Longitudinal Submerged Arc Welding Pipe

Product Details:

What are the differences between the two forming processes of longitudinal submerged arc welded steel pipes?

LSAW pipes for oil pipeline engineering are generally manufactured using two processes: UOE and JCOE. The conventional production process is that after the steel pipe blank is UO formed or JCO formed, it undergoes pre-welding, internal and external final welding, diameter expansion, non-destructive inspection, Pipe end processing, hydraulic pressure test, weighing and length measurement, visual inspection of steel pipe markings.

UOE ( U -O -Expanding ):

The UOE forming process first requires beveling, flattening, and bending the edges of the steel plate, and then pressing it into a U shape through a forming machine, and then bending it into an O shape. After the steel pipes are jointed, they are pre-welded using gas-shielded welding, and then Submerged arc welding is used for internal and external final welding, finally, the segmented mechanical diameter expansion process is used to coldly expand the entire pipe body. After the steel pipe forming welding is completed, a series of inspections are performed. This process is currently the most widely used, mature, and quality-recognized large-diameter straight seam submerged arc welded pipe production process in the world.

Main features of UOE welded steel pipe:

1) The forming process and the welding process are separated and belong to discontinuous single-piece production.

2) It can produce thick-walled steel pipes, with the maximum wall thickness up to about 4Omm.

3) The weld length of the steel pipe is only half that of the spiral weld under the same length, and the probability of weld defects is less.

4) High output. The output of one UOE unit is generally equivalent to the total output of 2 to 4 spiral-welded pipe units.

5) The diameter expansion process is adopted to improve the strength and dimensional accuracy of the steel pipe.

6) UOE steel pipes have straight seams, making pipe laying and maintenance easier.

7) The equipment is larger than the spiral welded pipe unit and the investment cost is high.

JCOE ( J -C -O -Expanding):

Compared with the UOE molding method, the JCOE molding process cost is relatively low, process adaptability is strong, molding mold wear is small, and molding mold is light, its process and products are widely used. The JCOE pipe-making process is to form the steel plate in the order of J forming - C forming - O forming. After the steel pipe is jointed, gas-shielded welding is used for pre-welding, then submerged arc welding is used for internal and external final welding, and finally, the segmented mechanical diameter expansion process is used to carry out cold expansion of the entire pipe body, and finally conduct a series of inspections.

Main features of the JCOE process:

Each forming process of JCOE is completed on a large press. The steel pipe adjustment operation requires high technical requirements and the forming unit takes a long time. Due to multiple moldings, the processing efficiency is low compared to the UOE process, but there are fewer molds and lower equipment investment. Therefore, the number of domestic JCOE units is greater than that of UOE units; because JCO is multi-step pressing, the dimensional accuracy of steel pipes is lower than that of UOE, so UOE steel pipes are mostly used in marine pipelines.

JCO Molding Quality Control:

In the JCO forming process, the steel plate is gradually fed into the forming mold through a steel pusher and needs to be re-aligned before each side is formed. It is finally processed into a straight-slotted steel pipe, and finally, the seam pre-welding and final welding are performed. JCO molding machines generally adopt automated control. The molding machine is designed with a short stroke and the maximum pressure can reach 9000t. Before replacing molds with different pipe diameters, clean the lower mold cushion block and ensure that it is flat after being installed to avoid affecting the accuracy in the thickness direction.

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