1、Lessons Learned Entry: 1389Lesson Info:a71 Lesson Number: 1389a71 Lesson Date: 2004-02-13a71 Submitting Organization: MSFCa71 Submitted by: Prince Kalia/ Lisa CarrSubject: Observed Heat/Fire Hazard Due to Soldering Iron Switch Failures Abstract: This lesson is intended to broaden awareness of an obs
2、erved problem with some models of the Weller Model TCP12P Soldering Iron. Recommendations apply to soldering irons in general.Description of Driving Event: NASA has issued a Government Industry Data Exchange Program (GIDEP) ALERT, #H1-A-04-01 regarding the Weller Model TCP12P Soldering Iron. Due to
3、a mechanical temperature control switch which works based on a ferromagnetic sensing action, two previously undocumented failure modes were observed with this model. The failures were observed in a laboratory setting with minimal damage. The worst of these two modes involves the switch sticking in t
4、he “Full On“ mode. If this occurs, the soldering iron will go into a “Thermal Runaway“ condition, which will allow the iron to reach temperatures of approximately 1200 F, at the heater/tip interface. Obviously, this could result in possible fire, injury, and/or damage to any article being processed.
5、 This temperature estimate is based on the mass and length of the soldering iron tip, and may vary depending on which tip is installed at the time the failure occurs. A tip with larger mass and greater length will lower the maximum temperature possible during the “Thermal Runaway“ condition. A tool
6、holder that surrounds the heated portion of the soldering iron is available, and with this holder in place, the overheat condition should be generally harmless to the working environment. The second additional failure mode is more minor, involving the Ferromagnetic Switch sticking in a “Full Off“ mo
7、de, which means the tool will not heat at all.Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Soldering irons can experience undocumented failure modes that result in significant damage, including the potential for serious fires.Re
8、commendation(s): The exact cause of the failures in this switch is still unknown. Appropriate hazard controls should be in place to prevent a catastrophic event in case a thermal runaway condition occurs. For flight systems that may be potentially affected by this hazard, additional controls should
9、be implemented, including material testing which includes verification by inducing a thermal runaway failure and recording results. Evidence of Recurrence Control Effectiveness: NADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aerona
10、utics ResearchAdditional Key Phrase(s): a71 Fire Protectiona71 Industrial Operationsa71 Parts Materials & ProcessesAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2004-04-26a71 Approval Name: Lisa Carra71 Approval Organization: MSFCa71 Approval Phone Number: 256-544-2544Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
