1. long pass tack welding lap welding means dislocation after bonding two side portions of the tube formed by stacking the together. In length, have a lap weld length of the points, usually over a few meters, or even longer. There is slightly dislocated dislocation in terms of tenths of a millimeter, and is completely equal to the wall thickness of the dislocation. Resulting in a long pass tack welding are the following factors:
(1) Due to the squeeze roller axially moving string squeeze rollers and squeeze rollers positioning is unstable, and in the assembly, the other parts of the complex is not close to zero the amount of waste and other factors formed, will appear the pressing roller shaft to traverse and radial wobble, then squeeze roll pass will not fit caused by lap welding.
(2) bearing damage bearings damaged, it will destroy the normal position squeeze roller. In two roller pressing roller device, for example, generally have built-in squeeze roll up and down two sets of bearings, when one set is damaged, squeeze roll out of control, will be higher than the weld caused by lap welding. In the production campaign, we can observe swing squeeze roller. When the upper end of the bearing is damaged, the roller swings larger, the lower end of the bearing is damaged, the roller swings on smaller, bearing the extent of damage that there is a certain relationship. After the guide roller bearing is damaged, not only can not properly control the direction of the weld tube, and the tube guide ring also may be caused by the edge pressure loss, the weld height changes, take a little improper welding accidents will happen .

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(3) squeeze rollers roll bending still two pressing roller device, for example, squeeze rollers bending there are two reasons: First, the lack of long-term pressure on the top wire of the outer curved; the second is too much pressure on the top wire inside bending. Inspection, release the top tight device can facade steel ruler placed on the end face of the roller, to check the angle of inclination of the end face of the steel ruler another roller. When the inner shaft bent, scratched by not bending roller shaft caused.
(4) extrusion pressure pipe take this situation generally occurs in the production of thin-walled tube. Because the production of thin-walled tubes, steel tube of the poor, once the pressing force is too large, the width of the tube in the hole produced after much margin can not be accepted, and to take other spatial movement caused by welding . So pass the designer to select the appropriate radius and grooved roll seam allowance depending on the pipe wall thickness, and pay attention to appropriately adjust the pressing amount. Of course, as long as we guarantee the quality of the rolls, this lap welding phenomenon can be overcome.

2. The cycle lap welding lap welding is intermittent appear from time to time, lap weld length of varying length. Sometimes lap welding is equidistant appear more regular, and sometimes take the welding position of comparative law have occurred. For these lap welding phenomenon, we referred to as cyclical lap welding. Periodic lap welding generally occurs in the later stages of the production, mainly caused by the following reasons:
After After (1) pass closed guide ring rupture when worn, it can not effectively control the normal operation of the tube, so the tube inside pass back and forth, while the guide ring rupture appears gap, tube during operation, the edge will guide ring gap is pressure sink, thereby forming a ride pipe production. Pipe welding cycle ride this ride the same length, regularity, relatively easy to determine. With the rupture of the general guide ring rotation, it can be found in the indentation marks.