Fuel Economy Counts
Fuel Consumption for Forestry Machines
The design, maintenance practices and operating conditions of forestry machines, as well as how they are used influence fuel consumption. As the owner of forestry machines, you can reduce the impact of increased fuel prices by purchasing new equipment that is proven to have low fuel consumption. You also need to be well informed on how to adequately maintain and correctly operate your equipment so as to reduce fuel consumption.
According to various experts, fuel consumption differs among the different types of equipment. These differences can be explained by three main factors: the design of the machine, the engine technology and the operator’s work methods. Purchasing the wrong machine for the job can clearly have a considerable impact on fuel consumption.
Equipment choice and fuel efficiency
Choosing accessories wisely and using them appropriately can have a strong impact on fuel consumption.
Diesel engines provide a wide range of power outputs but operate at different degrees of efficiency for each power level. In general, these engines are most efficient when operating at the speed where they develop their maximum torque and use 75% of this torque. An engine operated in this manner will consume less fuel. Therefore, when the machine requires less power, operators should reduce engine speed so as to maintain a high output torque. [BTB editor’s note: This does not apply to machines that require full engine speed in order to maintain hydraulic flow to an attachment.] Remember that the combination of high engine speed with low output torque increases fuel consumption. Operators of forestry equipment should avoid traveling in the woods at excessive engine speed. The use of moderate engine speed can save fuel and reduce maintenance and repair costs without decreasing productivity.
Pollution controls and fuel efficiency
Emissions Tiers were initiated in the 1990s by the US Environmental Protection Agency (EPA), with the goal of reducing particulate matter, unburned hydrocarbons, carbon monoxide (CO) and oxides of nitrogen (NOx). This goal was realized but fuel consumption increases were commonly observed. With the introduction of Tier IV Interim, fuel consumption improvements have been observed and Tier IV Final engines should result in even better fuel efficiency in most operations.
Thermostatic fans and hydraulically driven variable speed fans improve fuel consumption only if the machine’s cooling system is up to the job. In general, the fan should not be required to work at full speed under all working conditions. A fan that operates continuously at full speed consumes 1-2 L/h. [BTB editor’s note: For a Tigercat 800 series machine, the range is 2-7 L/h, running the fan at low speed versus full speed.]
The power train
The power train must be matched to the engine capacity to operate efficiently. Mechanical transmissions should provide a range of gear speeds so the operator can reduce engine speed to the lowest speed needed. Hydrostatic transmissions are often equipped with an electronic control. The acceleration pedal then signals the desired travel speed to the computer, which adjusts the engine speed and fuel flow in response. This approach minimizes fuel consumption.
Automatic differential locks sometimes engage at inappropriate times and the resulting slippage of one or more wheels increases fuel consumption. A manual differential lock, used when needed, is more efficient. The use of manual differential locks at appropriate times can reduce fuel consumption. However, operators must pay careful attention to wheel behavior to obtain good results.
The effectiveness of a hydraulic system depends on several factors that are difficult for a buyer to determine. It is possible to lose considerable efficiency through a poor choice of the mechanical and hydraulic components of a forestry machine. Load-sensing hydraulic control systems are generally the best choice for forestry machines, followed by constant-pressure systems. Load-sensing systems regulate the hydraulic pump’s pressure and flow to meet the demands of the machine’s hydraulic functions. Load-sensing systems are particularly appropriate for situations in which the load varies.
It is preferable to install flexible hydraulic oil hoses of appropriate diameter and to be particularly careful to avoid elbow fittings or tight bends in the lines.
Hydraulic oil cooler
Hydraulic oil coolers should be equipped with a thermostat that lets the oil warm more rapidly and maintain its optimal temperature longer. Oil viscosity varies depending on the type of oil used (summer vs. winter). Too-thick oil slightly increases fuel consumption, whereas too-thin oil increases component wear.
Maintenance and optimal machine use
Optimal use of a machine and good preventive maintenance are effective means of saving fuel. Here are some other simple, practical tips that can help:
• Use work lights only when required. Their use can increase fuel consumption by up to 0,5 L/h.
• For machines equipped with a loading boom, fuel consumption during boom use can be reduced, up to 5%, by moving the machine close to the load and not maximizing boom reach.
• Choose tires of adequate dimensions so as to minimize sinking and loss of traction. According to studies conducted by FPInnovations, skidders equipped with high-flotation tires have lower fuel consumption than skidders with narrow tires on soils prone to rutting. However, the narrow tires provide greater mobility in deep snow. Thus, it would be best to use different tires in each season.
• Keep all tracks and chains properly tensioned. Slack chains or tracks increase fuel consumption due to excessive slippage.
• Keep the fuel-supply system components in good shape, since leaks and spills increase fuel costs.
• Minimize engine idling. A typical feller buncher engine can consume up to 2,5 L/h while idling.
• Follow the cold weather start-up procedures specified for your machine so as to shorten the warm-up period. Depending on the temperature, let the engine idle for 5-10 minutes. Next, use the hydraulic functions slowly, keeping the engine speed at around 1 100 rpm. If you hear noise from the pumps, reduce the speed.
• Keep the radiator and oil cooler clean. This helps keep the oil at the right temperature, thereby reducing fan operation for thermostat controlled fans.
Per hour or per tonne?
Dividing daily fuel use by hour meter reading will yield liters consumed per hour. However, lower values may not necessarily indicate a more efficient machine, as long idle durations or low productivity can create the illusion of good fuel economy. In other words, low fuel consumption per hour does not pay if there is very little production. A better measure is liters of fuel consumed per cubic meter (or tonne) of wood produced. This measure of fuel intensity is the best method for measuring your cost of production in terms of fuel use and will help you gauge improvements in operator methods or work practices. Measuring productivity on a daily basis can be challenging, but newer machines with on-board computers can track productivity on a relative basis.
Measuring fuel is the first step in managing fuel
In the woods, fuel tanks are rarely fitted with a fuel filter, but their use is essential to maintaining your equipment. Installing fuel tank filters is easy and less costly than machine downtime. It is recommended that filters that remove water (water separator) in addition to particles be used to ensure clean and dry fuel. Fuel meters The first step in reducing fuel consumption is measuring how much you currently consume. Simple, inexpensive mechanical flow meters will provide the required information and are available from any fuel supply company. Properly maintained and calibrated, most are capable of an accuracy of 1-2%. Nutating disc meters are recommended for their high tolerance to dirt and foreign objects, rugged construction, and compact design. Follow the manufacturer’s instructions for calibration and take note that they are not as accurate as meters intended for commercial fuel sales.
Using fuel meters and recording the information will let everyone on the crew know that fuel tracking and use is important! Furthermore, it provides the operator with a benchmark that allows comparison between operating conditions and is the first step towards embarking on a fuel conservation effort. Many operations claim “noticeable” reductions in fuel consumption following the implementation of a simple fuel monitoring program.
Operating tips for reducing fuel consumption
Track feller bunchers and harvesters
• On firm ground with few obstacles, try to work using the middle range of the boom’s reach (4-6 m) in front of the harvester; this reduces the energy required to move the boom. [BTB editor’s note: On a Tigercat with an ER boom, it is most efficient to move the boom and not the machine, similar to the point about telescoping booms below.]
• On soft or stony ground, or when travel becomes more difficult, try to harvest the maximum number of trees while staying at the same position.
• Telescoping booms permit faster movement of the felling head towards the tree, require less power and reduce fuel consumption.
• Avoid sharp changes in direction during travel; gradual turns produce less skidding and consume less fuel than sharp turns.
• For machines equipped with a cab-leveling system, use the hydraulic cylinders provided for this purpose to keep the cab level; swinging a tilted cab requires more power and consumes more fuel.
• Avoid unnecessary swing and boom movements.
• Exert as little pressure as possible on the delimbing knives and feed rollers while still maintaining high delimbing quality.
• Use the energy of the falling tree to help you move forward or to delimb the stem. This move requires considerable skill. However, the energy provided is free.
• Keep the saw chain and delimbing knives sharp; cutting and processing of logs requires more power, and thus more fuel, when the cutting surfaces grow dull.
• Immediately replace damaged or worn saw teeth; this will require less power, thereby increasing productivity and improving the cut quality.
• Stop the saw motor during prolonged travel on the cutover.
Skidding and forwarding
• Minimize turns while traveling with a load; it’s preferable to turn gradually, since this consumes less fuel than sharp turns.
• Install landings and extraction trails at the most appropriate locations; this approach both decreases fuel consumption and increases productivity.
• Try to travel on soils with a good bearing capacity; traveling in soils with poor bearing capacity requires more power, thus consuming more fuel.
• Use tire chains or tracks only when required to provide better mobility or flotation; these accessories require more power, thus more fuel.
• Where possible, plan work so that landings are located downhill. Moving loaded equipment uphill requires more fuel.
• Transfer as much of the load as possible onto the skidder. By raising the load higher and closer to the cab, you reduce the friction of the tops on the ground and thus decrease fuel consumption.
• Balance the pressure between the front and the rear tires. The rear tires deflect more, increasing the amount of friction against the ground, when the machine is under load.
• For cranes with a telescopic extension, pull the logs as close as possible to the machine using the telescoping feature before lifting the logs onto the forwarder; lifting the logs at full extension requires more power and thus more fuel.
• Avoid raising the logs high above the stakes. Position the forwarder as close as possible to the log piles and try to pass the logs between the stakes rather than above them, since fuel consumption increases the higher you raise the logs.
For further information contact FPInnovations:
FPInnovations is a world leader that specializes in the creation of scientific solutions in support of the Canadian forest sector’s global competitiveness and responds to the priority needs of its industrial and government members and partners. It is ideally positioned to perform research, innovate and deliver state of the art solutions for every area of the forest sector’s value chain, from forestry operations to consumer and industrial products. The following reprint by Tigercat, a leading forestry equipment manufacturer, underscores the practical value of FPInnovations’ work in promoting fuel efficiency in all phases of forest operations.
All Tigercat FPT engines require fuel filters and diesel fuel that meet certain minimum standards.
Adapted with permission from FPInnovations’ Guide “In Forestry Operations: Fuel Economy Counts! 2nd Edition”.