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Maintenance Standards Framework / Spare parts

Spare Parts Management in Maintenance

The right part, at the right time, without cash sitting on the shelf.

The best-planned maintenance job fails if a single critical part is missing. This guide covers how to classify parts, measure availability, optimise stock, control the budget and manage the risks.

Why spare parts matter

Spare parts are the backbone of maintenance readiness. This is one of six pillars in the Maintenance Standards Framework.

The cost of poor spare parts management is not only the value of the stock. It is the cost of lost time, emergency buying and, sometimes, damage to your reputation with customers.

Do not ask how often a part is used. Ask: what happens if it is not there when needed?

Foundations

Three building blocks every stores system needs.

Classification

Critical or not

Separate parts that stop production or create a safety risk from parts that only cause inconvenience.

Inventory types

ROP, Min/Max, JIT

  • ROP: reorder at a set stock point
  • Min/Max: keep stock between two limits
  • JIT: receive just in time for use
Supply

Lead time and supplier reliability

A part that takes 16 weeks to arrive needs a different rule from one available the same day.

Hidden tipTie spare parts to asset criticality, not only to consumption. A low-use part may be essential to a critical asset.

Smart classification

Classify parts by value and by criticality together. Many systems do only one, which leads to overstocking the wrong parts.

A: high value
B: medium value
C: low value
V: VitalStops the line or creates a safety risk
Control tightlyForecast demand, hold safety stock, consider consignment.
Hold stockAlways keep on the shelf and review often.
Always holdCheap but critical, like the O-ring below.
E: EssentialSlows production or affects quality
Order to planKeep stock low and buy against the PM plan.
Min/Max ruleSet levels from usage and lead time.
Simple Min/MaxBuy in bulk, low effort.
D: DesirableLittle effect on output
Avoid stockBuy when needed. High value, low need.
Minimal stockKeep the smallest practical amount.
Review for removalCandidates to stop stocking.
ABC: by consumption value VED: by criticality (Vital, Essential, Desirable) FSN: by movement (Fast, Slow, Non-moving)
Real exampleAn $8 O-ring sits in category C for value. If it seals a hydraulic cylinder on a mission-critical press line, it belongs in category V for criticality.
Practical insightMaintenance teams often order "just in case". Build their confidence in the system with visible, tracked data, instead of fighting the habit.

Key metrics to watch

Numbers tell the story, and they align stock availability with reliability goals. See the full KPI dictionary for how each is calculated.

Efficiency

Inventory turnover

How often inventory is used and replenished.

Availability

Stock-out rate

How often a part is not available when needed.

Service

Service level

How well internal requests are fulfilled.

Reliability

MTTR

Mean time to repair, directly affected by parts availability.

Hidden tipLook beyond annual averages. A part with zero stock-outs most of the year still counts as a failure if it was missing during a plant shutdown.
Hidden tipReview obsolete inventory quarterly. Many companies do it yearly, which locks up cash and space.

Inventory optimisation

Inventory is not about quantity. It is about purposeful holding.

Forecast

Use CMMS history

Use failure modes and work-order history to predict demand, not only past usage.

Kitting

Group parts by PM plan

Build a kit for each preventive task. It saves technician time gathering parts and avoids missed items.

Clean-up

Manage obsolete stock

Aging stock clutters the store, hides needed items and ties up budget, often for machines decommissioned years ago.

Handling obsolete parts

  1. Review every 90 days
  2. Flag parts unused for 3+ years in the CMMS
  3. Tag and quarantine
  4. Decide: scrap, sell or donate
  5. Annual physical count and review

Technology and automation

Technology helps visibility and accuracy, but only when the data behind it is right.

CMMS

Structured with BoMs

The system must hold bills of materials and be kept up to date.

Identification

Barcoding or RFID

Speeds up transactions and prevents entry errors.

Analytics

Predictive models

Flag overstocked or high-risk items before they cause a problem.

Hidden tipAutomatic reordering often fails because BoMs are out of date. Keep your parts list aligned with current asset specifications.
Practical roleAssign a "spare parts librarian" who keeps part specifications, suppliers and asset links up to date.

Cross-functional collaboration

Spare parts are not only a maintenance concern. Four groups have to work together.

MaintenanceKnows what is needed.
ProcurementKnows how to get it.
FinanceControls the budget.
OEMsKnow long lead times and technical specifications.
Success storyOne facility reduced lead time by 40% by involving suppliers in quarterly reviews. Procurement moved from a reactive role to a strategic partner.
Hidden tipNegotiate vendor-managed inventory (VMI) or consignment for slow-moving but critical parts. It moves the holding cost to the supplier.

Risk management

Four kinds of risk to plan for.

Supply chain

Single-source or overseas suppliers. Use backup suppliers and manage long lead-time items.

Operational

A breakdown that cannot be fixed because the part is missing.

Financial

Capital tied up in stock, or emergency orders at premium prices.

Disaster recovery

A plan for restoring critical equipment after a major event.

Hidden tipDocument technician knowledge. A retiring technician often knows which part replaces which, even when it is not in the CMMS. Capture it now.

Common mistakes to avoid

Three classic mistakes, and how to prevent them.

Ordering by gut feel

Stocking based on guesswork instead of data.

Poor storage

Parts stored without labels, dates or protection against damage.

Ignoring shelf life

Using expired items such as degraded rubber seals, electronics or lubricants.

Case in pointOne site had three pump failures caused by expired mechanical seals. A simple oversight with a large consequence.
Hidden tipSet shelf-life alarms in the CMMS. For example, flag grease and rubber parts after 12 to 18 months.
Hidden tipStart a parts-kitting programme for planned maintenance. It prevents last-minute shortages and speeds up work orders.

Budget discipline

Money is silently tied up in stock, or spent through last-minute emergency orders. Availability and budget have to be planned together.

Annual spare parts plan

Build it by asset or system from PM schedules, failure trends and known shutdowns.

Spend per equipment

Tag every part issued to a work order, then roll up cost by asset or department.

Three budget buckets

Split into preventive, reactive and strategic parts so priorities are clear when budgets tighten.

Approval gates

Require supervisor or manager review for off-plan purchases or any above a set threshold.

Monthly reporting

Show usage against budget in a simple dashboard for leadership.

Emergency reserve

Set aside about 5 to 10% of the budget. If it is used, review and justify it.

Hidden tipUse ABC for budget control. Focus cost reviews on A and B parts, and manage C parts by standard stocking rules. Do not spend hours approving $2 bolts while $5,000 actuators are replaced unplanned.

Try this

Pull your last 12 months of spare parts spend. Which 10 parts cost the most? Were they planned or emergency purchases? That alone can show where the budget is leaking.

Provisioning for cost control and risk

In asset-intensive industries, a budget "provision" is set aside for parts that will be needed later, which avoids sudden budget shocks.

What gets provisioned

  • Long lead-time or high-cost items (motors, turbines, circuit boards)
  • Major overhauls and shutdowns
  • Aging or obsolescent equipment
  • Parts not needed now but crucial for future readiness
Form A

Financial

Money is allocated in the budget or a reserve account to cover future purchases, especially CAPEX items and large shutdowns.

Form B

Physical

The part is bought and kept, but coded separately ("strategic stock") and not available for general use.

Hidden tipCreate a separate inventory code in the CMMS for provisioned or strategic parts. They stay visible and managed, but protected from accidental use.

Future trends

The future is digital and dynamic. These are already in use in aerospace, automotive and advanced manufacturing.

Digital twins

Condition meets stock

Match real-time asset condition with spare part needs.

AI forecasting

Learns and adjusts

Learns demand patterns and adjusts inventory levels.

3D printing

On-site production

Make rare or custom parts when needed.