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Publication numberUS3703213 A
Publication typeGrant
Publication dateNov 21, 1972
Filing dateOct 21, 1970
Priority dateOct 21, 1970
Publication numberUS 3703213 A, US 3703213A, US-A-3703213, US3703213 A, US3703213A
InventorsJohnson Gary R, Kammerer Archer W Jr
Original AssigneeBaker Oil Tools Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Mud saver apparatus
US 3703213 A
Abstract
Mud saver apparatus to be disposed at the lower end of a kelly adapted to be secured to a string of drill pipe and to pass through a rotary table, which can rotate the kelly, drill pipe, and bit secured thereto, for the purpose of drilling a bore hole in a formation while drilling mud is being pumped through the kelly drill pipe and bit, the apparatus including a tubular body and an elastic bladder disposed across the body passage by a gas under pressure to close the passage when drilling mud or other fluid is not being pumped through the kelly, but which is deflected to passage opening position by drilling mud pumped through the kelly and body passage at a pressure exceeding the gas pressure. Automatic closing of the body passage by the gas pressure when pumping of drilling mud ceases prevents the drilling mud from dropping out of the kelly when it is disconnected from the drill pipe therebelow.
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United States Patent Kammerer, Jr. et al.

[54] MUD SAVER APPARATUS [72] Inventors: Archer W. Kalnnlerer, Jr., Fullerton; Gary R. Johnson, Anaheim,

both of Calif.

[73] Assignee: Baker Oil Tools, Inc., Los Angeles,

Calif.

[22] Filed: Oct. 21, 1970 211 Appl. No.: 82,757

[52] US. Cl. ..17S/3l8, 166/224, 251/5, 175/320 [51] Int. Cl. ..E2lb 33/00 [58] Field of Search ..175/207, 211, 218, 232, 243, 175/317, 318, 320; 166/126, 133, 142, 151, 166, 224, 242, 224 S, 225; 251/5 1 Nov. 21, 1972 2,945,665 7/1960 Regan et al. ..25 H5 X 3,556,461 1/1971 Little ..251/5 3,566,964 3/1971 Livingston 1 66/224 Primary Examiner-David H. Brown Attorney-Kendrick, Subkow & Kriegel and Bernard Kriegel 1 5 7] ABSTRACT Mud saver apparatus to be disposed at the lower end of a kelly adapted to be secured to a string of drill pipe and to pass through a rotary table, which can rotate the kelly, drill pipe, and bit secured thereto, for the purpose of drilling a bore hole in a formation while drilling mud is being pumped through the kelly drill pipe and bit, the apparatus including a tubular body and an elastic bladder disposed across the body passage by a gas under pressure to close the passage when drilling mud or other fluid is not being pumped through the kelly, but which is deflected to passage opening position by drilling mud pumped through the kelly and body passage at a pressure exceeding the gas pressure. Automatic closing of the body passage by the gas pressure when pumping of drilling mud ceases prevents the drilling mud from dropping out of the kelly when it is disconnected from the drill pipe therebelow.

10 Claims, 14 Drawing Figures PATENTED um 21 m2 SHEET 2 0F 4 MW 2 $1 f w M r H M4 13 a WWW 29 PATENTEDuuvzn I972 sum 3 or 4 a M I E 2m K M m W W@ Z f 5 W 3 m g MUD SAVER APPARATUS The present invention relates to well bore apparatus, and more particularly to apparatus for controlling the flow of fluid from a kelly or grief stem forming the upper part of a rotary drilling string used in the rotary drilling of a well bore.

In the rotary drilling of well bores and the like, drilling mud is circulated through the kelly at the upper end of the string of drill pipe and through the drill pipe itself, discharging from the drill bit secured to the lower end of the pipe string to clean and cool the bit and flush the cuttings produced by the bit from the drilling region upwardly around the drill pipe string to the drilling rig. As drilling of the well bore progresses, additional lengths of drill pipe must be added to the string, requiring elevation of the kelly above the rotary table used for rotating the drilling string, disconnection of the kelly, addition of drill pipe, reconnection of the kelly to the added drill pipe, and reinsertion of the kelly into the rotary table for transmission of its rotary motion and torque to the drilling string and bit.

Upon disconnecting the kelly from the drill pipe therebelow, the drilling mud in the kelly and mud hose that feeds drilling mud to its upper end dumps or spills out the lower end of the kelly, wetting personnel and equipment on the derrick floor, as well as the derrick floor itself. Hazardous conditions are thereby presented to the work area, equipment and personnel, valuable drilling mud is lost, substantial time being required in cleaning the spilled mud from the equipment and derrick floor, all of which entails substantial cost. In ocean drilling, the lost mud is a source of pollution to the ocean water.

Automatically operated valves have been proposed for incorporation at the lower end of the kelly, which are to close when pumping through the kelly and drill string ceases, and to open when such pumping recommences. However, prior valves have been relatively complex, sand up and stick or jam, and are susceptible to the erosive action of the drilling mud pumped through it, all of which contribute to a relatively short life of the valves and their lack of dependability in operating properly.

With the present invention, dependable automatically operated drilling mud saver valves are provided, insuring closing of the valve whenever pumping of drilling mud, or other fluid, through the kelly ceases, or the drilling mud pressure drops below a predetermined value. In addition, the valves are far simpler, consisting essentially of only a single movable or shiftable part, which is an elastomeric bladder pressurized by air, or other suitable gas, which constantly urges the bladder to a valve closing position across the valve body passage, the bladder being shifted by the pressure of the circulating fluid, acting against the pressure of the gaseous medium, to a position opening the body passage. As the circulating pressure of the fluid increases, the bladder is shifted to a greater extent from the path of fluid flow through the body passage, thereby providing a greater opening through the passage, minimizing the pressure drop through the valve and permitting fluid flow through the valve at higher circulation rates. The valve will not jam, sand up or stick, and will not plug the drill pipe. By insuring closing of the lower end of the kelly whenever it is disconnected from the drill pipe, drilling mud is prevented from spilling from the kelly and the mud hose connected thereto, thereby saving the drilling mud, insuring the maintenance of the derrick floor in a dry and safe condition, as well as avoiding the wetting of equipment and personnel. Moreover, ocean pollution by drilling mud does not occur.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present specification. These forms will now be described in detail for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense. Referring to the drawings:

FIG. 1 is a side elevational view of an embodiment of the invention secured to the lower end of a kelly and to the upper end of a drill pipe string;

FIG. 2 is an enlarged vertical section taken along the line 2-2 on FIG. 1;

FIG. 3 is a cross-section, on an enlarged scale, taken along the line 33 on FIG. 2',

FIG. 4 is a side elevational view taken along the line 4-4 on FIG. 2;

FIG. 5 is a fragmentary vertical section through the apparatus disclosed in FIG. 2, with the valve in closed position;

FIG. 6 is a cross-section, on an enlarged scale, taken along the line 6-6 on FIG. 5;

FIG. 7 is a section taken along the line 7-7 on FIG. 5;

FIG. 8 is a vertical section through another embodiment of the invention, with the valve in open position;

FIG. 9 is a view of the valve similar to FIG. 8, but with the valve in its closed position;

FIG. 10 is a cross-section taken along the line l0 10 on FIG. 8;

FIG. 11 is a vertical section through still another form of the invention;

FIG. 12 is a section taken along the line 12-12 on FIG. 11;

FIG. 13 is an enlarged cross-section taken along the line 13-13 on FIG. 11; and

FIG. 14 is a partial longitudinal section through still another specific form of valve element to be embodied in the apparatus illustrated in FIGS. 8 and 1 1.

In the form of invention illustrated in FIGS. 1 to 7, inclusive, a tubular main body or sub 10 is provided that has an upper threaded box 11 for threadably securing the upper end of the body to the lower end of a kelly 12, a threaded pin 13 at the lower end of the body being threadably secured to an adjacent section of drill pipe 14 forming a portion of a drilling string, to the bottom end of which a drill bit (not shown) is secured. As is well known in the art, the kelly 12 provides a slidable spline connection with a rotary table 15 for rotating the drilling string and drill bit during the drilling of the well. When additional lengths of drill pipe are to be added to the drill string, as result of the drilling of the well bore, the kelly 12 and the kelly sub 10 are elevated above the rotary table 15 and the lower end of the kelly sub disconnected from the drill pipe 14. Upon adding the desired length of drill pipe to the drill string, the lower end of the sub is reconnected to the drill pipe 14 and the drilling string is lowered in the well bore to again place the drill bit on bottom and with the kelly 12 disposed within the rotary table 15.

As noted above, each time the kelly sub or body 10 is disconnected from the drill pipe 14, the drilling mud in the kelly 12 and in the rotary mud hose (not shown) connected to a swivel (not shown) secured to its upper end would spill out through the lower end of the kelly sub, wetting the derrick floor, equipment and personnel, as well as resulting in the loss of valuable drilling mud. A valve apparatus 16 is provided for automatically closing the passage 17 through the body 10 thereby trapping the mud in the kelly.

The body 10 has a window 18 extending from its central passage 17 to its periphery, the inner portion 19 of the window being generally rectangular with curved corners 20 merging into its sides 21, top 22 and bottom 23, whereas the outer portion 24 of the window is enlarged to provide an outwardly facing shoulder 25 around the inner window portion or opening 19.

The opposed sides 21 of the inner portion 19 of the window are parallel to one another and are tangent to the cylindrical wall 26 of the body passage at diametrically opposite points 27, being perpendicular to a central vertical plane of the body passing through its axis and tangent points 27. The top 22 and bottom 23 of the inner portion of the opening are also parallel to one another and are normal to the above-mentioned central vertical plane. As stated above, the corners 20 between the top and bottom and sides are curved.

An elastomeric bladder 30 is inserted through the window 18 being of generally cup shape. This bladder has an inner closed portion 31, the central part 32 of which has a radius of curvature conforming to the radius of the body passage such that the end closure 32 of the bladder will fit closely and seal against the curved wall 26 of the body passage. This semi-cylindrical portion 32 of the bladder has a substantial longitudinal extent (FIG. 3) merging into outer side walls 33 of the bladder that extend snugly and seal against the opposed side walls 21 of the valve body 10. The elastomeric diaphragm 30 has top and bottom sides 34, 35 conforming to the top 22 and bottom 23 of the inner window portion 19 of the body, these top and bottom portions 34, 3S and the side portions 33 of the diaphragm merging into curved corners 36.

The outer portions of the diaphragm 30 are integral with an outwardly extending flange 37 adapted to overlie the body shoulder 25. When the bladder is inserted through the opening 18, the flange engages the shoulder, the inner semi-cylindrical portion 32 of the diaphragm bearing against the cylindrical wall 26 of the body passage opposite the window, with the parallel side walls 33 of the diaphragm engaging the companion side walls 21 of the window, and with the top 34 and bottom 35 of the diaphragm, together with the rounded corners 36, effecting a full closing of the body passage 17, the top 34 and bottom 35 hearing against the top and bottom walls 22, 23 of the body. A cover and clamp plate 40 is mounted in the body cavity 24 hearing against the flange 37 of the diaphragm, screws 41 passing through holes 42 in the margins of the cover plate, and through holes 43 in the diaphragm flange 37 into companion threaded holes 44 in the body, which when tightened will firmly clamp the flange 37 in leakproof relation against the body shoulder 25.

A suitable one-way valve 50 is mounted in the cover and clamp plate 40, establishing communication between a suitable source of air under pressure, or other gas under pressure, and the interior of the cupshaped bladder 30, air also being stumble in the chambers 50a in the cover plate 40. This valve 50 may be of the type used in inflating automobile tires. Air or other gas under a suitable pressure from the source is introduced through the air valve into the interior of the cup-shaped bladder, tending to hold such bladder firmly sealed against the walls 21, 22, 23 of the inner window, and retaining the semi-cylindrical portion 32 of the diaphragm firmly sealed against the curved wall 26 of the body passage 17. As an example, the air under pressure may be of the order of about to p.s.i., such compressed air usually being available on a drilling rig.

The diaphragm 30 can be made of any suitable elastomeric material. As an example, it may be made of semi-hard nitrile rubber, and is preferably reinforced with nylon cloth which may be of several plies with additional plies provided in the flange and at the corner portions 20a where the flange 37 merges into the walls 21, 22, 23 of the diaphragm.

The bladder or elastomer diaphragm 30 will remain in its closed position across the body passage 17 so long as the pressure of the drilling mud within the kelly 12 and kelly saver sub 10 does not exceed the gas pressure within the bladder, tending to maintain it in its extended closed condition. Assuming the kelly to be about 60 feet in length and filled with drilling mud, the hydrostatic head of such drilling mud will exert a pressure of about 30 p.s.i., or far less than the inflation pressure (for example, 100 psi) in the bladder. Accordingly, in the absence of pressure applied to the mud or fluid in the kelly 12, the valve will remain closed. Elevation of the kelly 12 and the kelly saver sub or body 10 above the rotary table 15 and disconnection of the sub from the drill pipe 14 therebelow will result in the retention of the drilling mud in the kelly. On the other hand, with the kelly sub 10 connected to the drill pipe 14 therebelow, and with the drilling operation occurring which includes the circulating of drilling mud down through the kelly, sub, and string of drill pipe, the circulating pressure normally exceeds the inflation pressure in the bladder. As a result, it will deflect the bladder to one side (FIGS. 2,3), as to its flange side, opening the passage 17 through the body 10 and permitting the drilling mud to be pumped therethrough. The greater the circulating pressure, the greater the deflection of the bladder 30 out of the path of the drilling mud and the greater the effective circulating area through the body passage 17 where the bladder 30 is located. Thus, the valve arrangement automatically compensates for higher circulation pressures and volumes of circulating fluids by automatically increasing the effective area through the body passage 17 as the circulation pressure increases.

Upon decrease of the circulation pressure below the inflation pressure of the bladder 30, the bladder is expanded by the compressed air or gas back to its initial condition fully closing the body passage (FlGS. 5,6).

Thus, a mud saver valve apparatus is provided that has only a single moving part, which automatically closes when the circulating pressure decreases below a predetermined value, and which automatically opens when such pressure is exceeded, the extent of opening automatically increasing as the circulating pressure increases.

In the embodiment illustrated in FIGS. 8 to 10, the kelly saver sub or body 10a has an elastic bladder 60 therein which is adapted to be inflated by compressed air, or other gaseous medium, to constrict its central portion 61 inwardly to close the central passage 17 through the body. The elongate elastic bladder 60 is disposed within a mounting sleeve or member 62 with the ends 63 of the bladder vulcanized to the inner wall of the sleeve 62. A protector and retaining sleeve 64 is placed within each end of the elastic bladder, being secured thereto and to the mounting sleeve by screws 65, the heads 65a of the screws being disposed in counterbores 66 in the mounting sleeve, and the threaded shank portions of the screws being threaded into the retaining sleeve 64.

The mounting sleeve 62, elastic bladder 60 and protector and retaining sleeves 64 are inserted in the body 10, the lower end of the sub-assembly bearing against an upwardly facing shoulder 68 in the body. A plurality of circumferentially spaced pipe plugs 69 are threaded radially into the body and extend into openings 70 in the mounting sleeve to secure the sleeve, as well as the elastic bladder 60 and protector sleeves 64 in place. Insertion of the plugs 69 and their removal is facilitated by providing access counterbores 71 in the body opening through the periphery of the body. One of these counterbores 71a provides access to an air valve 72, such as of the type used in inflating automobile tires, threaded into a companion radial bore 70a in the body and opening through the mounting sleeve to the exterior of the elastic bladder 60. Compressed air around the bladder communicates through a plurality of perforations 73 in the mounting sleeve with circumferential air chambers 74 formed in the interior of the body 100. These air chambers are for the purpose of storing the compressed gaseous medium and also to act as expansion chambers. They are provided in the body between suitable side seal rings 75, such as elastomeric O-rings, disposed in internal grooves 76 in the body on opposite ends of the air chambers 74 and sealingly engaging the periphery of the mounting sleeve 62.

Air of other gas under suitable pressure is inserted through the valve into the chamber 80 surrounding the exterior of the bladder 60 and disposed between it and the mounting sleeve 62, this air under pressure also passing through the perforations 73 into the storage and expansion chambers 74. As in connection with the description of the other form of the invention, the air under pressure may be of the order of 100 to 120 p.s.i. It tends to contract the elastic bladder 60 between its ends inwardly into a generally hour glass configuration (FIG. 9), with the intermediate portions 61 of the bladder constricted to fully close the passage 17 through the valve body. To facilitate closing of the passage, the intermediate portion 61 of the bladder may be formed with a thinner wall.

With the apparatus secured to the lower end of a kelly 12 and to a string of drill pipe 14 therebelow, and

with air under suitable pressure disposed in the chambers 80, 74, the elastic bladder 60 will assume its closed condition in the absence of circulation fluid being pumped through the drilling string. The application. of pressure to the mud in the drilling string to a value substantially exceeding the air pressure causes the drilling mud to force or expand the valve members 60 to a passage opening condition (FIG. 8), the drilling mud flowing through the elastic bladder and then downwardly through the drill pipe 14. As the pressure of the drilling mud increases, the extent of outward expansion of the bladder 60 increases to automatically open the valve to a greater extend as the pressure differential continues to increase, so as to minimize the restriction by the bladder to the How of the circulating fluid therethrough.

Upon decrease in the pressure of the drilling fluid below the value of the compressed gas in the chambers 74 and in the space surrounding the bladder 60, the gas under pressure will reshift the bladder inwardly to its closed condition (FIG. 9).

If desired, as disclosed in FIG. 11, a central stem can be provided within the bladder 60a and against which the latter can seal when forced inwardly by the compressed air. This stem has a tapered upper end 91 to facilitate downward flow of fluid there around, its lower end being suitably secured to a spider 92, the outer end of which is constituted as the lower protector and retaining sleeve 64, the spider holding the stem in its central or coaxial position.

When the air pressure exceeds the pressure of the fluid within the bladder 60a it will shift and retain the elastic bladder in its generally hour-glass shape sealed against the periphery of the stem 90. When the fluid pressure within the kelly 12 exceeds the air pressure, it expands the bladder 60a outwardly, flowing therethrough and around the stem 90, passing through the openings of the spider 92 and into the valve body passage therebelow.

Different specific embodiments of bladders are illustrated in the drawings. In FIG. 8, the bladder 60 is of cylindrical form when it is not subjected to pressure, having the intermediate thinner or weakened section 61 to facilitate its contraction into its closed condition. This bladder is made of a suitable elastomeric material, such as 60 hard nitrile rubber. It has a substantially fully opened passage therethrough when not subjected to the pressure of a contracting gas, thereby avoiding any substantial impediment to the downward flow of drilling mud. When subjected to the predetermined gas pressure, it will close inwardly upon itself at its weakened region, when the drilling mud pressure is lower than the air pressure, expanding outwardly when the circulating fluid pressure through the body exceeds the air pressure, the compressed air being shifted back through the perforations 73 into the storage chambers 74.

The bladder illustrated in FIG. 14 is essentially the same as in FIG. 8, except that the thinner section 61 is not provided. Instead, reinforcing cloth 94a, 94b is molded into the main rubber portion of the bladder, there being an upper section 94a of reinforcing cloth and a lower section 94b separated from one another by a short distance 95 to facilitate contraction of the.

rubber sleeve inwardly into the generally hour-glass shape (FIG. 9) and full constriction of the intermediate unreinforced portion 95 of the rubber to fully close the passage through the elastomer sleeve.

In the form of bladder illustrated in FIG. 11, it may initially be formed into a general hour-glass shape, containing a reinforcing material 96, such as one or more plies of nylon cloth. Air pressure can retain the rubber inwardly with its intermediate portion closing upon itself; whereas the circulating pressure will enlarge the opening through the hour-glass throat, enlargement continuing up to a maximum value as the circulatingair differential pressure increases. The relieving of the pressure differential causes the reinforced bladder to inherently move back to its initial hour-glass shape, and when the circulating pressure decreases sufficiently, the air pressure will fully close the bladder.

All of the bladder constructions illustrated in FIGS. 8 to 14 can, if desired, be used in conjunction with the central stem 90, being shifted inwardly by the gas under pressure externally of the bladder into sealing engagement with such stem.

We claim:

1. In valve apparatus for incorporation in a tubular string at the lower end of a kelly: a body having a fluid passage therethrough and adapted to be disposed at the lower end of the kelly; a generally cup-shaped elastic bladder in said body adapted to extend across said passage to close the same, said body having a lateral opening communicating with said passage, said bladder having an open end portion in said opening and sealed against said body, said bladder having a portion projecting from said end portion laterally across said passage and adapted to conform to and seal against a substantial portion of the wall of the body defining said passage, and means for feeding a gaseous medium under pressure through said open end portion into the interior of said bladder to exert an inflating force in said bladder tending to retain it in extended position sealed against said body passage wall to close said passage.

2. In apparatus as defined in claim 1; said feeding means including a valve adapted to permit introduction of the gaseous medium into said bladder but preventing return flow of the gaseous medium to the exterior of the body.

3. In apparatus as defined in claim 1; and closure means in said opening closing said opening and securing said open end portion in sealed relation to said body.

4. In apparatus as defined in claim 1; closure means in said opening closing said opening and securing said open end portion in sealed relation to said body; said feeding means including a valve in said closure means adapted to permit introduction of the gaseous medium into said bladder but preventing return flow of the gaseous medium to the exterior of said closure means and body.

5. In apparatus as defined in claim 1; closure means in said opening closing said opening and securing said open end portion in sealed relation to said body; said closure means having gas storage means therein communicating with the interior of said bladder.

6. In apparatus as defined in claim 1; closure means in said opening closing said opening and securing said open end portion in sealed relation to said body; said feeding means including a valve In said closure means adapted to permit introduction of the gaseous medium into said bladder but preventing return flow of the gaseous medium to the exterior of said closure means and body; said closure means having gas storage means therein communicating with the interior of said bladder.

'7. In valve apparatus for incorporation in a tubular string at the lower end of a kelly: a body having a fluid passage therein and adapted to be disposed at the lower end of the kelly; and elastic bladder sleeve in said passage; means confining the end portions of said sleeve against laterally inward movement in said passage; and means for feeding gaseous medium under pressure into said body for action upon the exterior of said bladder to contract an intermediate portion of said bladder inwardly of said passage to substantially fully close the same; said bladder sleeve having an inherent hour-glass shape when not subjected to fluid pressure differential acting upon the interior and exterior of said bladder sleeve.

8. In apparatus as defined in claim 7; said confining means including a mounting sleeve secured in said body; said bladder being disposed in said mounting sleeve with its end portions secured thereto.

9. In apparatus as defined in claim 7; said confining means including a perforate mounting sleeve secured in said body; said bladder being disposed in said mounting sleeve with its end portions secured thereto, said body having one or more expansion chambers therein externally of said mounting sleeve and communicating through the mounting sleeve perforations with the exterior of said bladder to permit flow of the gaseous medium between the exterior of said bladder and said one or more expansion chambers as said intermediate portion contracts and expands.

10. In apparatus as defined in claim '7; and a stern disposed in said body passage against which the bladder seals when contracted.

Patent Citations
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3847214 *Apr 13, 1972Nov 12, 1974Cushman WWell and pipeline construction
US3970144 *Aug 11, 1975Jul 20, 1976Boykin Jr Robert OSubsurface shutoff valve and control means
US3997009 *Jan 31, 1975Dec 14, 1976Engineering Enterprises Inc.Well drilling apparatus
US4303100 *Dec 18, 1978Dec 1, 1981Geosource Inc.Kelly valve
US4335791 *Apr 6, 1981Jun 22, 1982Evans Robert FPressure compensator and lubricating reservoir with improved response to substantial pressure changes and adverse environment
US5205325 *Nov 12, 1991Apr 27, 1993Piper Oilfield Products, Inc.Flow control valve
US6053191 *Feb 13, 1997Apr 25, 2000Hussey; James J.Mud-saver valve
US7703477 *Apr 14, 2003Apr 27, 2010Novamedix Distribution LimitedFluid control valve
US20060163506 *Apr 14, 2003Jul 27, 2006Novamedix Distribution LimitedFluid control valve
DE2730554A1 *Jul 6, 1977Sep 28, 1978Malo Carlos SchottBohrgeraet
EP0347172A1 *Jun 13, 1989Dec 20, 1989Torus Equipment IncPressurised check valve
Classifications
U.S. Classification175/318, 175/320, 166/326, 251/5
International ClassificationE21B21/00, E21B21/10
Cooperative ClassificationE21B21/106
European ClassificationE21B21/10S