Patent ID: 12222054

DETAILED DESCRIPTION

FIGS.1-3illustrate an embodiment of a swivel assembly10formed of a corrosion-resistant material in which a hardened swivel joint12is employed to advantage. According to some embodiments, the corrosion resistant material is formed of a stainless steel, including for example, grades of stainless steel comprising X20Cr13, X36CrMo17 (1.2316), X17CrNi16-2 (1.4057), X48Cr13 (1.4034), F6NM, 9Cr, and X10CrMoVNb9-1Mod that exhibit properties of corrosion-resistance.

Referring specifically toFIG.1, the swivel assembly10includes a first pipe section14, a second pipe section16, and a third pipe section18, each rotatable with respect to each other via a respective swivel joint12. In the embodiment illustrated inFIG.1, each of the pipe sections14,16and18are formed having outer surfaces19,20,35and inner surfaces21,22,36, at least a portion of the inner surfaces21,22,36forming a fluid passageway24for directing fluid through the swivel assembly10during operation. It should be understood, however, that the swivel assembly10may be otherwise configured. For example, in some embodiments, the swivel assembly10may include a greater or fewer number of pipe sections14,16and/or18and associated swivel joints12.

During operation, corrosion, pitting, as well as erosion assisted corrosion. This results in reduced wall thickness, thus, compromising ability of the wall to sustain the high working pressure; further, the pitting results in a substantially higher stress concentration factor and, in turn, accelerates formation of cracks that leads to component fracturing and/or bursting of the pipe sections14,16and/or18. To reduce or substantially eliminate the likelihood of such cracking, the pipe sections14,16and/or18may be formed of a corrosion-resistant material, such as, for example, a stainless steel grade material or a polycarbonate material. However, and as explained in greater detail below, in order to maintain sufficient hardness within the swivel joints12to reduce and/or substantially eliminate the likelihood of damage thereto, at least a portion of the swivel joints12may be treated (e.g., heat-treated or otherwise) in order to provide surfaces with increased hardness that are more conducive to typical operating conditions.

Referring specifically toFIGS.1and2, the swivel joint12is formed having a first pipe section14having a first end fitting15and a second pipe section16having a second end fitting17. In the embodiment illustrated inFIGS.1and2, the first end fitting15defines a male fitting and the second end fitting17defines a female fitting that corresponds to the male fitting. The female fitting is sized to receive at least a portion of the male fitting therein so as to coaxially interconnect the first and second end fittings15,17along a central axis30. In operation, the swivel joint12permits the male and female fittings, and thus, pipe sections14and16to pivot and/or otherwise rotate, in relation to each other, about the central axis30while still maintaining a high pressure seal therebetween.

With continued reference to the embodiment illustrated inFIGS.1and2, the swivel joint12includes the second end fitting17of the second pipe section16positioned at least partially around the first end fitting15of the first pipe section14. As explained in greater detail below, the male end fitting and the female end fitting can be treated to form a hardened first area100and a hardened second area102, respectively, wherein a plurality of raceways44are defined (see, e.g.,FIG.2). In use, a plurality of ball bearings60are disposed within corresponding ones of the plurality of the raceways44to facilitate the rotational movement of the swivel joint12. WhileFIGS.1and2illustrate the plurality of bearings as the ball bearings60, it should be understood that the bearings60may be roller bearings or ball bearings, such as, for example, linear roller bearings, or any other type of bearings.

When the second end fitting17of the second pipe section16is disposed around the first end fitting15of the first pipe section14, the inner surface22of the second end fitting17is positioned adjacent the outer surface19of the first end fitting15so as to provide surfaces to accommodate the raceways44. In particular, and with specific reference toFIGS.2and3, the inner surface22of the second end fitting17includes a plurality of grooves58(FIG.3), which are positioned and otherwise formed on the inner surface22to align with a plurality of corresponding grooves58(FIG.3) that are positioned and otherwise formed on the outer surface19of the first end fitting15, the grooves58forming the raceways44, such that, when aligned, the raceways44support a plurality of ball bearings60therein. In some embodiments, a plug11and a pin13may be used to close a passageway23, through which the plurality of ball bearings60are inserted within the at least one raceway44. According to some embodiments, a sealing element62is disposed between an end of the first end fitting15and the inner surface22of the second pipe section16. The sealing element62substantially eliminates or prevents leakage of fluid from the passageway24to an annular area between the outer surface19and the inner surface22, (e.g., the annular area where the raceways44are defined and the plurality of ball bearings60are disposed).

During extensive operations, it is common for the swivel joint to undergo or otherwise be exposed to stresses due to frequent movement of the frac lines (e.g., pipes) connected to the swivel assembly10. Additionally, fluid flow within the frac lines (e.g., with high pressure, high velocity, and/or high turbulence) can cause damaging stresses. Therefore, the swivel assembly10should preferably have a sufficient ductility to withstand such stresses. For example, the pipe sections14,16and/or18may be formed of stainless steel material having at least one of the following grades: X20Cr13, X36CrMo17 (1.2316), X17CrNi16-2 (1.4057), X48Cr13 (1.4034), F6NM, 9Cr, and/or X10CrMoVNb9-1Mod, having, for example, chemical compositions shown in Tables 1-7. However, the raceways44within the pipe sections14,16and/or18must have hard surfaces sufficient for receiving and supporting the plurality of bearings60during operation. For example, a regular hardness of low alloy steel of grade4715, which is within a range of about 30 to about 39 HRC (Hardness Rockwell C), that is used in association with a pipe section14,16and/or18(in particular, within the raceways44wherein the plurality of bearings60are disposed) is insufficient to withstand typical operating stresses within the swivel joints12. As such, in some embodiments, at least a portion of the swivel joints12may be treated to increase the hardness thereof.

TABLE 1Chemical composition of steel grade X20Cr13.RangeElements(weight %)C0.16-0.25Mn0-1.5Si0-1P0-0.04S0.03-0.015Cr12-14

TABLE 2Chemical composition of steel grade X36CrMo17 (1.2316).RangeElements(weight %)C0.33-0.43Mn0-1Si0-1Cr15-17Ni0-1Mo1-1.3

TABLE 3Chemical composition of steel grade X17CrNi16-2 (1.4057).RangeElements(weight %)C0.12-0.22Mn0-1.5Si0-1P0-0.04S0-0.03Cr15-17Ni1.5-2.5

TABLE 4Chemical composition of steel grade X48Cr13 (1.4034).RangeElements(weight %)C0.43-0.5Mn0-1Si0-1P0-0.04S0-0.03Cr12.5-14.5

TABLE 5Chemical composition of steel grade F6NM.RangeElements(weight %)C0-0.05Cr11.5-14Mn0.5-1Mo0.5-1Ni3.5-5.5P0-0.03S0-0.03Si0-0.6

TABLE 6Chemical composition of steel grade 9Cr.RangeElements(weight %)C0.09-0.15Mn0.3-0.6Mo0.9-1.1Cr8-10Ni0-0.25Cu0-0.25P0-0.02S0-0.01Si0-1Al0-0.04

TABLE 7Chemical composition of steel grade X10CrMoVNb9-1Mod.RangeElements(weight %)Cr7.5-10.0Mo0.6-1.3Mn0-0.8Si0-0.6V0.10-0.5Ni0-0.4Cu0-0.5C0.06-0.2Nb0.06-0.1N0.01-0.1Al0-0.08P0-0.025S0-0.03

Referring toFIGS.1-3, in order to accommodate an increased hardness, in some embodiments the outer surface19of the first pipe section16and the inner surface22of the second pipe section16can be specially treated to form the hardened first and second areas100and102, respectively. Referring specifically toFIG.2, the hardened first and second areas100and102form a portion of first and second end fittings15and17, and in particular, the hardened first and second areas100and102are formed around and include the raceways44. However, it should be understood that the hardened first and second areas100and102may be otherwise configured. For example, the hardened first and second areas100and102may form an entirety of the first end fitting15and the second end fitting17, respectively. In other embodiments, the hardened first and second areas100and102may extend beyond the entirety of the first and second end fittings15and17. Furthermore, while the embodiment illustrated inFIG.2illustrates the hardened first area100extending only partially between outer and inner surfaces19and21, it should be understood that the hardened first area100may extend to and include both the outer and inner surfaces19and21. Additionally, the hardened second area102is illustrated inFIG.2extending partially between the outer surface20and inner surface22. However, it should be understood that the hardened second area102may extend to and include the outer and inner surfaces20and22, respectively.

Several different methods may be used for hardening the hardened first and second areas100and102. For example, hardening may be performed by one or more heat-treatment methods. However, with heat-treatment processes, a balance between ductility and hardness must be preserved to avoid unwanted brittleness within swivel joints12, which can exacerbate cracking and premature failure. For example, in some embodiments the heat-treatment methods should achieve such Nitrogen diffusion through the steel surface so as to: (i) obtain sufficient hardness of surfaces in the range of 56-62 HRC; (ii) obtain a sufficient amount and sufficient depth Nitrogen diffusion through the steel surface; (iii) maintain material ductility, and/or (iv) secure minimum tensile strength requirement for the swivel joints12.

In some embodiments, heat treatment processes and surface hardening methods may include carburizing, induction heat treatment, nitriding as well as variations of traditional nitriding, and/or quench and tempering optimization.

According to an embodiment disclosed herein, a method of manufacturing a swivel assembly10is provided. In the embodiment illustrated inFIGS.1-3, a hardened first area100is formed on at least a portion of an outer surface19of a first end fitting15of a first pipe section14that is formed of a corrosion-resistant material. In some embodiments, the hardened first area100has a hardness value greater than a hardness value of a non-hardened first area of the outer surface19of the first pipe section14. In some embodiments, the hardened first area100may include at least one groove58defined on an outer surface of the hardened first area100, wherein the at least one first area groove58is configured to fit a plurality of ball bearings60therein.

In some embodiments, the method of manufacturing the swivel assembly10may include forming a hardened second area102on at least a portion of an inner surface22of a second end fitting17of a second pipe section16formed of corrosion-resistant material. In some embodiments, the hardened second area102has a hardness value greater than a hardness value of a non-hardened second area of the inner surface22of the second pipe section16. The hardened second area102may include at least one groove58defined on an inner surface of the hardened second area102, wherein the at least one second area groove58is configured to align with the at least one first area groove58to define at least one raceway44therebetween when the swivel assembly10is fully assembled.

The method of manufacturing the swivel assembly10may further include inserting the hardened first area100of a first end fitting15into the hardened second area102of a second end fitting17thereby fluidly coupling the first and second pipe sections14and16, respectively, via the swivel assembly10. In some embodiments, the method also includes disposing the plurality of ball bearings60into the at least one raceway44of the swivel assembly10.

While the present application discloses the swivel joints12, it should be understood that coupling fittings having the plurality of bearings disposed therein may be defined within one or more pipes, a rotary union, or any other type of rotatable fittings.

In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “left” and right”, “front” and “rear”, “above” and “below” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear.

In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.

Furthermore, invention(s) have been described in connection with what are presently considered to be the most practical and preferred embodiments and it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.