Bill of Materials
A bill of materials, or BOM, is the structured list of components, spare parts, quantities, and assemblies associated with an asset or equipment system.
What this term means in maintenance
A bill of materials, or BOM, is the structured list of components, spare parts, quantities, and assemblies associated with an asset or equipment system.
Why an equipment BOM matters
An equipment bill of materials helps maintenance teams identify the correct spare part without searching through manuals, old work orders, or supplier emails.
Typical BOM information
An asset BOM may include:
- Component or spare-part code
- Manufacturer part number
- Description
- Required quantity
- Position or assembly
- Approved alternatives
- Drawing reference
- Supplier
- Criticality
- Installed and spare quantity
Practical example
A centrifugal pump BOM lists the mechanical seal, bearings, gaskets, coupling insert, impeller nut, and approved lubricant. The technician can identify the correct parts before planning the repair.
BOM and asset hierarchy
The asset hierarchy shows how equipment is organized. The BOM shows which components and spare parts belong to the equipment.
Keeping the BOM accurate
BOMs should be updated when equipment is modified, a component is replaced with a new model, or an approved alternative is introduced.
Common mistake
Copying a generic manufacturer BOM without confirming the actual installed configuration can lead to incorrect purchasing and repair delays.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Spare Parts Inventory
Spare parts inventory is the controlled stock of replacement components and consumables kept available to support equipment maintenance and reduce avoidable downtime.
Asset Register
An asset register is the controlled list of equipment, systems, and maintainable items for which an organization needs identification, ownership, maintenance, and lifecycle records.
Critical Spare
A critical spare is a replacement part whose unavailability could cause unacceptable equipment downtime, safety exposure, quality risk, or business interruption.
Bill of Materials FAQs
- What is the difference between an equipment BOM and an asset hierarchy?
The hierarchy shows equipment relationships. The BOM lists the components and spare parts associated with the equipment.
- Should a BOM include approved alternatives?
Yes, when engineering has confirmed that an alternative is technically acceptable.
- When should an equipment BOM be updated?
Update it after equipment modification, component replacement, design change, or approval of a new part.