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# Important Questions and Answers: Principles and Practices of Maintenance Planning

Mechanical - Maintenance Engineering - Principles and Practices of Maintenance Planning

1. Define maintenance?

Maintenance is the routine and recurring process of keeping a particular machine or asset in its normal operating conditions

So that it can deliver the expected performance or service without any loss or damage.

2. Define reliability?

Reliability is defined as the probability that a component /system, when operating under given condition, will perform its intended functions adequately for a specified period of time. It refers to the like hood that equipment will not fail during its operation.

3. State the benefits of reliability analysis in industries?

The main advantages of imposing reliability requirements are increased productivity and reductions in forced outage equipment due to planned maintenance activity.

4. Define failure rate?

Failure rate is the ratio of the number of failures during particular unit interval to the average population during that interval.

This failure rate is also known as hazard rate and instantaneous failure rate.

5. What is Mean Failure Rate?

The mean failure rate h is obtained by finding the mean of the failures rates for specified period of time.

h = (Z1 + Z2 + Z3+....+ZT) / T

where Zt represents

failure rates over the specified period of time T.

6. Define Mean Time to Failure.

Let t1 is the time to failure for the first specimen, t2 is the time to failure for the second specimen and t n is the time to failure

for the Nth specimen. Hence the mean time to failure for N specimens are MTTR = (t1+t2+......+t N) /N

7. What is Mean Time between Failures (MTBF)?

Mean Time between Failures (MTBF) is the mean or average time between successive failures of a product. Mean time between failures refers tom the average time of breakdown until the device is beyond repair.

8. Define Mean Time to Repair (MTTR)?

Mean Time to Repair is the arithmetic mean of the time required to perform maintenance action. MTTR is defined as the

Ratio of total maintenance time and number of maintenance action.

MTTR = Total maintenance time/ Number of maintenance action.

9.  Define Maintenance Action Rate?

Maintenance action rate is the number of maintenance action that can be carried out on equipment per hour.

10. Define Failure Density?

Failure Density is the ratio of the number of failures during a given unit interval of time to the total number of items at the very beginning of the test.

11. State the types of reliability?

Reliability can be generally of two types:

(i) Inherent Reliability: It is associated with the quality of the material and design of machine parts.

(ii) Achievable Reliability: It depends upon other factors such as maintenance and operation of the equipment.

12. Draw the equipment life cycle and name the various phases ln it?

Phase I - Failure pattern inherent in a new product because of manufacturing or design defects.

Phase II - Life period of an equipment

Phase  III -  Failures  due to  wear  out  conditions  because to  aging  of  the

equipment.

13. Define maintainability?

Maintainability is defined as the probability that a unit or system will be restored to specified working conditions within a given period when maintenance action is taken in accordance with the prescribed procedures and resources.

14. Define availability?

Availability is the ratio of the time at which equipment is available for the designated operation/service to the total time of operation and maintenance of the equipment. It is also defined as the ratio of equipments uptime to the equipment uptime and downtime over a specified period of time.

15. State the advantages of life cycle cost analysis.

(i)  Integration of engineering, economics and financial aspects lead to the way of robust metric for the selection and purchase equipment required for the industry.

(ii) Reduced operating and maintenance cost of equipments due to cost analysis over          span of  time.

(iii) It leads to the selection of proper and economically viable equipment.

16.            Draw the curve to determine the economic life of equipment?

The economic life of equipment depends on the maintenance and repair costs, availability and operational efficiency. A plot of cumulative efficiency and maintenance and repair cost per cumulative hours Vs operating hours of the equipment to find the economic life of the equipment is shown in the figure.

17.                        State the components of maintenance cost?

The maintenance cost is comprised of two factors:

(i) Fixed cost: This includes the cost of support facilities including the maintenance staff.

(ii)    Variable cost: This includes the consumption of spare parts, replacement of components and cost other facilities requirements of maintenance.

18. State the role of maintenance budget

The maintenance budget is used to set aside certain amount of money to meet the expenditures incurred in achieving the objectives of maintenance.

19. State the types of maintenance budget?

(i) Appropriation Budget: Budget used to allocate money for each activity independently.

(ii) Fixed Budget: Fixed used to allocate money for a specified period of time.

(iii)Variable Budget: Dynamic allocation of expenditure based on maintenance requirements and activities.

20. List the main factors of maintenance cost?

The maintenance cost is comprised of two factors:

(i) Fixed cost: This includes the cost of support facilities including the maintenance staff.

Variable cost: This includes the consumption of spare parts, replacement of components and cost other facilities requirements of maintenance.

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Mechanical : Maintenance Engineering : Principles and Practices of Maintenance Planning : Important Questions and Answers: Principles and Practices of Maintenance Planning |