Pipe joints or couplings – Particular interface – Interlocked or overlapped
Reexamination Certificate
2001-06-11
2002-05-07
Browne, Lynne H. (Department: 3629)
Pipe joints or couplings
Particular interface
Interlocked or overlapped
Reexamination Certificate
active
06382684
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for connecting piping sections of a pipeline through which a medium flows. The invention contains a number of tension elements disposed so as to be distributed over the circumference of pipe ends of the pipeline. In this case, the expression pipeline refers in particular to a pipeline through which a hot medium, for example steam, under high pressure flows.
On account of the steam parameters to be expected in future power plants, having a steam or live-steam temperature of more than 600° C. and a steam pressure of more than 250 bar, correspondingly high demands will be imposed on the pipelines and piping connections. In such a steam feed line, the connecting point between pipe sections of the pipeline carrying steam may be configured to be welded and thus undetachable or may be configured to be detachable like a flange connection. Such connections are also provided between the pipeline and a steam inlet valve of a steam turbine and between the steam inlet valve and the turbine casing. Whereas known detachable connections, on account of the low residual material characteristics of conventional materials related to the temperature, can only be used to a limited extent, welded connections, in particular in the event of an inspection, have disadvantages with regard to ease of assembly and dismantling.
The use of conventional pipe connections like a flanged and screwed pipe joint, a screwed pipe joint by a cap nut or a clamped connection, is problematic at high and maximum steam states for different reasons. The flanged and screwed pipe connection requires the availability of a screw material of sufficient strength. In addition, on account of the round screw cross section, only a limited proportion of the flange surface, i.e. of the space available radially around the pipeline, can be utilized for applying tensile forces. Furthermore, the round supporting surface of the nut requires a minimum distance from adjacent constructional elements, so that a minimum flange outside diameter results from the outside diameter of the pipeline and the minimum distance between adjacent nuts on the pitch circle and also from the outside diameter of the supporting surface. The resulting distance between the pipe outer wall and the center of the screw bolt produces a relatively high flange moment, a factor that constitutes a considerable disadvantage in particular with low available material characteristics.
In a pipe connection using a cap nut, a stress concentration occurs in particular at the transition from the cylindrical region to the axial bearing region. With low material characteristics related to the temperature, a limit in the creep deformations in this region has to be taken into account in the configuration of the cap nut, a factor which leads at high steam states to relatively large components, which can therefore only be handled with difficulty. Since a flange, after the cap nut has been inserted, has to be welded to, for example, the valve to be connected, this has an adverse effect on both the production, when welding correspondingly large wall thicknesses, and on the overall length of the connection. In addition, a relatively large, radial and axial space is required at high temperatures.
The relatively large radial expansions also result in a clamped connection disclosed, for example, by Published, Non-Prosecuted German Patent Applications DE 197 11 580 A1 or by DE 24 52 770 A1, in which a clamped connection of a number of connecting elements in the form of claw-like or clamp-like ring segments are disposed on the circumference of the flange-like connection. In addition, in a flange connection with such connecting elements, there is the disadvantage that the latter do not have sufficient strength to absorb the tensile forces, especially as the connecting elements, as a result of radially surrounding the outsides of the flange, are also subjected to a bending load in addition to a tensile stress.
Specific cooling in the region of such pipe connections between the medium carried by the pipeline and the flange connection is also problematic, since flange cooling requires an additional radial distance between the flange and the pipeline for the cooling medium. In addition, heat losses may occur due to such cooling, and these heat losses, in a steam line, may lead to a loss of working capacity, that is to an energy loss of the medium carried in the pipeline.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for connecting piping sections which overcomes the above-mentioned disadvantages of the prior art devices of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a combination of a pipeline having connecting pipes with pipe ends and contact surfaces, with a device for connecting the pipes through which a medium flows. The device contains shaped elements disposed at the pipe ends of the pipes and a number of tension elements disposed distributed over a circumference of the pipe ends of the pipes. Each of the tension elements have a tension shank with ends and extend in a longitudinal direction of the pipes between the shaped elements and the tension elements are disposed adjacent to each other in a circumferential direction of the pipes. Each of the tension elements have shaped parts with one of the shaped parts disposed at each of the ends of the tension shank and the shaped parts extend in a transverse direction of the tension elements. The shaped parts engage in the circumferential direction of the pipes behind the shaped elements at an end remote from the contact surfaces of the pipe ends.
The object is achieved by a number of tension elements. The tension elements extend with their tension shanks in the longitudinal direction of the pipe between shaped elements which are disposed at the pipe ends and are disposed adjacent to each other in the circumferential direction of the pipe. Shaped parts provided at the ends of the tension shank of the respective tension element and extending on both sides of the tension element in its transverse direction engage behind or overlap the shaped elements provided at the pipe ends in the circumferential direction of the pipe preferably in a positive-locking manner.
The connecting device has a plurality of the tension elements preferably disposed so as to be uniformly distributed over the circumference of the piping sections to be connected. The connecting device has at the same time a high strength and also at a high temperature and a high pressure of the medium carried in the pipeline, ensures an especially compact configuration of the connecting elements with especially low radial expansion compared with the known flange connections, in particular compared with the known clamped connections. In addition, stress concentrations as a result of force deflections are reduced. Furthermore, an especially advantageous equilibrium of forces, while avoiding a bending load on the tension elements, is achieved on account of the symmetrical configuration and in particular on account of the symmetrical configuration of the tension and shaped elements.
By the suitable forming of the shaped parts of the tension element or of each tension element and of the shaped elements on the respective pipe end, an especially favorable ratio between tensile cross section of the tension element and the effective areas can be set inside the positive-locking connection.
With regard to the tension elements and their shaped parts and with regard to the shaped elements of the pipe sections, a variant in which the shaped elements are formed by radial projections which are attached to or integrally formed on the respective pipe end and are therefore discrete is especially advantageous. The radial projections may also be produced by incorporating grooves in an annular bead integrally formed on the pipe end. In this variant, the shaped parts preferably integrally formed on the ends of the tensi
Haje Detlef
Scholl Lothar
Bochna David E.
Browne Lynne H.
Greenberg Laurence A.
Mayback Gregory L.
Siemens Aktiengesellschaft
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