How to manage spare parts for equipment
Spare parts for equipment start with which parts to stock, which models they fit, the minimum and the maximum, who signs receipt and issue, and whether a part is reserved or available. Lease or buy decides who holds the asset at the end of the term. Predictive maintenance decides when a measurement opens a work order. This page is whether the part on the shelf has a quantity and an identifier that match.
On this page
- Keep spares apart from lease-or-buy, predictive maintenance, and returns
- Name which parts to stock, and which models they fit
- The company writes the minimum and the maximum
- Give the part its own identifier, separate from the equipment
- Receipt and issue are each signed
- Reserved and available are two states
- Update the list when a part is fitted or removed
- A part is on the spare list when model, quantity, and signatures are written
Keep spares apart from lease-or-buy, predictive maintenance, and returns
Lease or buy answers who holds the asset at the end of the term and when cash leaves. Predictive maintenance answers which measurement, past a written limit, opens a maintenance work order. Return inspection answers whether a rented unit, on the way back, matches its identifier, condition, accessories, and sanitization certificate. Spares answer a different question: which parts are kept for which models, what the minimum and maximum are, who signs receipt and issue, and whether this unit is reserved for a work order or free to issue. The four records point at the same equipment identifier. Limits and thresholds stay in the maintenance note. The checks on the day of return stay in the return note. See How to do predictive maintenance for equipment, How to choose whether to lease or buy equipment, and How to inspect rented equipment on return.
How the asset, the contract, the calendar, maintenance, and the return share one identifier is in How to choose an equipment rental management system. Equipment can be bought, leased, or taken forward with development in the same project. That is the block Buy, lease, or plan it with development on the homepage. The spare list does not answer whether to lease, and it does not turn a measurement limit into a stock quantity.
Name which parts to stock, and which models they fit
Read on 27 October 2026, the opening of NIST SP 800-53 Rev. 5 gives September 2020 and includes updates as of 10 December 2020. The DOI is 10.6028/NIST.SP.800-53r5. MA-6 says to obtain maintenance support, spare parts, or both, for the organization-defined system components, within an organization-defined time period of failure. The discussion says the organization names the components whose failure raises risk to operations, assets, individuals, other organizations, or the Nation, and that obtaining maintenance support includes having the appropriate contracts in place. The control states no number of days and no quantity to keep on the shelf.
The spare list therefore starts as a list: the part name, which models it fits, which equipment identifiers those models map to, how soon after a failure the part is meant to be on hand, and who agreed that period on which day. A row with no period is not on the spare list. A sentence in a contract about arrival or supply stays in the contract. The spare list records the contract number and date. It does not turn the contract into a stock quantity. Enhancements of MA-6 separate preventive maintenance from predictive maintenance. How a measurement opens a work order is in How to do predictive maintenance for equipment. This page does not set those limits.
The company writes the minimum and the maximum
The minimum is the available quantity below which someone replenishes. The maximum is the available quantity plus reservations, which is not to be exceeded. Both numbers sit on the same row for that part and that model, with who set them, on which day, and whether the basis is the maker's recommendation, a history of issues, or the owner's decision. The basis points at a document or a record. An integer with no basis is not written into a rule that triggers replenishment.
The control does not say what the minimum must be. When the available quantity is below the minimum, a replenishment item is opened with the part identifier, the quantity available, the minimum, and who is responsible. That item is not a purchase order. The order still goes through the purchasing the company already uses, and the amount stays on the purchase document. The spare list records the purchase-document number. It does not add a price beside the shelf label. Quantity above the maximum is marked for a decision. The person who set the minimum signs whether it stays, goes back to the supplier, or moves to another model.
Give the part its own identifier, separate from the equipment
CM-8 in the same publication says to develop and document an inventory of system components that accurately reflects the system, includes the components in the system, does not double-count a component or count a component assigned to another system, is granular enough for tracking and reporting, and includes the information the organization defines for accountability. The inventory is reviewed and updated at an organization-defined frequency. The discussion says that avoiding double-counting needs a unique identifier for each component. The inventory specifications it names include date of receipt, cost, model, serial number, manufacturer, supplier, component type, and physical location.
Each part that is stocked therefore has its own identifier, separate from the equipment identifier it serves. The quantity on the shelf is recorded against the part identifier. After the part is issued or fitted, the same unit is not counted both on the shelf and on the equipment. Cost stays on the purchase document. The spare list records the document number. The physical location is the bin. A pile of parts with no identifier does not enter the available quantity. How an equipment identifier is written on the day of delivery is in What to check when equipment is delivered.
Receipt and issue are each signed
On receipt, three places are compared: the part identifier or model on the delivery note, the mark on the object, and the row on the spare list. If they do not match, the row is written "not matched" and the quantity is not added to what can be issued. When they match, the person who received the parts signs, with the quantity, the date, and the bin. If the company uses the delivery checklist for the other checks, the spare list points at that record. It does not repeat the whole delivery acceptance.
Issue is signed twice: by the person who handed the part out, and by the person who received it. Both lines record the quantity, the part identifier, the equipment identifier, the work-order number, and the time. One signature leaves the quantity on the shelf, and the work order does not say the part was received. If the recipient is away, the deputy already named on the work order signs. A spoken "I already have it", without the two signatures, does not reduce the available quantity.
Reserved and available are two states
Reserved means this unit, or this quantity, is already assigned to a work order and an equipment identifier, and someone else cannot take it. Available is the quantity on the shelf minus what is reserved. The reservation line records the work-order number, the equipment identifier, the quantity, who reserved it, and the day the reservation ends. A reservation with no work-order number does not stand, and the quantity returns to available.
If the reservation day passes and the part has not been issued, the quantity returns to available, with who released it. Moving a reserved quantity to a different work order starts with the original person releasing it, then the new work order reserving it. Both steps are signed. When available is zero, the issue cannot be signed. The work order says "none on the shelf" and whether a replenishment item has been opened. A reserved quantity is not also counted as available.
Update the list when a part is fitted or removed
An enhancement of CM-8 says to update the component inventory as part of installations, removals, and system updates. The discussion says that if the inventory is not updated at those times, it is more likely to miss the change. When a part is fitted, the spare list moves that quantity from available or reserved to fitted, with the equipment identifier and the work-order number, and the component inventory records the same day that the part is on that equipment. When it is removed, the line says it returned to a bin, was scrapped, or went for repair. One of those three is chosen, and the person who removed it signs.
The same unit in a bin and on the equipment is a double count. At the weekly check, or at the frequency the company has written under CM-8, the owner compares, for the part identifier, whether available plus reserved plus fitted equals receipts minus scrap. A difference is written on the same row and is resolved before the quantity is changed. If no frequency is written, there is no agreed day for that comparison. The list still follows the receipt and issue signatures. A cycle is not invented in place of the missing frequency.
A part is on the spare list when model, quantity, and signatures are written
If the part name, the models it fits, the minimum and maximum, the part identifier, or the bin is blank, the row is not on the spare list and a work order cannot reserve it. Quantity received without a signature is not available. Quantity issued with only one signature has not left the shelf. Quantity reserved without a work-order number is not reserved.
The time to obtain the part after a failure stays on the MA-6 line, filled in by the company and dated. The control does not supply the number of days or the number of parts. The row counts as a managed spare when three things are true: it matches a model and an equipment identifier, the minimum and maximum have a date, and the receipt and issue signatures are enough to compute what is available. While a work order is still open, quantity reserved for it stays with that work order. It does not become available only because the equipment is back on the floor.