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The bend is used to change the direction of run of pipe.it advantage is can matach long distance transition requirements,so it is commonly that bends dimension according to customer design.

I. Acceptance and Acceptance of Raw Materials

1. Raw materials shall meet the requirements of relevant standards or technical specifications.

2. The surface of raw materials should be free from oil pollution, excessive rust corrosion and obvious dent defects, low melting point metal pollution, etc.

3. Check the quality certificate, furnace number, batch number and specifications of raw materials, manufacturers and implementation standards.

4. Mechanical rust removal of raw materials with wire brushes to meet the requirements of non-destructive testing.

5. Dimension testing of raw materials (length, width, thickness and unevenness of steel tubes).

6. After entering the factory, the steel pipe and steel plate should be re-examined by ultrasonic wave. Grade I is qualified.

7. Physical and chemical testing, chemical element analysis, mechanical properties and hardness testing of steel pipes and steel plates are carried out according to furnace batch number and specifications. The test results should meet the requirements of raw material standards.

8. After reexamination, the factory shall register the number according to the factory regulations.

3. Manufacturing process

(1) Selecting material and cutting material, choosing appropriate steel plate or steel pipe for elbow, cutting with oxygen-acetylene flame or sawing machine with template marking, and clearly marking the furnace, batch number and pipe fittings specifications, engineering name and number of raw materials.

(2) Rolling and welding the steel plate.

(3) The mandrel is loaded into the pusher by crane, the blank is further cleaned up, the inner wall is coated with graphite, and then mounted on the pusher (according to the length of the blank, more than one can be installed at a time). The mandrel is locked with a plug board, and the internal mould is preheated to the appropriate temperature for pushing (heating temperature and propulsion speed should be the best match).

(4) Adjust the intermediate frequency heating ring, heating the billet to the required temperature, and control the propulsion speed.

(5) To remove the end, according to the specification of the elbow, align it on the beveling machine with suitable tools, then fix the cutting gun, cut off the excess billet, and leave the processing allowance for the beveling machine.

(6) Shaping, clamping elbow with special tire and shaping port on press with brace.

4. Heat treatment: According to the heat treatment process, the elbow is put into the furnace for heat treatment.

5. Surface treatment: After heat treatment, the surface oxide scale of the pipe is removed by sandblasting machine.

6. After surface treatment, 100% of the welding seam of elbow was tested by X-ray, and the second grade was qualified.

7. Mechanical properties testing: According to relevant standards, mechanical properties of elbows are tested to ensure that the mechanical properties of elbows meet the standards, and the testing items and sampling directions should meet the requirements of relevant standards.

8. End processing: mechanical end processing grooves according to design confirmation drawings. Within the range of 50mm from the end of the pipe, the excess height of the internal and external welds is grinded by an angle grinder.

9. Appearance detection

There should be no cracks in the elbow and no hard spots on the surface.

Welding repair is not allowed for any defect on elbow body.

10. Dimension inspection: The company's relevant inspectors, according to the drawings and pipe fittings of the relevant standard requirements for dimensional inspection, and to meet their tolerance requirements.

11. Surface treatment: The inside and outside surface of the elbow should be smooth, without any damage to strength and appearance defects, such as scars, scratches, heavy skins, etc. After finding the defects, it should be repaired. The thinning of the repaired area should be no less than 93.5% of the original wall thickness. The repaired area should be smooth and be cleared by coloring agent or magnetic powder inspection to confirm the defects.

12. Nondestructive testing of elbows

After heat treatment of elbow, the company holds relevant qualifications certificate personnel, according to the standard requirements for magnetic powder, ultrasound, the test results reached the level I qualifications.

13. Identification

Mark with a spray-brush or low-stress impression, and clearly mark the contents required by the standard on the outer wall in sequence.

14. Piling and transportation of elbows

The elbow should not contact any part of the carriage during transportation, so as to avoid collision.