Seminar Reliability

RELIABILITY AND LIFE CYCLE COST

SEMINAR BY SELVA

INDTRODUCTION :

LCC is the evaluation came up as a convenient tool for reducing the production cost of operating plant.

The short term objective of the LCC analyze the performance of investment into engg product.

The long term objective is optimise profitability and survival of the enterprise.

– The important project evaluation technique basically need by management for decision making.

– First application of LCC was by U.S Department of Defence ”to combat the inability of the low bid method to accommodate and allow for the high operating cost of plant ownership”.

– The LCC forms a sound base for decision making in case of terotechnological problems.

TOTAL LIFE CYCLE COST

– Significance of LCC was felt in arriving at decision in regard to plant performance, low cost of product ,high survival rate and reliability based desigens.– Indian Standard Institution, has already

progressed in its endeavour to identify the basic factor of LCC and establish necessary draft standards for the methodology and procedure involved in LCC.

THE COST OF MAINTENANCE OVER THE LCC

• Type of maintenance • Incidents of failure• Repairable or Non Repairable system

–Normally all industrial machinery belong to repairable category, subject to large variation of load .

–A failure becomes imminent when the working loads applied exceed the strength of components comprising of the total system.

RELIABILITY ANALYSIS AND FAILURE

• In repairable system, failure follow exponential distribution.

• Replacement restores the system into original state.

FAILURE DENSITY, HAZARD RATE

• The failure density fd(t) :– Is a measure of the overall rate at which failure

occur.

• The hazard rate h(t) :– Is a measure of the instantaneous rate of failure.

BATH TUB CURVE

• Early failure region.• Random failure region. • Wear out failure region.

EARLY OR INITIAL OR RUNNING IN FAILURE REGION

• When a batch of new items just produced or assembled is placed in operation, the initial failure rate is generally somewhat higher than that encountered a short time later.

• This is due to mainly to the initial failure components owing to weaknesses or manufacturing defects like fits and tolerances, Insulation and assembly defects which are not found during inspection.

INCIDENTAL OR RANDOM FAILURE REGION

• This is the middle region in which fewer failures take place but it is difficult to determine their cause.

• In general, they seem to occur when the environmental or operational stresses exceed the design strength of the part.

• It is difficult to predict either the environmental stress or part strengths meeting upto them as deterministic function of time.

WEAR OUT FAILURE REGION

• AS a part or the equipment reaches old age, there are signs of deterioration and many failure occur.

CONCLUSION

• Since technoeconomic life indicates the most useful and economic life time of a machine, planning can be done to utilise it efficiently. This help in certain decision making in regard to repair or replace the machine.

• Reliability effort function to offset the time dependent declining reliability by increase additional cost, apart from scheduled maintenance cost, lead to refinement of the existing model of the life cycle costing.

• Hazards rate curve plotted with reference to a real life case, gives useful data in regard to application of diagnostic tool for prediction of failure and use of predictive preventive maintenance in specific zone of hazard rate curve having random failures.

• Hazards rate in the “random failure region“ ,does not remain same or steady, in real practice, but has a tendency to rise up.

• From the failure data record, it may be worthwhile to operational availability of a machine and its variation with time.

• Total life time cost requires to be minimised through varies methodologies of terotechnology and tribo analysis.

THANK U

BY SELVA.G