Forum: Reliability & Maintainability Questions and Answers

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Posted by: Bob Valerius (rvalerius@ngc.com )
Organization:Northrop-Grumman Oceanic Systems
Date posted: Fri Jun 4 14:06:30 US/Eastern 2004
Subject: Solid State Relays
Message:
Hi. I was looking through RAC's 1991 Failure Mode/Mechanism Distribution Guide. On page 2-23 relays are said to have failed by a spurious trip 26% of the time. Should I assume that is for electro-mechanical relays and is not applicable to solid state relays (SSR), so that a spurious trip of an SSR is extremely unlikely? Thanks for the help.

Replies:
Relay Failure Modes
bwd Wed Jun 9 15:00:30 US/Eastern 2004

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Posted by: Berni (berni.itNO_SPAM_REMOVE@tiscali.it )
Organization:Student
Date posted: Thu Jun 3 2:46:33 US/Eastern 2004
Subject: Part Stress Calculation
Message:
When I perform a part stress analysis (MIL 217F2)which electrical condition should I use?
For example, if I have a resistor with a sinusoidal tension applied, how can I compute the actual power dissipation? Should I use the max or the mean tension?

Replies: (list all replies)
Stress Analysis
bwd Wed Jun 9 15:37:04 US/Eastern 2004
Part Stress Calculation
Berni Fri Jun 11 7:53:39 US/Eastern 2004
extreme value analysis
bwd Fri Jun 11 9:30:15 US/Eastern 2004

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Posted by: Bob Valerius (rvalerius@ngc.com )
Organization:Northrop-Grumman Oceanic Systems
Date posted: Wed May 26 10:44:42 US/Eastern 2004
Subject: Underwater Connector Failure Rates
Message:
Hi. I am looking for current failure data on underwater connectors. Do they typically follow an exponential or a Weibull distribution? Has there been any recent studies I can access? What are the current maintenance recomendations as well? Thanks!

Replies: (list all replies)
Underwater connectors
bwd Wed Jun 9 15:13:57 US/Eastern 2004
Cloarec
Jean-Marie Wed Jun 16 23:51:49 US/Eastern 2004

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Posted by: Murali (murali_913@yahoo.com )
Date posted: Sun May 16 7:26:21 US/Eastern 2004
Subject: Quality factor for Resistors
Message:
Can some body help me out please? I am working for resistor Reliability prediction methods. I am following MIL-HDBK 217F. In the Reliabiltiy Prediction Calculation it is mentioned that Quality Factors for resistor as S,R,P,M. Can you please give some idea about these abbreviations.
Thanks in advance.

Replies:
Resistor Quality Factors
bwd Mon May 24 15:14:13 US/Eastern 2004

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Posted by: Dan Panachyda
Organization:Sensis Corporation
Date posted: Wed May 5 17:34:48 US/Eastern 2004
Subject: validity of M-Demo approach
Message:
I'm working on a project which in the past had conducted a MIL-STD-470 Maintainability Demonstration to verify a system mean time to repair requirement of 30 minutes. Now we are modifying the system by removing an entire subsystem containing some items with high failure rates and adding a few components with low failure rates. Our customer believes that as long as the MTTR for the new components is less than 30 minutes, the system MTTR remains less than 30 minutes. Our position is that this is statistically invalid because of the removal of components. Who is correct and where can I find simple explanatory documentation which can be used to justify that position?

Replies:
System MTTR Predictions
Joe Dzekevich Thu May 6 12:51:11 US/Eastern 2004

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