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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

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Posted by: Richard Smith
Date posted: Thu Apr 12 14:26:10 US/Eastern 2001
Subject: Sparing Estimations
Can somebody point me to good reference (or better still a website) that goes through some sparing estimations based on equipment MTBF and mission times ? Thanks in advance. Richard.


Subject: Sparing Estimations
Reply Posted by: Ned Criscimagna ( )
Organization: Reliability Analysis Center
Date Posted: Wed May 2 9:42:14 US/Eastern 2001
Found that the following methods and tools for spares determination are available and may give better results for your analysis: (1) CARE® LSA - Logistic Support Analysis (). The Mini-LSA module, one of the CARE® family members, provides the logistics engineer with analysis and planning capabilities for the project Logistics Support requirements. As part of the Integrated Logistics Support Plan (ILSP), the system maintenance engineers define the maintenance concept that is required to keep the system working. The Mini-LSA uses this definition in order to produce the maintenance reports and calculate the spare parts quantities. The Mini-LSA tool provides very simple and straightforward method to define the system maintenance concept and provide details for each one of the system assemblies. The CARE® Mini-LSA follows the guidelines of MIL-STD-1388-2, DOD Requirements for a Logistics Support Analysis Record and commercial philosophy. (2) RAM Commander - SpOpt (ALD) . SpOpt is the spare parts analysis and optimization module based on the cost and logistics criteria. RAM Commander is the world pioneering software providing everything for reliability prediction & modeling based on one of the prediction models for electronic (MIL-HDBK-217, Bellcore, British Telecom, French Telecom, ItalTel, etc.), as well as mechanical and electro-mechanical equipment . RAM Commander performs additional tasks related to reliability analysis and evaluation: Reliability Allocation, Pareto Analysis, Reliability Growth, Temperature curve, Mission Profile, RBD with Monte Carlo Simulation, Spare Parts Optimization, Maintainability Prediction, comprehensive parts libraries, user-friendly interface and easy to use Import/ Export (including to/from FMECA and FMEA). (3) SpareCost. This software was developed by ITEM Software () to calculate the spares required for equipment supported at sites and base. It optimizes scale of spares at sites for minimum cost. It appears from my browsing of ITEM’s web site that the software is no longer offered. You could contact them directly for more information. (4) NAVSHIPS 94324. This method is described in a spare parts nomograph, Maintainability Design Criteria Handbook for Designers of Shipboard Electronic Equipment, published by the US Navy. An example of using this method is given in Logistics Engineering and Management, Benjamin S. Blanchard, 2nd Edition, Prentice-Hall International Series in Industrial and Systems Engineering, Englewood Cliffs, NJ, 1981, pages 54-58. (5) RAPTOR. RAPTOR is a simulation model originally developed by the USAF Operational Test and Evaluation Center. Although the software can be downloaded () free of charge, no help or operating manuals are available. The software is now available from ARINC, an engineering consulting company that provides training on using RAPTOR. With RAPTOR, users model their systems graphically by drawing reliability block diagrams (RBDs) and answering questions about the way components fail and are repaired. By placing blocks on the screen and connecting them with links and nodes, one can easily describe the series-paralleled relationships of blocks to the entire system. The effects of varying the sparing levels on availability can be determined. (6) LCOM. LCOM is a Monte Carlo simulation model, written in SIMSCRIPT II.5, used to model the interaction of maintenance, operations and supply functions for any type of system (mechanical, electronic or weapon system). The model can and has been used to develop and analyze baseline comparison systems, perform tradeoffs and evaluations, and evaluate the interaction of Integrated Logistics Support elements. For more information, contact either: Richard Cronk Alan Wallace Phone: 513-255-8060 Phone: 513-255-8060 E-mail: E-mail:

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