5.3　Backing Ring

Ⅰ　Dominant Items

5.3.1　In case of welding for assembly of backing ring，the welding procedure qualification（WPQ）shall be carried out with report，based on which the welding procedure and the operation instruction for welding shall be determined or prepared.

Quantity to be checked:100%.

Inspection method:Check WPQ report and the operation instruction for welding.

5.3.2　The internal quality of butt welds in case of the assembly of backing ring shall comply with the requirement of the design technical document，or that of GradeⅢof weld quality grading criteria of

Construction and Acceptance Code for Welding Work of Field Equipment and Industrial Pipeline（GB 50236）in case of no requirement in the above document.

Quantity to be checked:100%.

Inspection method:Check the ultrasonic inspection record.

5.3.3　The appearance quantity of butt welds in case of backing ring assembly shall meet the requirement of the design technical document，or that of Appendix E of the Code in case of no requirement in the above document.

Quantity to be checked:100%.

Inspection method:Observe or check with a magnifier.

5.3.4　The postweld heat treatment of butt welds in case of backing ring assembly shall meet the requirement of the design technical document，or that of Appendix F of the Code in case of no requirement in the above document.

Quantity to be checked:100%.

Inspection method:Observe and check the record of heat treatment.

5.3.5　The tightening force for the bolts of backing ring connected with flanges shall comply with the requirement of the design technical document.

Quantity to be checked:100%.

Inspection method:Observe at site，check with a torque wrench，and check the tightening record.

5.3.6　The工-shaped key for backing ring connected with flanges shall be assembled according to the requirement of the design technical document.

Quantity to be checked:100%.

Inspection method:Measure by a feeler gauge and a micrometer.

5.3.7　The water-cooled backing ring shall be subject to hydrostatic test and flushing test according to the requirement of the design technical document.In case of no related requirement in the above document，the test shall meet the following requirements:the test pressure shall be 1.25 times of design pressure；booster the pressure up to the test pressure and hold for 10min，and then lower it to the working pressure and hold for 30min.The test is qualified if there is no leakage and pressure fall.In case of flushing test，the water shall be able to flow in and out smoothly and freely for at least 24h，without any leakage.

Quantity to be checked:100%.

Inspection method:Observe，and check the records for pressure test and flushing test.

Ⅱ　General Items

5.3.8　The allowable deviation for assembly dimensions of backing ring shall comply with the requirements in Table 5.3.8.

Quantity to be checked:100%.

Inspection method:See Table 5.3.8.