Dear Colleagues,

Can someone please tell us about MTBF & MTTR? Does Time Over Run means the time over and above the prescribe time. and Same with the cost.

Regards,

hitesh

Dear Hitesh,

Find the details required by you :-

MTBF - It stands for MEAN TIME BETWEEN FAILURE for any equipment.This factor is calculated with the help of data of past performance. MTBF depends on quality of maintenance and quality of operations. Higher the MTBF, better it speaks for the O & M of the equipment.Good coordination between Operations and Maint is necessary to achieve highr MTBF. MTBF is normally monitored for critical and big equipments like turbines,compressors etc

MTTR - It stands for MEAN TIME TO REPAIR for any equipment. This factor is calculated with the help of past data and making a repair model based on optimun use of resources. This factor is a true reflection of quality of maintenance. Lower the MTTR, better it is. As in case of MTBF, this factor is monitored for large and crtitical eqpt.
Regarding projects, you are right. The time and cost overruns mean overshooting the originally estimated time and cost estimates.

Hope this helps ;)

MTBF is average failure statistics of any equipment / component or group of similar equipments or similar components over a given time period. When we measure MTBF for a group of similar equipments or components the formula can be written as follows

Total No. of similar equipment x 1/ failure rate i.e. (No. of failures /month)

= Total No. of similar equipments or component x month(review period)/ No. of failures

For single equipment or if the group is considered as single unit then MTBF would be 1/ failure rate. The statistical information that lies with calculated MTBF figure assume "A" months is, with the existing failure rate it would take "A" months to fail all the equipments or similar components. The MTBF figure varies with failure rate and the trend is a useful information for maintenance planning, RCFA, and criticality score analysis.There are many ways to calculate MTBF but all are avarage & directional only computed based on actual failure rate. MTBF also indicates area of concern and is a maintenance performance index too.

The conceptual difference between “mean time between failure” and “mean time between repair” is related to the effective maintenance concept and practices. The MTBF is applicable where equipment’s repair is viable on failure only, either as a practice or by design. But if through a comprehensive and effective condition monitoring exercise, the potential failure modes are detected and corrective repairs are under taken before failure, in such cases MTBR phenomenon is applicable.

Regards,

Boman