Abstract: A connector arrangement used for connecting and locking tubular members. The connector consists of two tubular members and a coupling member. The tubular members are threaded together to create a threaded connection. The locking arrangement is provided by a pathway formed on the tubular member whereby a locking member can be inserted in to the pathway to lock the threaded connection. The locking arrangement is also provided by a plurality of castellation members disposed on each tubular member. The connector also has a separate coupling member which has opposite right-hand and left-hand threaded ends to threadedly mate with the threads of the two tubular members.

Abstract: A shoulder ring (10) for installing in the J-space between the installed pin ends within a coupling collar is taught having a body with a central opening therethrough, a first end face (12) on the body, an opposite end face (14) on the body, an inner surface (16) adjacent the central opening and extending between the first end face and the opposite end face and an outer surface (18) extending between the first end face and the opposite end face, the body having a substantially uniform cross sectional shape between the first end face, the opposite end face, the inner surface and the outer surface and the ring shaped such that its radius to the outer surface varies around the outer surface circumference to form a plurality of lobes (12).

Abstract: Makeup plates on the abutting surfaces of a tool joint pin and a tool joint box are provided. The makeup plates are recessed in a short distance from the outer diameter of the tool joint elements, such that when the joint is made up, the makeup plate develops an easily visible gap between the tool elements. In this way, a quick determination may be made, without measurement, as to whether the joint can be refaced, or require re-machining.

Abstract: A lubricating coating composition in which at least one basic lubricant selected from a basic sulfonate, a basic salicylate, and a basic phenate is dissolved in a volatile solvent is applied to the frictional surface of a box and a pin constituting a threaded joint for oil well pipes. The composition may further contain one or more of a thermoplastic resin powder, another lubricant, and an extreme pressure agent. The surface roughness of the frictional surfaces preferably has an Rmax in the range of 5-40 micrometers.

Abstract: A first flux-loop inductive coupler element electrically couples with a second flux-loop inductive coupler element. The first flux-loop inductive coupler element comprises a first ring-like core having high magnetic permeability and a conical-section annular first face transverse to the plane of the first core. The first face has a first annular groove separating a first conical-section larger-diameter face and a first conical-section smaller-diameter face. A first coil is wound within the annular groove. The first and second cores form a low-reluctance closed magnetic path around the first coil and a second coil of the second flux-loop inductive coupler element. A first current-loop inductive coupler element electrically couples with a second current-loop inductive coupler element.

Abstract: A pipe fitting has a body with an internally threaded bore and at least one female starter thread. The at least one female starter thread is disposed either within the bore or immediately outside of the bore. The starter thread is axially aligned with the bore threads. The starter thread is made from a material which is stronger than the material from which the bore threads are made.

Abstract: A corrosion-resistant threaded connection including a first tubular member having an outer metal tube of corrosion-prone material and an inner metal lining of corrosion-resistant material, the first tubular member forming a first pin connection having a nose portion comprising a ring of corrosion-resistant material secured, e.g.

Abstract: A joint connecting a pair of members rotatable about a common axis end to end includes a first member having a threaded end portion and a non-circular exterior surface rearwardly of the threaded end portion, a second member having a threaded socket wherein the threaded end portion of the second member can be engaged, and a non-circular exterior surface, a sleeve having a non-circular profile on an inner surface thereof whereby the sleeve can be slidably mounted on the non-circular exterior profiles of the first and second members when such profiles are brought into alignment by rotation of one member relative to the other in a manner effective to pass torque from one member to the other by means of the non-circular profiles, a first pair of alignable holes in the sleeve and first member to receive a fastener to secure the sleeve to the first member and a hole in the second member penetrating the threaded socket and positioned to receive a fastener to secure the second member to a third member in place of the

Abstract: The threaded connection between the pin and the box ends of two pipes is sealed externally and internally to protect the threads in the connection from exposure to corrosive fluids. Seals are provided at each axial end of the threads. External seals are formed by metal-to-metal engagement between the pin and box and a third metal body secured circumferentially about the pin. The metal body may be fashioned into a desired annular pin seal surface to mate with and seal with the box at full makeup of the connection. The metal body can be removed and replaced as required to repair or reconstructed the pin seal surface.

Abstract: Threaded joint for pipes consisting of a male member (1) and a female member (2), which are provided on the outer and inner surfaces respectively with two threading portions presenting a lead-in flank ? such that 10°???25°, an abutment surface (9) being present at the end of said male member for abutment to a corresponding annular abutment surface (10) of the female member. The lead-in flanks of the male (1) and the female (2) members, upon make-up and with unloaded joint leave a gap (in the direction parallel to the axis (21) of the joint) varying from 0.01 to 0.12 mm. The internal and external diameters D3 and D4 (of the pipe portion not involved in the coupling with the female member) of said male member, the inner and outer diameters D1 and D2 of the abutment surface of the female member are linked by the relationship: (D22?D12)/(D42?D32)?0.5.

Abstract: A threaded pin and box pipe connection having makeup shoulders that contact when the pin and box threads are fully engaged. Upon initial engagement of the shoulders, load flanks of the pin and box threads furthest from the makeup shoulders engage each other and begin progressively separating from each other by an increasing amount along the length of the engaged threads in a direction from the end of the pin to a gauge point of the connection. Upon application of the makeup torque, the separation between the load flanks distributes the torque forces between the makeup shoulders along the length of the engaged threads to prevent concentration of stress forces near the base of the pin thread. The progressive separation of the load flanks is achieved by progressively changing the pitch of the load flank of the pin and/or box thread to vary the thread width. The separation of load flanks is achieved without modifications of the stab flank pitch.

Abstract: A hydraulic device having a nut part with a threaded hole which has an internal screw thread with a defined nominal diameter and with a defined, uniform pitch, and having a screw part which has an external screw thread with the same nominal diameter as the threaded hole and with a defined, uniform pitch, which is screwed into the threaded hole. (In hydraulic devices, screw parts, in particular nozzle bodies, are generally adhesively bonded in place, in order to prevent them from becoming detached. Adhesive bonding has certain drawbacks, since the screw threads have to be free of grease, and in the case of nozzles there is a risk of blockages, adhesive can enter the hydraulic circuit and also process reliability is not ensured during application.) There is provided a slight difference between the pitch of the internal screw thread of the nut part and the pitch of the external screw thread of the screw part.

Abstract: The premium threaded tubular connection comprises, on at least one threaded element, a distal abutment surface (7) at the free end of a threaded element and a lip sealing surface (5) at a given distance from the threading.

Abstract: A pipe fitting has a body with an internally threaded bore and at least one female starter thread. The at least one female starter thread is disposed either within the bore or immediately outside of the bore. The starter thread is axially aligned with the bore threads. The starter thread is made from a material which is stronger than the material from which the bore threads are made. The starter thread most proximate to the threads of the internally threaded bore has a pitch diameter which is at least two percent greater than the pitch diameter of the most proximate thread within the internally threaded bore.

Abstract: A threaded pipe connection is shown which features a cylindrical metal-to-metal containment seal. In addition to the cylindrical sealing surfaces, the connection utilizes a separate ramp or ramp regions that simulate a pin swaging or a box expansion which results in the ability of the cylindrical components of the seal to assemble without interference or with only slight interference.

Abstract: The taper and pitch diameter of a conventional API eight round thread coupling are varied over the axial length of the threads. The variations are held within the allowable tolerances of the applicable API specifications. The variations minimize the interference and galling occurring in the first and last engaged threads between the coupling and a pipe end having an externally formed API thread that is screwed into the coupling beyond the maximum API penetration.

Abstract: This invention relates to a threaded joint for steel pipes which comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion and which can be prevented from galling during repeated fastening and loosening without application of a compound grease. A solid lubricant coating which comprises a lubricating powder such as molybdenum disulfide and a resin binder is formed on the contact surface of at least one of the pin and the box. The solid lubricant coating has a hardness of 70-140 on the Rockwell M scale and an adhesive strength of at least 500 N/m as determined by the SAICAS (Surface And Interfacial Cutting Analysis System) method, and it exhibits excellent galling resistance even in the environment of high-temperature oil wells. Inclusion of ultraviolet screening fine particles such as titanium oxide fine particles in the solid lubricant coating increases the rust preventing properties of the threaded joint.

Abstract: A quick-acting closure (1) for connecting a mixer tube (3) and a connecting part (2) of an extruder unit. The connecting part (2) has a connector (9) with a conical threaded base member, on which an external thread (12) is arranged. The mixer tube (3) has a conical threaded base member, on which an internal thread (19) is arranged. The internal thread (19) on the connector part (16) of the mixer tube (3) is a multi-path internal thread.

Abstract: A threaded joint for steel pipes comprising a pin 1 and a box 2 each having a contact surface comprising a threaded portion 3 or 4 and an unthreaded metal contact portion 8 is provided with improved anti-galling propertied by forming a lubricating coating on the contact surface of at least one of the pin and the box, the lubricating coating exhibiting a self-repairing function by liquid lubrication and having a decreased greasiness. The lubricating coating is (1) a coating which comprises a lower lubricant layer which is in liquid form in the temperature range of above 0° C. and below 40° C. and an upper lubricant layer which is in solid form at 40° C., or (2) a coating which is semi-solid or solid at 40° C. and is formed of a mixture comprising a lubricating oil which is in liquid form in the temperature range of above 0° C. and below 40° C. and a wax which is in solid form at 40° C.

Abstract: Oil country tubular goods and other types of tubular members are provided with threaded and coupled connections satisfactory for use in drilling and completing wellbores. The threaded and coupled connections are used to join sections of casing with each other to form a casing string which may be used to drill and complete a wellbore. Each tubular member has first and second pin ends with approximately the same thread form and thread profile with different pitch diameters. Standard API couplings may be used with the casing string.

Abstract: A threaded joint which economically imparts effective sealing properties to a metal-to-metal seal portion and which can prevent seizing at the time of make-up comprises a steel pipe 1 having at its tip a male thread 1b and an unthreaded sealing surface 1a, and a coupling 2 having on its inner surface a female thread 2b and an unthreaded sealing surface 2a. With the yield pressure of the inner surface of the pipe being Py, (1) the average pressure Pm of the annular contact portion satisfies Pm/Py≧3, and the width in the axial direction of the portion which receives a pressure Ps which satisfies Ps/Py≧1 in the annular contact portion is at least 1 mm (or at least 2 mm), and the surface roughness Ry of both unthreaded sealing surfaces is at most 25 &mgr;m (or at most 30 &mgr;m), or (2) the relationship between the average pressure Pm of the annular contact portion and the surface roughness Ry (&mgr;m) of the unthreaded sealing surface satisfies Pm/Py≧0.0032×Ry2+1.

Abstract: The threaded connection between the pin and the box ends of two pipes is sealed externally and internally to protect the threads in the connection from exposure to corrosive fluids. Seals are provided at each axial end of the threads. The external seals may be formed by metal-to-metal engagement between the pin and box or may be provided by an annular, elastomeric ring engaging the pin and box of the connection. A threaded compression ring may be used to compress the elastomeric seal between the pin and box. The seals protect dynamically loaded threaded connections from fatigue-induced failure in corrosive environments.

Abstract: A data resource specific to a pipe coupling centrally positioned within the coupling, intermediate the coupling ends. Multiple couplings are employed to connect together a string of well pipe. The data resource is adapted to be deployed at the coupling center in the space formed between the abutting ends of pipe made up into the coupling. The data resource provides information regarding the physical characteristics and locations of the coupling, the attached string pipe or the environment within which the coupling is disposed. The data resource may be a read-only component or it may be a readable and writeable component. The resource communicates with an instrument movable through the pipe and coupling. The data resource may be removably positioned at the center of the coupling or it may be permanently cemented in place. The data resource may take on the form of an annular ring with a crushable structure and suitable recesses for holding a data resource module.

Abstract: This invention relates to a threaded joint for steel pipes which comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion and which can be prevented from galling during repeated fastening and loosening without application of a compound grease. A solid lubricant coating which comprises a lubricating powder such as molybdenum disulfide and a resin binder is formed on the contact surface of at least one of the pin and the box. The coating is formed by applying a coating fluid and drying the applied coating by first stage heating in the temperature range of from 70° C. to 150° C. and second stage heating in the range of from higher than 150° C. to 380° C.

Abstract: Pipes (2, 3) made of a difficult-to-weld material to be used at a high temperature are internally (3a) and externally (2a) threaded at their end portions, an are thread-fastened to each other. The inner and/or outer faces of the jointed pipe portion (1) is sealed by seal means (7, 9), so that the pipes (2, 3) made of difficult-to-weld material to be used at a high temperature are joined by the screw structure, thereby to retain mechanical strength of the jointed pipe portion (1). At the same time, the inner and/or outer faces of the jointed pipe portion (1) is sealed by the seal means (7, 9) to retain the gas tightness of the jointed pipe portion (1).

Abstract: A threaded tubular connection comprises two elements, male and female, made up one into the other to a given torque in which, prior to making up, at least one thread face under contact pressure (125) has a convexly rounded shape that is continuous over its width with a radius of curvature in the range 2 to 60 mm and is in point contact with the corresponding face (26) of the mating element. Such a threaded connection has an increased resistance to breakout or to overtorquing.

Abstract: A threaded joint for steel pipes which is capable of metal-to-metal sealing and which can be subjected to repeated fastening and unfastening without the application of a liquid lubricant containing a heavy metal powder comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion. The contact surface of at least one of the pin and the box are coated with an undercoating layer and a lubricating coating layer atop it. The undercoating layer is a porous metal coating having a porosity of 5-80% and a thickness of 1-30 &mgr;m and preferably a hardness of 50-250 Hv. The lubricating coating is a solid lubricating coating or a liquid lubricating coating, the latter containing substantially no heavy metal powders. The total thickness of the undercoating layer and the lubricating coating layer is at most 100 &mgr;m.

Abstract: Described herein is a threaded joint, in which the threads are coated with a layer of dry lubricant having a thickness of between 5 &mgr;m and 30 &mgr;m and in which the nominal void volume NVV of the space (6, 7) between the thread of the male tube and the thread of the female tube, is sized by means of the following formulae: 1 NVV ⁡ [ cm 3 ] ≤ 4 × OD ⁡ [ inch ] NVV ⁡ [ cm 3 ] OD ⁡ [ inch ] × Wt ⁡ [ mm ] ≤ 1 g T ≤ 0.

Abstract: A tubular assembly 10 is disclosed for passing fluids within a hydrocarbon recovery well. The tubular assembly 10 has an insulated connection 12 between insulated tubing segments 14, 16. Tubing segments 14, 16 are connected via a threaded connection, and the resulting joint 10 is insulated by an external insulating sleeve 18. The insulating sleeve 18 may have unitary construction, such that the sleeve 18 may only be installed or removed by first breaking apart the joint 10. Alternatively, the sleeve 18 may comprise a plurality of arcuate partial-sleeves, which may be assembled about or removed from the completed joint 10 without first breaking apart the joint 10.

Abstract: An expandable tubing assembly comprises a tubular connector defining overlapping longitudinal slots, the connector comprising end portions and an intermediate portion. The slots extend over the whole length of the connector, but the only slot overlap occurs in the intermediate portion. The assembly further comprises lengths of expandable tubing defining overlapping longitudinal slots and having end portions defining nodes between and beyond the ends of the tubing slots. Tubing threads are formed on the end most tubing nodes. The connector end portions define threads and are coupled with the threads formed on the nodes of the respective end portions of the tubing lengths.

Abstract: A male threaded joint tipped with a male lip having a male seating face and a male stop transverse surface proximate to the male seating face. A female threaded element includes for co-operation with the corresponding male threaded element, a female seating face and a female stop transverse surface provided on a female shoulder and proximate to the female seating face. The annular female shoulder zone is subjected to axial compression forces resulting from the pressure of the male and female stop surfaces and has an inner peripheral surface, the diameter of which is at least locally proximate to the female stop surface smaller than the diameter of the inner peripheral surface of the male lip. The ratio R of the two diameters is less than 1 but not less than 0.9.

Abstract: Oil country tubular goods and other types of tubular members are provided with threaded and coupled connections satisfactory for radial expansion within a wellbore. The tubular members may include couplings formed using electric resistant welding technology. The threaded and coupled connections may be used to join sections of casing with each other to form a casing string to complete a wellbore.

Abstract: An electrical isolation connector subassembly for interconnecting adjacent tubular drill rods of a drilling system used in drilling bore holes in earth formations, the connector comprising an electrically insulative sleeve being sandwiched between two electrically isolated subassembly components, the sleeve providing an exterior gap between the edges of the spaced apart electrically isolated components, the exterior gap having a width of less than 50 cm.

Abstract: The present invention provides a connector arrangement for connecting a first tubular to a second tubular. In particular, the present invention relates to a method for connecting tubulars in such a way that the connection is prevented from becoming unmade in response to expansion of the tubulars in a wellbore. More particularly, the present invention provides a tubular connection using a helical or spiral thread insert to seal and maintain mechanical strength in a tubular connection after expansion.

Abstract: A threaded pipe connection having box and pin members is provided with inner engageable thread means on the box and pin members, the thread means including a helical dove-tail thread having negative flank angles extending along the lengths of the box and pin members, and a helical intermediate thread having positive flank angles extending along the lengths of the box and pin members adjacent the dove-tail thread. Upon makeup, the intermediate threads generate hoop tension in the box member and hoop compression in the pin member, and the dove-tail threads generate hoop compression in the box member and hoop tension in the pin member.

Abstract: An elongated drive string assembly includes a plurality of hollow sucker rods and connecting elements with an axis, connected together and between a drive head located at the surface of an oil well and a rotary pump located deep down in an oil well. Each hollow sucker rod has at least a first end including an internal female threaded surface engaging an external male threaded surface on a connecting element, such as a nipple. The first end also includes a torque shoulder, which engages a torque shoulder formed on the connecting element. The threads are frusto-conical, non-symmetrical threads with a differential diametral taper. The torque shoulders have a maximized mean diameter and cross-sectional area to resist storing reactive torque in the drive string. The nipple has a wall cross-section that increases towards the torque shoulders from each free end, to increase fatigue resistance.

Abstract: A submersible pump drop pipe and casing assembly and method of manufacture is disclosed. The drop pipe/casing has a seated connector and base. The seated connector has a first and second cylinder section, the first cylinder section being used to align and direct the base into the seated connector and to provide lateral strength to the pipe.

Abstract: There is disclosed a tubing connection arrangement and a method of coupling expandable tubing sections together. In one embodiment, there is disclosed a tubing connection arrangement (10) comprising a first expandable tubing section (12) defining a male portion (16); a second expandable tubing section (14) defining a female portion (18), the first and second expandable tubing sections (12, 14) being engageable with one another; one of the first and second expandable tubing sections (12, 14) including a restraining member (40) for restraining part of the other expandable tubing section (12, 14); and the first expandable tubing section (12) including a tapered shoulder (42,44) for co-operating with a corresponding tapered shoulder (46,48) of the second expandable tubing section (14).

Abstract: A chemical conversion treatment liquid which can stably form a phosphate-type chemical conversion film on a steel material for a joint portion of an oil well steel pipe containing 0.5-13% Cr is developed. Using a chemical conversion treatment liquid to which a prescribed amount of potassium is added, a chemical conversion film containing a prescribed amount of potassium compounds and having a prescribed thickness can be formed on the threaded surface of a joint portion of an oil well steel pipe.

Abstract: A fatigue resistant waisted threaded tubular element for threaded tubular connection, and resulting threaded tubular connection. The threaded tubular element is waisted by a groove formed in the material beneath the threading to reduce the stiffness of the wall at the level of the first engaging threads. The groove can prevent an increase in the transfer of tensile loads at the level of the first engaging threads of the threaded element on which it is formed and on the corresponding last engaging threads of the mating threaded element intended to be connected thereto to form a threaded tubular connection. This improvement in load transfer limits the risk of initiating a fatigue crack in threaded tubular connections subjected to a cyclic load without reducing their static performances.

Abstract: An elongated drive string assembly comprising a plurality of hollow sucker rods and a connecting elements with an axis, connected together and between a drive head located at the surface of an oil well and a rotary pump located deep down hole in an oil well. Each hollow sucker rod has at least a first end comprising an internal female threaded surface engaging an external male threaded surface on a connecting element, such as a nipple. In order to further optimize the stress distribution between the elements, frustro-conical, non-symmetrical threads with a differential diametral taper are used. The torque shoulders have a maximized mean diameter and cross-sectional area to resist storing reactive torque in the drive string. A modified nipple preferably has a small seal at its free end to decrease corrosion erosion problems. A modified rod may have a series of holes at each extreme end, to substantially increase the flow of fluid extracted.

Abstract: A threaded metallic pipe for oil extraction industry has a threaded end portion with treated surface in which the metal surface has a roughness (Ra) comprised of 2.0 &mgr;m and 6.0 &mgr;m, which is covered by a uniform layer (7) of a dry corrosion inhibiting coating and a second uniform layer (8) of dry lubricant coating. Alternatively the layers (8, 9) combined into one uniform layer (9) of a dry corrosion inhibiting coating containing a dispersion of particles of solid lubricant.

Abstract: An expandable tubular coupling (23) comprises a threaded male portion (28) and a corresponding threaded female portion (30), wherein the thread portions (28,30) feature thread profiles configured such that the coupling (23) may be made up to a predetermined extent, and once made up to the predetermined extent may be made up no further. In a disclosed embodiment the thread profiles are a combination of a square thread profile (36, 38) and dovetail thread profile (32, 34).

Abstract: A threaded tube joint for oil extraction industry has a trapezoidal thread and a toroidal sealing surface (11) placed at its end near the thread and engages, for sealing, a corresponding frusto-conical sealing surface (12) wherein the toroidal sealing surface (11) has a radius Rs value comprised within the range given by the formula 1 E 2 ⁢ Vo ⁢ ( b 2.

Abstract: In a threaded joint for steel pipes comprising a pin and a box capable of mating with each other, the pin having an externally threaded portion and an unthreaded metal contact portion as a mating surface, and the box having an internally threaded portion and an unthreaded metal contact portion as a mating surface, the mating surface of at least one of the pin and the box is coated with a lower porous zinc or zinc alloy layer by blast plating and with an upper coating which is either a solid lubricating coating (comprising a lubricating powder in an organic or in organic binder) or a liquid, heavy metal powder-free coating (e.g., a liquid coating based on a highly basic organic acid metal salt such as a highly basic metal sulfonate).

Abstract: An expandable tubular coupling (10) includes first and second thread portions (12,14) each comprising a plurality of inter-engaging teeth (20,22), wherein at least one tooth on the first thread portion (12) engages a corresponding tooth on the second thread portion (14) and the remainder of said inter-engaging teeth (20,22) define respective gaps (32) therebetween.

Abstract: A threaded pin and box connection having thread geometries and/or dissimilar thread fits that prevent the pin thread of a connection from hanging up in the box thread as the pin is being stabbed into or destabbed from the box. Dissimilar geometries and/or threads include dissimilar thread types, dissimilar leads, overlapping leads, thread tooth widths of one component greater than thread grooves of the other component, multiple start threads, and combinations thereof.

Abstract: A wellbore assembly is provided that is operable in wellbores in the range of six to six and one-half inches for obtaining large diameter cores, e.g., cores greater than or equal to two and seven-eighths inches in diameter. The wellbore assembly may preferably be utilized with drill pipe so that standard drilling rigs may be utilized in drilling and coring operations therewith. The drill pipe in accord with the present invention may be formed by modifying standard API drill pipe such as API four and one-half inch IF (Internal Flush) drill pipe in a special manner that renders the drill pipe still suitable for the type of drilling operations of interest and also suitable for handling by any drilling rig capable of using standard API drill pipe. Alternatively, the drill piper may be initially manufactured in accord with the specifications of the present invention.

Abstract: Makeup plates on the abutting surfaces of a tool joint pin and a tool joint box are provided. The makeup plates are recessed in a short distance from the outer diameter of the tool joint elements, such that when the joint is made up, the makeup plate develops an easily visible gap between the tool elements. In this way, a quick determination may be made, without measurement, as to whether the joint can be refaced, or require re-machining.

Abstract: Connectors and connections that enhance mechanical and sealing engagement between the ends of tubular bodies that are radially expanded by a forging tool. The connectors are designed to maintain or restore mechanical and sealing engagement following expansion. The connections are made by joining components that exhibit different spring back characteristics following mechanical deformation. Dissimilar material may be used for the connectors or the connected components can be made of the same materials but dimensioned and configured to exert an interfering force between engaged components following expansion. In operation, a material or component with a high spring back characteristic is positioned adjacent a material or component having a lower spring back characteristic. Following passage of a forging tool, the expanded components spring back differently toward their original unexpanded dimensions to produce the enhanced seal or mechanical engagement.