1、Lessons Learned Entry: 1267Lesson Info:a71 Lesson Number: 1267a71 Lesson Date: 2002-07-10a71 Submitting Organization: JPLa71 Submitted by: Albert WhittleseySubject: Hazards of Arc Welding Near Electronics (1985) Abstract: Starting voltages in excess of 400 volts during orbital arc welding may propag
2、ate at significant levels across interfaces into electronics. Some electronic devices may be sensitive to stray voltage levels as low as a fraction of a volt.Use the referenced damage mitigation procedures, use a weld head that features a “touch start” feature, and avoid welding near electronic circ
3、uits.Description of Driving Event: The JPL Galileo project used automatic orbital arc welding to join spacecraft propulsion system tubing, despite a recognized risk to sensitive spacecraft hardware. An orbital arc welding system utilizes a weld head that clamps around the tubing to be butt-welded. T
4、he weld electrode is controlled to rotate around the tubing, with the weld current synchronized with the rotation of the electrode. This automated process can provide a quality weld that is not subject to the irregularities of hand welding. Such welding on the Galileo Rocket Propulsion Module (RPM)
5、tubing in the late 1980s, as described in Reference (2) below, led to concern that this high voltage process may pose a risk to spacecraft electronics. Initiation of the weld arc uses starting voltages as high as 40,000 volts, with resultant stray voltages on the tubing in excess of 400 volts. This
6、could propagate at significant levels across interfaces into electronics. Some spacecraft electronic devices (e.g., detectors) may be sensitive to stray voltage levels, even as low as a fraction of a volt. References Provided by IHSNot for ResaleNo reproduction or networking permitted without licens
7、e from IHS-,-,-1. Electric Welding Hazard to Spacecraft Electronics (Click on title for .pdf file), A.C. Whittlesey and J.M.Lumsden, Proceedings of the International Symposium on Electromagnetic Compatibility, 8/18-20, 1981, Boulder, pp. 224-228.2. “Galileo Arc Welding Anomaly,“ NASA Lesson Learned
8、No. 0399, June 7, 1995.Additional JPL Key Words: EEE parts electrical overstress, transient voltages, short circuit, sneak circuit Lesson(s) Learned: Automated arc welding may provide results superior to hand welding, but the arc start voltage transient may pose risks to sensitive spacecraft hardwar
9、e.Recommendation(s): 1. When using automated welding processes with a high voltage arc starter, use the damage mitigation procedures described in Reference 1, updated for the specific welding system and the electronics in proximity. JPL has had no reported electronic parts failures resulting from we
10、ld arc starting voltages in those instances where the procedures described in Reference 1 were used.2. 3. To mitigate the risks of high voltage arcs, use a weld head that features a “touch start“ feature. This does not eliminate the need to characterize and evaluate the effects of stray voltage.4. T
11、he preferred solution is to avoid welding near electronic circuits.Evidence of Recurrence Control Effectiveness: Corrective Action Notice No. Z84171 was opened by JPL on June 23, 2004 to initiate and document appropriate Laboratory-wide corrective action on the above recommendations.Documents Relate
12、d to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronautics ResearchProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Key Phrase(s): a71 Aircrafta71 Computer-Aided Design/Manufacturing/Engine
13、eringa71 Flight Equipmenta71 Ground Equipmenta71 Hardwarea71 Industrial Operationsa71 Parts Materials & Processesa71 Safety & Mission Assurancea71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 2002-08-12a71 Approval Name: Carol Dumaina71 Approval Organization: JPLa71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
