Water Well Journal
Issue link: http://read.dmtmag.com/i/740475
the boom in all positions (end, side, and corner). If making a series of lifts, the levelness should be periodically checked. Side Loading Load chart ratings apply only to freely suspended loads and when the load is picked up directly under the boom tip. If the load is to either side of the boom tip, side loading occurs, which affects the crane's capacity. Side loading is one of the most common causes of boom failure and usually occurs without warning. Side loading can occur when a load is dragged or pulled sideways, when the load starts swinging rapidly, when the crane is not level, and when exposed to high wind speeds. Tilt-up construction meth- ods can also cause side loading of the boom. Increasing Load Radius The load radius may increase during a lift if the hoist line is not vertical at all times. An increasing load radius may be caused by lifting a load that is outside or inside of the boom tip radius. For such lifts, the load will start to swing in and out after the load clears the ground, which increases the load radius, thus reducing the rated capacity of the crane. Lifting "on rubber" can also cause the load radius to increase due to deflections in the boom, tire, and carrier. Shock Loading Load charts do not allow for impact loads. Shock loads can be caused by rapid acceleration, sudden stopping, sudden load release, and sudden load snatching. For instance, the shock loading increases by nearly 35% if the hoist line is traveling at a speed of 400 feet per minute and stops with a stopping distance of only 2 feet. The shock load- ing only increases by about 0.5%, though, if the hoist line is traveling at a speed of 100 feet per minute and with a stopping distance of 10 feet. In addition to sudden deceleration and the other conditions mentioned above, pick-and-carry operations also produce impact loads to the machine. High Duty Cycle Load chart ratings may not apply when cranes are used in high-speed production operations. The manufacturer will ei- ther specify in the load chart the rated capacities must be re- duced by a percentage for high duty cycle operations or will supply a separate load chart for such operations. The capacity reductions are recommended since the speed of these opera- tions produces side loading as well as higher temperatures in critical components such as brakes, clutches, pumps, and motors. High Wind Speeds Winds blowing at high speeds affect the capacity of a mobile crane by increasing the side loading on the boom and the load radius and by decreasing the tipping (both forward and backward) capacity. In addition, performing lifts in windy conditions makes it more difficult to handle the load. Hoisting activities should be restricted or stopped completely, and the boom properly secured, in windy conditions. Make a List Because many factors affect a mobile crane's rated capac- ity, using a pre-lift checklist when planning a lift is generally a good practice. If a lift cannot be made under the configura- tion and conditions specified in the lift plan, the lift should be reevaluated and approved by a qualified person. Follow these steps if you don't want to become one of the 89 crane-related deaths that occur each year in construc- tion work. WWJ SAFETY from page 52 Jerome E. Spear, CSP, CIH, is president of J.E. Spear Consulting and has more than 22 years of experience helping organizations prevent injuries and illnesses, control losses, and achieve regulatory compliance. He held the positions of technical services manager with XL Specialty Risk Consulting and corporate industrial hygiene manager for Chicago Bridge and Iron Co., a worldwide steel fabricator and construction company. waterwelljournal.com DACUM Codes To help meet your professional needs, this column covers skills and competencies found in DACUM charts for drillers and pump installers. DO refers to the drilling chart. The letter and number immediately following is the skill on the chart covered by the column. This column covers: DOA-4, DOD-5, DOD-6, DOK-9, DOK-10 More information on DACUM and the charts are available at www.NGWA.org. R C N CTERIA! 096 2 . ORE, ALER! USH + WELL Jr. Blvd. • Lubbock, TX 79404 747.2096 • coteychemical.com N BA FOR CHOICE WEAPONS R W 806 7 U A M 7 4410 MLK 806.7 54 November 2016 WWJ