The MRO supply chain covers the maintenance, repair and operations items a facility needs to keep running but that do not become part of the product: spare parts, tools, lubricants, safety equipment, fasteners, cleaning supplies and similar goods. MRO supply chain management aims to have the right item available when equipment needs it, without tying up excess cash in stock.
Why MRO is different from production materials
Production materials follow a bill of materials and a production plan. MRO demand is irregular and often unpredictable, because it depends on when equipment wears or fails. Many items are bought rarely, in small quantities, from a large number of suppliers. A missing part can stop a line, so the cost of a stock-out can far exceed the price of the part.
Classifying MRO items
Treating all MRO items the same wastes effort. Classification by criticality and usage helps decide how to stock and buy each one.
| Class | Description | Typical approach |
|---|---|---|
| Critical spares | Failure stops production or creates a safety risk; often long lead time | Keep on site, or hold a defined backup; consider supplier-held stock agreements |
| Routine consumables | Frequently used, low value, many suppliers | Min-max reorder rules, catalogues, vendor-managed supply |
| Slow-moving, low-risk items | Rarely used, easy to buy quickly | Do not stock; buy on demand |
| Repairable parts | Can be refurbished and returned to service | Track as rotating spares with repair loops |
Steps to manage MRO inventory
- Clean the item master. Remove duplicates, standardize descriptions and link parts to the equipment that uses them.
- Assess criticality. Ask what happens if each part is unavailable, how long a replacement takes, and whether alternatives exist.
- Set stocking rules. Decide min and max levels from usage history, lead time and criticality, and review them regularly.
- Control the storeroom. Use locations, issue records and cycle counts so stock records match what is on the shelf.
- Link to maintenance planning. Reserve parts for planned work orders so they are available when the job starts.
- Review obsolete stock. Identify parts for equipment that has been retired, and decide whether to return, sell or dispose of them.
MRO purchasing practices
- Consolidate suppliers for routine items to cut order handling.
- Use blanket orders or catalogues for repeat purchases.
- Negotiate service levels and emergency delivery for critical parts.
- Consider vendor-managed inventory or consignment for high-use consumables.
- Compare equipment manufacturer parts with approved alternatives, taking warranty and quality into account.
- Track maverick buying, where staff purchase outside agreed channels at higher cost.
Systems and analytics
MRO is usually managed in a computerized maintenance management system or an enterprise asset management module, connected to ERP purchasing. Analytics can show usage patterns, repeat failures and slow-moving stock. Machine learning applied to sensor and failure history may indicate when a part is likely to be needed, which supports predictive maintenance. Results depend on good maintenance records, and many sites need to improve data capture first.
Measures to track
- Stock-out rate for critical spares.
- Inventory value and turns for the storeroom.
- Share of obsolete or inactive items.
- Emergency purchase frequency.
- Equipment downtime linked to parts availability.
Common questions
How much MRO stock should a plant hold?
There is no standard figure. It depends on equipment criticality, supplier lead times, failure patterns and the cost of downtime compared with carrying cost.
Is MRO part of direct or indirect spend?
It is normally classed as indirect spend, since the items support operations instead of becoming part of the finished product.