Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1275515
www . machinerylubrication.com | July - August 2020 | 35 However, by training the appropriate equipment on proper inspections; we now have the opportunity to watch the equipment in near real time. It is important to point out that during the failure mechanisms; the goal is to catch the failure as high up on the PF curve as possible. Predictive tools, when used correctly, can certainly catch a failure very high on this curve. Simple machine inspec- tions can catch them high as well, provided they are doing the inspections to a high degree of thoroughness. Simply looking at oil levels and checking for leaks will not likely result in an early catch, but likely result in a "surprise" failure if not corrected. Inspections can be thought about like using your senses to determine what is going on with your equipment. Often times when the term inspections is used, most tend to think only about visual inspections. While the majority of inspections will have a visual component to them, that is far from the only sense that should be used when ensuring equipment is functioning correctly. Your sense of smell, hearing, and touch are all just as powerful. We will breakdown inspection types by the different senses and discuss what can be deter- mined using each of them. Visual inspections Visually inspecting a piece of equipment is more than just what you see, it should also include what you don't see. As a machine oper- ates, several things in and around it will likely change that indicate potential failures or faults. We can typically lump visual inspections into two categories; internal machine inspections and external machine inspections. Both can be performed at the equipment, but some are more intrusive than others. We want to minimize the exposure of the equipment to the outside environment as much as possible so many of these inspections will require modifi- cation of the equipment. Internal Machine Inspections: • Check working surfaces – by utilizing inspection windows or during normal maintenance, the internal frictional surfaces should be inspected wear and abnormal deposits. Common surfaces that would be inspected are gears, shafts, bear- ings and equipment casings. Any showing signs of wear, varnish, scorching or any other defect should be noted and further analyzed before returning to service. • Magnetic plugs – these simple devices are great for the quick indication of ferrous debris in the systems. While they are crude, it is worth installing them on equipment, especially those that may not be included in a condition-monitoring program. e ferrous debris build-up is certainly a lagging indicator of an issue, but it can be checked and may provide insight into a problem before it turns catastrophic. • Varnish – as lubricants age and begin to breakdown they produce polar "soft" impurities that exist in a dissolved state with the oil. Once they build to the point that the oil can no longer dissolve them, they become insoluble and begin to build up on machine surfaces. Over time these polar contaminants cure into a hard lacquer-like finish that may require mechanical cleaning to remove. The varnish builds up and impairs movement of the lubricant and even of the machine parts themselves. It can also decrease the heat-transfer capabilities of the equipment. • Reservoir deposits – the inside of the reservoir should be checked periodically for any buildup of sediment on the bottom, or signs of varnish or rusting on the sides. If the oil has been impaired or grossly contaminated it is common to find a "bathtub ring" along the top side of where the fluid level normally resides. You should also be checking the fluid surface for signs of foaming, air entrainment and emulsified water. • Filter deposits – filters are like bank vaults filled with valuable information about how our machine is operating as well as how well our contamination control efforts are working. By cutting open and inspecting used filters, you will be looking at what has been flowing through the system and what the machine parts have been exposed to. You would obviously want to look for any metal debris in the filter as well as any unusual contaminants such as paint chips, fibers, or lint. Knowing what is in the filter will allow you to adjust your contamination control strategy. • Corrosion probes – a common approach to understanding if a lubricant is staying healthy or if water contamination is taking place is by utilizing a corrosion probe in contact with the oil in a system. is probe is periodically checked for signs of varnish build up or rust. Probes of different material such as steel or copper can be used to match the most common metallurgy of the equipment to provide insight into what may be happening on the machine working surfaces that are harder to inspect. External Machine Inspections • Oil level sight glasses – while most check these devices quickly just to make sure the oil is at the proper level; there is much more that you can learn by looking at them. You should be looking at the color and clarity of the fluid to see if there is any noticeable darkening of clouding associ- ated with contamination and failure of the lubricant. Also look for indications of foam or emulsions. If you have a laser pointer, shining it into the sight glass will help identify the presence of wear debris as there will be a noticeable sparkling visible. • Breather ports – most pieces of equip- ment will have a port through which air is allowed to pass. is is to keep the headspace from becoming pressurized or developing a vacuum which could impact performance and damage components such as seals. e ports themselves should be inspected for evidence of dirt build up or oil misting. Oftentimes the oil will escape the breather port and there will be a spot of dirt that is sticking to the oil wetted surface. You may notice this in areas other than the breather port such as any loose fasteners holding down a hatch. ese are good indications that your contamination control strategy likely ML