CS205409B1 - Plant for electric heating of field welds of large-diameter pipeline - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to an apparatus for the electrical heating of assembly welds of large diameter pipes. .

Up to now, the heating of the welded joints on the large-diameter pipeline has been done by hand-held gas burners, respectively. segment fixed gas burners. Large diameter pipes with a large number of assembly welds, such as those found in hydroelectric power stations, are often assembled and welded in narrow galleries where external access is not possible. Preheating, welding and annealing of welds must therefore be carried out from the inside. In gas preheating, executors are exposed to harmful combustion products along with the unfavorable thermal effect of hot combustion products. The preheating temperature is very uneven and difficult to control, resulting in increased stress and thus greater cracking. It is furthermore known to use electrical resistance or induction heating, wherein the heating elements together with the insulation are fixedly placed on the pipe surface and must be laboriously dismantled and re-fastened to the next weld after heating.

These drawbacks are overcome by the present invention, which is directed to an apparatus for the electrical heating of assembly welds on a large diameter pipe having a plurality of internally located flexible heating elements. It is an object of the invention that the flexible heating elements, for example, the resistance annealing chains, are coupled to the insulating segments of the boom pivoted in a plane parallel to the axis of the pipes supported on the supporting rings. The supporting rings are mounted on both sides of the pipe weld in the direction of the pipe axis on the frame. The arms are attached to the supporting rings by means of pressure elements, for example springs. The frame has a travel in the pipeline derived from the trailing element and is secured in the working position by a locking device. A working platform for the operator is located on the frame.

Compared with the prior art, the device according to the invention brings a significant reduction in the time required for the preparation and heating of the assembly welds and thus a significant increase in the productivity of the work. A uniform preheating temperature is achieved, thereby reducing the risk of stresses and cracks. The working conditions of welders who are deprived of the necessity of long-term stay in hygienically harmful environment will be significantly improved.

An exemplary embodiment of the device according to the invention is shown schematically in the accompanying drawing, in which Fig. 1 is a view of the device in the pipeline and Fig. 2 is a cross-section of the pipeline which shows the expanded and clamped in the right half ramei205409

5 na.

The device according to the invention consists of flexible heating elements 6, which are fastened to the insulating segments 4 of the arms 3. The arms 3 are pivotably mounted in a plane parallel to the axis of the pipe 1 on bearing rings 5 The arms 3 are coupled to the support rings 5 by means of thrust elements

8. The frame 2 has a travel in the pipe 1 derived from the trailing element 9. A working platform is arranged on the frame 2, which is secured in the working position in the pipe 1 by the locking device 7.

The device works by sliding the device into the assembled section of the pipe during the establishment of the next section of pipe. After the next section has been set and the weld edges are fixed, the clamped arms 3 are moved to the working position above the weld by means of the trailing element 9 and locked in this position by the locking device 7. By sliding the supporting rings 5 along the frame 2 so that the axis of the heated weld is in the middle between them. This is followed by clamping the arms 3 by means of the pressing elements 8 and thereby attracting the flexible heating elements 6 to the surface of the pipe 1. After connecting the flexible heating elements 6 to the power source, the pipe 1 is heated in the vicinity of the insulating elements.

Claims (1)

Subject Apparatus for electric heating of large-pipe pipeline assembly welds on a supporting structure with internally placed flexible heating elements, characterized in that the flexible heating elements (6), for example resistance annealing chains, are fixed to the insulating segments (4) of the arms (3) (1j) mounted on support rings (5) that are on both sides 409 segments 4 to a temperature that can be automatically controlled by changing the power supply. Surrounding of the weld between insulation segments 4 It is free for welding, inspection, repair of the weld, etc., which can be done from a working platform mounted on the frame 2. In the case of annealing, the support rings 5 move along the frame 2 such that the insulating segments 4 completely cover the weld joint. Upon completion of the heating, when the pressure elements 8 are released, the arms 3 with the coupled insulating segments 4 are clamped, the device is unlocked by releasing the locking device 7 and moved to a new working position on the next assembly weld. Resistance annealing chains, resistive cables or inductive or inductive heating elements can be used as flexible heating elements. and other flexible electric heating elements. The device may be towed either by pulling the trailing element 9, which may be a rope, chain or the like, or it may have its own winding device in the fixed trailing element 9. The device according to the invention can be used for preheating or annealing assembly welds in the continuous assembly of large-diameter pipelines for hydro or nuclear power plants. In accordance with the invention, the pipe (1) is mounted slidably in the direction of the pipe axis (1) on the frame (2), the arms (3) being coupled to the supporting rings (5) by means of pressure elements (8) e.g. in the conduit (1) is derived from a trailing element (9), e.g.