Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
Wear part Currently, no binding definitions exist for the term “wear part”. Nonetheless, various terms circulate that are used and perceived similarly. Particularly, the term “spare part” is used with alike connotation. Worksheet No. 7 (2002) of the German Society for Tribology (
www.GfT-ev.de) reveals the following definitions for “wear part” under entry #116: “Part stressed by wear. Predominantly used for parts subject to wear stress”.
Every equipment, machine or system is composed of individual components or assemblies (hereinafter referred to as “part”). Each part may fail or become obsolete for various reasons, making continued operation impossible. Ideally, every worn, defective or obsolete part is replaceable. Subsequently, every part is potentially also a spare part or ultimately a “replaceable part”. As a result, any kind of functional subsystem loss leads to a loss of usability of the entire product. Conversely, this means that all subsystems causing foreseeable functional loss, regardless of the mechanism causing it, must be replaceable. Function- maintaining spare parts needing to be replaced on a regular and intended basis are frequently summarised as wear parts, regardless of their failure mechanism. However, they are not faulty or defective. Instead, they are parts to be replaced as scheduled prior to the end of the product’s useful life, if the product was used as intended. Such parts are hence considered consumables as per EU/2024/825 directive for empowering consumers for the green transition and as such materials intended for “consumption in use”, e.g. wiper blades, tyres, brake pads and brake rotors/discs.
A wear part is therefore a replaceable component (or assembly) that can be substituted with a spare
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part, that is functionally identical or has overlapping functionality, in order to maintain (in the sense of preventive maintenance) or restore the function and value of a worn-out, failure-prone, or defective product or component.
Functional losses resulting from pure wear mechanisms represent only a subset of possible wear-out pathways. Such wear-out failures are described in EN 45552:2020 as failures caused by cumulative degradation due to stress during normal use. Fatigue, material embrittlement, corrosion, degradation, oxidation, diffusion, and exposure to environmental/weather impact. are other potential mechanisms leading to failure (defects, part degeneration) or to the depletion of the intended function.
In terms of tribological functionality, also the lubricant1
constitutes a potential wear part. In machine and system manufacturing, wear parts include spare parts intended to be replacing as precautionary measure to maintain functionality (preventive maintenance), e.g.: • legally prescribed replacement intervals, • elements to be replaced periodically for safety reasons (e.g. suspension cables, chains, bearings),
• parts composed of ageing or degrading materials (e.g. hydraulic hoses).
When elaborating on maintaining functionality, a spare part often offers improvement of machine or system as a retrofit, by modernisation or tuning instead of replacing the original part 1 by 1. Instead, a more sophisticated or, after many years of operation, more advanced state-of-the-art technology is incorporated. Due to their ease of replacement, lubricants are particularly well-suited for retrofitting
The main purposes of lubricants are to reduce friction, minimize wear, and protect against adhesive failure (scuffing). Therefore, all aspects of resource and energy efficiency apply equally to lubricants. A lubricant is also a valuable source of information for observing the temporal changes over time on the wear parts it lubricates. Lubricants ensure wear protection and protection against adhesive failure (scuffing, seizure) through functional additives forming tribo-films, which in turn wear or wear out and can only be replenished from the lubricant in the tribo-contacts. At some point, additives for replenishing are no longer available resulting in a functional loss. Ultimately, the lubricant is consumed and thus “worn out” and seen as “wear part”.
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LUBE MAGAZINE NO.193 JUNE 2026
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