Maintenance Technology August 2016 - (Page 38)

LUBRICATION STRATEGIES Practical Oil Analysis: Why and What For? Simply hoping your lubricants are operating within their protective-specification limits doesn't make it so. LUBRICANTS ARE DESIGNED and chosen to perform as finite and perishable, integral components of host machines. Rarely, if ever, will a lubricant be employed in identical application and environmental conditions. Enter oil-analysis testing. Why we test The uniqueness of lubricants reflects how and when they must be tested, maintained (filtered and temperature controlled), and changed out. Stresses and influences such as load-induced shear stress, thermal degradation, various types of contamination, and wear-metal-catalyzing alter and prematurely degrade lubricant properties. Oil is made up of a base oil and an additive package that's designed to combat ambient and working environmental stresses/ influences and deliver reasonable lubricant life. Outside stresses produce an array of detrimental effects, including oxidation, polymerization, cracking hydrolysis, and evaporation that manifest as thickening or dilution of viscosity, acid buildup, and sludge. Additionally, when oil loses some of its protective ability, its host bearings can come into contact with one another and release metal-wear particles into the lubricant, which then act as a bearingattacking abrasive material (three-body abrasion). These effects and conditions are why we analyze oil. This testing is how we ensure lubricants are serviceable and bearing surfaces are protected. What we test for Oil analysis is analogous to a blood test wherein a single, properly extracted fluid sample is used for a variety of diagnostics that indicate machine and lubricant conditions. To ensure an accurate interpretation of results every time-reliable ones suitable for trending and historical analysis-samples must be collected in a consistent manner and sent to the same laboratory for testing on the same equipment. The lab will also require a virgin sample of any lubricant to be tested. This sample is used to document baseline measurements of base-oil type, additive-package levels (metals and chemicals), cleanliness level (dirt-contamination level), and viscosity and acidity. A set of initial samples detailing how and where each was taken will also be required for each machine. Good laboratories also document an operational profile for each machine tested. Based on it, they can recommend additional beneficial testing, e.g., a Karl Fischer water-contamination test for 38 | MAINTENANCE TECHNOLOGY Ken Bannister MEch Eng (UK) CMRP, MLE Contributing Editor Standard Elements Tested by Oil Analysis Element Aluminum Barium Boron Calcium Chromium Copper Iron Lead Magnesium Molybdenum Nickel Phosphorous Silicon Silver Sodium Tin Vanadium Zinc Additive Contaminant Wear Metal Coolant X X X X X X X X X X X X X X X X X X X X X X The table shows elements that are tested in a standard oil analysis. To establish a baseline, labs require a virgin sample of any lubricant to be tested. a food plant with daily machine wash downs; tests for soot and glycol in mobile equipment and generator engines; or ferrographic analysis of metal particulates to determine specifically how a bearing is failing. Basic oil analysis concentrates primarily on fluid property and fluid contamination. Fluid-property testing In analyzing fluid properties, laboratories typically look at viscosity, acidity, and additive elements-the "big three" characteristics that make oils unique-and which, through their changes in service, can tell us how to better maintain our lubricants. Viscosity. The viscosity rating of new oil is typically measured in centistokes (cSt), i.e., oil's kinematic viscosity depicting measured resistance to flow and shear by the force of gravity. As oil thickens or dilutes over time, however, its specific gravity changes, leading to errors in gravity-based tests. A more consistent measurement is achieved by checking for the absolute viscosity rating depicting oil's resistance to flow and shear through measurement of its internal friction. Because absolute viscosity is measured by multiplying kinematic viscosity by the actual specific gravity, it's an accurate, error-free trending method of choice for most laboratories. To understand which tests your lab used, note the measurement AUGUST 2016

Table of Contents for the Digital Edition of Maintenance Technology August 2016

Editorial
Uptime
On The Floor
Accepting The Challenge
Advanced Software In The Jungle
Put Efficiency in MRO Storerooms
Rethink Overall Vibration Monitoring
Reliable Pumping Supplement
Practical Oil Analysis: Why and What For?
SAP Tips and Tricks
Maximize Ethernet
Compressed Air Care
Nurture STEM Learning
Heed Drive-Belt Temps
Internet of Things
ISO 55000
Products
Showcase
Ad Index
Final Thought

Maintenance Technology August 2016