About five years ago, Waste Management (WM) identified three major items—brakes, tires and hydraulics—as the biggest chunks of the maintenance pie with the most opportunity to help us cut maintenance costs," says Larry Horning, technical maintenance manager for truck bodies with the giant waste handler's collection-vehicle fleet. "We knew hydraulic systems were a big issue, but before a centralized cost accounting system, we wouldn't have thought they were on the same scale as tires and brakes."
They discovered WM was spending about 16 percent of its annual maintenance budget on hydraulic systems. A study of maintenance practices indicated that the most frequent reason for service calls was hose failures.
"First we upgraded our hose specification," Horning says. "We're changing from a two-wire to a supplier's four-wire hose while maintaining the same SAE bend requirements and installation dimensions. Based on our testing, we expect to increase hose life four-fold, while seeing only a 15 percent increase in hose cost."
Hydraulic cylinders have been responsible for the greatest repair costs. The WM maintenance group developed a Cylinder Exchange Program (CEP) to reduce average replacement-cylinder cost, to upgrade specifications, and to gather information on usage. Contracting with major OEM suppliers ensures that replacements match new-cylinder performance and quality.
"A CEP cylinder is equal to a new cylinder with certain defined minimum upgrades to seal packages, bearings and rod hardness," Horning says. "It carries a true warranty, not an implied warranty from a local rebuilder."
CEP also delivers critical management data. Returned cylinders are inspected and causes of failures are identified. The growing database records how long each cylinder lasts and the vehicle on which it was used. This data will allow WM to calculate typical life expectancy and compare cylinder life by supplier and location. It will help WM and its suppliers improve cylinder design and justify investments in longer life.
Fluid cleanliness is a major factor in determining the life of hydraulic components. High operating temperatures and seasonal demand for startups in extreme cold led WM to choose Castrol's Dual Range 46 (5W 20) multi-grade hydraulic oil.
"One of the big paybacks of standardized oil purchases through one supplier is a uniform fluid analysis program and single-source reporting for the entire fleet," Horning says.
Using particle counts as a guide, WM found contamination levels of ISO 23/21/19 (that's a measure of the concentration of 2-micron, 5-micron, and 15-micron particles per milliliter of fluid). In a system that flows 50 gallons per minute, that kind of contamination will push almost 7,000 pounds of dirt through a pump every year. (In contrast, oil with a cleanliness rating of ISO 14/12/9 will circulate 14 pounds of dirt.) The WM goal became a very aggressive ISO 18/15/13.
"We started to work on getting clean hydraulic systems from the moment we get our hands on the truck," Horning says. "The truck-body manufacturers had to change their production and final-inspection process to hit the target cleanliness."
It worked, and WM no longer has to change hydraulic oil in new trucks after 100 hours. It's a significant savings for a corporation that takes delivery of more than 1,200 vehicles per year.
Then WM figured out a way to share with body suppliers the responsibility for keeping oil clean.
"In effect, we said, 'Here are our filtration specs (ISO 18/15/13). You can specify the filters you wish, but you have to certify that the system will stay within our cleanliness specification for six months working in our typical operation,'" Horning says. The new preventive-maintenance program requires hydraulic oil samples at the B service (300 hours) and filter changes at six months.
Truck-body makers went to five-micron return-line filters. Some trucks also get a high-efficiency pressure-side filter. Specifications for breather filters were upgraded significantly. Hydraulic-system filler necks are sealed and quick-connect filler ports are plumbed upstream from the return filter. All new trucks come with quick-connect sampling ports.
In addition to changes to the truck hydraulic systems, Castrol also upgraded the breathers on its bulk storage tanks and WM has added a filter between the tanks and point of dispensing.
Of course, preventive maintenance remains the key to keeping hydraulic systems clean. Oil analysis measures solid and liquid contaminants in the hydraulic oil as well as its viscosity, acid number and other characteristics. Results come back within two days, and WM has established limits that dictate if the oil should be changed or fine-filtered with a filter cart. Carts are equipped with three-micron filters. Trucks that need the filter cart are flagged for more-frequent sampling—usually at the A service—to watch for repeated contamination.
Oil analysis is also the backbone of WM's extended oil-drain intervals. Hydraulic oil used to be changed every six months. Now, just 18 months into the new preventive-maintenance system, the group plans to keep hydraulic oil in service for two years in new trucks that are maintained in compliance with the PM program. If only half of WM's 25,000 trucks comply with the new maintenance program, the savings in hydraulic oil and filters alone should top $3.3 million per year.
Field experience has been encouraging. Phil Watkins, WM's area maintenance manager in Minnesota recently put 10 new trucks to work.
"They went through a nasty period where we were changing a lot of hydraulic components, working through some design problems," Watkins says. "That creates a lot of opportunity for contamination. But at the end of six months, all 10 trucks exceeded our ISO cleanliness targets. It was a major success, and we know we can do the same thing with 750 trucks in this area."
The greatest cost-saving potential lies in extended warranties WM has been able to negotiate because of the new PM program.
"If you get the oil clean, keep it clean, and monitor its condition, OEMs will stand behind their systems," Horning says. "On bodies, our warranties typically last five years, and cover most components. There are still some pumps that are covered for only three years, and hoses are at three years, but we're working on those items."
Three years ago, WM instituted a centralized warranty-tracking program and is using that information system, much like the hydraulic-cylinder exchange program, to build a database.
"Before long, we'll have more data on our component suppliers' products than our suppliers have," Horning says. "My goal is to be able to go back to our suppliers and show how components work in our applications, where theirs have weaknesses, and how to build a better mousetrap."
