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Chapter: Mechanical : Maintenance Engineering : Repair Methods For Basic Machine Elements

Important Answers: Repair Methods For Basic Machine Elements

Mechanical - Maintenance Engineering - Repair Methods For Basic Machine Elements


1. Define the term failure.

The term failure may be defined as


1.     Any loss that interrupts the continuity of production

2.     A loss of assets availability

3.     The unavailability of equipment

4.     A deviation from the status quo

5.     Not meeting target expectations

6.     Any secondary defect.


2. What are the various possible causes for a failure?

U n e x p e c t e d and unintentional damage \ W o r k m a n s h i p


i m p r o p e r design Manufacturing defects


Incorrect usage of equipment


3. Define failure analysis?


Failure analysis is the process by which information/data about failure occurring in equipments/ systems are collected and analyzed to find the root cause of failures, and the causes are addressed to prevent recurrence of failures.


4.Name the three types of failure models? Predictable failure model Unpredictable failure model Running-In-Failure model


5. What are called age-dependent failures?

Time dependent failures are called age dependent failures


6. What are predictable failures?


In spite of all the working conditions maintained at same level, the cause of failure will be random in nature and cannot be assigned to any particular mechanism of failure. This type of failures is called Unpredictable Failures.


7.     What are Running In Failures?


Suppose if some components/ equipments are installed with unnoticed defects, may fail in a short duration after installation than during its useful life. This type of failures is Running In Failures.


8.     Define Fault tree diagrams


Fault tree diagrams are logic block diagrams that display the state of a system in terms of the states of its components.


9.     Write down the capabilities of Fault Tree Diagram.

1.     Fault tree analysis and failure modes and effects analysis,


2.     Design for reliability


3.     Design for safety



10.            Define Event tree Analysis


An event tree is a visual representation of all the events which can occur in a system. As the number of events increases, the pictures fans out like the branches of a tree


11.            What is the aim of event tree analysis?


The aim of event tree is to determine the probability of an event based on the outcomes of each event in the chronological sequence of events leading up to it. By analyzing all possible outcomes, we can determine the percentage of outcomes which lead to the desired result.


12.            Define Root cause analysis?


RCA is a step by step method that leads to the discovery of faults first or root cause. Every equipment failure happens for a number of reasons. There is a definite progression of actions and consequences that lead to a failure. An RCA investigation from the end failure is back to the root cause.


13.            Define FMEA?


FMEA is methodology for analyzing potential reliability problems early in the development cycle where it is easier to take actions to overcome the issues, thereby enhancing reliability through design.

14.            Define Risk Priority Number(RPN)


Risk priority numbers is the product of the numerical severity, occurrence and detection ratings.


RPN = (S) X (O)X(D)


15.             Name the factors based on the satisfactory performance of gears/drives. I. Proper design and manufacture of drive


II. Selection of proper type and size III. Proper installation


IV.  Proper use of service

V.    Proper maintenance of unit in it entire life.


16.            Name the factors that contribute to tooth breakage.


The common reasons for gear tooth breakage may be due to any of the following reasons



            Heavy wear




17.            list some of the inspection performed on gears

1.     Pitch error

2.     Axial and

3.     Radial run out

4.     Tooth profile etc.



18.Name some of the geometric properties that are checked for guide ways.

1. Straightness


2. Flatness

3.     Parallel both on horizontal and vertical surfaces.


19.      What are the factors influence the performance of sleeve bearings. The following are the factors that affect the bearing performance:

1. Dirt

2. Fatigue

3.     Hot Shot phenomenon and

4.     Crush problem


o       Define Crush


Normally, the bearings are manufactured so that they are slightly longer circumferentially than the mating housing. The bearing will be elastically deformed during assembly. If the amount of crush is insufficient, relative motion occurs between the bearing and its bore, which causes fretting and makes the bearing back a highly polished or pitted.



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