Hydraulic Systems: Avoiding an Oil Crisis

May 1, 2004
Without hydraulic power, most grading and excavation machines wouldn’t exist. Not only does hydraulic power make lifting and scooping heavy loads possible, but it also allows the heavy machines to move their own massive weight.“Hydraulics are a force multiplier and are included in just about every function on every earthmoving machine,” says Rudy Urbano, senior marketing consultant for Caterpillar Inc.’s Hydraulic Parts Products. “In addition, a hydraulic motor converts horsepower into torque, which propels the machine’s wheels or tracks.”Although the term hydraulics implies the use of water (it is from the Greek word for “water organ”), in most applications, hydraulics use oil. “There are some water and special-fluid combinations of hydraulic machines, such as those used in steel mills, for example, but most hydraulic machines usually use a special 10-weight hydraulic oil,” Urbano explains. “You need a lower-viscosity weight so the oil flows very freely; in some ambient conditions, such as very low temperatures, oil viscosity increases or thickens, increasing the resistance to flow. In some low ambient temperatures, a 5-weight oil must be used. Customers have machines working in Siberia that have a – 60°F ambient temperature.”In addition to the correct viscosity, hydraulic oil receives special ingredients that reduce hydraulic system wear. “Most hydraulic oil contains a zinc additive, which acts as an antiwear component,” Urbano goes on. “Cat oils have the highest percentage of zinc of any commercial oils. The zinc provides a barrier between the two metal pieces working to direct oil flow, such as valve bodies and control spools. The zinc does not get filtered out, but it does get depleted from the two parts in close tolerance trying to break through the film of oil. This zinc additive cannot be replenished because the zinc is added at the refining stage.”A Clean MachineA clean machine is a healthy machine, and a variety of items can contaminate hydraulic oil. Over time, moving metal parts can scrape off minute metal filings, rubber gaskets and hoses can deteriorate, and dust and other airborne particles can get into the system. Cleanliness begins at the Caterpillar factory; all of the hoses used on Cat machines are cleaned using compressed air that pushes a special type of nylon projectile like a bottlebrush through the hose assemblies before they are installed. Of course, once the machine is at the work site, dust becomes a major enemy.“All machines tend to work in dusty conditions,” Urbano says. “Some types of dust are smaller – measured in microns – which makes it easier for the dust to enter the hydraulic system. In extremely dusty conditions, the hydraulic, fuel, and engine filters may require more-frequent change intervals than the normally recommended periods.”For certain environmental conditions, Caterpillar recommends the use of protective “boots,” which cover the exposed portions of hydraulic cylinder rods. “They’re made of an industrial-grade fabric and protect the rods from falling debris. This debris can scratch the cylinder rods. Then the scratches provide the access to the hydraulic system for dirt and water contamination.”Reducing unnecessary full-engine speed reduces system wear while keeping the air cleaner. “Cat hydraulic systems operate on standby or on-demand use. This is one reason why our oil change recommendations were raised from 2,000 to 4,000 hours: because the oil isn’t flowing through the system all of the time,” Urbano explains. “In standby system mode, the oil doesn’t move until the operator asks it to perform work. Then, of course, the more oil that flows through the system, the more power the machine produces. This standby mode also reduces the engine horsepower requirement; when you’re not using the horsepower, you’re not emitting exhaust into the atmosphere. Our ACERT engine technology, combined with standby hydraulic systems, makes our machines some of the most environmentally friendly machines ever produced.”Oil and Water Don’t Mix!A working machine creates heat, and temperature can pose a problem for hydraulic systems; as the working interior is warmer than the outside ambient air, condensation can form in the hydraulic lines. “Diesel fuel has similar problems with cold temperatures. Water can get into the fuel line from heat and condensation. We get condensation in hydraulic systems, but our oil lines are generally larger – the smallest is three-eighths-inch in diameter; the largest is 2 inches – and that allows more oil to wash the water away.“Moisture is considered an oil contaminator, just like metal particles,” Urbano continues. “It breaks down the oil film and zinc protection and can cause rust buildup on metal parts. This rust becomes a small, hard, raised spot that can break through the oil film separating moving parts. If water and oil mix together under pressure and water bubbles implode, this implosion puts a ‘pothole’ between the metal surfaces the oil’s protecting. If your system has 4% moisture content, you have to change the oil. Even at less than 4%, moisture can cause problems; check the oil filter to see if moisture is present. And check the oil in the hydraulic tank. If there is water present, the oil will have a milky cream color after the machine’s hydraulic system has been operated.”Atmospheric moisture takes advantage of the slightest opportunity: “If you leave the hydraulic-tank cap off for a period of time before topping off the oil, the moisture vapor in the air is attracted to the oil and gets into the system.” Stored oil also can gather moisture contamination. “This is generally caused by temperature-related expansion and contraction in 55-gallon barrels; that’s why we recommend that oil be kept indoors and covered with a protective plastic lid.”Prevention PaysThe human factor has a big impact on the life of a machine: “Poor operation can have a very adverse effect on machine life. By the same token, a good operator is your first defense on the machine’s operation. The operator can notice changes in machine performance and handling to some degree. But with the design improvements over the past 20 years, some of the signals they used to have are gone. When our engines’ decibel levels were significantly lowered, operators thought their machines weren’t working properly because they didn’t hear the engine change during different workloads. So that became an awareness issue.”Given the high cost of overhauling hydraulic system components on machines, Caterpillar offers its customers inspection programs and recommendations on how to prevent problems before they start. “We offer customers our Site Operations Maintenance Assessment, or SOMA, which illuminates the factors that can improve a machine’s operational life,” Urbano notes. “We’ll look at the type of machines the customer uses, the environmental conditions the machines are working in and what work they’re doing, as well as the type of operator using the machine. There’s also our exclusive Custom Hydraulic Service inspections and Technical Analysis [inspections]. These are PC-based programs that can determine exactly how well a machine is performing against new machine specifications. Then specific recommendations are given to the customer to bring the machine and its hydraulic system back to like-new performance.”Ensuring that hydraulic oil remains uncontaminated is often a case of simple housekeeping. “We suggest that customers clean their machine shops daily and that they should do machine maintenance at the beginning of the shift, before dust is raised on the site,” Urbano says. “Once dust is in the air, it can travel into the machine shop from open doors and then get whisked all around the area by the fans used to keep workers cool. “Our dealers have recognized the contamination problems in hydraulic systems and component rebuilds. During a shop-operations review, [we learned that] one dealer had experienced several problems when rebuilding hydraulic components. During our review of the shop, we realized dust was coming in through the building’s 16-foot overhead doors. However, it was much too hot outside – 110°[Fahrenheit]! – to turn off the fans. Our mutual conclusion was that it was less expensive to air-condition the repair shop than it was to rework all of the hydraulic components because of dust contamination.”Caterpillar’s worldwide network of dealers is a crucial factor in maintaining a machine’s hydraulic health. “Our dealers sell both new and used machines, as well as attachments for them. They provide repair service, as well as needed advice, to Cat owners. For example, if you were moving equipment to a vastly different site – say, from the upper Midwest to Arizona – you would want to talk to your local Caterpillar dealer. They can make suggestions for operating the machines in the new environment, such as in a desert.”Urbano underscores why avoiding onsite contamination is one of the best ways to keep a hydraulic system running well: “Not only do you want to avoid breakdowns, which cost money in repairs and downtime, but also work sites can be several hundred miles from a dealer – another reason why you want to keep hydraulic systems in good working condition. Our machines are engineered to be rebuilt. However, with good maintenance, a Cat just keeps on running; we have machines out there operating that are 60 years old!”A Clean Shop for a Clean MachineMany Cat machines in the Northeast receive their health care from Southworth-Milton Inc., a Cat dealer in Milford, MA, known for its high contamination-control standards.“We’re approaching Caterpillar’s five-star level; we have a number of three- and four-star locations now,” says Southworth-Milton’s Bill Leary. “Our road to contamination control started in 1998 when we wrote a contamination control procedure and policy, which was later adopted by Caterpillar overall and sent to their other dealerships. Rudy Urbano and I had been doing inspections long before Cat’s five-star program was initiated; they used the checklist Rudy and I came up with in 1998 and ’99.“A big part of contamination control is mandatory training for support employees. And that training was for everyone – from Jack Milton, founder of the firm, to the guys on the shop floor.“We created the process of having a ‘champion’ appointed to support and promote contamination control; since the beginning, that’s been me. We needed to create awareness of the dirt you cannot see – sized 40 microns and lower – and to prevent that from contaminating hydraulic systems. To further reinforce this program, Southworth-Milton tied contamination control ratings to a Service Manager’s Compensation package; they have to increase their site’s Contamination Control Review scores, which are performed by the Caterpillar rep semiannually.”Leary explains how small changes can create big results: “For example, by covering your work and by using caps and plugs on hoses that are taken apart, you avoid contamination. We have a clean room for rebuilding pumps and motors. Components are disassembled, cleaned, and inspected before they’re taken in for reassembly. No tools that will generate particles or contaminants are used in there. The room is closed, the air coming in the room is filtered, and the room has positive pressure to keep out contaminants. After pumps are assembled, we have a separate area for testing, and we filter the fluid in the test bench to ensure that pumps are being calibrated and tested with clean oil meeting Caterpillar’s spec of ISO 16/13.”Although the Hydraulic Rebuild Clean Room and the Fuel Pump Rebuild Room are air-conditioned, the rest of the service shop isn’t. “We do keep the doors closed as much as possible and have a sweeping program to keep airborne dust down,” Leary explains. “After each job, we clean the bays and sweep and scrub the floors. We also sweep the yards on a regular basis, once per week in the summer. We’ve also put epoxy sealers on the cement floors, which keeps dust down. To further combat dust, we don’t use absorbents like Speedy Dry or kitty litter – only absorbent pads.”
After taking all of these precautions, Southworth-Milton takes more steps. “We also use the Cat hose-cleaner group for hoses and tubes, which shoots foam rubber projectiles sized to fit hoses of various sizes through the tubes. At least three projectiles are shot through the new hoses to make sure they’ve been cleaned correctly. We use this tool in the parts department for newly built hoses, in the service shop, and in our field-service trucks, which are used for repairs to hydraulic systems.”Once the components are sufficiently cleaned, Southworth-Milton workers turn their attention to the hydraulic oil itself. “Our 90-gallons-per-minute filter carts, which contain a bank of four or eight 10-micron filters, filter oil in the machine while we’re working on it. We call it a ‘kidney machine’ because it’s like a dialysis machine for oil. We measure readings on the hydraulic fluid with a portable particle counter; after measuring the contaminants, we clean the oil up to Caterpillar’s cleanliness standards of ISO 18/15. This saves the customer the expense of replacing fluid.”Much care is taken to protect stored liquids from contamination. “We also have filters on all of our bulk oil-storage tanks, both hydraulic oil and transmission oil,” Leary says. “The oil is filtered to the 10-micron level not only for the service shop but also for the trucks that go out to the field to perform preventative maintenance on our customers’ machines. As an added precaution, the lube trucks also have 10-micron filters on their discharge lines, and this is monitored on a monthly basis to ensure that the oil being put into customers’ machines meets Caterpillar’s ISO 16/13 spec.“We also monitor oil conditions in our customers machines and engines to be sure they meet Caterpillar standards,” he goes on. “We partner with another Cat dealer in Pennsylvania on an oil-analysis lab. We use our portable particle counters for shop work when immediate results are needed.“We haven’t found water to be a significant contamination problem with our oil-storage systems, but we do check fluids for water content,” Leary says. “All bulk oil containers have 2-micron filters as breathers. On some of our larger tanks, we use a dessicant breather. Our lube trucks are enclosed, insulated, and heated so tanks, pumps, and reels are kept clean and oil pumps easier.”Southworth-Milton’s dedication to cleanliness also has been preached to its customers. “We do customer training on contamination control; it’s important that our customers know the importance of contamination control and follow the same standards as we do in our shops,” Leary concludes. “They have to be aware, when they open the system up, that they are opening it to airborne dirt. Also any other containers they may be using to pour oil could be contaminated; they should use the original can and hopefully use a pump and filter arrangement when adding oil.”Clean Softly, but Carry a Big Filter“Good manufacturers adhere to good manufacturing processes, and this includes delivering clean products. We clean our hydraulic components, subassemblies, and systems during the final steps of manufacturing,” says Ed Blackford, Eaton Hydraulics’ manager of proactive maintenance and filtration. “We use oil that has been filtered to specifications that exceed customer requirements. There was a time when manufacturers sometimes produced and delivered items that were less clean than the system required. The user was expected to clean up the system at startup. Now the burden has shifted to the manufacturers. Good manufacturers produce, package, and certify hydraulic products to a cleanliness code. Customers should verify that the manufacturer adheres to a cleanliness code requirement when evaluating suppliers.”Those tiny contaminants must be filtered out using the cleanest oil possible. “If there were other particulates in the oil, that would make matters worse,” Blackford says. “The intense pressure inside a hydraulic system can turn small particulates into big problems. As a comparison, the typical home has water pressure of about 40 to 50 pounds per square inch. Many hydraulic systems run pressure of 3,000 to 6,000 pounds per square inch. At this pressure, a small particle coursing through the system will abrade, or ‘sand,’ the surface inside the system, breaking down into more particulates and creating more problems.” As is the case with other engines or vehicles, new hydraulic systems require a break-in period; overstressing the system during this time could cause damage. “It’s much like when you get a new car and you’re supposed to drive it gingerly the first 500 miles,” Blackford explains. “If anything like metal filings would shed off the new engine components, the oil system would filter them out.” Although hydraulic systems are secure and closed most of the time, contaminants still can get inside from outside sources. “While many operators believe the system is closed, operators do open the hydraulic systems to the atmosphere – for example, when changing a part, or when adding oil – and this is when many contaminants enter the system.” Most systems are continuously exposed to the atmosphere through a reservoir breather. These systems are designed to draw and return oil from and to a reservoir. The reservoir would implode if it didn’t have a vent to the atmosphere, but through this vent contamination can enter the system. “Common forms of contamination include dust and moisture. Most people in our industry use breathers or vents that are little more than mesh screens. These screens keep out large items like screwdrivers or rags but do nothing to block dust and moisture. If a customer looks at oil and thinks it looks clean, looks can be deceiving. The human eye can only see objects as small as about 40 microns, but most oil contaminants are about 5 microns. The reality is that we can’t see most of the things that will damage hydraulic systems.”Is there a solution to this problem? “More than 90% of hydraulic system failures are preventable. These problems could be remedied with adequate filtration,” Blackford states. “Some filters will reduce the number of particles in oil. Others can reduce the number of particles and take out water. The ones that take out water work like GORE-TEX fabric raincoats; they let air breathe in and out, but the water stays on the outside.”Eaton Corporation developed new filter technology and packaged in a reservoir breather product called the H2O-Gate. The H2O-Gate vent breather prevents water vapor from entering the oil reservoir while permitting air to escape, which lowers the relative humidity inside the reservoir and significantly reduces condensation.Designed to withstand the most rugged hydraulic environments, the lightweight H2O-Gate is effective down to 40°F, and it’s easily installed; it only needs to be hand-tightened onto an adapter. The internal media surface incorporates a layer of oil attractant, which coalesces any oil splashes and drains them back to the reservoir. Proprietary media within the filter not only reduce dew-point temperature, but they’re also 99.7% efficient in blocking particles 3 microns and larger.Blackford suggests that, whenever possible, operators should use gauges or indicators to signal when it’s time to change the filter. “Every operator should have a proactive maintenance program, a plan to prevent problems before they start, because, when systems fail, it costs you money. It costs more to fix a problem than to prevent it,” he says.Avoiding Wear – There’s the RubAnother way to prevent problems is by avoiding damage and wear. “On earthmoving equipment, some hydraulic hoses are on the outside of the machine,” notes Bill Dorton, vice president of sales and marketing of South Bend, IN’s Clean Seal Inc. “We make hose-protection systems to prevent abrasion, to keep hoses from rubbing together. Lots of times, hoses rub against metal, which eventually wears a hole in the hose; once the hose has gotten bad, you can’t really fix it. We have a system that protects hoses – a sleeve made of 66 nylon that goes over the hose.”In many cases, only a small portion of the hose will be vulnerable to wear. “Sometimes you’re trying only to prevent wear in an area about an inch long. Our hose protectors can be attached with nylon ties in the areas that need it most. We also offer spacers and looms, which keep hoses of the same size away from each other, locked down, keeping them from touching and wearing,” Dorton adds.Oil’s Well That Ends WellDespite the best-laid conscientious prevention plans, there’s still a chance that something might go wrong. Are there diagnostic tools or procedures that can point out potential problems? BP-Castrol Off-Road Marketing Manager Jim Burke suggests his company’s computerized oil-analysis services.“Take a hydraulic oil sample, send it to us, and we will analyze it,” Burke says. “We need to know the make and model of the unit and the amount of hours on that oil. We will measure the parts per million of metallic substances, from which data we can tell you where the system might be moving toward catastrophic failure. Particle counting is the key to sampling. Our lab counts particles of different sizes; learning that data is a better way to find out where wear is taking place.”Castrol’s computerized oil analysis doesn’t work on a one-time-only basis; a series of samples must be taken over a period of months to establish the machine’s baseline readings. “Just as when your blood shows high bad-cholesterol levels, your doctor will warn you of the possibility of a heart attack, high levels of a certain substance in your hydraulic oil can point to a problem. Let’s say we find elevated levels of copper over previous tests,” Burke explains. “Only a few items inside a hydraulic system use copper in their construction, so we’d tell you that you should check on those items. It’s certainly easier to tear down the pump, for example, and find out what’s going on rather than tear the entire system down.” Can this testing have an impact on oil changes and other maintenance? “We always recommend seeking to meet the machine’s manufacturer’s recommended drain schedules, but with our oil analysis, maybe you can extend that schedule,” Burke says. “You might say to your equipment dealer, ‘Can I go 750 hours between oil drains and not invalidate my warranty? I’m using Castrol’s samples.’ In some cases, the manufacturer might let you work with them on warranty guidelines if you send them Castrol’s reports.”Machine owners who are already Castrol customers need only ask their rep about how to have computerized oil-analysis services done on their machines. Others interested in the program can get more information at www.castrolhdl.com, or by phoning 800/777-1466 and then following the voice prompts.“Of course, we hope you’re using Castrol Blue Hydraulic Plus oil, which is dyed blue for leak detection,” Burke notes. “But anyone can purchase our computerized oil analysis, no matter what oil they use.”

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