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Title: Failure analysis of rutile sleeves in MC3080 lightning arrestor connectors.

Abstract

The purpose of this SAND Report is to document efforts in the extraction and failure analyses of sleeve-style Lightning Arrestor Connectors (LACs). Several MC3080 and MC3079 LACs were recovered from the field and tested as part of the Enhanced Surveillance Campaign. A portion of these LACs failed retesting. Terry Ernest (01733), the LAC Component Engineer, provided eleven MC3080 LACs for evaluation where four of the LACs failed IR/DCW and one failed FRB requirements. The extraction of rutile sleeves from failed LACs was required to determine the source of failure. Rutile sleeves associated with connector function failures were examined for cracks, debris as well as any other anomalies which could have caused the LAC to not function properly. Sleeves that failed FRB or that experienced high FRB exhibited high symmetry, smooth surface, long-flow amicon, and slightly over-sized inside diameter. LACs that failed DCW or IR requirements had rutile sleeves that exhibited breakdown tracks.

Authors:
; ; ;
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
883464
Report Number(s):
SAND2004-4584
TRN: US200614%%635
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; FAILURE MODE ANALYSIS; BREAKDOWN; CONNECTORS; EVALUATION; LIGHTNING; RUTILE; SLEEVES; EQUIPMENT PROTECTION DEVICES; ELECTRICAL PROPERTIES; Weapon 80; Electrical measurement; Weapons systems.

Citation Formats

Kilgo, Alice C., Monroe, Saundra L., Watson, Chad Samuel, and Ernest, Terry L.. Failure analysis of rutile sleeves in MC3080 lightning arrestor connectors.. United States: N. p., 2006. Web. doi:10.2172/883464.
Kilgo, Alice C., Monroe, Saundra L., Watson, Chad Samuel, & Ernest, Terry L.. Failure analysis of rutile sleeves in MC3080 lightning arrestor connectors.. United States. doi:10.2172/883464.
Kilgo, Alice C., Monroe, Saundra L., Watson, Chad Samuel, and Ernest, Terry L.. Wed . "Failure analysis of rutile sleeves in MC3080 lightning arrestor connectors.". United States. doi:10.2172/883464. https://www.osti.gov/servlets/purl/883464.
@article{osti_883464,
title = {Failure analysis of rutile sleeves in MC3080 lightning arrestor connectors.},
author = {Kilgo, Alice C. and Monroe, Saundra L. and Watson, Chad Samuel and Ernest, Terry L.},
abstractNote = {The purpose of this SAND Report is to document efforts in the extraction and failure analyses of sleeve-style Lightning Arrestor Connectors (LACs). Several MC3080 and MC3079 LACs were recovered from the field and tested as part of the Enhanced Surveillance Campaign. A portion of these LACs failed retesting. Terry Ernest (01733), the LAC Component Engineer, provided eleven MC3080 LACs for evaluation where four of the LACs failed IR/DCW and one failed FRB requirements. The extraction of rutile sleeves from failed LACs was required to determine the source of failure. Rutile sleeves associated with connector function failures were examined for cracks, debris as well as any other anomalies which could have caused the LAC to not function properly. Sleeves that failed FRB or that experienced high FRB exhibited high symmetry, smooth surface, long-flow amicon, and slightly over-sized inside diameter. LACs that failed DCW or IR requirements had rutile sleeves that exhibited breakdown tracks.},
doi = {10.2172/883464},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2006},
month = {Wed Feb 01 00:00:00 EST 2006}
}

Technical Report:

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  • Contact resistances of greater than 40 milliohms have been associated with hermetic connectors and lightning arrestor connectors (LAC) during routine testing. Empirical analysis demonstrated that the platings could be damaged within several mating cycles. The oxides that formed upon the exposed copper alloy had no significant impact upon contact resistance when the mated contacts were stationary, but effectively disrupted continuity when the mating interfaces were translated. The stiffness of the pin contact was determined to be about five times greater than the socket contact. As the pin contact engages the socket, therefore, the socket spring member deflects and the pinmore » does not deflect. Hence, the pin contact could easily remain centered within the socket cavity in a mated condition, contacting the hemispherical spring at a localized point. Thus the only avenue for electrical conduction is between two contacting curved surfaces-the pin surface and the socket contact dimple surface. This scenario, coupled with the presence of corrosion products at the contacting interface, presents the opportunity for high contact resistances.« less
  • Contact resistances of greater than 40 milliohms have been associated with hermetic connectors and lightning arrestor connectors (LAC) during routine testing. Empirical analysis demonstrated that the platings could be damaged within several mating cycles. The oxides that formed upon the exposed copper alloy had no significant impact upon contact resistance when the mated contacts were stationary, but effectively disrupted continuity when the mating interfaces were translated. The stiffness of the pin contact was determined to be about five times greater than the socket contact. As the pin contact engages the socket, therefore, the socket spring member deflects and the pinmore » does not deflect. Hence, the pin contact could easily remain centered within the socket cavity in a mated condition, contacting the hemispherical spring at a localized point. Thus the only avenue for electrical conduction is between two contacting curved surfaces-the pin surface and the socket contact dimple surface. This scenario, coupled with the presence of corrosion products at the contacting interface, presents the opportunity for high contact resistances.« less
  • The Lightning Arrestor Connector (LAC), part “M”, presented opportunities to improve the processes used to fabricate LACs. The A## LACs were the first production LACs produced at the KCP, after the product was transferred from Pinnellas. The new LAC relied on the lessons learned from the A## LACs; however, additional improvements were needed to meet the required budget, yield, and schedule requirements. Improvement projects completed since 2001 include Hermetic Connector Sealing Improvement, Contact Assembly molding Improvement, development of a second vendor for LAC shells, general process improvement, tooling improvement, reduction of the LAC production cycle time, and documention of themore » LAC granule fabrication process. This report summarizes the accomplishments achieved in improving the LAC Production Readiness.« less
  • Previous development, TMS and FPU activities established that lightning arrestor connectors (LAC's) utilizing the dielectric stimulated arc concept provided warhead lightning protection. This early development included very few current capability tests in excess of 20 kA. Simulated severe flash current (approx. = 200 kA) testing of LAC's (the MC2796 eighteen pin and MC2797 thirty-two pin) are described. The current generator, electrical circuitry, currents, voltages and test results are discussed. The generator provided 3 components (strokes) with 60 milliseconds between strokes. The first component was created by discharging 56 ..mu..F charged to 38 kV. The output current was a damped oscillatorymore » wave that had a frequency of 15.6 kHz, resulting in a rise time of 16 ..mu..s to the crest of the first half cycle. The current at the first peak was 190 kA. The total charge transferred was 45/sup 0/C. The second component was created using 140 ..mu..F charged to 13.5 kV. The output current wave had a frequency of 8.9 kHz, a rise time of 28 ..mu..s to the crest of the first half cycle and a current of 93 kA at the first peak. The total charge transferred was 33/sup 0/C. The third component was supplied by a three-phase half wave rectifier circuit. The initial peak was 2 kA for 0.02 s. A circuit series resistance was shunted with a fuse resulting in a drop to 357 A when the fuse opened. The 357 A continued for 0.27 s. The total charge transferred was 129/sup 0/C (total of all components equalling 207/sup 0/C). Fifty LAC's (25 MC2796 and 25 MC2797) were subjected to the tests. The maximum voltage measured at the solder cup terminals of the LAC's was 1325 V which is well within the specified 2000 V limit. The average was 746 V. Melting of the internal parts (web and pins) occurred. Some burning and melting at the mating connector interface was observed. The LAC'S functioned as required during exposure to the simulated severe lightning flash current.« less
  • The success of the MC2796 and MC2797 lightning arrestor connectors (LACs) in providing lightning protection for several weapon systems has resulted in requests for other LACs with other protection capabilities. Among these has been the request for lower breakdown voltage. Some of the initial work on techniques for achieving this goal are described. Techniques investigated included modifications to the electrode geometry, the use of rare gas at reduced pressures surrounding the electrodes, and radioactive ionization of the gas. Tests with LACs included controlled electrical breakdown with slow-rising and fast-rising waveforms. From tests at SLA and General Electric Company, an optimummore » configuration was chosen. The final configuration which achieved 30 to 50 percent lower average breakdown than original LACs, used a modified web and argon gas. This design was implemented in the MC3114 low breakdown voltage LAC.« less