What is a Bill of Materials?
A Bill of Materials (BOM) is a structured record that details every material, part and component required to construct, operate or maintain an asset. A BOM captures the full scope of items tied to an equipment record or project, creating the backbone for reliable procurement,
maintenance planning and lifecycle management.
BOMs are essential because they provide a single reference point that connects engineering design with procurement and ongoing operations. When BOMs are missing or inaccurate, technicians may struggle to identify parts, procurement could create duplicates and repairs might be pushed back.
Types of BOMs
Different stages of an asset’s lifecycle require different types of BOMs. Each plays a unique role:
- Engineering BOM (EBOM): Defined by the design team, this captures the components from the engineering perspective. It reflects what the asset is intended to be, down to specifications, drawings and design revisions.
- Manufacturing BOM (MBOM): Used in fabrication or construction, this version adds the consumables, raw materials and processes needed to actually build the equipment or facility.
- Maintenance BOM (Service BOM): Developed for operations, this links spare parts and replaceable components directly to the asset. It becomes critical during repairs and preventative maintenance because it tells technicians exactly what is needed to keep equipment running.
In practice, organizations often struggle to reconcile these BOMs. For example, the design team may specify a pump model, but the maintenance team needs the exploded view of that pump along with part numbers for seals, bearings and gaskets.
Bridging these perspectives is one of the key challenges in BOM management.
Purpose of a BOM
The purpose of a BOM is to provide a common point of truth that supports both day-to-day operations and long-term planning. It exists so that:
- Engineering intent becomes actionable. The BOM translates design drawings into structured part lists that procurement and construction teams can actually use.
- Procurement avoids guesswork. With defined part numbers and quantities, supply chain teams can purchase and stock exactly what is required.
- Maintenance teams stay prepared. When an asset fails, the BOM tells technicians which spares, tools and subassemblies are tied to that equipment.
- Compliance is traceable. In regulated industries, BOMs link equipment to approved materials and documentation, making audits smoother and safer.
In short, BOMs serve as the practical foundation for how physical assets are built, maintained and sustained.
Structure of a BOM
A well-structured BOM contains more than part names. It captures attributes that allow teams to use the information consistently across systems and departments. Typical elements include:
- Part Numbers: Unique identifiers for every component.
- Descriptions: Clear names or functions of the part.
- Quantities: How many of each part are required.
- Assemblies & Subcomponents: Hierarchical relationships showing how parts fit together.
- References: Links to drawings, specifications or vendor information.
- Associations: Connections to the asset, system or location where the part is installed.
By holding this detail in a structured format, a BOM provides both granularity and context, making it a bridge between engineering data and
operational readiness.
