MRO Glossary
Definitions for common Maintenance, Repair, and Operations (MRO) terminology used in industrial settings.
A
- Aftermarket
- Parts produced by companies other than the original equipment manufacturer. May offer cost savings but should meet OEM specifications for critical applications.
B
- BOM
- Bill of Materials - a comprehensive list of components, parts, and materials required to build or maintain equipment.
C
- Consumables
- Materials used up during operation or maintenance that must be regularly replenished. Includes lubricants, filters, cleaning supplies, and safety equipment.
- Criticality
- The relative importance of equipment to operations. Criticality analysis considers safety, environmental, production, and cost impacts of failure.
D
- Dynamic Load Rating
- The load a bearing can handle for one million revolutions with 90% reliability. Used to calculate bearing life for specific applications.
F
- Form-Fit-Function
- Design criteria requiring a replacement part to match the original in physical dimensions (form), mounting interface (fit), and performance characteristics (function).
I
- Interchangeability
- The ability to substitute one part for another without modifications. Interchangeable parts simplify maintenance and reduce inventory requirements.
L
- Lead Time
- The time between ordering a part and receiving it. Critical for spare parts planning and inventory management strategies.
M
- MOQ
- Minimum Order Quantity - the smallest quantity a supplier will sell. Affects inventory costs and ordering strategies for low-usage parts.
- MRO
- Maintenance, Repair, and Operations - encompasses all activities and supplies required to keep facilities and equipment operating.
- MTBF
- Mean Time Between Failures - the average time a system operates between failures. A key reliability metric used to predict equipment availability and maintenance intervals.
- MTTR
- Mean Time To Repair - the average time required to repair a failed system and restore it to operating condition. Critical for calculating equipment availability.
O
- OEM
- Original Equipment Manufacturer - the company that originally designed and manufactured the equipment. OEM parts are made by or to the specifications of the original manufacturer.
- Obsolescence
- When parts are no longer manufactured or supported. Requires strategies including lifetime buys, alternative sourcing, or equipment upgrades.
P
- Predictive Maintenance
- Condition-based maintenance using monitoring data to predict when failures will occur. Technologies include vibration analysis, thermography, and oil analysis.
- Preventive Maintenance
- Time-based or usage-based maintenance performed on a schedule to prevent failures. Includes inspections, lubrication, adjustments, and part replacements.
R
- Repairable
- Parts that can be economically restored to serviceable condition after failure. Repair-versus-replace decisions depend on cost, lead time, and criticality.
- Rotables
- Repairable components that are removed from equipment, refurbished, and returned to inventory for future use. Common for expensive assemblies.
- Run-to-Failure
- A maintenance strategy where equipment operates until it fails. Appropriate for non-critical equipment where failure consequences are minimal.
S
- Spare Parts
- Components kept in inventory to replace failed or worn parts during maintenance. Proper spares management balances availability against inventory costs.