flow of drilling mud passes through the groove and is vented to the exterior of the outer housing via the second fluid flow passage.

The invention provides for grooves in the seal faces which turns the mechanical seal into a Flow Restricter. Incorporated within the design is allowance for axial movement which enables the mechanical seal to self-adjust in order to maintain its effectiveness in the face of tool wear. The biasing means permits axial adjustment of the positioning of the first seal support and second seal support as wear occurs.

These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein:

FIG. 1 is a longitudinal section view of a Flow Restricter cartridge constructed in accordance with the teachings of the present invention.

FIG. 2 is a detailed view of a seal face from the Flow Restricter cartridge illustrated in FIG. 1.

The preferred embodiment, a Flow Restricter generally identified by reference numeral 10, will now be described with reference to FIGS. 1 and 2.

Flow Restricter 10 was first developed as an integral part of a bearing assembly for an earth drilling motor. At the request of customers who were experiencing similar "washing" problems, but had their own bearing assembly design, Flow Restricter 10 was placed into a "cartridge" format. The cartridge form of Flow Restricter 10 is illustrated in FIG. 1. In the cartridge form Flow Restricter 10 is inserted into bearing assemblies constructed by several manufacturers.

Referring to FIG. 1, the primary components of Flow Restricter cartridge 10 are a cartridge housing 12, an inner cartridge member 14, a first seal support 16, and a second seal support 18. Cartridge housing 12 and inner cartridge member 14 are of cylindrical tubular construction. Cartridge housing 12 inner surface 13 defining an has an interior bore 20. Inner cartridge member 14 has an exterior surface 22.

First seal support 16 has a first annular seal ring 23 with a first seal face 24 at one end 26 and a plurality of axially extending passages 28 at an opposed end 30. A plurality of pins 32 are provided each of which has one end 34 secured to an annular shoulder 36 within interior bore 20 of cartridge housing 12 and an opposed end 38 which extends axially. Each opposed end 38 of pins 32 is telescopically received within axial passage 28 first seal support 16. In this manner first seal support 16 is non-rotatably coupled to cartridge housing 12 and yet remains axially movable in relation to cartridge housing 12 on pins 32. Second seal support 18 has a second annular seal ring 39 with a second seal face 40. Second seal support 18 has a plurality of axially extending key 42 which matingly engage axially extending keyways 44 on exterior surface 22 of inner cartridge member 14. In this manner second seal support 18 is non-rotatably coupled to exterior surface 22 of inner cartridge member 14 and yet remains axially movable in relation to inner cartridge member 14 on axially extending keyways 44. Second seal face 40 is at all times in axial alignment with first seal face 24. A plurality of coil springs 46 are disposed in pockets 48 in annular shoulder 36 in interior bore 20 of cartridge housing 12 serve as biasing means. Each of coil springs 46 have a first end 50 which engages annular shoulder 36 and a second end 52 which engages end 30 of first seal support 16. Coil springs 46 exert a biasing force axially upon first seal support 16 to bring first seal face 24 into sealing engagement with second seal face 40 to form a mechanical seal, generally identified by reference numeral 41. Mechanical seal 41 has a first side 43 adjacent cartridge housing 12 and a second side 45 adjacent inner cartridge member 14. A retainer ring 54 serves as a stop means for limiting the movement of second seal support 18. Retainer ring 54 is held in place by snap ring 56. A groove 55 is provided along interior bore 20 of cartridge housing 12. A screw 57 extends through retainer ring 54 into groove 55 to prevent rotation of retainer ring 54. A first fluid flow passage 58 extends through cartridge housing 12 to first side 43 of mechanical seal 41. A second fluid flow passage 60 extends from second side 45 of mechanical seal 41 along exterior surface 22 of inner cartridge member 14 to exterior of Flow Restricter cartridge 10. Referring to FIG. 2, a plurality of grooves 62 in seal faces 24 and 40 extend through mechanical seal 41 from first side 43 to second side 45. Grooves 62 are angled across seal faces 24 and 40 such that the flow of drilling mud through groove 62 is directed against an inner circumference 64 of one of annular seal rings 23 and 39. In order to prevent drilling mud from bypassing first fluid flow passage 58, elastomer seals 66 and 68 are provided. Seal 66 prevents drilling mud from passing between cartridge housing 12 and first seal support 16. Seal 68 prevents drilling mud from passing between cartridge inner member 14 and second seal support 18. A seal 70 is provided on exterior surface 72 of cartridge housing 12. A seal 74 is provided along interior bore 76 of inner cartridge member 14. An annular member 78 is provided at one end 80 of outer cartridge 12. The purpose of seal 70 seal 74, and annular member 78 will be hereinafter further explained with respect to the use and operation of the invention.

The use and operation of Flow Restricter Cartridge 10 will now be described with respect to FIGS. 1 and 2. Flow Restricter cartridge 10 must be installed as a component of a bearing assembly for a drilling motor before it can function. When the drilling motor is operating, drilling mud passes through first fluid flow passage 58 of Flow Restrictor cartridge 10. As the drilling mud passes through first fluid flow passage 58 it exerts a force upon second seal support 18 which causes springs 46 to be partially compressed. When the flow of drilling mud reaches first side 43 of mechanical seal 41, the drilling mud bleeds through grooves 62 angled across seal faces 24 and 40. This would normally cause a washing action, however, the flow is directed against inner circumference 64 of annular seal rings 23 and 39. This causes the flow to spiral, thereby losing some of its potentially damaging force. The force would create a washing action in softer metals, however, annular seal rings 23 and 39 are made of silicon carbide, tungsten carbide, or a similar hard material so as to be able to withstand the force of the fluid flow. The pressure with which first seal face 24 and second seal face 40 engage is determined by the force exerted upon coil springs 46. Coil springs 46 are therefore selected based upon the flow rate deemed suitable. In the past, as the bearings in a drilling motor having mechanical seals began to wear, axial movement occurred as between the outer housing and the inner tubular member and a gap was created between the first seal face and the second seal face resulting in an eventual "washing" out of the tool. With Flow Restricter cartridge 10 allowance is made for axial movement by first seal support 16 and second seal support 18. Axial movement which occurs within drilling motor 100 as a result of wear is accommodated with the range of movement of first seal support 16 and second seal support 18. As first seal face 16 and second seal support 18 move axially, coil springs 46 maintain first seal face 24 and second seal face 40 in engagement at a constant pressure. A continuous flow of drilling mud passed from first side 43 to second side 45 of mechanical seal 41 through grooves 62, and is vented to exterior of flow restrictor cartridge 10 via second fluid flow passage 60.

It will be apparent to one skilled in the art that Flow Restricter 10 addresses the problem of self-adjustment in the face of tool wear present in the art. It will also be apparent to one skilled in the art that modifications may be made to the preferred invention without departing from the spirit and scope of the invention as defined by the claims.