Guide
Spare parts management: why inventory control is not enough
Most plants manage spares as a stock problem. It is a capital-risk problem. This guide shows how to rank assets by criticality, size stock against that ranking, pool across sites and close the obsolescence gap.
Spare parts management is the discipline of holding the right part, in the right place, at the right moment — without freezing capital in a warehouse that never turns. Every maintenance organisation claims to do it. Very few can say which of their parts protect revenue and which simply protect a habit.
The gap is rarely software. It is the missing link between the asset and the money. A min/max level derived from past consumption tells you what a plant used to break. It says nothing about what a failure would cost tomorrow. That is why plants simultaneously run millions in dead stock and still lose production waiting on a part.
The fix is to invert the order of work: score assets by capital risk first, then let stock policy fall out of that score.
Criticality
Rank assets by capital risk, then stock against the rank
Indess uses the ICC-CVM model — Integrated Criticality Classification and Capital Value at Risk — to express each asset as a downtime-cost exposure rather than a colour. Four tiers drive four different stocking behaviours.
Tier 1 — Capital-critical
Failure stops the line or breaches safety and environmental limits. Downtime cost per hour exceeds the full value of the spare. Hold stock on site, even at low turns, and dual-source the part.
Tier 2 — Constrained
Failure degrades throughput or forces a workaround. Lead time, not price, is the risk. Pool across sister plants or hold a shared regional buffer instead of duplicating stock nine times.
Tier 3 — Tolerable
Redundancy or buffer stock absorbs the failure. Buy on demand, keep supplier lead times documented, and free the working capital for Tier 1 coverage.
Tier 4 — Obsolete-exposed
The asset still matters, but the OEM no longer supplies the part. Reverse-engineer and qualify a machined equivalent before the failure, not after.
Method
Six steps to a defensible spare parts strategy
Build one clean asset register
Parts management fails on data, not discipline. Consolidate the asset hierarchy, part numbers, OEM references and equivalences into a single register before you touch stock levels. Duplicate part numbers are the most common source of both stockouts and dead stock.
Score criticality in capital terms
Rank every asset by downtime cost per hour, safety and environmental exposure, redundancy, lead time and obsolescence risk. The output is not a colour-coded matrix — it is a value at risk figure per asset that a finance director recognises.
Set stock policy per tier, not per part
Min/max, reorder points and safety stock should be derived from the criticality tier and the supply lead time distribution. Setting policy part-by-part is why spreadsheets drift within two quarters.
Pool across the fleet
Multi-plant groups typically hold the same slow-moving spare in several warehouses. A pooled buffer with visibility across sites cuts total inventory while raising availability on the parts that matter.
Pre-qualify the obsolete tail
For parts the OEM has discontinued, capture drawings or scans and qualify a machining supplier ahead of failure. The cost of a qualified drawing package is a rounding error against an unplanned outage.
Measure and re-score quarterly
Track service level, stockout hours on Tier 1, inventory turns, dead-stock value and emergency-freight spend. Re-score criticality when the production plan, the asset base or the supply market changes.
Pooling
One buffer for the fleet beats nine warehouses of the same part
Parts pooling is the fastest structural saving available to a multi-plant group. When each site stocks its own insurance spare for the same drive, gearbox or valve, the group pays several times for a risk it only carries once.
Pooling works when three conditions hold: a shared part register with resolved equivalences, agreed transfer rules and lead times between sites, and a criticality score that everyone accepts. Without the third, the plant that gives up the spare always feels it lost the argument.
The practical target is to keep Tier 1 coverage local, pool Tier 2 regionally, and buy Tier 3 on demand from a qualified supplier network.
Obsolescence
The part nobody sells any more
Ageing fleets fail on availability of supply, not on stock policy. Once an OEM discontinues a component, min/max is irrelevant — there is nothing to reorder. Surplus marketplaces and on-demand machining are the two routes back to supply.
Treat obsolescence as a scored risk inside the register: for every Tier 1 and Tier 2 part, record whether an active source exists. Where it does not, produce a drawing package and qualify a machining supplier before the asset forces the issue.
Measurement
Six metrics that show the strategy is working
Tier 1 availability
Share of capital-critical parts available on demand. Target above 98%.
Stockout downtime hours
Hours of lost production directly attributable to a missing spare.
Dead-stock value
Value of parts with no movement in 36 months and no Tier 1 justification.
Emergency freight spend
Expedited logistics cost — the clearest proxy for planning failure.
Inventory turns by tier
Low turns are correct on Tier 1 and a defect on Tier 3.
Obsolescence exposure
Tier 1 and 2 parts with no active supply source identified.
Tooling
What to demand from spare parts management software
Most spare parts management software is an inventory ledger with a maintenance skin. It will tell you what you hold and what you consumed. It will not tell you what a failure costs. When evaluating tools, insist on the following.
- Criticality scoring that outputs capital risk, not just a 3x3 matrix
- Stock policy generated per tier, with lead-time variability included
- Multi-plant visibility and pooling logic across the fleet
- Obsolescence flags linked to a real sourcing and machining route
- Supplier and quoting workflow inside the same system as the register
- Audit trail on who changed a stock policy, and on what evidence
Next step
Score your fleet before you rewrite your stock levels
Indess combines the ICC-CVM criticality model with a verified supplier network, a surplus marketplace and on-demand machining — so the ranking you produce can actually be executed.