Pipe Bending Technology And Pipework Fabrications (2)
- May 31, 2018 -

Pipe Bending Technology And Pipework Fabrications (2)


10. The minimum thickness of the bent pipe must not be less than the designed wall thickness of diameter.

11. The center deviation of the pipe end of the elbow shall be in accordance with the following regulations:

1) In the GC1 pipeline and the C pipeline for fluid, the elbow whose degree of transmission toxicity is an extremely dangerous medium or whose design pressure is greater than or equal to 10MPa, the center deviation value of each tube end (Figure 2) shall not exceed 1.5mm.When the straight pipe length is more than 3m, the deviation must not exceed 5mm.


2) For other pipe bends, the center deviation of per meter (Figure 2) must not exceed 3mm. When the straight pipe length is more than 3m, the deviation must not exceed 10mm.


pipe bending

1 - Requested center;

2 - Actual center;

L - Straight length of elbow;

pipe bending - Pipe end (Tube end); 


12. The allowable deviation of the flatness for the Π shaped pipe bending (Figure 3) should meet the requirements of Table 3.

pipe bending

L - Straight length of elbow;

pipe bending - Flatness


Table 3 Flatness tolerances of Π-shaped elbow (mm)

Straight length L≤500>500~1000>1000~1500>1500
Flatness pipe bending≤3≤4≤6≤10


13. In GC1 grade pipelines and C class fluid pipelines, after the elbow is made, whose degree of transmission toxicity is an extremely dangerous medium or whose design pressure is greater than or equal to 10MPa, the surface should be checked by non-destructive testing according to the current national standard "Non-destructive testing of pressure equipment" JB/T4730. Heat treatment should be done before non-destructive testing.When there are defects, grinding can be done. The wall thickness of the pipe bending elbow after grinding shall not be less than 90% of the nominal wall thickness of the pipe and shall not be less than the designed wall thickness.


14. After the bent pipe is qualified, it shall fill out the “Processing record of pipe bending” and “Pipeline Heat Treatment Report” respectively. Its format specification shall refer to “Construction standards for industrial metal pipeline project” Table A.0.3 and A.0.4.


A.0.3 The format of processing record for pipe bending

Project NumberProject NameSub-project Name/Number
Pipeline NO.Pipeline NumberMaterialsSpecificationBending RadiusAngle or Size DeviationRoundnessPleat Height(Fold Height)Pipe ThicknessHeat Treatment TemperatureHardness Value HBNon-destructive Testing Results




















































































Sketch and description:

Engineer:                                Quality inspector:                      Construction workers:    


Date:   


A.0.4 Report format of pipeline heat treatment

Project NumberProject Name

Sub-project Name/Number:

Pipeline Number
Materials
Specification
Welding Material Number

Weld Number

Pipe Number

Heating Rate (℃/h)Heat Treatment Temperature (℃)Constant Temperature Time (h)Cooling Rat (℃/h)

Note































Thermocouple arrangement:




Heat treatment curve:

(Attachment: automatic recorded heat treatment curve)



Engineer:

Quality inspector:

Operator:

Date:


15. The Scope

This standard is according to GB/T9711 standards series, in Table 4 specifies three levels of heating bent pipe by steel induction, the base material meets GB/T9711 quality requirements on the basis of technical condition of steel pipe delivery and additional quality requirements.

When the mother material meets the standards of other steel pipes except GB/T9711, the quality requirements and classification methods are agreed by consensus, but the load carrying capacity must be guaranteed.


Table 4 Induction Heating Of Pipe Bending Grades And Related Steel Pipe Standards


Steel pipe bending grade

Related steel pipe standards

Grade AGB/T9711.1
Grade BGB/T9711.2  √
Grade CGB/T9711.3


16. Normative reference documents

The clauses in the following documents have been adopted as references to this standard.For dated reference documents, all subsequent amendments (not including errata content) or revisions do not apply to this standard. However, encourages all parties that reached agreement under this version to use the latest version of these documents. For dated references, the latest edition is applicable to this standard.

GB/T2288; Method for tensile testing at room temperature

GB/T232; Metal Material; Bending test method

GB/T246; Metal tube; Flattening test method

GB/T2358; Test method for crack tip opening displacement of metallic materials

GB/T8923; Corrosion grade and derusting grade of steel surface before painting

GB/T9445; Qualification and certification for non-destructive testing personnel 

GB/T11344; Thickness measuring method of contact ultrasonic pulse echo

GB/T18253; Steel and Steel Products; Types of Inspection Documents