Question

Assume that an engineering system can fail due to a maintenance error caused by factors such as poor equipment design, inadequate training, poor work environment, use of deficient maintenance manuals, or inadequate work tools. Two major factors for poor equipment design are oversight or “no formal consideration of the occurrence of maintenance error”. The “no formal consideration to the occurrence of maintenance error” factor can be caused by either no requirement in design specifications or insufficient allocated funds. Two important factors for “poor work environment” are inadequate lighting and inaccessibility. Similarly, two main causes for the “use of deficient maintenance manuals” are unavailability of compatible maintenance manuals or poorly written maintenance procedures.

1. (a) With the aid of the following partially-filled fault tree in Figure below for the top event “Engineering system failed due to maintenance error”, develop and complete the tree with appropriate logic symbols and event names.

2. (b) Assume that the probability of occurrence of events Ej for j=1 to 9 is 0.02. Calculate the probability of occurrence of the top event P(T), i.e., engineering system failed due to maintenance error.

   Engineering system failed due to maintenance error Inadequate work tools Poor equipment design Poor work environment Poor training Over- sight Ez E6 Esſ Unavailability of compatible maintenance manuals Poorly written maintenance procedures E3

Answer 1

Answer: a

The fault Tree is made as per the given partial fault tree, the details of each open box is filled as below.

The information in the open boxes are filled from the information given in the question.

the gate information is same as shown in the partial fault tree in the question.

Engineering system failed due to maintenance error Poor Equipment Deign Poor Work Environment Inadequate work tools Use of Deficient Maintenance Manuals Poor Training No formal Consideration for the occurrence of maintenance error Over Sight inadequ ate lighting inacces sibility poorly written maintenance procedures. no requirement in design specifications insufficient allocated funds unavailability of compatible maintenance manuals

Answer b:

The probability of Ej (j start from 1 to 9) = 0.02

Then the probability of the Ii (I tart from 2 to 4) will be = 0.03

Thus the probability of happening of the top event P(T) will be = probability of Jj events + Ii event = 0.02 +0.03 = 0.05