Unlike a truck or automobile that barrels down the highway at 70 mph, off-road equipment doesn’t get much airflow through the radiator beyond what the cooling fan provides. In addition to the engine cooling, off-highway machines can also have half a dozen or so additional heat exchangers for things like air-to-air charging, air conditioning and cooling of hydraulic, lube oil and transmission fluids. And today’s EGR engines recycle exhaust gasses back into the combustion air mix, raising engine temperatures considerably.
To keep all this heat under control, heavy equipment cooling fans create a powerful airflow. But in certain applications this airflow can also draw in significant quantities of dust and debris, which clogs the radiator and degrades your cooling system performance. Radiators can be cleaned with compressed air, but this is a time-consuming task and one that runs the risk of damaging delicate radiator fins.
Tolerating a dirty radiator does more than raise your engine and component temperatures. Since fans siphon off a certain amount of horsepower from the engine, the less efficient your system, the more horsepower you spend on cooling. The end result is less horsepower available to get the job done. High temperatures also shorten the life of any component and can lead to seal failure and prematurely degrade or compromise the performance of lube oils and hydraulic fluids.
And too much heat is just half the problem. In extreme cold conditions a fixed blade fan running at a constant speed may delay the engine and fluids from heating up to their optimum temperatures.
In applications where these conditions threaten to reduce the productivity or durability of a machine some OEMs and a handful of aftermarket fan manufacturers offer optional cooling fans designed to cope with these problems. There are a variety of solutions in the market, from fans that reverse blade pitch to fans with variable blade pitch and all-electric fans as well.
Keeping a clean machine
Machines that create a lot of debris are prime candidates for reversible cooling fans. Chippers and grinders as well as most machines used in the forestry industry benefit from regular radiator debris purging. “In mulching applications, the suction fan from the factory draws in all those fine particles and plug the radiator up,” says Mark Ditrich, manufacturing manager at Huber. “You can go from the suction to the blower position and clean your radiator out. Or a lot of times you can leave the fan in the blower position when you’re using it to load.”
Wood chips and forestry applications also carry an increased threat of fires and variable pitch fan blades can help. “In some applications our customers are hooking up our controller to their fire suppression equipment,” says Mark Vandenhouten, sales and marketing manager, Flexxaire. “If it detects a fire on the machine, prior to releasing the fire suppressant the blades will go into zero pitch so it’s not creating airflow across the engine compartment. The suppressant is able to do its job rather than be blown out.”
Dozers and wheel loaders working in landfills and recycling operations are also increasingly available with reversible fans. In that environment a single plastic bag can be sucked up against a radiator grill and immediately choke off most of the airflow through the radiator. Plus just the constant exposure to airborne debris can quickly clog radiators. A quick, regular purging, sometimes once an hour, often as frequently as every 20 minutes, keeps operators in the cab and these machines up and running.
Cold weather applications
Fan blades with automated variable pitch will flatten when the temperature is cold and increase their angle relative to the fan hub when the temperature is high. The steeper the blade angle, the more air it pulls through and the more cooling you get.
But in cold weather you don’t need this cooling power, and by flattening the pitch of the blades you’re saving on fuel and horsepower, says Michael Ische, engineering manager, Novatrax International (which markets the Cleanfix brand of fans). “You end up with very flat operating temperatures,” he says. “As the engine heats up it gives you a little more angle. As it cools off it gives you less. You run pretty close to where your thermostat is supposed to be.”
When using skid steers in snow removal applications a reversible fan can bring operators an extra measure of comfort, pulling warm air toward the cab, Ditrich says. “A lot of the old timers called them winter and summer fans,” Ditrich says. “A summer fan is a blower fan. A winter fan is a suction fan.” Ditrich credits the founder of his company with developing a reversible fan after the man’s boss told him one warm spring day he couldn’t switch the fans because it would take three or four hours. “Now it takes just a few minutes to go from one position to another,” Ditrich says.
Other machines used in snow removal can sometimes suffer from having moisture pulled from outside through the radiator and blasted against the engine’s electronics. Reversible fans here help keep the engine dry. “We’ve seen several bulldozers short out their alternators because the fan pulls water into the engine compartment, Ditrich says.
Different fans with different approaches
Here’s a look at what these aftermarket manufacturers offer. Note that no two fan systems here work exactly alike. Each takes a slightly different path toward similar goals. A couple of things they all have in common are that they can conserve horsepower (which also cuts down on fuel consumption and helps the machine run quieter), they keep the cooling system cleaner and they help regulate temperatures.
Using an electrically driven pneumatic cylinder with an eccentric linkage, the pitch of the blades on Cleanfix’s fans can be reversed with the push of a button inside the cab – even at full speed. “You have a sudden change in air pressure, volume and direction and that’s really what cleans the radiator because it hits the dirt and debris and sends it flying,” says Ische. “We use the cup side of the blade in both directions. That’s how we can clean multiple layers of radiators.”
The Cleanfix fans sold in the aftermarket are set up with a timer, Ische says. For the OEM market the fans can be set up with a timer as well as be programmed into the machine’s engine control monitor so that anytime the engine gets too hot, the fan reverses and purges the radiator. “The nice thing about timers is that they’re proactive rather than reactive,” he says. “It doesn’t allow the chance for dirt to build up in the radiator if it doesn’t get hot enough in the winter.”
Cleanfix also now offers its VP-series (variable pitch) fans. With variable pitch the blades will flatten when the temperature is cool and turn to a steeper angle, gradually creating greater airflow, when the temperature rises.
The variable pitch fans from Flexxaire change blade pitch on the fly via pneumatic (the AX series) or hydraulic (the FX series) action, and the company recently introduced a manual version for smaller, simpler applications. The hydraulically actuated fans are the most popular on heavy equipment like dozers and wheel loaders, says Vandenhouten.
Purging occurs when an actuator inside the fan temporarily moves the blades into a reversed pitch position and reverses the airflow. This can be accomplished automatically with a timer, or done by the operator as needed with the push of a button. An optional temperature sensor can also regulate the blade pitch angle in accordance with the temperature of the engine. The blades are configurable between 15 and 40 degrees of pitch in both directions.
“One of the benefits is that we go through a position we call zero pitch, so the blades at some point while they’re purging are totally flat, creating a rotary air dam effect,” says Vandenhouten. “If cooling isn’t required, the blades return to zero degree pitch so you’re not wasting horsepower turning a fan and moving air that doesn’t need to be moved.”
Unlike the automated systems mentioned above, Huber reversible blade fans are manually rather than automatically rotated.
“With ours you stop the engine and manually rotate each individual blade,” Ditrich says. A switch locks out the ignition to prevent accidental start-ups during the process. Blades are pushed in to turn and spring loaded to lock into position. Blade pitch is fixed at one angle, anywhere from 20 to 40 degrees.
The selling point for Huber fans is that they’re less expensive than models that automatically rotate the blades. In landfill operations and applications where you need to be constantly purging the radiator, automated systems may be worth the extra cost, Ditrich says, if they prevent the operator from leaving the cab or stopping the machine to change fan blade direction. But if you only need to purge your radiator once a day or so, need to leave the fan in one position for the specific needs of a job, or if you only want to reverse fan direction seasonally, then a manual system may be a better fit, he says.
The electric-drive option
While all the fans mentioned above are driven off a belt and the engine’s crankshaft, EMP’s fans don’t draw horsepower from the engine, but rather take current from the machine’s alternator. And while they’re not used as the main or primary cooling fan for engines, they can supplement engine cooling needs as well as be configured to provide cooling for transmissions, charge air coolers/intercoolers, oil, hydraulics, jacket water HVAC, EGR and electronics. They can also be set up in single, double or three-fan arrangements.
Dave Allen, executive vice president for sales and marketing at EMP, cites three reasons for considering a supplemental electric cooling fan. First is the fuel economy. “Your primary fan is trying to cool any one of six or seven things,” he says. “Yet at any given time it might be that only one of those components needs cooling. So the other items are getting cooling whether they need it or not. That’s not very efficient. What we try to do is keep the main fan off.”
The second reason has to do with engine ratings. Because of high heat loads in certain applications and conditions an engine may not be able to produce all the horsepower it’s rated for. “What we’re trying to show is that with a simple heat-exchanger type cooler and two fans you can uprate an engine’s horsepower,” Allen says.
The third benefit is reversible air flows. An electric fan motor easily reverses direction, without changing blade pitch or orientation, to blow out debris that clogs radiators. Reverse actuation can be set up on a timer or operator actuated.
In most cases EMP’s fans will receive sufficient current from your machine’s alternator to run. If you’re looking at a high powered two- or three-fan system you may need to upgrade your alternator to the next biggest size, Allen says. The fans can be set up to run on a temperature sensor, or a pressure transducer if cooling just an HVAC or jacket water unit, or can be tied into a machine’s electronic control module.
For off-road diesel applications the company currently makes an 11-inch fan and is coming out with a 15-inch model. The company refers to its fans as “diesel grade,” which means they are built with heavy-duty aluminum shrouds, long life brushless motors and are IP 67 compliant, meaning they’re fully submersible and corrosion and water resistant. A smaller 8- or 9-inch model is on the drawing boards. Further out, Allen says the company intends to field a primary cooling fan that’s all electric. “The bottleneck right now is the electric power available,” he says. “You need to replace the alternator with a belt driven generator. An alternator might be 45 to 50 percent efficient, but a generator will be closer to 90 percent, which is what we need to electrify the main fan. Once that’s ready we’ll have a whole belt-less solution available for our customers.”