Given all of these variables and details, several organizations decided to come up with a way to characterize lubricating oils so that members of their respective organizations would have a uniform and simple way to communicate, educate and ultimately protect their interests.
The purpose of the ISO system of classifying viscosity grades is to establish a viscosity measurement method so that lubricant suppliers, equipment designers and users will have a common standardized basis for designating or selecting industrial liquid lubricants. Different approaches were thoroughly considered before the ISO Technical Committee TC23 settled on an approach that is logical and easy to use.
There were a few important criteria to keep in mind from the beginning, such as:. Using a pattern that conforms to uncertainties imposed by dimensional manufacturing tolerances. The reference temperature for the classification should be reasonably close to average industrial service experience. It should also relate closely to other selected temperatures used to define properties such as viscosity index VI , which can aid in defining a lubricant.
For the classification to be used directly in engineering design calculations in which the kinematic viscosity of the lubricant is only one of the parameters, it was necessary that the viscosity grade width range of tolerance be no more than 10 percent on either side of the nominal value. This would reflect an order of center point uncertainty in calculations similar to that imposed by dimensional manufacturing tolerances.
This limitation, coupled with the requirement that the number of viscosity grades should not be too large, led to the adoption of a system with gaps between the viscosity grades.
For petroleum-based liquids, this covers approximately the range from kerosene to cylinder oils. The 20 viscosity grades with the limits appropriate to each are listed in Table 1. The classification is based on the principle that the midpoint nominal kinematic viscosity of each grade should be approximately 50 percent greater than that of the preceding one.
The division of each decade into six equal logarithmic steps provides such a system and permits a uniform progression from decade to decade. The logarithmic series has been rounded off for the sake of simplicity. Even so, the maximum deviation for the midpoint viscosities from the logarithmic series is 2. Table 2 pulls together some popular viscosity measurement methods into one table. If the practitioner is comfortable with one particular measure but would like to see the correlating viscosity range in another measure, all he must to do is place a straight horizontal line through his chosen viscosity type and see its correlation within the other types of measures.
While it is true that some viscosity grades will be left out of the mix as companies move toward adopting the ISO designation, it is not necessary that the users of those products have to move away from them. Further, there is no intention to offer quality definition of lubricants with this scale.
But, we do need to concern ourselves with miscibility of the oils. On this score, you won't get any peace of mind from the oil companies. It's highly unlikely any oil blender will tell you that it's OK to mix its oil with a competitor's - and for good reason, too. When oils with different additive chemistry are mixed, there is always a risk of additive "drop-out".
At the very least, you should be doing a thorough oil drain, reservoir clean and filter change as part of switching oils. But unless it's practical or possible to drain every part of the hydraulic system, a small percentage of the original oil will remain and be mixed with the new oil. A Check Step Before Switching Before making the switch, it's a good idea to mix equal parts of the original and new hydraulic oil in a glass jar and shake vigorously.
Wait half an hour and observe the solution. Look for obvious changes in color, clarity, viscosity and sediment. Next, filter milliliters of the original, new and mixed oils through a patch filter - noting the time taken for each.
If nothing abnormal is observed, it should be safe to proceed. Track My Delivery. Read more about A wind of change. Language English. Toggle navigation. Start Products Base oils Base oils.
Recommended for the formulation of industrial, automotive and metal working fluids. Note that the presence of any yield stress detectable by this method constitutes a failure regardless of viscosity. This fact should be taken into consideration in any producer-consumer relationship. ISO Viscosity classification.
The ISO viscosity classification is recommended for industrial applications.
0コメント