The production process of welding elbow products is as follows:
The process flow of welding elbow production, if you want to make a long radius elbow, you must first select the standard and propose the pipe material. The diameter expansion rate, through theoretical calculation, generally the diameter expansion rate is between 33% and 35%, and it can be pushed back.
The general diameter expansion rate of a short radius of 219mm is 50%. After selecting the material, cut the material according to the standard of the elbow, and then consider the radius of curvature. For example, the curvature of the 90° elbow can be calculated according to the curvature of how long the material can be processed. 90° elbow.
It can be calculated through theoretical calculation, and then cut off with the length as the fixed length. Finally, the material is heated and pushed. You may have seen the push machine, the practice is very simple. It is a horn-shaped mandrel or mandrel, the mandrel changes from thin to thick, and the pushing process is a process of bending the expanding belt.
There is a support at the back, and the feeding pipe section is inserted into the mandrel, and there is an arch frame at the back to fix the mandrel. There is a trolley in the center, some of the trolleys are driven by hydraulic pressure, and some are driven by mechanical transmission, that is, the screw, and then push the trolley forward.
The trolley pushes the pipe along the mandrel, and there is an induction coil outside the mandrel for welding the elbow, which heats the pipe, and then the trolley pushes the pipe down, and one is processed. After pushing, the elbow should be shaped in this hot state.
Because some elbows will be distorted if they are not handled properly, which is not allowed. In addition, after the head is pushed, the outer diameter of the front end is generally large, and it needs to be shaped by a plastic mold. A plastic mold is actually a press machine, and there must be a set of molds, two semi-circular arcs, one for the upper and lower.
The outer diameter after shaping has reached the size requirement of the finished product. The wall thickness is controlled by the wall thickness of the incoming material. The wall thickness tolerances of elbows and pipes are the same, both are ±12.5%. During the pushing process, the wall thickness should not change under normal circumstances.
However, if due to tool reasons, some parts of the welded elbow will have a wall reduction phenomenon, so when lifting the material, some margin should be added to the wall thickness. For example, if the wall thickness of the elbow is 8.18mm, generally a pipe of about 8.5mm should be lifted. , to prevent over-tolerance due to partial thickness reduction during pushing.
After the shape is adjusted, the outer diameter and wall thickness of the elbow meet the requirements. Next, the finishing process is carried out, and the oxide scale on the inner and outer surfaces of the elbow is removed by shot blasting, and the two ends are grooved to facilitate welding.
After inspection, steel lettering, paint spraying, packaging and other processes, it can leave the factory. The above is the production method of the elbow with a seamless steel pipe as the raw material below 24〃. After 24〃, it is more than 600mm, and the large elbow is between 2.032 meters and 2.80 meters, which is made of steel plate.
After the steel plate is cut into materials according to the requirements, its shape is UOE, and it is stamped into a circle through a die. Divided into two parts, then spliced and welded. Because of the presence of welds, non-destructive testing is necessary.
Because of the presence of welding stress, heat treatment is also required. There are also two processes for welding elbows: one is flaw detection and the other is heat treatment. Other procedures are the same.
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