In brief
Critical spare parts are parts whose absence causes plant downtime or a safety risk and which cannot be procured at short notice.
Contents
What is Critical spare parts?
Whether a part is critical is determined not by its price but by the consequences of a failure. Typical assessment criteria are the importance of the plant for production, safety and the environment, the probability of the part failing, the replenishment lead time, the number of available sources of supply and the possibility of temporarily bridging the failure. These criteria result in a criticality class.
Critical parts are subject to their own rules. They are usually kept in stock even if they are rarely consumed. These include so-called insurance spares, i.e. expensive individual parts such as gearboxes, motors or pump shafts that are only needed in the event of damage, but then immediately. In addition, storage conditions, shelf life and regular functional checks are specified.
The classification should be carried out jointly by maintenance, production and procurement and reviewed whenever plants or the supplier situation change. It is important to keep the list of critical parts up to date and to check stock regularly for condition and completeness.
In practice: maintenance and procurement
Critical parts with only one source of supply or a discontinuation notice deserve particular attention. Alternatives or stock quantities should be clarified for them before a failure occurs.
Synonyms and abbreviations: critical spares · insurance spares · strategic spares · capital spares
Frequently asked questions
How do you determine which spare parts are critical?
A common tool is an assessment matrix: one axis shows the consequences of a failure for production, safety and the environment, the other the ease of procurement, i.e. replenishment lead time and number of sources. Parts with severe failure consequences and poor availability are considered critical. The assessment is best carried out per plant, because the same part can be of differing importance in different places.
Do critical spare parts always have to be kept in your own store?
Not necessarily. Alternatives include a shared stock across several sites, a consignment stock at the user's premises or stock reserved contractually at a supplier. What matters is that the part is available quickly enough when needed. The shorter the tolerable downtime, the closer to the equipment the part should be stored.
What should be considered when storing critical spare parts?
Many parts age even on the shelf. Elastomers need cool, dark and dry storage, electronic assemblies protection against moisture and electrostatic discharge. For large motors or pumps, it is often recommended to turn the shaft by hand at intervals so that the bearings do not suffer standstill damage. Regular visual inspections and documented shelf-life data prevent unpleasant surprises at installation.