Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1289708
30 | September - October 2020 | www . machinerylubrication.com this undesirable interaction between surfaces. ere are a multitude of noted causes that drive this unwelcome contact and they boil down to roughly four main driving forces: 1) extreme or inadequate loading, 2) elevated temperatures and pressures, 3) acceleration or deceleration in the load zone, and 4) excessive moisture present in the load zone. As mentioned above, having a sufficient lubricating film thickness and additive package in place to combat against the concerns of loading as well as a sound understanding of the maximum oper- ating temperature when selecting lubricants will aid in reducing these concerns, but as temperatures exceed the identified target range, moisture becomes notably present, and excessive loading begins to take place; one or more of these scenarios will likely rear their head and begin the adhesive wear generation process. e most common components that will be directly affected by adhesive wear are rolling element bearings, cylinders, gearboxes, pistons, and swash plates. Presence and Development Acknowledging the presence of adhesive wear in lubricating systems is key and knowing what this wear looks like as well as how it progresses can aid in minimizing concern. e overall appearance of adhesive wear will almost always vary depending on its level of severity. is severity range is commonly broken down into three specific areas: 1) normal or mild wear, 2) moderate wear, and 3) excessive or severe wear. Normal or mild adhesive wear occurs during initial, small scale wear and tear of the asperities and may be seen as polishing. is wear may appear during a break-in period of machine operation or more commonly during the initial stage of adhesive wear. is early stage wear is often not visible with the naked eye alone but is commonly noted with further inspection of the small weld tears that frequently form in a line. It is important to note an early indication of this wear pattern but continued use of the equipment is typical. Moderate adhesive wear becomes much more noticeable and often forms darkened color lines or marks on the component. Some bluing of the machine surface may also start to become apparent due to the thermal nature of the scuffing present at this stage. Additional weld tears become noticeable and often lead to metal "pull off " and some mild scuffing of the component. It is important to track and trend the development of wear at this stage and work to execute a plan in the near future Figure 1: Adhesive wear interaction between surfaces Figure 2: Examples of surface wear progression Juncture (Cold Weld) Fragment (Transfer Material) Normal Mild/Wear Moderate Wear Excessive/Extreme Wear to address this concern during equipment downtime. Excessive or severe adhe- sive wear is the most damaging stage of adhesive wear. In this stage of wear metal "pull-off " begins to become excessive and accumulate as it moves along the surface, taking on the appearance of being "smeared." is leads to more noticeable scuffing, torn surfaces, cracking and macropitting. In more severe cases, the surface layer can dislocate from the subsur- face due to high tangential friction, resulting in a material pile up or avalanching effect which further promotes the advancement of this "smeared" outcome. If excessive or severe adhesive wear is noted, there is much greater concern for equipment failure and a plan should be established to remove this equipment from service and perform a replacement as soon as feasibly possible. It is worth mentioning, like any other wear progres- sion it is imperative to identify which wear pattern is present and work to isolate and sepa- rate certain patterns from one another. Doing so will aid in driving correct root cause analysis results. Detection and Analysis Identifying the detection of each stage of adhesive wear gener- ation is imperative and there are PERSPECTIVE