{"id":45428,"date":"2026-06-29T14:21:06","date_gmt":"2026-06-29T08:51:06","guid":{"rendered":"https:\/\/www.verdantis.com\/?p=45428"},"modified":"2026-07-13T17:16:02","modified_gmt":"2026-07-13T11:46:02","slug":"safety-stock-for-spare-parts","status":"publish","type":"post","link":"https:\/\/www.verdantis.com\/fr\/gestion-des-pieces-de-rechange\/safety-stock-for-spare-parts\/","title":{"rendered":"Gestion des stocks de s\u00e9curit\u00e9 de pi\u00e8ces d\u00e9tach\u00e9es : un guide pratique pour 2026"},"content":{"rendered":"
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23%<\/div>
of unplanned downtime is caused by a spare part that was not on hand<\/div>
Source: CPCON<\/div><\/div>
20 to 40%<\/div>
of MRO inventory at the average facility is excess or obsolete<\/div>
Source: CPCON<\/div><\/div>
3x to 5x<\/div>
cost premium on emergency procurement versus a planned purchase<\/div>
Source: CPCON<\/div><\/div>
$125K<\/div>
median cost of a single hour of industrial downtime<\/div>
Source: ABB, 2023<\/div><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Most safety stock problems do not announce themselves as safety stock problems.<\/p>\n

They show up as a missing seal on the morning of a turnaround, a six-figure emergency air freight to get a pump back online, or a storeroom shelf full of parts for a machine that left the plant two years ago.<\/p>\n

All three trace back to one decision: how much of each part to hold, and when to reorder it. That logic gets set during ERP go-live, and in most plants nobody revisits it again.<\/p>\n

The numbers make the stakes hard to ignore. Roughly 23% of unplanned downtime<\/a> is caused by a spare part that was not available when the job started. Set that against Siemens' finding that the world's 500 largest companies lose close to $1.4 trillion a year to unplanned downtime<\/a>, about 11% of revenue, and safety stock stops being a storeroom housekeeping task. It is a working capital and uptime decision that sits on the operations leadership desk.<\/p>\n

This playbook is written for the people who own that decision: maintenance and reliability directors, supply chain VPs, and the SAP CoE leads who inherit the min-max tables everyone else is afraid to touch.<\/p><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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What spare parts safety stock actually is<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Safety stock is the buffer you carry above expected lead-time demand to absorb two separate kinds of uncertainty: how fast a part gets consumed, and how long a supplier takes to replenish it.<\/p>\n

Strip away the jargon and it answers one question. If demand runs hot or the supplier runs late while you wait for a replenishment order, how much cushion keeps the line running.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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That cushion is not the same as your reorder point, and the two get confused constantly. The reorder point is the stock level that triggers a new order. Safety stock is the portion of that level set aside purely for protection, the inventory you hope never to touch.<\/p>\n

The scope is wider than most storeroom policies treat it. Safety stock logic has to cover routine consumables that move every week, repairable rotables that cycle through the shop, slow-movers that turn once or twice a year, and the insurance spares that may sit untouched for a decade until a critical asset fails. Each behaves differently, and a single blanket rule applied across all of them is exactly how plants end up overstocked and exposed at the same time.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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What getting it wrong actually costs<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Spare parts and maintenance materials are not a rounding error in the budget. Industry analysis puts 30% to 40% of the maintenance budget<\/a> into spare parts and materials, which makes the stocking policy a direct lever on operating cost.<\/p>\n

The trap is that the cost shows up on two opposite sides of the ledger, and fixing one side tends to make the other worse.<\/p>\n

On the overstock side, carrying cost runs 20% to 30% of inventory value every year<\/a> once you add warehousing, insurance, shrinkage, obsolescence write-offs, and the opportunity cost of cash. A $40 million storeroom can quietly burn $8 million to $12 million a year just sitting there. McKinsey estimates that 10% to 40% of MRO spares in heavy industry are slow-moving<\/a> and rarely consumed.<\/p>\n

On the understock side, the math is brutal in a different way. When a critical part is missing at the moment of failure, the response is an emergency order at 3x to 5x the planned cost, plus the production loss while the asset is down. A single hour of stopped output at $125,000 dwarfs the price of almost any part on the shelf.<\/p>\n

Both failures coexist in the same plant because the safety stock policy was never tied to part-level risk. Buffers got set by category, by gut feel, or by copying whatever the last planner did.<\/p><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Failure mode<\/th>What it looks like on the floor<\/th>Where the cost lands<\/th><\/tr><\/thead>
Understock on a critical part<\/td>Asset down, no spare, emergency expedite or production hold<\/td>Downtime loss plus 3x to 5x procurement premium<\/td><\/tr>
Overstock on a slow-mover<\/td>Shelves full of parts that turn once a year or less<\/td>20% to 30% carrying cost per year on locked capital<\/td><\/tr>
Obsolete buffer<\/td>Stock held for assets that were retired or modified<\/td>Full write-off, plus storeroom space and audit effort<\/td><\/tr>
Blanket service level<\/td>Same target applied to a $5 fuse and a $90k motor<\/td>Simultaneous exposure and excess across the catalog<\/td><\/tr><\/tbody><\/table>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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\n\t\t\t\t\tWhere Are Your Buffers Wrong?<\/span>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Get a part-level read on stockout risk, excess buffer, and obsolete stock across your storeroom, and the working capital it frees.<\/p><\/span>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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