February 1, 2008
Contaminated fluid systems can lead to shortened component and fluid life, reduced productivity, and even catastrophic failure.
by Carmen L. Rose
Controlling contamination in oils and diesel fuel has grown in importance as aggregates operations work to increase productivity with machines that deliver more power, greater breakout forces, and faster cycle times. To meet those requirements, most machines use electro-hydraulics, higher-system pressures, and tighter clearances. As a result, modern fluid systems — hydraulics, transmissions/final drives, fuel systems, and engines — are more sensitive to contamination.
Keeping the shop clean helps keep dirt out of components during repairs.
Good contamination control
Contaminated fluid systems can lead to shortened component and fluid life, reduced productivity, and even catastrophic failure as well as the resulting costly downtime associated with unscheduled repairs. Tests prove that clean oil and fuel extends machine life and maintains machine productivity.
Instituting good contamination control procedures has proven to have positive effects for all organizations that have engaged the program.
The concepts of contamination control are simple; the real work is in the detail. Categorizing the sources of contamination lends perspective. Contamination can be built in at the factory; contained in new fluids; introduced through worn seals, pitted rods, vent ports, and incorrect maintenance practices; and generated in the machine system.
The steps that aggregate operations can take to control contamination range from the straightforward, such as good housekeeping, to the uncommon, such as particle counting. The basic procedures focus on clean facilities, clean components, clean processes, and clean fluids.
Housekeeping encompasses all that it takes to keep maintenance facilities and service vehicles clean. A clean shop means there is less dirt, dust, and grit to get into components or to be transferred into components. Cleaning floors frequently, cleaning up spills immediately, keeping workbenches free of debris, and limiting use of the floor for storage all contribute to keeping machine systems clean. Use absorbent mats to soak up fluids spills rather than using absorbent particles, which create airborne dust. Washing heavy equipment and large components thoroughly before they enter the shop helps keep dirt out.
Storing parts in their original packaging and with caps on hoses keeps dirt out.
Proper parts handling and storage goes hand in hand with good housekeeping practices. Keep components packaged until they are ready to install, and store them in clean, dry areas. Return parts to storage in their packaging. Protect components in the assembly/maintenance area, and clean components properly before assembly.
Hoses, fluids, and filters
Hydraulic hose assembly and storage require special attention. Hoses and tubes should be cleaned and capped. The hose assembly process creates contaminants. As a result, it’s recommended to clean the inside of each hose assembly with a hose cleaner, which pneumatically fires a cleaning projectile.
Covering work in progress keeps dirt out. Absorbent pads don’t generate dust as some oil absorbing products do.
Oil storage and transfer processes can introduce contaminants. Both oil and diesel fuel storage tanks should be equipped with desiccant breathers to keep dirt and water out. Barrel covers should be used to keep dirt and water from entering around the bung. Even new oil can contain thousands of microscopic particles, and oil picks up contaminants if it is stored in dirty drums or bulk tanks or transferred through dirty lines. Filter oil before it fills a machine by using a transfer filter cart. Fuel, too, should be filtered before it fills a machine’s tank. And when machines are serviced, using a filtration cart to remove contaminants from fluids has been shown to extend component life.
Remove parts from packaging just before assembly.
Change filters carefully. Oil and filter change intervals should be met. The used filter should be removed carefully at change time to ensure that contaminants do not reenter the system. The new filter should be kept in its package until it is ready to be installed.
Filling filters with oil before installation is not recommended because the process can introduce contaminants into the system. Inspect used filters for metal particles and other indicators of problems. High-efficiency filters are recommended after any system repairs have been made.
Inspections and particle counting
Exercise care in operation and maintenance. Well-trained and alert operators and service technicians are an important element in contamination control efforts. Make sure equipment is inspected daily for leaks and fixed immediately if any are found.
Using a filter cart, often called a kidney loop filtration unit, will clean up oils after repairs have contaminated reservoirs and at other times when the particle count is high.
Always keep the hydraulic tank between “full” and “add.” Insufficient fluid levels are the leading cause of pump cavitation, which can lead to pump failure and contamination of the entire system. Low fluid levels also can result in high oil temperatures, which can cause oil to degrade. Maintain oil cooler and relief valves properly. Use cylinder rod protectors when conditions warrant. Monitor system temperatures and heed warnings when operating.
A particle counter can quickly identify contaminated fluids to help guide the maintenance process and to determine the success of clean-up work.
Use particle counting to measure contamination control efforts. Particle count identifies the number of particles in a 1-milliliter sample of oil. It cannot identify specific elements or distinguish metal from non-metal, but unlike spectrographic analysis, particle counters handle a wide range of 4 microns to greater than 70 microns in size.
Covering lubricant drums helps keep rust from forming on the plugs and keeps water and dirt from getting into them when they are opened for use.
Particle counting is critical because the human eye can’t see most of the dirt that damages machine systems — and it doesn’t take very much. Only one-half teaspoon of dirt, about 160 milligrams, in a 208-liter barrel of oil pushes the contamination past the ISO standard for fill oil.
A breather containing a 4-micron filter and a desiccant to remove moisture should be used on each bulk tank.
Implementing a contamination control program is an effective way to get more from your mining machines while reducing costs. Get started with help from your equipment dealer’s contamination control specialist.
Carmen Rose is a senior consultant with the Caterpillar Marketing Product Support Division in Peoria, Ill. He initiated contamination control procedures in the East Peoria, Ill., track-type tractor manufacturing plant in the early 1990s. In 1999, he started taking those concepts to Caterpillar dealers and customers worldwide. Rose is respectfully known as the ‘Father of Contamination Control.’
Clean and cap hoses and tubes.
Equip oil and diesel fuel storage tanks with desiccant breathers to keep dirt and water out.
Use barrel covers to keep dirt and water from entering around the bung.
Inspect machines daily for leaks and fix them immediately.
Always keep the hydraulic tank level between full and add.
Use particle counting to measure contamination control efforts.
Maintain oil cooler and relief valves properly.
Use cylinder rod protectors when conditions warrant.
Monitor system temperatures and heed warnings when operating.
Train operators and service technicians in contamination control practices.
Change filters carefully. The new filter should be kept in its package until it is ready to be installed. Filling filters with oil before installation can introduce contaminants into the system.
High-efficiency filters are recommended after any system repairs have been made.