For diesel engine users, temperature control is a bigger concern than ever as engine makers wrestle with meeting Tier 3 and 4 emissions requirements. While electric fans, clutches, or variable pitch blading can do the job, hydraulic motors are stepping in more often to handle it. Using sophisticated controllers that provide temperature control within a narrow range, hydraulics are cooling diesels and using fewer watts in the process. Here is a look at a few applications of these hydraulic fan systems.
Mobile blasthole driller
A 565 hp Caterpillar six-cylinder diesel powers this big rig, both in transit and at the drill site. Parker Hannifin supplies a piston pump, hydraulic motor, and a DFC-2 fan drive controller. Reichdrill says the hydraulic fan drive has helped reduce overall fan power use by some 40 percent, which, on some of the company's largest rigs can be as much as 70 hp. The hydraulic motor can run the fan at a speed independent of engine rpm and takes temperature data from engine coolant and an air compressor discharge sensor. Parker uses cast iron in its hydraulic fan motors, not aluminum, based on the material's ability to better stand the high temperatures and pressure of today's diesel engine cooling systems. For a brochure on Parker Hannifin fan drive systems, visit http://rbi.ims.ca/4398-520.
The Eaton electro-hydraulic fan drive systems are designed for rear engine bus and recreational vehicles, mobile construction equipment, and agricultural machines. The systems use a variable displacement piston pump, a hydraulic motor, and an optional two channel amplifier which can accept analog and digital inputs. The simplest system dispenses with the two channel amp, and relies on the engine control module to direct a proportional valve on the pump. For engines without ECMs, a two channel amp can be configured to manage a number of operating conditions, such as running with or without air conditioning. A third system uses the two channel amp in consort with the engine control module to provide a fail-safe mode and the ability to communicate with sensors that reside outside the ECM loop. For a brochure describing Eaton hydraulic fan systems, visit http://rbi.ims.ca/4398-521.
Hydrostatic fan drives have been around for a least a decade, according to Don Fisher, director of gear products for the Bosch Rexroth mobile division. But pending government regulation of emissions for heavy construction vehicles has diesel engine makers and mobile equipment OEMs looking at them anew. In Europe, where fuel costs have been higher than in the U.S., transit buses already use hydrostatic fans to boost efficiency, Fisher says. Bosch-Rexroth systems grow in complexity from basic gear pump-motor combinations with thermal relief valves to sophisticated variable speed axial piston pumps and motors that use no reservoirs and employ full electronic controls. System size has some influence on selection, with pricing starting around that of belt/clutch systems and rising from there. The biggest advantages for any system are the way it can reside separately of engine location and the way it can relieve heat independent of engine speed. For a brochure on Bosch Rexroth hydraulic fan drives, go to http://rbi.ims.ca/4398-522.