Stockout
A stockout in MRO (Maintenance, Repair, Operations) occurs when a required spare part reaches zero inventory while active demand exists, forcing maintenance work to stop, be rescheduled, or completed with risky workarounds. It is a metric measuring the percentage of requests where an item is unavailable, directly impacting operational efficiency and equipment reliability.
On the shop floor, a stockout disrupts planned maintenance when a technician retrieves a work order from the CMMS (e.g., ServiceGrid) and finds the part physically missing despite system availability. This causes immediate work stoppage, shifting efforts to emergency firefighting. Teams respond by cannibalizing parts from other assets, issuing rush orders with high freight costs, or running equipment with temporary bypasses that increase failure risk. Preventive strategies include setting Min-Max inventory levels based on actual consumption and lead times, and calculating Reorder Points (ROP) using the formula: ROP = (Avg Daily Usage × Lead Time) + Safety Stock.
- Poor Inventory Tracking: Inaccurate or outdated CMMS records lead to 'phantom inventory' where the system shows stock but the part is physically missing, causing deferred critical repairs.
- Neglecting Critical Spares: Failing to stock parts for single points of failure with long lead times based solely on low usage history, resulting in catastrophic extended downtime.
- Inadequate Safety Stock: Miscalculating the Safety Stock threshold (e.g., ignoring max usage or lead time variability), leaving the storeroom vulnerable to supply chain disruptions and demand spikes.
How is the Stockout Rate calculated in a CMMS?
Stockout Rate (%) = (Number of Stockout Events / Total Part Requests) × 100.
What is the relationship between Stockouts and Inventory Accuracy?
Stockouts on critical spares are reliability failures; organizations should target ≥97% inventory accuracy to ensure CMMS data matches physical stock, preventing deferred work orders.
How does a stockout differ from general retail out-of-stock?
In maintenance, a stockout implies zero usable inventory when a work order requires the part, whereas retail allows substitutions or delayed purchases; maintenance stockouts directly drive extended downtime costs.
What is the impact of a stockout on MTBF (Mean Time Between Failures)?
Stockouts delay preventive tasks, causing assets to run longer than intended, which accelerates wear and reduces MTBF by increasing the frequency of unplanned failures.