Hey all, I am doing research on Hydraulic Fan Drives, anyone ever done a conversion on their machine, I have read a couple of case studies where they state a 5-14% decrease in fuel consumption, increased engine power available for other functions because you do not need to run the fan at high rpm constantly. On larger engines the HP required to drive the fan is large, upwards of 40HP. In one case study, they converted a haul truck, the unit got a 14% increase in fuel mileage and increased speed, which meant they did more fill dump cycles per shift, and reduced particulate emissions. They conversion was paid off in about 3 months, after that is was making money for the company. Any thoughts??
14% seems absurdly optimistic.
The article speaks for itself, a 14.5% decrease in fuel, and an 8% increase in cycle time. Here is the link: http://machinedesign.com/article/hydraulic-drives-cleaner-air-0920 At the bottom of the article is the summary of the case study, pretty interesting.
Like many studies, they confirm what the writer wants to say even if they have to FUDGE the numbers to say it. Your mileage may vary Later Bob
Yair . . . Interesting stuff Waindude. I notice quite a bit of gear comes with hydraulic fans and had assumed that hydraulic or electric was pretty much the standard. Most folks don't realise just how much power fans consume. We were Dynoing a 350 Chevy for a Hovercraft we were building in Christchurch and discovered it was soaking up nearly 50hp to cool it. Cheers
A clutch fan drops power consumption by a large factor as compared to a direct drive. A clutch fan to a hydro fan seems unlikely to produce a 14% decrease in fuel consumption. I'll check the study out when I get off work.
A few thoughts. 1. Clutch Fans like Rockford are notoriously unreliable and have a tendency to blow seals, especially the ones I've worked with. They are good in operations in really cold temperatures where you don't need the fan running flat out all the time to get the cooling you need. If a clutched fan is running at full RPM anything more than 60% of the time you might as well rip it and fit a direct drive fan IMO. 2. A lot of machines these days use hydraulic fans to reduce fan noise which believe it or not is one of the major noise generators in a piece of equipment. if you don't believe me try removing the fan belts, run the engine without the fan, and compare before and after. According to manufacturers I've spoken to there is basically no other reason for going hydraulic. 3. I can't see how the fuel consumption could drop signficantly. Whether you're burning fuel to produce the HP necessary to run a direct-drive fan or burning fuel to run a hydraulic pump to turn a hydraulic fan you're burning fuel just the same. A simple belt drive is likely to be much more mechanically efficient than a hydraulic system with a pump, motor, & valving. 4. I would take issue with the comment in the article that peak cooling is only required for about 1% of the machine operating time. They obviously aren't running it very hard if that's the case .......... 5. Hydraulic fan conversion kit cost and payback period..? Nowhere to be seen. 6. Nowhere in the comparison study does it take any account of how many tons the machine hauled. I don't know about anyone else but we look at cost/tonne moved, not cost/hour. The article is a very superficial treatment when it comes to the comparison study IMHO.
The absolute best thing about hydraulic fans is that they can be reversible as an option. Very, very useful in hot and severely dusty environments as we've seen in my location with the drought in the last couple of years. Purges the dust from the radiators and makes them run cooler and makes the AC more efficient. Nothing scientific but we had two D6K's on rent, and the one with the optional reversible fan used less fuel(without the fan running constantly) and required less maintenance on the radiator each day(blowing out the fins) and the AC worked better at the end of the day. A giant plus on a 106 degree day in a cedar thicket that you can't see daylight through.
I haven't seen a new wheel loader or excavator in the last two years that didn't have a hydraulic motor driven fan. Rule of thumb on belt drives was ten horsepower per belt. How many big machines run less than three belts? The reversible fans are pretty much required now days in land clearing and logging. The are all computer controlled and use a variable stroke pump to turn them. They don't have to run the same speed as the and engine are directly proportional to the cooling capacity required for the amount of horse power the engine is generating. Yes they save fuel. Does the extra cost off set the fuel savings? Only time and life cycle costing will tell.
When they design a belt driven fan, they have to design it for maximum expected cooling needed at any given rpm and power load at maximum rated ambient temperature. So any time the machine isn't actually pulling it's guts out on a hot day the fan is wasting horsepower moving more air than is needed to carry away the excess heat. Simple physics. I'm not saying that in some instances you might not see a lot of savings, but for the most part variable hydraulic drive is far superior to any mechanical drive. The only close second would be the variable pitch fans that are available. Cheers.
Good discussion everyone, what I need are hard numbers on what how much fuel reduction I can expect. I have at my disposal a hydraulic test bench with about 250HP available at the bench. What I plan on doing is setting up a hydraulic motor with a truck engine fan on it, I can record exactly how much horse power is required to turn the fan at a given rpm by monitoring the flow and pressure at the motor. I will post the results. Reason I am doing this is up here in the frozen north, (its April 10 and still below freezing overnight), we have about 6 months of cold weather, this has an effect on engine cooling, I presume that due to colder air, the fans shouldn't have to run as fast to keep the engine cool even at near max engine HP capacity. Up here, lots of guys run their units 24-7 when it gets really cold, just so they dont cool down too much. I want to figure out just how much a person can expect to save by going to hydraulic fan drive.
Thanks, looking forward to your completed test. I've always wondered just how much that direct driven fan was needed in cold weather.
Based on your location use a Rockford hydraulic fan clutch (despite what I said about them earlier). Fuel consumption savings - assume zero and take whatever you get with gratitude. Lets face it how many people actually manage to achieve EPA mileage estimates ..?
Run without a fan for a while, and things could get real quite :lmao
Flexxaire Fan Corporation is based out of Alberta. I'm sure they have spent great amounts of time and money researching the sort of data you seek even though their product isn't hydraulic, the savings will be similar. You might want to contact them. They are pretty forthcoming with info and share some great stuff online. This is a good start for anyone wanting to understand radiator airflow and cooling loads: http://www.flexxaire.com/documentation/modern_cooling_system_theory.pdf Flexxaire has an advantage over hydraulic in efficiency. Hydraulic systems generate heat that needs to be dissipated by the fan.. abit of a catch-22. The best hydraulic fan drive is about 93% efficient in power transmission. Mechanical drive can be 99% Case studies are not very valuable unless it is on an identical machine with identical loads. The engine cooling fan rarely cools only the engine radiator on heavy equipment. All the cfm needs of trans coolers, hyd oil coolers, air conditioning condensers etc has to be considered. There are some hydraulic fans on heavy equipment that are not variable at all. The original objective of hydraulic fans on many machines was never efficiency but meeting one particular part of emissions regulations. When engines started to be closed into sealed compartments by manufacturers to control block ambient temps to meet regs, there was no convenient way to drive a fan. Hydraulic solved that issue. Cat's small wheel loaders are a good machine to follow the evolution of hydraulic fans on. For example the original 928G used a gear pump and gear motor. Fan speed was directly proportional to engine speed - i.e. just a hydraulic fan belt. Later G series used a thermal bulb to signal a LS pump giving variable speeds with no electronics. Then along came ECM control and reversible options.