Several design classifications and standards apply to loader cranes. A typical one is DIN 15018 H1 B3. It is based on the expected number of cycles made during an average loader’s operating life and the assumption that three average lifts creates the same amount of fatigue as a single maximum capacity lift (see table). The B-classification relates to the service life of the crane’s bearing parts and there is also a B5 rating for two million work cycles.
Units can be downrated, a B3 to a B2 for example, but, because the manufacturer has little or no control of end use, this could still mean that a crane designed for general hook work could be used for heavier grabbing or attachment duties.
Palfinger claims to have been the first manufacturer to produce all its units to B3 as a minimum, a move which most manufacturers have followed. Downrating a B3 crane to a B2, or a B4 crane to B3 would reduce capacity by about 15%.
Cranes used in forestry applications have a particularly arduous duty-cycle requirement that requires a B4 rating. Palfinger models for use in forestry applications have twin slewing cylinders for more torque, needed when operating on a slope for example. Jonsered’s timber cranes and production loaders are designed to DIN 15018, class H1/B4. The H1 or H2 part of the classification considers additional dynamic forces such as if the boom is stopped suddenly while lowering a load. H1 is to withstand 30% additional dynamic force and H2 is 60%. Jonsered says the use of modern hydraulic components in its cranes means additional forces can be limited to a maximum of 30% and therefore builds all its cranes to classification H1 and at least B4.
Further classification defines Jonsered’s forestry cranes or production loaders as suitable for either intermittent or continuous operation. Truck or trailer mounted timber handling units used for self- loading normally work one or two shifts and are stowed during transportation, which is classified as intermittent operation. It might be a long way or take a long time to get from the forest to the timber’s destination so the crane will last longer even if it runs at full capacity when it is operating.
Continuous operation is often applied to static cranes, at sawmills, scrapyards and docks for example. These might work several shifts a day and are likely to be exposed to more stress than truck mounted cranes. In addition, Jonsered recommends that static mounted cranes for continuous operation should have hydraulic pressure, and therefore lifting capacity, reduced by 20%. In effect, this means that the purchaser should select a higher capacity crane that can be operated intensively but still give good service life.
Production loader cranes on static mountings can do much more than simply load and unload materials. Improved controls, better attachments and versatile boom systems mean they can now play a much bigger part in the material handling needs of an industrial process. Operations include:
grab and move
raise and lower
feed and hold
stack and empty
place and position
detach and sort.
Typical applications in addition to forestry include sorting scrap and recyclable materials at yards, power stations, harbours, on boats, etc. Jobs with intermittent use could be heavy or valuable loads, or handling dangerous waste where power, precision and safety are priorities. Speed, durability and high productivity are major concerns for continuous operation.
