A Practical Framework for Spare Parts Criticality
- Mohammed Boualam
- Aug 27
- 3 min read
Updated: Sep 16
Every maintenance manager knows this kind of scenario: a production line stops because a $50 bearing failed, and you don't have it in stock. Meanwhile, your warehouse holds $200,000 worth of parts that haven't moved in two years. Sound familiar?
One of the main root causes is the lack of a systematic approach to defining spare parts criticality.
Why Criticality Matters
Spare parts criticality directly impacts your bottom line through:
Capital efficiency: Your inventory budget isn't infinite. Stock what matters, reduce what doesn't.
Operational reliability: Critical parts need higher availability. Non-critical ones don't deserve premium shelf space.
Resource allocation: Your procurement team can't chase every purchase order (PO) with equal intensity. They need clear priorities.
How do you currently define the criticality of spare parts?
0%Structured decision framework
0%Experience and intuition
0%No, everything is “critical.”
0%Depends on who you ask
A Decision Tree Example
The decision tree example below is simple but effective as a starting point. You can start asking the right questions in the right order:
First: Is this part on the Bill of Materials (BOM) for a critical asset? If not, it's maybe already non-critical. Move on.
Second: Would failure stop or severely degrade that asset? Not every part on a critical asset is critical itself.
Third: Do you have an approved substitute or workaround?
Fourth: Can you source it within acceptable downtime windows? Two qualified suppliers with same to next-day delivery? Different story than a single-source part with 16-week lead time.
Etc.
From Criticality to Action
Once you've classified your parts, the real work begins:
Critical parts get:
Higher safety stock levels
Multiple qualified suppliers
Expedited procurement processes
Premium storage conditions
Regular inspection cycles
Non-critical parts get:
Minimal or zero stock
Standard procurement workflows
Opportunistic ordering
Basic storage
The key is integrating this criticality into your master data. When it lives in someone's head or an Excel file on their desktop, it's useless. When it's in your ERP/CMMS, it drives daily decisions automatically.
The Inventory Optimization Connection
Here's where it gets interesting: criticality classifications translate directly into target service levels. A critical part might require a 98% service level, while a non-critical part might run at 85%.
Feed these service levels into your inventory optimization models, and suddenly you're making data-driven stocking decisions. Your working capital naturally shifts toward parts that protect production, and away from "just in case" inventory that ties up cash.
Where to start?
Implementation isn't complicated, but it requires discipline:
Start with your most important assets. Don't try to classify 50,000 SKUs on day one.
Involve the right people. Maintenance knows failure impacts. Procurement knows supply markets. Both perspectives matter.
Document your logic. When someone asks why Part X is critical, you need a better answer than "Bob said so five years ago."
Review regularly. Supply chains change. What's critical today might not be tomorrow and vice versa.
Final Thoughts
Companies that master spare parts criticality consistently achieve 10-30% inventory reductions while improving equipment availability. It's the natural result of putting stock where it matters and cutting where it doesn't.
The decision tree is just a tool. The real win comes from systematically applying business logic to inventory decisions. In today's environment of stretched budgets and supply chain volatility, that discipline separates the operations that thrive from those that merely survive.
If you want to see what proper MRO/Spare parts criticality classification could save you. Our Flash Diagnostic delivers real numbers in just 2 weeks. Contact us to get started.
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