Problem:
Company X is about to award a contract for an electrical switching device to Integrated Switches Corporation of Charleston, South Carolina. The switch will be used on the next version of infantry carrier vehicles. One obstacle that remains to be resolved, however, is that Company X requires a reliability of 0.995 for the device. ISC is studying its test data to determine if there is a practical way that its product can be made to meet Company X's reliability requirement. The switching device has four critical interacting component parts with the following test data:
Component Number of Parts Number of Hours Number of Failures
Part Tested of Testing
B13 400 2,500 2
X9 650 3,800 1
M22 275 1,750 0
R5 1,600 4,200 3
Requirements:
Q1. What is the present system reliability of the switch? Does the switch meet Company X's system reliability requirement?
Q2. Company X has suggested redundancy in design of the switch. Determine the reliability of the switch with each component as a candidate for redundancy. Can Company X's suggestion meet the system reliability requirement?
Q3. One of ISC's engineers has suggested to Company X that it buy ISC's switching device as it is now and use two of the devices in parallel, one as the primary device and one as a backup device. Evaluate this proposal as a means of meeting Company X's system reliability requirement.
Q4. Which alternative would you recommend for meeting Company X's system reliability requirement? Why?
Q5. Discuss the concept of component redundancy as a practical means of increasing system reliability. What are the advantages and disadvantages of this approach?