Wednesday, Jun 6, 2018
Product Data Sheets
A typical product data sheet (PDS) reads like a laundry list of listed specifications. While all these specifications denote something important about the product, it can be hard to distinguish between those specifications that indicate in-service performance characteristics and those that do not.
For example, some specifications merely indicate the properties of a lubricant to help determine its suitability for a given application instead of providing any context as to the performance of that lubricant in that application.
With that in mind, in this two-part series, we’ll take a closer look at key specifications on a typical PDS and explain what they mean.
In this week’s post, we start with basic specifications that clarify product characteristics – meaning they do not reflect performance:
Viscosity, cSt (ASTM D445): This denotes the kinematic viscosity, ν, of the lubricant by measuring the time for a volume of liquid to flow under gravity through a calibrated glass capillary viscometer.
Viscosity Index (ASTM D4684): This test covers the measurement of the yield stress and viscosity of engine oils after cooling at controlled rates over a period exceeding 45 h to a final test temperature between -10 and -40°C. Basically, the temperature range they can operate within.
Color (ASTM D1500): This identifies the color, which has no bearing on product performance.
NLGI Grade: Expresses a measure of the relative hardness of a grease, as specified by a standard classification determined by the National Lubricating Grease Institute (NLGI). The classification has nine grades.
Grease Thickener Type: Thickeners are particles that are partially soluble in lubricating fluid; they arrange themselves in such a way that they impart a semi-solid consistency to the grease. Some thickeners are better suited to certain applications than others, but this specification alone won’t give you that clarity.
Worked Penetration (ASTM D 217): Measures the consistency of lubricating greases by the penetration of a cone of specified dimensions, mass, and finish. The penetration is measured in tenths of a millimeter.
Dropping Point (ASTM D 2265): The dropping point measures the heat resistance of the grease.
Total Base Number (ASTM D2896): The number itself does not represent performance of new oil, it is simply a value. A higher Total Base Number (TBN) does not necessarily mean better. The test is more helpful during used oil analysis – when the TBN remains close to its original value, it tends to indicate that there is good oil life remaining.
Sulfated Ash and Phosphorous, both wt% (ASTM D874 and ASTM D4047): These tests measure the level of sulfated ash and phosphorous in new lubricating oils. Certain additives can contribute to sulfated ash or phosphorous levels. Some applications require lubricants that can meet certain sulfated ash/phosphorous thresholds.
Flash Point, ºC (ASTM D92): The flash point measures the temperature at which a lubricant will form a flammable mixture with air under controlled laboratory conditions.
Density @ 15.6ºC, g/ml (ASTM D4052): Density is a fundamental physical property of a lubricant. Many systems are designed to pump lubricants with a specific density.
Pour Point, ºC, (ASTM D 97): The pour point of a lubricant is an index of the lowest temperature that it can perform in service.
Finally, the following specifications are often misrepresented as indicators of lubricant performance. Some lubricant manufacturers will say that having higher values is better, but that is not the case. Similar to TBN, these tests are more useful when analyzing used oil to determine if the lubricant has maintained its quality and is suitable for continued service.
RPVOT, (ASTM D2272): Evaluates the oxidation stability of new and in-service turbine oils by measuring composition in the presence of water and a copper catalyst coil at 150°C.
TOST, time to 2.0 NN hours, (ASTM D943): The Oxidation Stability Test is widely used to evaluate the oxidation stability of various industrial lubricants in the presence of water.
Neutralization Number, mg/KOH g (ASTM D974): This test method determines the number of acidic or basic constituents in a lubricant.