Question 1

What is asset criticality analysis?

Accepted Answer

Asset criticality analysis ranks equipment by the consequence of its failure, combining factors such as production impact, safety, and cost. It tells a plant where to concentrate reliability effort, because a small share of assets usually drives most of the downtime risk.

Question 2

What is a CMMS?

Accepted Answer

A CMMS is the software a plant uses to manage maintenance: work orders, asset histories, PM schedules, and parts. Its real value is the data it captures, which is what makes it possible to measure reactive percentage, backlog, and downtime and to find where the plant leaks money.

Question 3

What is first-time-fix rate?

Accepted Answer

First-time-fix rate is the percentage of maintenance jobs completed correctly on the first visit, without a callback or repeat work order. A high rate signals good planning, parts, and skills; a low rate is a direct measure of rework leak.

Question 4

What is a maintenance backlog?

Accepted Answer

A maintenance backlog is all identified work that has been raised but not yet completed, usually expressed in crew-weeks: the total backlog hours divided by available weekly maintenance hours. A healthy ready backlog is around 4 to 6 crew-weeks; a growing total backlog signals the plant cannot keep up.

Question 5

What is maintenance overtime percentage?

Accepted Answer

Maintenance overtime percentage is overtime hours as a share of total maintenance hours. Rising overtime alongside flat output is a classic symptom of a reactive plant, where emergency work fragments the day and pushes jobs past normal hours.

Question 6

What is mean time between failures (MTBF)?

Accepted Answer

MTBF is the average operating time between failures of a repairable asset. A higher MTBF means a more reliable asset. It is calculated by dividing total operating time by the number of failures over a period, and it is most useful as a trend on critical equipment.

Question 7

What is mean time to repair (MTTR)?

Accepted Answer

MTTR is the average time taken to restore a failed asset to working order, from the failure to the return to service. A lower MTTR means failures cost less downtime. It is calculated by dividing total repair time by the number of repairs.

Question 8

What is overall equipment effectiveness (OEE)?

Accepted Answer

OEE is a single percentage that captures how effectively equipment runs, combining availability, performance, and quality. World-class OEE is often cited around 85 percent; many plants operate in the 40 to 60 percent range, which represents large hidden capacity.

Question 9

What is PM compliance?

Accepted Answer

PM compliance is the percentage of preventive maintenance tasks completed within their due window. It measures whether the plant is keeping up with the proactive work that prevents failures. Best practice is around 90 percent or higher, often measured within a defined grace window such as plus or minus 10 percent of the interval.

Question 10

What is planned work percentage?

Accepted Answer

Planned work percentage is the share of maintenance work that is planned and scheduled before execution, with the parts, tools, and procedures ready. Best practice is around 80 to 90 percent planned. It is the mirror image of the reactive percentage.

Question 11

What is predictive maintenance?

Accepted Answer

Predictive maintenance uses condition monitoring, such as vibration, thermography, oil analysis, or sensor data, to detect developing faults and act just before failure. It aims to do the right work at the right time, rather than on a fixed calendar.

Question 12

What is preventive maintenance?

Accepted Answer

Preventive maintenance is work performed on a fixed schedule, by time or usage, to reduce the chance of failure: inspections, servicing, and component replacement before things break. Done well and on the right assets, it lowers unplanned downtime and total cost.

Question 13

What is reactive maintenance percentage?

Accepted Answer

Reactive maintenance percentage is the share of total maintenance work, usually measured in labour hours, that is unplanned and done in response to a failure rather than scheduled in advance. A healthy plant runs below about 20 to 30 percent reactive; many under-managed sites sit above 50 percent.

Question 14

What are repeat work orders?

Accepted Answer

Repeat work orders are jobs raised more than once against the same asset and failure mode within a period. They are a direct measure of rework: effort spent on problems that were treated as symptoms rather than fixed at the root cause.

Question 15

What is root cause analysis in maintenance?

Accepted Answer

Root cause analysis is a structured method for finding the underlying cause of a failure so it can be eliminated rather than repeated. In maintenance it converts recurring breakdowns into one-time fixes, which is how reactive work is permanently reduced.

Question 16

What is maintenance schedule compliance?

Accepted Answer

Schedule compliance is the percentage of scheduled maintenance work that is actually completed as planned in the period it was scheduled for. It is a core measure of whether a maintenance organisation is in control. Best practice sits around 90 percent or higher.

Question 17

What is short interval control?

Accepted Answer

Short interval control is the practice of checking performance against plan in short, frequent intervals, often hourly or per shift, so problems are caught and corrected within the day rather than discovered in a monthly report. It is the core mechanic of operating rhythm.

Question 18

What is unplanned downtime?

Accepted Answer

Unplanned downtime is production time lost to events the plant did not schedule, mainly equipment failures. It is the most expensive form of lost capacity because it combines lost output with emergency labour, expedited parts, and knock-on disruption.

Question 19

What is wrench time?

Accepted Answer

Wrench time is the proportion of a tradesperson's paid shift spent actually doing hands-on maintenance work, as opposed to waiting, travelling, finding parts, getting permits, or attending meetings. Many plants sit around 25 to 35 percent wrench time; well-planned operations reach 50 percent or more.

Industrial Maintenance and Reliability Glossary

Asset Criticality Analysis

CMMS (Computerised Maintenance Management System)

First-Time-Fix Rate

Maintenance Backlog

Maintenance Overtime Percentage

Mean Time Between Failures (MTBF)

Mean Time To Repair (MTTR)

Overall Equipment Effectiveness (OEE)

PM Compliance

Planned Work Percentage

Predictive Maintenance

Preventive Maintenance

Reactive Maintenance Percentage

Repeat Work Orders

Root Cause Analysis (RCA)

Schedule Compliance

Short Interval Control (SIC)

Unplanned Downtime

Wrench Time

See where your plant is leaking profit.