DE2834538A1 - Pressure pipe esp. primary coolant duct with peripheral weld - has internal ring covering weld to limit aperture if weld ruptures - Google Patents

Abstract

A pressure pipeline has a weld between adjacent sections. Inside the pipe a ring covers the region of the weld seam. More specifically, the ring is attached to the internal lining of the pipe or duct. The ring may be composed of a number of parts connected together. Used esp. for prim. coolant ducts in a nuclear power plant, where the fracture of a peripheral weld may be regarded as the max. credible accident. The ring stops the two parts of the pipe from sepg. if a crack should arise in thise region; in this way, only a comparatively small leak results. Access from the outside for inspection purposes is still possible.

Description

Pressurized pipeline

The invention relates to a pressurized pipeline, in particular for nuclear power plants, with weld seams between pipe sections. The area weld seams are generally more vulnerable than the pipe sections themselves. Therefore it can be assumed that, if at all, with a break in the pipeline it is to be expected that this will take place in the area of the weld seam. This view is also the basis for the accident considerations for nuclear power plants, with the largest Accident to be assumed is the tearing off of a pipeline in the primary cooling circuit in the Area of welds is assumed.

Attempts have already been made to counter the consequences of a rupture in the primary cooling lines to protect. For example, it is stated in the German Offenlegungsschrift 24 17 397, that there is an area between the reactor pressure vessel and one in the primary cooling line arranged Shut-off valve through an external one, the primary cooling line enclosing tube covers. Such a cover is only relative great effort to realize if the entire coolant circuit are protected target.

In addition, this restricts the accessibility of the primary KUh1 circuit, which is required for exams.

Therefore the invention seeks another possibility, the consequences of one Limit crack in the pipeline.

According to the invention, a weld seam is inside the pipeline arranged overlapping ring.

In the event that a crack occurs, it prevents that from occurring formed pipe ends gape apart and so the one that is routed with the pipe Medium can escape unhindered. In other words, the pipeline retains In spite of the crack, it retains its original position, and that of the pipeline Medium only escapes in correspondingly small quantities. Still the pipeline is fully accessible from the outside for the tests mentioned above.

The ring can advantageously be fixed on the inside of the tube be. For example, the ring can be embedded in the pipeline. this applies especially for the case that often occurs in reactor technology that the pipeline carries a layer of corrosion-resistant material on the inside. In such a Layer can be let into the ring.

The ring can also consist of several connected within the pipeline Parts exist if it is subsequently introduced into a largely finished pipeline who- the should. However, it is cheaper in terms of production and strength to use a one-piece ring and prior to making the Insert weld seam in the pipeline.

For a more detailed explanation of the invention is based on the enclosed Drawing an embodiment described in Fig. 1 is a section through shows a pipeline along the pipe axis and in Fig. 2 a section from the Fig. 1 on a much larger scale.

The pipeline 1 consists of high-strength steel and belongs to the primary cooling circuit a pressurized water reactor.

Their diameter is, for example, 700 m has a temperature of at least 300ob, it is under a pressure of 160 cash or more.

The pipeline 1 comprises in the area shown in the figures two sections 2 and 3 which are connected by a weld 4. The weld 4 is a round seam, i.e. it runs in a plane that is perpendicular to the dash-dotted line indicated pipeline axis 5 is around the entire circumference of the pipeline.

As can be clearly seen in FIG. 2, the pipeline 1 is applied on its inside a layer of austenitic steel called plating 7. A locking ring 8 is inserted into this layer in the area of the weld 4, which also consists of austenitic material. The locking ring 8 is a Cylinder the one with a slightly smaller outer diameter Da than the Inner diameter Di of the pipeline 1 without the cladding 7. The wall thickness of the Cylinder 8 is at least the same size as the thickness of the cladding 7. In relation to the thickness of the pipeline 1, it is in the exemplary embodiment about 15%.

The ring 8 covers the weld 4 because its length L is considerable greater than the maximum width B of the weld seam 4. In the exemplary embodiment, the length L more than 1/4 of the diameter of the pipe 1 and therefore more than that 3 times the width B of the weld 4.

The ring 8 is fixed on the inside of the pipeline 1 because as can be clearly seen in FIG. 2, it is embedded in the plating 7, which is reinforced in this area 10. With the gain there will be a smooth transition to the reduced inner diameter with the ring 8, so that the flow the primary cooling water is affected as little as possible

Claims (4)

Claims 1. Pressure pipelines, especially for nuclear power plants, with weld seams between pipe sections e 1 c h -n e t that inside the pipeline (1) a weld seam (4) overlaps Ring (8) is arranged. 2. Pipeline according to claim 1 with an inner layer (cladding), d a d u r c h e k e n n z e 1 c h -n e t that the ring (8) on the inner layer (7) is fixed. 3. Pipeline according to claim 1 or 2, d a d u r c h g e k e n n z e i c h e t that the ring (8) is let into the pipe (1). 4. Pipeline according to one of claims 1, 2 or 3, d a d u r c h e k e n n n e i c h n e t that the ring (8) consists of several within the pipeline (1) connected parts.