Wellhead Drive Brake

Abstract

A braking arrangement for drive heads or pump heads, to be preferably used in a progressing cavity pump (PCP) system in oilfields, consisting of at least one disk moving inside a viscous fluid and facing a static disk, in which mechanical energy is transformed into heat. The viscous brake is a device acting as a function of the rotation speed, in which a higher speed generates a higher braking power caused by the increase of friction among the disks and the fluid. The arrangement may comprise more than one mobile and static disk assemblies, as well as a hollow axis instead of a solid one, to allow housing the pumping rod inside the axis, and may also comprise an anti-reverse bearing.

Claims

1. A braking arrangement for pumping heads to be used in oil fields, comprising extraction pumps with movement transmission systems, the arrangement comprising: an axis, one or more disk pairs, one mobile and one static, submerged inside a viscous fluid, and wherein said axis is connected with said movement transmission system of its corresponding extraction pump.

2. The braking arrangement according to claim 1, wherein said axis is hollow, by which the pumping rod may be installed inside it.

3. The braking arrangement according to claim 1, wherein the connection of said axis with the movement transmission system is made by means of gears.

4. The braking arrangement according to claim 2, wherein the connection of said axis with the movement transmission system is made by means of gears.

5. The braking arrangement according to claim 1, wherein the connection of said axis with the movement transmission system is made by means of belts and pulleys.

6. The braking arrangement according to claim 2, wherein the connection of said axis with the movement transmission system is made by means of belts and pulleys.

7. The braking arrangement according to claim 1, wherein the connection of said axis with the movement transmission system is direct.

8. The braking arrangement according to claim 2, wherein the connection of said axis with the movement transmission system is direct.

9. The braking arrangement according to claim 1, wherein the braking power is a direct function of the following parameters: rotor geometry; disk diameter; rotation speed; fluid density and viscosity; and number of contained disks.

10. The braking arrangement according to claim 2, wherein the braking power is a direct function of the following parameters: rotor geometry; disk diameter; rotation speed; fluid density and viscosity; and number of contained disks.

11. The braking arrangement according to claim 2, wherein the brake is engaged to the polished bar of the pumping rod placed inside the hollow axis.

12. The braking arrangement according to claim 11, wherein the brake is engaged to the polished bar of the pumping rod by means of an anti-reverse bearing.

13. The braking arrangement according to claim 12, wherein said anti-reverse bearing consists of two rings or tracks and several balls or rolls which are in contact both with those elements.

14. The braking arrangement according to claim 1, wherein said viscous fluid shows a dynamic viscosity of at least 1,000 centipoise.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1A shows the way brake parts work, and in detail the placement of each of these.

[0038] FIG. 1B shows a cutaway view through line B-B of FIG. 1A.

[0039] FIG. 2 shows a crosswise cutaway view of the arrangement of the present invention.

[0040] FIG. 3 shows an explosion view in detail of the components of the braking head indicating the required quantities of each of these.

DETAILED DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1A shows a preferred embodiment of the present invention in which it may be seen a supplementary positioning base 1 that allows changing height h1 and also screw 2 that sets the position and adjusts the lid-separator-housing arrangement. Next to it may be seen eyebolt 3 that allows raising the bake arrangement. In a lower position it may be seen slot 4 that makes it easier the soldering of the internal cylinder to the lid. The plug 5 for covering the fluid loading port is shown at the upper end, and at one side the nut and the locking nut 6 make pressure on the mobile disk/bearings arrangement, and below these may be seen the screw 7 that locks the mobile disk and its support. At one side of it may be seen the mobile-disk holder 8 that engages the mobile disk to the axis and the pin 9 that avoids rotational movement of the mobile disk support. In a lower position it may be seen the bearing spacer 10 which decreases the torque absorbed by the bearings. At a lower end it may be seen the pin 11 which prevents the rotational movement between the anti-back-movement bearing 12 and the brake axis. In slightly higher position it may be seen a packing 13 that seals to avoid fluid losses and at the central portion the mobile disk 14 may be seen, that transmits the shear stress to the fluid. Screw 15 engages the brake to the reduction gear box and the plug 16 allows emptying the fluid through element 17 that helps its flow. Above disk 14 it may be seen that slot 18 helps the soldered bond of the internal cylinder to the static disk. The fluid level may be visually verified through both apertures (oxeyes) 19 placed at 90 one from the other, so that the brake's fluid level may be verified when it is not operating, even in a slanted position. In a higher position it may be seen an O-ring 20 that seals any possible fluid leak.

[0042] FIG. 1B shows a cutaway view through line B-B of the arrangement of FIG. 1A, in which a slot 21 allows fastening the axis when mounting and dismounting it and pre-stressing the mobile disk/bearing arrangement.

[0043] FIG. 2 shows a cutaway cross view of a preferred embodiment of the brake arrangement in which it may be seen plug 5 at its upper lid, the bearing spacer 10 at its lower portion, emptying plug 16 at one side, the central axis 24 of the brake, and the brake support 25.

[0044] FIG. 3 is an explosion view of a preferred embodiment of the present invention showing screws 2 which are preferably Allen (ANSI M6x1x35), screws 7 which are preferably Allen (ANSI M6x1x25), the mobile disk support 8, pins 11, ball bearings 12 which are preferably type SKF 7208 BECBJ, packing 13 preferably type DBH 8804 Mx, mobile disk 14, oxeye 19, O-ring 20 preferably of a type Parker N2-383, adjusting nut 21, break housing 22 and the lid/brake arrangement 23.

[0045] The developed brake arrangement is mainly based on the friction among disks making contact through a viscous fluid. The viscous brake is a device that operates as a function of rotation speed, in which a higher speed produces a greater braking effect because the friction among the disks and the viscous fluid increases, transforming the mechanical energy into heat. The arrangement may comprise more than one mobile and static disk sets, and may have a hollow axis instead of a solid one, thus allowing that the pump rod goes operates through it.

[0046] The way a viscous braking arrangement operates is variable and depends on: fluid viscosity, disk separation and disk surface.

[0047] The braking effect is created by the rotation of mobile disk 14, also called rotor and which is immersed in a viscous environment. The axis must be connected to the movement transmission elements of the progressing cavities pump. These elements may be implemented with gears, belts, pulleys, in direct transmission, or any other way that allows transmitting rotational movement of the parts involved. This is most important for the moment in which a true backspin control is required. The braking effect is given by the shear stress generated in the fluid in contact with the disk surface, because it is enclosed in a reduced closed space. It is very important to keep this effect is under control because the braking power depends very tightly on the distance between the housing's wall and the disk.

[0048] When the brake is activated, the fluid tends to rotate at the same angular speed as the disk. In this way, if no slippage occurs between the surfaces, the fluid in contact with the mobile disk will have the same speed as the disk's periphery and the fluid in contact with the housing will be still. The speed gradient resulting in the fluid layer generates the shear stress already mentioned to cause the braking effect.

[0049] The braking power of the developed arrangement depends on the following factors: [0050] Rotor's geometry [0051] Disk diameter [0052] Rotation speed [0053] Fluid type [0054] Mainly, density and viscosity [0055] Number of disks to be used

[0056] The braking power is inversely proportional to the free space between the disk and the housing. In other words, a smaller free space allows greater braking power and vice versa. A small change in the free space is enough for obtaining a great change in braking power.

[0057] The main features of the brake's design are its reliability, toughness and simplicity.

[0058] Placement of the Brake

[0059] The pumping head has a reduction gearbox linking the motor axis with the pump rod, for speed reduction in the motor-to-rod direction and increases it in the opposite direction. Therefore, based on the principle of power conservation, it may be affirmed that at the motor axis there is always a higher rotation speed than at the polished rod.

[0060] Since the backspin effect is not exceptional, the angular speed at the motor is also greater when this effect takes place than. This situation has an important consequence: the viscous brake will be capable of applying a greater braking torque if applied at the polished rod (in this case using a hollow rod). It is so because the braking torque depends directly on the rotation speed, and therefore will be so many times greater as the transmission multiplication relation.

[0061] In a preferred embodiment, the braking arrangement is connected by means of an anti-reverse bearing, which should allow rotation in one direction and block the internal ring with the outer one in the opposite rotation direction.

[0062] An anti-reverse (or unidirectional) consists of two rings or tracks and several balls or rollers in contact with both of those. Compared to a simple roller bearing, its difference is that it has the capacity of automatically connecting or disconnecting the inner and outer tracks, depending on the rotation direction. In this way, the braking action will take place without the need of any additional mechanism. The bearing is selected as a function of torque to be transmitted and the maximum admissible revolutions per minute.

[0063] Fluid Selection

[0064] The fluid is a fundamental element for establishing the braking power since it is the one that generates the shear forces that de-accelerate the system. It must be, at first, very viscous but also showing the following properties: [0065] High dynamic viscosity (minimum 1,000 centipoise) and showing the highest possible high temperature stability. [0066] High specific heat so that the heat generated by the braking effect does not increase its temperature too much. [0067] Good heat transmission feature, that is, high heat transmission coefficient and high convection rate for dissipating in the surrounding environment.

[0068] It should not degrade with high temperature.

ADVANTAGES OF THE PRESENT INVENTION

[0069] The system of the present invention does not generate wear-out of the static or rotating elements.

[0070] It increases the braking power as a function of the system's acceleration, allowing more efficient braking, that is, allowing the torque to disappear more quickly.

[0071] It does not require maintenance servicing of its parts.

[0072] The system is independent of the driving head gear and bearing lubrication fluids.

[0073] It allows adapting the braking power as a function of what is needed.

[0074] It reduces the number of components related with the braking arrangement.

[0075] It may be easily replaced when it fails.

[0076] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.