What is an Application Parts List (APL) in Maintenance?

What is an application parts list (APL)?

An application parts list (APL) is a list of the required parts for performing a maintenance activity separate from the bill of materials (BOM). Note that the application parts list would not contain similar items to the BOM like sealants, adhesives, etc.


It’s important to realize the primary differences between an APL and a BOM because at first glance they seem very similar - after all, they are both lists of parts used in a procedure. The difference is mostly a matter of specificity and depth.

For the most part, an APL is comprised of the parts needed to perform a maintenance procedure. For example, if a technician needs to replace a bearing and looks up the documentation for that procedure, they will find a parts list (APL) attached to that procedure that tells them what they need.

This is strictly different from a BOM, which typically contain sub-assembly details, consumables, drawings, routing instructions, and a variety of other information. In some ways, a BOM is a more in-depth, overall parts list that oversees the entirety of a process or product, while an APL serves to inform a technician only of what they need to complete the task at hand. To put it another way, a BOM often contains entire assemblies that are made of multiple parts (ie. air compressor or meter), while an APL contains only individual necessary parts (ie. belt or filter).

Application parts lists can be attached to procedures in a few different ways - sometimes internal procedural manuals have them written in, though with CMMS software it’s simpler to attach necessary parts lists to PM tasks for ease of reference.

Components of an application parts list

An application parts list will contain all parts necessary to perform the maintenance task, including tools and replacements. This could be as simply as a 1-2 item list for a simple procedure like switching out a light bulb or an entire page for something more complex.

An APL will typically not contain consumables or materials for a procedure unless they are specifically necessary for the maintenance task. For instance, if a technician wants to replace a part in an adhesive piping machine, the parts list will not contain the adhesive in the machine unless the maintenance task requires replacement adhesive. The BOM, on the other hand, would contain the adhesive because it is a comprehensive list encompassing the entire assembly.

Users of an application parts list

Application parts lists are primarily used by maintenance technicians, as they are the ones replacing and repairing parts throughout a facility. They need to be able to quickly gauge what tools and parts they need to fetch in order to perform maintenance tasks efficiently.

It’s also important for maintenance planners to look at APLs, as they need to understand which parts to stock in order for technicians to perform work. If a facility’s maintenance planner doesn’t look at parts lists, the creation of an APL doesn’t matter - the technician will be unable to complete their work without the necessary parts. The maintenance planner may also be responsible for uploading parts lists into the company’s CMMS, which is vital for technicians to access on the go.

Importance of the application parts list

At this point, it may not seem immediately obvious why there are separate lists for the APL and the BOM. We might ask why technicians don’t just immediately go to the BOM when they need to figure out how to replace a part in a machine.

The scope of a BOM is much larger than an APL, which also means that the typical size of a BOM is larger. This means that the BOM for a large piece of machinery or a room-sized assembly might be tens or hundreds of pages, which could make finding the specific part very difficult for a maintenance technician, especially one who isn’t seasoned at maintaining that specific asset.

In cases like these, an APL is a life-saver - it allows the technician to quickly understand which parts are needed, retrieve the parts, and complete their work. Much like a CMMS, an application parts list is a way of making the maintenance technician’s job slightly easier so they can perform their job as effectively as possible.


APLs allow maintenance technicians to gauge at a glance the parts they need to perform a facility’s maintenance work. As important as it is to have a BOM, it’s equally important to keep (and maintain) application parts list to expedite an organization’s maintenance efforts.

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