Boring or penetrating the earth – Bit or bit element – With fluid conduit lining or element
Reissue Patent
1998-07-22
2001-01-02
Tsay, Frank (Department: 3672)
Boring or penetrating the earth
Bit or bit element
With fluid conduit lining or element
C175S424000, C175S425000
Reissue Patent
active
RE037006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to replaceable nozzles for rock bits utilizing drilling fluid to remove detritus from an earthen formation borehole.
More particularly, this invention relates to weld-in sleeves utilized to secure replaceable nozzles in rock bit bodies. The sleeve provides a means to both minimize fluid erosion and assure a more uniform flow of drilling fluid contained within a plenum formed by the rock bit body to the nozzles.
2. Background
Replacement nozzles must have a means of being retained into rock bits. The more typical retention methods for securing nozzles are mechanical and are machined either directly into the bit body or into a sleeve that is in turn welded into bores formed in the rock bit body.
Weld-in nozzle sleeves have been used in rotary cone rock bits for several years for ease of manufacturing. An internal plenum interfaces with secured nozzles via a relatively narrow passage bore formed adjacent to the plenum, of which a portion of the passage way is included in the welded-in sleeve, if a sleeve is utilized.
Internal erosion, in and around nozzle bodies is a major problem. A loss of hydraulic pressure downhole results in a trip out of the borehole and often times the bit is replaced due to the extent of damage to the bit as a result of fluid erosion.
Internal erosion in a rock bit can typically be related to four parameters, mud weight, mud abrasiveness, flow velocity and geometrical discontinuities i.e. gaps, bend, comers and the like. The current nozzle retention configurations are limited in flow capacity by creating a high fluid velocity over a sharp comer formed in the bit adjacent the passage bore entrance. High flow rates cause the fluid flow to separate at the comer creating recirculation zones with sufficient energy to erode the surrounding metal surface that, as heretofore stated, has caused bit washout.
Another potential problem with the state of the art weld-in sleeve is gaps formed between the sleeve and the leg or bit body interface. Gaps may occur at this interface if correct manufacturing procedures are not followed. High fluid flow over gaps where the depth of the gap is much greater than the width will tend to cause recirculation zones within the gap with sufficient energy to erode the surrounding metal potentially leading to bit washout.
The present invention overcomes the above difficulties of the state of the art nozzle retention configurations by designing and securing the sleeve retention configurations in the rock bit body in a way to minimize the possibility of fluid erosion problems.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a nozzle sleeve that will increase the fluid flow capacity through a nozzle.
It is another object of this invention to provide a nozzle sleeve that minimizes internal erosion problems that lead to nozzle washouts.
A nozzle sleeve for the retention of replaceable fluid nozzles for rock bits is disclosed. The sleeve is secured within the body of the rock bit. A first upstream end of the sleeve communicates with a fluid plenum formed by the bit body. A second downstream end of this sleeve is adapted to receive the fluid nozzles.
A streamlined fluid entrance is formed at the first upstream end of the nozzle sleeve. The streamlined entrance is generally rounded or elliptical. The rounded or elliptical fluid entrance is formed at the first upstream end of the nozzle sleeve. The rounded or elliptical entrance begins at an outer peripheral edge formed by the first upstream end of the sleeve and proceeds inwardly toward a straight bore section formed by the sleeve and positioned about intermediate the first and second ends of the sleeve. The rounded or elliptical fluid inlet formed by the sleeve serves to increase the flow capability of fluid to the nozzles by reducing separation of the fluid which substantially reduces the erosive effects associated with high fluid velocities.
The weld-in sleeve of the present invention increases the fluid flow capacity through a replaceable nozzle by increasing the entrance flow area and by reducing geometrical discontinuities into the jet nozzle.
One of the design approaches resulted in a sleeve with an upstream rounded or elliptical entrance that blends into a straight bore section that interfaces with the nozzle receptacle. The sleeve is intalled (welded) in a straight bore hole formed in the bit body that proceeds from an external surface of the leg forging into the internal jet bore plenum formed by the bit body.
The straight bore section of the nozzle sleeve may be shortened or lengthened to move an exit plane of the nozzle closer to or further from a borehole bottom to improve bottom hole cleaning.
An alternative approach is to provide an erosion resistant material that extends into the jet bore plenum to shield high fluid velocity areas from erosion. Still another alternative approach is to provide an erosion resistant material that is rounded or elliptical at the entrance to the weld-in sleeve that will resist erosion while providing increased fluid flow capacity to the nozzle.
It is an advantage then over the prior art to provide increased fluid flow to the nozzles by providing a weld-in sleeve with a rounded or elliptical fluid entrance to the nozzles.
It is yet another advantage over the prior art to provide a weld-in sleeve that may be shortened or lengthened to locate a nozzle exit plane closer to or further from a borehole bottom to enhance the removal of detritus from the borehole bottom.
The above noted objects mid advantages of the present invention will be more fully understood upon a study of the following description in conjunction with the detailed drawings.
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patent: 4068731 (1978-01-01), Garner et al.
patent: 4533005 (1985-08-01), Morris
patent: 4567954 (1986-02-01), Voight, III et al.
patent: 4687067 (1987-08-01), Smith et al.
patent: 4759415 (1988-07-01), Pessier
patent: 4794995 (1989-01-01), Matson et al.
patent: 5072796 (1991-12-01), Shen et al.
patent: 5494122 (1996-02-01), Larsen et al.
patent: 5853055 (1998-12-01), Siracki et al.
patent: 2294073 (1998-04-01), None
Webster's II New Riverside University Dictionary, 1984, The Riverside Publishing Co., pp. 425 and 851.*
Larsen James L.
Siracki Michael A.
Conley & Rose & Tayon P.C.
Smith International Inc.
Tsay Frank
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