METHOD OF ATTACHING THE SEALING MEMBER OF A THREADED COUPLING TO ONE END OF HIGH-PRESSURE PIPE

Abstract: The claimed process introduces an improved con­ nection between a ball element (3) and pipe end (1) used in high pressure couplings. According to the process a copper ring (4), ball (3) and pipe end (1) are subjected to a heat treatment process at a range of 1110 - 1120°C. During this process copper brazing takes place be­ tween ball (3) and pipe end (1) whilst carbon dissolves into austenite hardening the ball, even over 58 HRC. It has thus been found and tested that the combination brazing and specific ball material subjected to one heat treatment performs an excellent connection between ball element (3) and pipe end (1) as well as good ball joint properties.

Description: Method of Attaching the Sealing Member of a Threaded Coupling to One End of a High-Pressure Pipe The invention relates to a method of attaching the sealing member of a threaded coupling to one end of a high pressure pipe, the end of the pipe being passed through a hole in the sealing member and fixed therein, which coupling additionally comprises a hollow nut slipped loosely over the pipe and abutting the sealing member, its interior engaging the sealing member to be screwed into a matching part. Heretofore, use has been made of a sealing member of hardened steel slipped over the pipe end, whereafter the inner edge of the part of the pipe inside the hole in the sealing member is expanded or rolled to secure the sealing member, generally spherical, on the pipe; or else a screw connection is used. In use of a threaded coupling having a sealing member fixed on the pipe by the known method, for handling a liquid under high pressure, for example to assemble a stuffing box around a bearing, leakage will often occur along the sealing member as a result of damage of the connection between sealing member and pipe when the hollow nut is tightened. The object of the invention is to provide an improved method of attaching the sealing member of a threaded coupling to one end of a pipe, the said sealing member being so fixed to the pipe end that no leakage can occur when a threaded coupling is applied. This object is accomplished, according to the invention, in that the sealing member is fabricated in a steel hardenable at a certain temperature and brazing material is applied around the pipe, so that a brazed connection can be formed at that temperature, whereafter the end of the pipe and the sealing member around it are heated to the said certain temperature, so that the brazing material will flow between the exterior of the pipe end and the hole through the sealing member, whereupon the parts are cooled so that a brazed connection is obtained between pipe and sealing member, and the sealing member is hardened. Preferably the sealing member is made of M2 steel, and copper is used as bra7.ing material, in which case the heating temperature is 1110 - 11200C. In this way a hard steel sealing member with a hardness of at least 58 HRc is obtained, while the brazed connection has a tensile strength greater than that of the pipe. The heating of the pipe and with the sealing member slipped over it may be carried out under a protective atmosphere, for example an atmosphere of cracked ammonia, whereby the sealing member acquircs a bright surface so that it need not be further polished. It is noted that British Patent 888.055 mentions a method of attaching the sealing member of a threaded coupling to- the end of a pipe wherein the said sealing member is soldered to one end of the pipe, with the disadvantage that deposits are formed inside the pipe in the process. Here, that is, the pipe end is not inserted in the hole in the sealing member. The invention will be described in more detail with reference to the drawings, in which Fig. 1 shows a pipe end with a sealing member slipped over it prior to heating, and Fig. 2 shows the pipe end with sealing member after heating and cooling. As shown in Fig. 1, a pipe end 1 is inserted in the hole 2 through the sealing member 3, of spherical shape. Around the pipe end 1, near the sealing member 3, brazing material 4 has been applied. The sealing member 3 consists of a hardenable steel, preferably M2 steel, and the brazing material preferably of copper. Then the assembly shown in Fig. 1 is heated for example to a temperature of 1110 - 1120 C, whereby the brazing material 4 is made to flow into the space between the interior of the hole 2 and the exterior of the pipe end 1, so that after cooling, the brazed connection 5 shown in Fig. 2 is obtained. By the heating and subsequent cooling, the steel of which the sealing member 3 consists is hardened. The heating is preferably carried out in a furnace having a continuous conveyer of wire mesh, in which furnace a protective atmosphere consisting for example of cracked ammonia is present. Reference numeral 6 designates the hollow nut forming the threaded coupling together with the sealing member 3.

Claims: Claims 1. Method of attaching the sealing member of a threaded coupling to one end of a high-pressure pipe, the end of the pipe being passed through a hole in the sealing member and fixed therein, which threaded coupling further comprises a hollow nut slipped loosely over the pipe abutting the sealing member, its interior engaging the sealing member to be screwed onto or into a matching part, characterized in that the sealing member is fabricated in a steel hardenable at a certain temperature, and brazing material is applied around the pipe, whereby a brazed connection can be obtained at that temperature, whereafter the end of the pipe and the sealing member around it are heated to the said certain temperature so that the brazing material will flow between the exterior of the pipe end and the hole in the sealing member, whereupon the parts are cooled so that a brazed connection is obtained between pipe and sealing member, as well as a hardened sealing member, 2. Method according to claim 1, characterized in that the sealing member is fabricated of M2 steel and the brazing material used is copper, in which case the connecting and the hardening take place 0 at a temperature of 1110-1120 C. 3. Method according to claim 1 or 2, characterized in that the connecting and the hardening of the pipe end together with the sealing member around it are carried out under a protective atmosphere. 4. Pipe coupling at the end of a pipe, comprising a sealing member having a hole in which an end portion of the pipe is fixed and a hollow nut slipped loosely over the pipe and abutting the sealing member, characterized in that the sealing member is connected to the pipe end by a brazed connection, while the sealing member consists of a steel hardenable at the temperature required to produce the said brazed connection. 5. Pipe connection according to claim 4, characterized in that the brazing medium consists of copper and the sealing member of M2 steel.

Inventors: VAN DE KOOI, JOHANNES MARIA
Applicants: SKF INDUSTRIAL TRADING & DEVELOPMENT COMPANY B.V.
Application year: 1981
Main classification: B23K1
IPC codes: F16L13, B23K1, F16L27, F16L19