If a machine is to provide service life past its warranty stage, its designer must envision and consider all operating conditions under which the machine will operate in the field. For example, to mitigate the effects of severe and semi-severe conditions, the design must be adjusted to protect bearing surfaces from contamination by water, heat, and fine particulate matter (dust, dirt, and manufacturing debris) that are present in such environments. The dictionary defines contamination as the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, wears, or reduces the fitness of a material, physical entity, or environment. Translation: Contamination is a machine killer. And sites that operate lubricated-equipment systems can’t afford to ignore it.
If a machine has any form of replaceable/washable filter, screen, or breather as part of its fluid-management systems, i.e., lubrication systems, hydraulic systems, pneumatic -air systems, and the like, we can assume the OEM (Original Equipment Manufacturer) designer/engineer fully expects the machine and its operator/maintainers to manage associated airborne and fluid-borne contaminants. Built-in sacrificial machine-filtration elements are specifically designed to provide an inexpensive method of controlling potential contamination issues and, accordingly, protect the delicate close-tolerance machine bearing surfaces. If, though, the equipment’s reliability and availability are to be truly maximized, contamination control (CC) through machine design must be backed up with a maintenance/operations-contamination avoidance (CA) strategy, once the unit has begun operating.
CONTAMINATION CONTROL (CC)
When bearing surfaces interact, they rely on a sufficient supply of clean, contaminant-free lubricant to separate and protect their surfaces. Strategically placed filters in the lubrication system ensure any particles or moisture is extracted and trapped in its media before the lubricant can enter the lubricated zone(s) and cause surface damage. Most filters for this type of contamination control incorporate a passive surface-attractant media that restricts and captures suspended contaminants (dirt or water) as a lubricant or lubricated air flows through or across it. Depending on the working conditions, the expected contaminate particle size, and the fluid-flow rate, filter-media construction can vary from simple wire mesh gauze, to, among other things, wire wool, pleated paper, cellulose, porous metal, fiberglass, diatomaceous earth, and felt.
With grease systems, due to heavier fluid viscosity and line-delivery pressures, heavy- gauge coiled wedge wire or wire mesh filters are employed to attract large solid contaminants that may be introduced into the lines from a dirty grease-gun nozzle.
Enclosed, sealed gearboxes and reservoirs require breather devices to equalize pressure and control solid and moisture contamination. Old-style breathers constructed of wire wool can only protect against large solid contaminants that are 40 + microns in size. Such breathers are now regularly replaced with the newer styles that employ desiccant-like silica gel hydrophilic media. This type of media allows reservoirs to breathe and prevent outside airborne particulates that are 3+ microns in size from entering the reservoir. It also can wick and capture moisture from inside the reservoir, while preventing outside moisture from entering the reservoir or gearbox chamber. Remember, though, that severe water contamination in a gearbox or lube reservoir isbest detected and drained off with the use of integrated external sight gauges (tube and bullet style) that employ drain and sample ports.
In severe environments, such as those involving substantial manufacturing-process-raw-material particulate, additional workplace contamination control methods may be required. These methods can include:
♦ physical protective barriers/covers over bearing areas
♦ positive- or negative-pressured manufacturing areas with air locks and
HEPA (high efficiency particulate air) filtration
♦ positive lock-on fill systems that require no fill caps or drains
♦ closed-loop expansion-tank designs that eliminate the need for breathers.
CONTAMINATION AVOIDANCE (CA)
Once a machine is operating in the field, it is up to the maintenance and operation staff to work as a team and ensure the workplace is kept as free of contaminants as possible.
Unfortunately, although contamination avoidance is a primary strategy for reducing and eliminating premature bearing failure, it is often conspicuous in its absence from many lubrication programs.
A good contamination-avoidance program requires little to no capital outlay; fits perfectly into any PM/PdM program; involves cooperation of both operators and maintainers; is based on common sense. Contamination avoidance simply ensures that contaminants are not allowed to come into contact with a machine and its bearing-protection systems.
Effective contamination avoidance calls for a good relationship between operations and maintenance teams and a healthy respect for machines and their components. The following five points sum up the foundational elements of any contamination-avoidance initiative:
1. Good housekeeping, Order, and Cleanliness: This refers not only to the machine, but to the lubricant-storage area
andl transfer equipment. Ensuring that dirt doesn’t accumulate on machinery and equipment surfaces is Preventive Maintenance 101. It’s also the responsibility of operators and maintainers alike. Introduction of a simple 5S program
5S program will facilitate this element.
2. Lubrication Training: Understanding the consequences of failing to arrest contamination is mandatory. The use of processes and procedures will ensure consistency of effort.
3. Lubricant Storage and Transfer Engineering: The use of dedicated, color-coded, and closeable storage and transfer equipment ensures lubricants are protected from the elements and cross-contamination exposure. Use of automated systems ensures minimum lubricant exchange/fill points.
4. Condition-Based Oil Changes: Too-frequent oil/filter changes can increase exposure to contaminants; infrequent
oil/filter changes can exhaust the filtration media and lead to degradation of the lubricating fluids. Condition-checking
allows operators and maintainers to become more familiar with the machinery.
5. Lubricant Cleanliness: This element means testing all new lubricants and bulk fluids to determine fluid cleanliness
and additive-package formulation before use and verify the products have been delivered in a clean-state specification.
THE FINAL WORD
Of course, every operation is unique and will require a tailored contamination- control/avoidance strategy. This type of strategy, though, is arguably the simplest, least- inexpensive, and most effective reliability program that a company can implement. As I’ve often said and written, now is the time to update yours. Why are you waiting?TRR
ABOUT THE AUTHOR
Ken Bannister has 40+ years of experience in the RAM industry. For the past 30, he’s been a Managing Partner and Principal Asset Management Consultant with Engtech industries Inc., where he has specialized in helping clients implement best-practice asset-management programs worldwide. A founding member and past director of the Plant Engineering and Maintenance Association of Canada, he is the author of several books, including three on lubrication, one on predictive maintenance, and one on energy reduction strategies, and is currently writing one on planning and scheduling. Contact him directly at 519-469-9173 or firstname.lastname@example.org.
Tags: reliability, availability, maintenance, RAM, lubricants, lubrication, lubricant storage and transfer, contamination control