The Death of Reliability: Is it Too Late to Resurrect the Last, True Competitive Advantage?. Nathan C. Wright
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In addition to determining the correct base oil, the selection of additives will enhance, add, or suppress properties within the base, and the lubricant’s performance. The additive package is determined by the type of base oil and the application that it will be used in. An example would be engine oil with a dispersant added. The dispersant keeps insoluble matter conglomerated together so it can be captured by the filter during circulation. Additives can improve anti-wear and extreme pressure performance. It can enhance seal performance and reduce or eliminate start-up wear. Allowing the supplier to dictate such an important decision should never happen. Again, this seemingly “free” advice is costing you thousands or even tens of thousands of dollars in unreliability caused by premature failure of your lubricated assets. Educating yourself on machinery lubrication is vital to the selection of the proper lubrications, as is selecting a lubrication partner who has the same goals you have—plant reliability, not their profits.
In an application that experiences extreme temperature, from hot to cold, a viscosity index (VI) additive would be used. The molecular construction of these additives has long, organic molecules that stay together in cold conditions, but they unravel in hot environments. This allows the oil to change its viscosity and flow better when it is cold while maintaining its high-temperature properties. The main concern most organizations should have with additives is that they can be depleted, requiring the oil to be changed to restore them to required levels. This was the “old school,” or supplier-preferred approach. In reality, you can re-infuse additives without a complete oil change. Working with a lubricant partner, you can determine what portion of transfusion is required to return the additives to desired levels. The combination of in-the-field filtration, base oil, and infusion is another cost savings. Most supplier representatives are not qualified to assist you in this decision so they will focus their efforts on sales and not your performance or cost savings. This is another aspect of reliability where you can save money to fund other reliability efforts.
FRICTION
The key objective of lubrication is to reduce friction, but it has a lot of other benefits. The lubricating film helps to prevent corrosion by shielding the metal surfaces from water and other substances. It also has a role in controlling contamination within the system. It serves as a conduit to move the contaminants to the filter for removal. Another aspect of lubrication is that it aids in controlling the temperature by absorbing heat and transferring it to where it can be dissipated. Accordingly, the selection of your lubricants needs to align with your reliability strategy and is key to its success. Selecting your supplier cannot be left to purchasing agents and supply chain managers. They are not qualified to make this decision. Selling the importance of lubrication is the job of Reliability Managers, and they can only do so if they have the experience and education to communicate this at all levels of the organization. Do not entrust this solely to your supplier; educate yourself in machinery lubrication so you can instruct your suppliers and not just hope they get it right.
Lubrication has three different types: boundary, mixed, and full film. Each of these is different, and they rely on both the lubricant and the additives to protect against wear.
There are two forms of full-film lubrication: hydrodynamic and electrohydrodynamic. Hydrodynamic is when two surfaces, relative to each other, in a sliding motion, are completely (fully) separated by a fluid film. Electrohydrodynamic differs from hydrodynamic in that the surfaces, relative to each other, are in a rolling motion. An additional difference between the two is that while electrohydrodynamic has a much thinner film layer, the pressure on the film is much greater. This is called electrohydrodynamic because the film elastically deforms the rolling surface to properly lubricate it. If you want to test your supplier, ask a basic question about this and see if they can answer it.
ASPERITIES
No matter how polished or smooth the surface appears, there are always irregularities present. At a microscopic level, they jut out from the surface like peaks and valleys. The peaks and valleys are called asperities. It is the peaks of these asperities that carry the load. To achieve a full film condition, the lubricating film must be thicker than the asperities. This type of lubrication is the most desired and protects the surfaces most effectively. By filling in the peaks and valleys, you can spread the load across the entire surface area, reducing friction.
In applications where there are shock loading and frequent starts and stops, boundary lubrication is preferred. Additives like extreme pressure (EP) or anti-wear (AW) protect surfaces where a full film cannot be accomplished because of load, speed, or other factors. These additives form sacrificial layers of protection by clinging to the surfaces, preventing wear. When surfaces are contacting in such a way that only an EP or AW layer will protect them, boundary lubrication must be used. However, this is not the ideal situation because of high heat, friction, and other undesirable effects.
In applications where you need both boundary and hydrodynamic lubrication, you can employ mixed lubrication. In this application, most of the surfaces are separated by a lubricating layer but the asperities will still come in contact. Because of this, you will need to employ additives.
Only with an understanding of the process will it be easy to determine which lubricants to use. The determination is between separating the surfaces or protecting them from friction, heat, wear, and other issues. Using oils, grease, gas, or other fluids will accomplish this. Next time you change the oil in your car, understand that there is a lot more going on than meets the eye.
When making the decision to undertake any project, you must understand what constraints you have. The constraint can be displayed as a triangle. A graphical representation of this decision making is shown in Figure 2.2. One leg of the triangle is costs, the next is time, and the final one, quality. The middle of the triangle is traditionally risk. I like to look at these projects with an eye on the opportunity and not the risk. All projects have associated risk and opportunity. Your job is to look at the risk and mitigate it to the best extent possible, or to look at the opportunity and maximize it.
My recommendation to all organizations is to never compromise on quality. This is always the approach I take. If I cannot do it with the quality I set, then I will not undertake the project. For me, the decision on how to approach the project comes down to cost and time. If cost is the determining factor in your organization, then it will take more time. The reverse is also true: if you want results in a quicker time, then the costs will increase. The decision on costs and time needs to be made by looking at the opportunity. Organizations that keep their eye on the opportunity will gain a competitive advantage over their competitors.
Figure 2.2 Project Decision Making.
When determining how much the potential savings will be when you undertake a lubrication project, you can use detailed information from your computerized maintenance management system (CMMS) or other cost tracking system or industry standards. Most organizations lack the detailed information to calculate the cost of not having a strong lubrication program, so I normally use percentages I have gathered throughout my experience. If your organization does not gather this information, you will need to determine potential savings.
ROI CALCULATION
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