The Lousiana, USA, crane hirer and dealer bought a National ENVI 690EU boom truck, with vegetable-based hydraulic oil. “We bought it for a job in the Lousiana wetlands where you couldn’t have oil spills,” says fleet manager Dillard Winn. “These cranes don’t leak much, but it bothers these people if they do. If they leak, the Environmental Protection Agency gets the oil out of the water, digs the dirt up, puts it in hazardous waste, and brings in new dirt. It can cost thousands.”
Scott Powerline rented the crane to Georgia Power for the wetlands work, and kept it for two years before selling it on to Chico Irrigation, a company that maintains pumps for catfish farms. “It’s perfect for them—you don’t want oil getting in the water and killing the fish.” Scott keeps a new fleet and has a policy of selling on older cranes every few years.
Winn says Scott has used the vegetable oil in other cranes when the job needs it. “Some powerline companies wouldn’t let cranes get on there with regular hydraulic oil.” The company has flushed and refilled other National cranes, digger derricks and Mantis telescopic crawlers with the oil. “We wouldn’t fill it all up, but enough to work every function. You won’t get every bit out, but enough that it won’t hurt if you blow a line. The Mantis cranes can pump 90 gallons a minute if you blow a line.” He admits that rather than fixing a minor leak on the 690EU boom truck, he just bought more oil to top up the hydraulics. “We figured that it wasn’t going to hurt anything.”
Winn took oil samples from the National ENVI 690EU crane for 18 months. He says the oil, proprietary blend EL 3046 from Terresolve, worked as well as mineral oil: “We didn’t have to change any filters or hoses. It was completely compatible with all the components. It is much better to work with and around, and there is only a very mild smell. They tell you that it smells like french fries and while the biodiesel has a vegetable oil smell, it’s not so much with the EL 3046. The mechanics prefer working with the EL 3046 because they know it’s not toxic and if they get some on their hands it’s not an issue. I heard that some guys say it makes their hands softer, but they have never said it to me.”
The oil’s chemistry offers users other benefits. Cranes running EL 3046 are a bit more responsive in the cold and maintain stability in the heat, says Mark Miller, CEO of Terresolve.
The oil has a much higher viscosity index (VI) than mineral oil. VI is an arbitrary measure of the fluid’s resistance to change as the temperature changes. The higher the VI, the more resistant a fluid’s viscosity is to change, and the broader the temperature range where equipment can work. Biodegradable fluids have a VI of about 200, while petroleum fluids are about 100.
One measure of the life expectancy of a hydraulic fluid is the rotary pressure vessel oxidation test, defined in ASTM D-2272. This measures the time, in minutes, lubricants take to reach a certain level of oxidation in controlled experimental conditions: this gives an indication of the oil’s life expectancy in the real world. Standard petroleum hydraulic fluids reach the specified oxidation level in 300 minutes; EL 3046 takes almost 400 minutes, or a third longer. Still, recommended service intervals are the same as mineral oil: every 5,000 hours.
The final difference between vegetable and mineral oil is price. In mid-January, Scott Powerline was quoting a price of EL 3046 about five times that of plain AW 68, or three times Shell Telus 32 hydraulic fluid for colder areas.
“Readily biodegradable fluids just cost more”, says Miller. “They start with more expensive base fluids and utilise more expensive chemistry which will give the performance required without reducing the environmental benefits.”
