SRC Forum - Message Replies
Forum: Reliability & Maintainability Questions and Answers
Topic: Reliability & Maintainability Questions and Answers
Topic Posted by: Reliability & Maintainability Forum
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998
Posted by: Julien Nico
Organization:Aérazur - Zodiac group
Date posted: Mon Mar 27 10:56:52 US/Eastern 2000
Subject: Reliability for a missile equipment
We are currently designing a fuel cell for a missile (fuel cell made with rubber).
The missile shall be store during 20 years then launched.
Our fuel cell is filled of fuel at the begining.
The missile can be subject to underwing carried flights and be launched after 20 years.
Time during launched phase is 10 minutes.
I have to define the MTBF for the fuel cell.
I don't know how to express the MTBF for the component. I can express a MTBF for the 10 operationals minutes but I don't know how to take into account the storage period. Is there a reliability means to express the storage period in the final calculation (fuel cell properties can changed during storage period).
Subject: Fuel Cell Storage
Reply Posted by: Bruce Dudley
Organization: Reliability Analysis Center
Date Posted: Tue Mar 28 14:05:34 US/Eastern 2000
Storage reliability for long term is difficult to calculate as there is little long term data available for any components. The Navy has a mechanical reliability handbook, NSWC-94/l07, produced by the Naval Surface Warfare Center Carderock Division in Bethesda, Maryland that has a model for compressor diaphrams based on liquid penetration of natural rubber, neopreme, butyl and other materials that could answer the life expectancy. Other models for gaskets and seals have effects for leakage, fluid pressure, material hardness and temperature indicated. The temperature effect for rubber material is quite significant at values lower that 10 degrees F. With some test information and these reliability models, one should be able to estimate the life of the fuel cells.