REG NASA-LLIS-1230-1999 Lessons Learned - Welds Near Tube Bends.pdf

1、Lessons Learned Entry: 1230Lesson Info:a71 Lesson Number: 1230a71 Lesson Date: 1999-01-21a71 Submitting Organization: JSCa71 Submitted by: Keith A Mason/ Ronald A. MontagueSubject: Welds Near Tube Bends Description of Driving Event: During dimensional inspection of orbital tube welds involving 316L

2、tubing, it was found that 8 of 8 welds failed because of weld mismatch. The weld joints were located between two bends that formed a “S“ bend. There was approximately 1 inch of straight tubing from each bend to the joint of the weld. The mismatch in this case is not to exceed 25% or 0.010 inch which

3、 ever is less.Root cause: Tube bending / shaping typically causes the tube to take an oval shape, creating matching problems during weld fitting. Engineering drawings provided insufficient length for oval / runout to occur of the shaped / bent tube prior to welding of the joint.Lesson(s) Learned: Sh

4、aping /bending of tubes must take into consideration the oval-shaped deformations that result when planning for subsequent weldsRecommendation(s): Design Engineering should use a non-welded configuration when close proximity bends are needed. Even though the orbital tube welding process requires onl

5、y 0.7 inches of straight tubing on both sides of the joint for clamping, approximately 1.5 diameters of straight tubing should be kept between a bend and a weld joint for ovality run-out. This will insure acceptable ovality that, in turn, will insure acceptable mismatch. Evidence of Recurrence Contr

6、ol Effectiveness: N/AProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Documents Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Industrial Operationsa71 NASA Standardsa71 Parts Materials & Processesa71 Safety & Mission Assurancea71 StandardAdditional Info: Approval Info: a71 Approval Date: 2002-06-27a71 Approval Name: Ronald A. Montaguea71 Approval Organization: JSCa71 Approval Phone Number: 281-483-8576Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-