With 50 to 60 gallons in reserve and 1,850 psi, escaping hydraulic fluid can make a real mess. Here’s how to keep it clean and safe.

By Joseph Lynn Tilton

Independent Shop Speaks Out
How Bad Is the Fluid Contamination Problem?
What’s in a Name?
Get the Whole Team Involved
Common Pump Problems
Those on the Front Line

It started so simply. The 8-yd.³ frontloading collection vehicle had picked up the Dumpster with its lift cylinders and had begun dumping the load into the hopper, just as it had done thousands of times before. The driver had barely banged the Dumpster a time or two to shake out the last little bit when a hose broke, spraying hydraulic fluid all over the building, the driveway, and the vehicle itself.

"A five-stage telescopic cylinder can average 30 to 33 gallons of fluid," notes Fred Sadock, product specialist for Hercules Hydraulics in Clearwater, FL. "You’re looking at reservoirs of 50 to 60 gallons. Add-in operational pressure of about 1,850 psi and you can really spray a big area when a hose breaks."

Sadock, who has been a product specialist for Hercules for 21 years, recalls an independent repair shop that attempted to test the operating pressure of a vehicle’s hydraulic system. The mechanic turned up the pressure to 3,000 psi—only to have the hose fail. Even worse, his hand was right over the failure point. "That hydraulic fluid blew a hole through his hand."

This specialist is quick to point out that operators and repair specialists must be sure they’re following the specs in the repair manual. "If a company is going to maximize the life of the hydraulic system as well as the fluid itself, then daily and weekly inspections are necessary. It needs to be familiar with the repair manual for the vehicle, use recommended fluids, and change filters at the recommended frequency," Sadock advises.

Users also need to take care when refilling hydraulic tanks. "A New York customer sent me some ruined urethane U-seals. They were badly damaged, severely twisted. The bottle of fluid smelled terrible." But the fluid wasn’t pure hydraulic fluid. "It turned out that the driver had filled the hydraulic tank with diesel oil. That, along with entrained air, exploded under pressure."

Some operators believe that route conditions are a major factor in the life and performance of the hydraulic system. Sadock responds, "I don’t feel hydraulics are much affected by route conditions. Sure, a route truck will perform many cycles per day, but if used properly, relief valves are set to open at a certain point to avoid overpressuring the system and initiating hose or component failure. These systems are designed to handle many thousands of cycles, to last many years."

Sadock notes that most vehicles use petroleum-based hydraulic fluids and most have antiwear and antifoaming additives. "Double-element return-line filters also help keep the fluid functioning properly."

He’s also a believer in scheduled maintenance. "Take hoses, for instance. The lining wears out and pieces of rubber become part of the hydraulic system. The fact that we sell a lot of seal kits tells you something about the need to maintain vehicles properly, to check hoses for wear." One early-wear clue is when the cylinder that’s supposed to stay up drifts down during the dump cycle.

"Remember to inspect the wiper rings. One way that contamination gets in the system is through worn-out wiper rings," Sadock points out. "The wiper is designed to exclude foreign objects, but wipers themselves can become the foreign objects."

One difference is the type of fluid used. "Some models require different seals than when used with petroleum-based oils. There has been some use of rapeseed oil and other vegetable oil, but not a lot of testing. Synthetic oils wear out faster than petroleum-based oils and don’t offer the life and lubricity that petroleum-based hydraulic fluids do."

Another factor is component wear. "The molecular structures are sheered and broken down, the fluid becomes acidic, and varnish builds," describes Sadock. He also emphasizes that few seals wear out. "Half of our business in seals is with those that haven’t had a chance to wear. Abuse, lack of attention, or contamination—especially in a vehicle without a filter—are common problems."

Sadock compliments the quality of work typical of today’s independent hydraulic shops. "That quality has grown tremendously over the years. The incentive is there because all shops rely on repeat business—and a good reputation—for staying in business. Generally speaking, those shops have made special improvements in shop cleanliness, and hydraulic repair has to be done under very clean conditions."

Independent Shop Speaks Out

One independent repair shop that includes solid waste fleets in its clientele is Clark Truck Equipment Company in Albuquerque, NM. Operations Manager Rick Tibbetts, who has 26 years’ experience in hydraulics, reports, "The problem is not in the components themselves but the wear and tear on the material around them. We do a tremendous amount of work on rearloaders, which are constantly subjected to dirt, and we have a lot of sand in this area. Sand kills hydraulics."

Tibbetts notes that vehicle downtime depends on the severity of the failure but can be from four days up to a month. "Packing blades and sweep blades take a lot of stress. We see a lot of cracks in stress areas that we have to reinforce. Fleets that inspect those areas and reinforce the crack when it first begins tend to have much less downtime. If they don’t get the crack repaired when it starts, then the blade can split apart and will have to be replaced."

Ironically, the drier environment of the Southwest, where trash haulers can last longer, leads to another problem: parts availability. "We have packers running around the Southwest that are 10 to 15 years old. Getting parts for that age of vehicle is harder than pulling teeth," Tibbetts remarks.

He emphasizes that proper system lubrication is essential to maximum hydraulic life. He sees getting maximum life as relatively simple. "Just read the book. Those people have been to college and have a degree in engineering. They know how to build hydraulic systems that will last. We get a lot of premature failures because the users didn’t grease it or didn’t maintain the vehicle. They forgot to read the instruction manual."

He recalls one municipal client who had fixed daily routes and sought a solution to overtime woes brought on by slow-moving employees. "The drivers were told when they finished their routes that they could go home for the day. They started increasing operational pressure to get a better pack and save trips to the landfill." Operators jumped the pressure from 2,200 up to 3,000 psi, which overtaxed the superstructure on the integrated frontloaders.

"We had to remove the structure and rebuild both body and superstructure," Tibbetts remembers. This took upward of three weeks and cost about $6,000 per vehicle. The client first had the shop varnish the valve with a tamperproof coating, then finally had Clark mechanics build a cage around the whole valve unit to keep the driver from changing relief-valve settings.

But a more common problem than haste has to do with leaks. "If fluid is coming out, contamination is getting in. Generally speaking, leaking hydraulics also means exterior operational surfaces are going to be wet. When you get on dirt roads with lots of sand, you’ll coat the lift cylinders with sand and wear the thing out. It’s not the fault of the manufacturer or operator, but it’s a fact of life," Tibbetts says.

One manufacturing change for the better that he has seen is the introduction of the dry valve and piston pump. "In this case, a driver with a power takeoff unit would forget to take it out of gear before moving to the next site. That increased friction would bake a pump. Now, the dry valve allows a given amount of oil to circulate to keep the pump cool. This is a case where the manufacturer has helped solve a problem involving driver error."

How Bad Is the Fluid Contamination Problem?

Contamination is a major ingredient in a hydraulic system’s failure. Tibbetts points to an article in the June 1997 issue of Machine Design. "At least 75 percent of hydraulic-system failures and maintenance actions stem from contaminated fluid," declares writer Don Norvelle, associate professor at Oklahoma State University in Stillwater, OK. Norvelle notes that part of the task is determining the type of contaminants, whether solid particles, heat, air, water, or chemicals.

According to Norvelle, solids are the most common and damaging. He continues, "These can be either hard, such as metals and dirt, or soft, such as seal materials and fibers from rags. Solids contribute to system failures classified as degradation, intermittent, and catastrophic." Norvelle points out that fluid deterioration also occurs rapidly when fluids are heated above 60°C. Heat can deteriorate seals and hoses, embrittle cellulose fiber material, weaken adhesives, and cause mechanical interference between moving parts. "Air bubbles collapsing under pressure can pit pumps, prematurely wearing them out."

Norvelle recommends biweekly in-house analysis of hydraulic fluids for particle level, comparative viscosity, quantitative acidity level and water. "About every two months, a commercial lab can make a more complete analysis that includes an [infrared] scan for additive depletion."

What’s in a Name?

An ongoing controversy with hydraulic fluid is whether to use a branded product or a private label, which frequently is priced well below its more famous counterpart. Greg Bussing, Conoco’s sales development manager for industrial lubricants, responds, "What you get in a brand, particularly in something a little different, is that most major brands are ISO 9000–certified. They have a quality program and a little bit more money invested in research and development. What you’re buying is peace of mind."

Bussing, who has been in lubricants for 10 years, reports the biggest changes he’s seen include the introduction of environmentally friendly products as well as increased cleanliness in the traditional hydraulic fluid itself. "We’re seeing more rust- and oxidation-inhibitive fluids. Their function is to keep the metal from rusting and the oil from oxidizing. This boosts the life of the oil and of the components. I’ve also seen companies come out with vegetable, biodegradable hydraulic fluids. They’re not popular here, but they’re in demand in Europe."

Proper maintenance leads to pollution-free operation of the trash-collection vehicle on this side of the Atlantic. "Ideally fleet managers have some sort of monitoring system and are pulling samples to ensure that their hydraulic fluids are doing their job, that if there is a problem, they catch it before it turns into a disaster. Pulling samples at 250, 500, 750, and 1,000 hours ensures minimum breakdown. You ensure the longevity of the components and have fewer leaks. The better you take care of your oil and equipment, the less you’re going to waste and the better off we all are," Bussing states.

He cites heat and contamination as two major issues, especially for collection vehicles. "Longevity depends on the operating environment. With trash trucks, hydraulic pressure is not a continuous environment, but pressure is part of the cycling process. The biggest thing is to keep it clean and repair any leaks immediately. Everybody sees the oil leaking out, but many don’t think of the dirt that’s getting inside the system. Dirt is really going to kill the antiwear factor of your oil."

Another factor that helps maximize hydraulic system life is the cleanliness of the oil. "When we worked with our fleet and used a cleaner, more robust hydraulic fluid, it was a little stronger in antiwear and cleaner going in. In reality, there are the ISO standards for cleanliness, including 15 microns, 5 microns, and less than 2 microns. A lot of hydraulic oils are sold at 18 to 15 microns, but when customers replace the oil with a 15 to 12, for example, they’re putting in a much cleaner product. Some have found cleaner fluids give them 50 percent longer hydraulic life. It pays to buy cleaner oils and it pays to filter," Bussing says.

When asked about vegetable oils, he responds, "Vegetable oils are not oxidative stable. They tend to form more carbon deposits and varnish. This makes valves stickier and makes the seals less elastic. If you can keep seals clean with well-maintained hydraulic oil, you’re keeping the interior environment cleaner and getting a longer operational life."

He notes that filters don’t take out varnish because that’s the oil itself breaking down. "Filters may help prolong the life of the oil before it oxidizes, but you still need to monitor the fluids. Sure, those will run $10 to $15 per sample, but if you set up a good program, you can learn the life of oil in the vehicles given your particular operating conditions. You then can determine the frequency with which you need to change hydraulic oil and reduce the number of samples you have to pull."

Get the Whole Team Involved

Successful collection companies, whether private or municipal, have both mechanics and operators involved in preventative maintenance (PM) and repair. "The key to operator care is to avoid overspeeding the hydraulic system, to listen for what is normal, and to immediately report the abnormal," says Stan Watkins, eastern district and national solid waste sales director for Muncie Power Products in Muncie, IN. The mechanic’s job is to determine the best repair for the problem. "Companies that take the time to educate both operator and mechanic have reduced finger pointing and a greater focus on prevention and repair. Besides attentive operators, we need maintenance people to walk their talk, take what they’ve been taught and shown, and apply it to good maintenance procedures."

This is especially vital in continuous-use situations. An automated sideloading residential unit will do 800-1,400 cycles a day, pumping 20-60 gal. of fluid per minute. Watkins points out, "As little as 10 years ago, average refuse-vehicle pump life was somewhere around one year. Today pump life is three to five years, a direct result of vendors, suppliers, manufacturers, and users working together to build a better piece of equipment, maintain it better, and better understand how to operate it correctly."

Common Pump Problems

Gary Whiteside, product manager for Pennzoil-Quaker State Company in Houston, TX, explains the pump is the heart of every lift truck’s hydraulic system, so it’s wise for both operator and mechanic to keep aware of pump problems. He cites Modern Materials Handling magazine, which explains that four common problems include noisy operation, high oil temperature, pump-seal leaks, and insufficient oil delivery.

Pumps are noisy when the oil level is low and dirty or the viscosity too high. Noise comes from worn internal parts, air leaks, or restrictions in the inlet line. High-temperature woes come from a low oil level, an oil-passage restriction, incorrect relief-valve settings, low oil viscosity, and air leaks or restrictions in the flow-control valve, the check valve, or the oil line. Sometimes attachment components cause a restriction during operation. "Leaking hydraulic oil commonly is a sign of a worn shaft seal, worn internal parts, or operating the pump with too low of an oil level, which causes suction on the seal." The leak also could be from a seal damaged during installation or when excessive heat has hardened and dried the lips of the seal. Failure to deliver sufficient oil may be from a low oil level, a restriction in the pump’s inlet, or air leaking into the inlet line because of loose mounting bolts or defects in the suction line. Other causes include a worn pump, pump-shaft failure, or pump bolts incorrectly torqued.

Those on the Front Line

While some cities prefer to contract-out trash collection or equipment maintenance, Phoenix, AZ, prefers in-house on both counts. "We also refurbish chassis and drive trains and install new bodies," says Jim Moody, equipment maintenance superintendent. Moody, who has been with the City of Phoenix for 27 years, reports that the city’s 5,800 pieces of mobile equipment include 114 solid waste collection vehicles. Sizes range from 18 to 33 yd. Residential vehicles average 1,200 stops a day, driving up to 200 mi. per 10-hour shift. "Heat and contamination are our two worst enemies. We’ll keep a solid waste truck seven or eight years, and it works in a lot of dust and dirt." Driver alertness and mobile mechanic response help the city minimize downtime. "We teach drivers how to recognize the start of a problem. They know, for example, if there’s a leak, slowness, or speed up in their vehicle’s hydraulic operation, they’re to call their central dispatch immediately. Phoenix is a spread-out city, but in most cases, one of our two roving mechanics can be on the site within 30 minutes." The most common problem is the need for pressure adjustments or corrections to the electronic system. Another woe is crimped hoses with an internal rupture, causing O-rings and packer-cycle valves to deteriorate. Moody reports, "We average about 10 hours a day of downtime."

Daily driver pretrip checkout is an important success factor. Driver attention helps find a wounded hydraulic pump before it disintegrates and contaminates the system—an eight-hour repair job. "The operator takes 15 to 20 minutes to check 45 to 50 items. The Solid Waste Division also has an analyst who spot-checks and verifies the operator’s findings," Moody says.

He notes that the post-trip check gives shop mechanics a chance to make repairs while the driver is off-duty. "We try to keep one or two of every part to the hydraulic systems, but with seven different makes of vehicles and five different brands of hydraulics, we can’t always replace a part overnight. Yet 90 percent of our hydraulic repairs can be made during the driver’s off time."

The city’s PM program also requires that each truck be in the shop every 1,500 mi. or 45 days for a thorough check by certified mechanics. "Preventive maintenance is the number-one key to fleet maintenance," Moody remarks. "This gives us more planned repairs and fewer unexpected repairs." He then adds that the summer before, when he was short 20 mechanics, preventive maintenance took a hit. During that time, the roving mechanics put in 20 or more hours a day.

Regular maintenance includes lube and oil changes, as well as inspecting for other possible problems. "We change the hydraulic oil and transmission fluid twice a year and flush the cooling system and differential annually."

Concerning fluids, he says, "We buy bulk from the lowest bidder. But we always take a sample to make sure the fluids we get meet the manufacturer’s specs. Unless a piece calls for a specific synthetic fluid, we use petroleum-based oils."

Another key this urban fleet manager sees is sending mechanics out for training. "They come back with new ideas. Vendors come in here, demo their products, and give classes. We’re adding filters to our systems, and vendors have demo’d them to our mechanics so they know how to maintain their particular filter systems."

So a combination of driver attention, mechanic knowledge, and components and fluids that work as well as they’re purported to help keep solid waste–vehicle hydraulics healthy and fully functioning, no matter how many cycles a day, how many miles a day, or what conditions are encountered.

MSW
January /February 2000