FR2593095A1 - METHOD FOR RECOVERING CURVED TUBES LONGITUDINALLY. - Google Patents

Abstract

Method of straightening a tube with a hexagonal cross section, curved longitudinally. An apparatus 10 to 18 is used which makes it possible to measure the magnitude of the deformation at various locations (a to e) distributed over the length of the tube 20 and from these measurements the locations suitable for the application of a load of corrective deformation 24. Application to the straightening of hexagonal lining tubes for nuclear reactor cores, warped during manufacture. (CF DRAWING IN BOPI)

Description

The present invention relates to straightening section tubes

  hexagonal right, which have been warped or curved longitudinally. It is applicable in particular to the lining tubes of combustible subassemblies such as those used in liquid metal-cooled nuclear reactors. Sometimes we notice

  in the manufacture of these tubes they present a cour-

  or unacceptable warping after operations such as the welding of wear pads on these tubes and a

  heat treatment. When the tubes have been treated

  As a result of the final thermal cost, it has been invested in the production of high costs, which is much higher than the actual price of the metal used, and it is therefore necessary to have a satisfactory method of correcting the longitudinal warping of the metal.

  to minimize the number of rejects.

  The method, according to the invention, of straightening of tubes with hexagonal cross section, bent longitudinally, comprises the following steps: a. we mount the tube so that it can

  turn on a well-defined axis of rotation coinciding

  approximately with its longitudinal axis; b. for each of various locations distributed axially along the tube, this is rotated stepwise on the axis of rotation, so as to bring each of its faces or edges to a measuring position and the position of each face or edge relative to a reference point that is common to all these faces or edges at the respective axial location; c. from these measurements, the direction of curvature prevailing over at least two regions of the length of the tube is deduced;

  d. for each of these regions, the location

  cement and the face or the edge on which a transverse load of deformation of the tube is applied; summer. this load is applied to each of these locations and selected faces or edges while supporting the tube on either side of each of said locations and

  supporting it internally at the respective location.

  After step (e), it is possible to execute step (b) again and, if the importance of the warping

  length continues to exceed acceptable limits

  tables, we can repeat steps (c), (d) and (e), then again step (T) and repeat again (c), (d), (e) and (b) as much as the must. Typically, steps (b) through (e) can be repeated three or four times at least before obtaining

  an acceptable correction of the longitudinal warpage.

  Preferably at least four locations are

  to measure the steps of step (b) and the measured values for each group of three adjacent locations can be analyzed to determine the predominant direction of the curvature over the length of. couyerte tube by these three locations. To promote a more complete understanding of the invention, we will now describe in more detail

  and by way of non-limiting example, a form of reali-

  FIG. 1 is a diagrammatic front elevation of a rectifying device for carrying out the method according to the invention; Figure 2 is an end view of the element which applies the load;

  FIG. 3 is an end view with sectional cutaway

  one of the mechanisms for lifting the device; Figure 4 is an end view of a hexagonal tube whose faces and edges are respectively designated by numbers and letters; and Figures 5A to 5E are typical measurement graphs made at various locations (a-e) along the length of a liner tube, and represent four phases of

the correction action.

  The device represented in FIGS. 1 to 3 comprises a bench 10 on which two sets 12, 14 of rollers are mounted, each of these sets 12, 14 being composed of two

  transversely spaced rolls (only one of which is

  each side of Figure 1), intended to contain, while allowing them to rotate, two rings halos 16, 18, respectively. Each of these rings 16, 18 is mounted near a respective end of the hexagonal tube 20 to be straightened. The rings 16, 18 are adjusted so that the same series composed of one of two faces

  of the tube are at least approximately concentric.

  Thus, with reference to FIG. 4, the rings 16, -

  18 can be adjusted so that the faces or plates 1,

  3 and 5 are concentric to both ends of the tube.

  The device also comprises a mobile gantry 22,

  slidably mounted along the bench 10, a hydraulic jack

  hydraulic 24 (Figure 2) mounted in the middle of this frame, two lifting mechanisms 26 (Figure 3) for raising and lowering the tube and a number of spacers 28, only one is shown in Figure 2. The cylinder 24 can engage with the tube 20 via a die 30, which is shaped to come into contact with this tube when it is oriented so as to have a face (Figure 2) or a ridge above. In the latter case, the edge comes into contact with the flanks of a V-shaped recess 32 of the die 30. The lifting mechanism 26 comprises supports 34, which are also intended to support the tube when it is underneath. a face or an edge and which are carried by the rods 36 of the pistons pneumatic cylinders 38, which have the effect of lifting the tube when they are fully deployed, discarding the rings of the rollers 12, 14 and allow to put the spacers 28 in place to support the tube at selected locations when

  have been removed. The spacers 28 have the dimensions

  read so that the rings 16, 18 remain well apart

rollers.

  When the tube 20 has been mounted as shown in FIG. 1, the procedure is as follows:

  this tube until one of its faces is above.

  We measure the position in height of this face to each of the

  locations a, b, c, d and e, using an instrument

  Proprie. Then the tube is rotated 600 and repeats the measurements on the face which is then above. These operations are repeated for each of the six faces, which gives for each location a to e a series of measurements, all obtained with respect to a common reference point. These measurements are then processed by calculating the difference between the values obtained for the opposite faces, i.e.,

  in FIG. 4, the faces 1 and 4, 2 and 5 and 3 and 6.

  ferences give a measure of the importance of

  median plane between each pair of faces at each location.

  cements a to e, because of the warpage of the tube.

  These difference values can be graphically figured as shown in Figs. A through 5E. So, in Figure 5A, which represents the importance

  warping before any corrective action, at the location

  difference for faces 1 and 4 is - 1.18 mm, at position b it is equal to + 0.15 mm, etc. Examination of FIG. 5A reveals that, over the length of the tube between locations a and c, for example, the curvatures in the median planes at faces 1 and 4 and 2 and 5, respectively, are quite large and oriented. in the same direction, while the curvature in the median plane at faces 3 and 6 is less. The predominant direction of curvature between locations a and c thus includes

  components normal to faces 1 and 4 and 2 and 5, respectively

  and it can be seen from this analysis that it is possible to perform a corrective action at the location b by applying a load on the edge A of the tube. Analogous analyzes made on the tube lengths between the locations b and d on the one hand, and c and e on the other hand indicate that it is possible to compensate the curvature

  which exists on these lengths, at locations c and d,

  by applying a load on the A edge

in both cases.

  When locations and faces have been determined

  or edges (in this case the six edges) on which it

  has just applied a load, the tube is raised by means of the mechanisms 26 and spacers 28 are inserted so as to

  support this tube, its edge D being below, these

  toises being arranged initially on either side of the location b, for example at locations a and c or in their vicinity. Two types of spacers are used to satisfy the case where the tube has to be supported by a face or an edge. When the spacers 28 have been put in place, the lifting mechanisms are moved back so as to rest the tube on them, the rings 16, 18 being spaced apart from the rollers 12, 14. The gantry 22 is brought to the location b and there is introduced into the tube a support not shown to this location b. This support is intended to prevent the tube from crashing when subjected to a load, by distributing this load on the underside

  of this tube. Said support is conveniently a hexagonal piece

  gonale having the desired dimensions to slide freely in the tube and mounted at the end of a rod, so

  to facilitate its implementation in this tube.

  Once the gantry and the inner support have been arranged at the location b, the actuator 24 is operated so that it comes into contact with the ridge A of the tube via the die 30, the value the applied load being chosen so that the tube is deformed beyond its elastic limit, creating a permanent deformation at the location b. In practice, the

  value of the appropriate load can be determined empirically

  However, considering the length of unsupported tube and the material of which this tube is made. The surfaces of the die 30 in contact with the tube are covered with a material which prevents this tube from being damaged. When a load has been applied to location b, the same operations are repeated at each of the other locations where a load is to be applied, i.e. locations c and d

in the present case.

  After the application of charges at locations b, c and d, the tube is lifted by means of the mechanisms 26, the spacers 28 are removed and this tube is lowered

  rollers 12, 14 support it through the

  rings 16 and 18. The measurements are then repeated.

  described above and the results are analyzed, see

  Figure 5B. Figure 5B shows that between locations

  cements a and c the curvature in the median planes at faces 1, 4 and 2, 5 is predominant, that between locations b and d, there is no predominant curvature and that between locations c and e. it is the curvature in the planes with the faces 1, 4 and 2, 5 which is predominant, the sense of this curvature being opposed to that of that which exists between the places a and c. It can thus be seen from this FIG. 5B that at the location b it is necessary to apply a load on the edge A of the tube and that at the location d it is on the edge D that it must apply a load. We undertake

  charging operations in the manner described above.

is lying.

  After this second phase of charges, in the example

  5C, with the conclusions that it was necessary to apply a load on the edge A again in the case of the location b, on the face 2 in the case of the location c and on this side 2 in the case of the location d. In the latter two cases, we see in Figure 5C that between locations b and d

  on the one hand and c and e on the other hand, the curvature is predominant

  in the middle plane to faces 2 and 5.

  Fig. 5D shows the result of the charges applied in accordance with the analysis of Fig. 5C. It can be seen that between the locations a and c there are in the three median planes components oriented in directions corresponding to the application of a corrective charge on the face 2. Between the locations c and e, it is not indicated significant curvature, and it was considered that it was not necessary to apply a load to the location

  d. Between locations b and d, the curvature is predominant

  in the median planes to faces 1, 4 and 2, 5 and he has

  It was therefore decided to apply a charge

  median of edge A, at location b. Figure 5E shows

  the result of the application of these charges and was considered to be an adequate correction

  to meet the tolerances required for the tube

sidered.

  Although, in the description above,

  have been made at five locations, more of these locations can be selected. Moreover, one can, if one wishes, to make the measurements on the edges of the tube instead of making them on the faces. he

  It is also possible to use some automation.

  For example, the measuring devices of each location can be operated automatically when the tube has been stepped at each of the measurement positions. The analysis of the results can be done by a computer and the setting up and the operation of the cylinder which applies the loads, the operation of the lifting mechanisms and the installation of the supports of the tube can be carried out automatically, so that each series of measures and

  corrective loads applied to the tube is automatically performed

matically.

  As previously mentioned, the value of the load applied at each location can be determined

  empirically. It is generally possible to determine

  This value should be reduced by experience, taking into account the fact that excess bending should be avoided, as this may result in the tube becoming more curved and the number of steps needed to be increased.

  return the warp to an acceptable value.

  It goes without saying that it is possible, without departing from the scope of the invention, to make various modifications to the

  tube straightening method described.

Claims (3)

  1. Method of straightening a section tube   hexagonal right, curved longitudinally, characterized   take the following steps: a. the tube (20) is mounted so that it can   turn on a well-defined axis of rotation coinciding   approximately with its longitudinal axis; b. for each of a number of locations (a to e, for example), distributed axially along the tube, the latter is rotated step by step on this axis of rotation of   way to bring, either each of its faces (1 to 6), or each   one of its edges (A to F) to a measuring position, and   measure the position of each of these faces or edges by   port to a reference point that is common to all said faces or edges at the respective axial location; c. the predominant direction of the curvature in at least two regions of the length of the tube is deduced from these measurements,   d. for each of these regions, the location   cement and the face or the edge where it is necessary to apply a transverse load intended to deform the tube; summer. this load is applied to each location and each selected face or edge, while supporting the tube on either side of the respective location and   internally supporting this site.   2. Method according to claim 1, characterized in that step (b) is repeated and, if the importance of   the longitudinal curvature is greater than linear values   acceptable mites, steps (c), (d) and (e) are repeated and again step (b), followed by steps (c), (d), (e) and (b) as many times as necessary.   3. Method according to one of claims 1 and 2,   characterized in that at least four locations are   to perform the measurements according to step (b), and the values obtained for each series of three are analyzed.   adjacent locations, so as to determine the   dominant of the curvature over the length of covered tube by these three locations.