Crane Safety CBT Script Welcome / Splash Screen Welcome to the Florida Department of Transportation’s computer-based training series on OSHA Construction Awareness Training. This is Chapter 12, Crane Safety. To begin, select the start button or press Shift+N on your keyboard. Welcome A Help button is located at the top of each page in this course. Selecting this button will bring up a PDF file with information on how to navigate and use this course. You may select the Help button now if you would like to review this useful information before you begin the course. Introduction Cranes and derricks are used at many FDOT jobsites to facilitate the movement of materials between levels of elevated roadways, and often to place sections of new roadways or bridges. However, cranes also pose special safety hazards. Moving, elevated loads can strike and injure workers, a crane boom can contact power lines, or employees working near the crane body can be struck by the chassis as it rotates. Following safe work practice and complying with OSHA’s standards for crane safety can help minimize these risks. General Requirements The manufacturer’s specifications and limitations on the operation of a crane or derrick should always be applied. When inspecting or observing a job site, always look for clearly posted load capacities, easily available load tables, and general knowledge on the part of crane operators and safety personnel. If the manufacturer’s specifications are unavailable, a qualified engineer competent in this field should determine a set of limitations for the crane or derrick equipment, and his or her determinations need to be documented, recorded, and complied with throughout the duration of the job. Any attachments used with a crane or derrick should never exceed the capacity, rating, or scope recommended by the manufacturer or determined by the engineer. The limitations of the equipment, like the rated load capacities, recommended operating speeds, and any special hazard warnings, should be conspicuously posted and should be obvious to any observer walking through the site. Any special instructions or warnings should be easily visible from the operator’s station in the cab.
The car and cab of the crane or derrick should be easily accessible to an operator in reasonable physical shape. Guardrails, handholds, and steps should be provided. If you are interested in more information about this issue, or if you suspect a safety violation, The American National Standards Institute, or ANSI, standard B30.5 further addresses this issue. If it’s important for rigging or service requirements, steps or a ladder should provide access to the roof of the cab. Any surface of the crane or derrick body that employees would stand on in the course of their work should be an anti-skid surface. Hand signals are often used in noisy jobsites to provide instructions to crane and derrick operators. The signals are described in ANSI standards for each type of crane; operators and signalmen should be familiar with all of the appropriate signals, and illustrations of the signals should be conspicuously posted at the job site. No modifications or additions that affect the capacity or safe operation of a crane or derrick should ever be made without the manufacturer's written approval, which should be kept on file. No change to the equipment can ever reduce its original safety factor. If the crane has been modified, the capacity, operation, and maintenance instructions should be changed accordingly. Inspection Each job site should have a competent person, who is responsible for inspecting each piece of machinery and equipment prior to each use. During the job, the competent person should also make sure the equipment is in safe operating condition. Defective or damaged equipment poses a serious safety hazard to workers, because its behavior is unpredictable. If any problems occur, the machine should be taken out of service, and repaired or replaced before it is used again. A thorough annual inspection of the hoisting machinery should be made by a competent person, or by an agency or company certified by the Department of Labor. FDOT and its contractors maintain records of the dates and results of inspections for each hoisting machine and piece of equipment, and these records should be available within a reasonable period of time upon request by a safety Cables and Rope Wire rope should be taken out of service when any of the following conditions exist:
In running ropes, six randomly distributed broken wires in one lay, or three broken wires in one strand in one lay. Wear of one-third the original diameter of outside individual wires. Evidence of heat damage from any source. Kinking, crushing, bird caging, or any damage that distorts the rope structure. Wear that results in a significant reduction from the nominal diameter of the rope. In standing ropes, more than two broken wires in one lay in sections beyond end connections or more than one broken wire at an end connection.
Physical Safety Moving equipment can cause many different kinds of physical hazards to workers, from pinching to friction burns to severe laceration. If belts, gears, shafts, pulleys, sprockets, spindles, drums, fly wheels, chains, or other moving parts are exposed to contact by workers at the job site, they should be covered by a guard (and usually a warning is posted). ANSI standard B 15.1-1958 Rev., the Safety Code for Mechanical Power Transmission Apparatus, contains specification for guards in situations like this. If you see an exposed moving part that could conceivably cause a hazard to employees, it is a safety problem. “Struck by” accidents for employees working near cranes are regrettably common safety hazards. Accessible areas within the swing radius of the rear of the rotating superstructure of the crane, should be barricaded in some way, so that employees cannot be struck by the crane body, or crushed against a fixed object. The barricade might be as simple as yellow tape around stakes, or as complex as a fixed fence or controlled access area. Loads should never pass directly over workers at the site, and in general, workers should be moved away from the path of travel of the load. Employees being struck by moving loads or loads falling from the boom are one of the most significant causes of serious and fatal accidents at construction sites. For similar reasons, under no circumstances should a worker ride a load, or be lifted by a crane or derrick under any circumstances except those outlined in the earlier module concerning personnel hoists. Exhaust, Fuel, and Fire Safety Gasoline exhaust contains carbon monoxide, which can pose a serious hazard to workers, and low concentrations of other potentially hazardous chemicals (depending on the particular fuel and the engine). Any time internal-combustion- powered equipment exhausts into an enclosed space at a job site, the space should be tested to make sure workers in the area are not exposed to toxic gases or oxygen-deficient atmospheres. The tests should be available to inspectors upon reasonable request. All exhaust pipes should be guarded or insulated if contact by employees is possible in the performance of normal job tasks. The fuel tank filler pipe should be located on the crane or derrick body in a position that doesn’t let spilled or overflowing fuel to run onto the engine, exhaust, or electrical equipment. If this is unfeasible, protection should be provided against the eventuality of fuel being ignited by a physically or electrically hot surface. 3
Overhead power lines pose a particular problem for crane operation. Unless the lines have been de-energized and visibly grounded at the point where work is being done (consider any overhead wire to be energized, unless it is visibly grounded and the project has specific indication from the owner), or insulating barriers have been put up to prevent physical contact with the lines, there are several important steps that should be taken to make sure the operator and anyone working near the crane are safe. These steps are vital, and their observance should be obvious to any inspector. Cranes and Electrical Safety In general, clearance of at least 10 feet should be maintained between power lines and any part of the crane or load. The specific clearance requirements are as follows: •
For lines carrying 50 kV or less, at least 10 feet.
For lines rated over 50 kV, 10 feet plus 0.4 inch for each 1 kV over 50 kV, or twice the length of the line insulator.
If the crane is in transit with no load and the boom lowered, 4 feet for voltages less than 50 kV, 10 feet for voltages between 50 and 345 kV, and 16 feet for voltages up to 750 kV.
In a situation where it is difficult for the operator to maintain clearance visually, one or more signalmen should help him or her stay far enough away from the lines and give any other appropriate warnings. Cage-type boom guards, insulating links, or proximity warning devices may be used on cranes, but the crane still needs to meet every other requirement of the OSHA standards. Transmitter towers, like cellular phone towers, can cause a particular problem. The electromagnetic energy they project can induce electrical currents in susceptible equipment or materials, and special care should be taken to make sure no charge is induced in the crane. Before work near a tower starts, the transmitter should be deenergized, or tests should be made to determine if a charge is induced on the crane. The following steps will help dissipate any electrical energy that might build up: •
An electrical connection between the upper rotating structure supporting the boom and the ground.
Jumper cables to an electrical ground, attached to any materials being handled by the crane’s boom
Nonconductive poles with large alligator clips or other similar protection can be used by crews to attach ground cables to the load. 4
All employees should be kept clear of loads about to be lifted and of suspended loads. Special Considerations Crawler, locomotive, and truck cranes All jibs should have positive stops, to prevent movement of more than 5 degrees above the straight line of the jib and boom on conventional-type crane booms. Using cabletype belly slings is not an appropriate substitute for following this requirement. All mobile cranes should meet the appropriate ANSI standards (particularly ANSI B30.51968, Safety Code for Crawler, Locomotive, and Truck Cranes). Instead of that standard’s inspection records, FDOT and its contractors have to keep a certification record which includes the date of inspection, the signature of the inspector, and a serial number or other unique identifier for that particular crane. The most recent certification record has to be kept on file until the next one is prepared, and (as with other inspection records) the record should be available to any safety inspector within a reasonable period of time. Hammerhead tower cranes As with any other crane, always maintain enough clearance between moving and rotating structures of the crane and fixed objects to allow workers to pass without the risk of injury. Any worker who has duties to perform on the horizontal boom of a hammerhead tower crane should have appropriate fall protection, like guardrails or a personal fall arrest system, as covered in the Fall Protection module of this safety course. Buffers should be provided at both ends of travel of the trolley, and cranes mounted on rail tracks should be equipped with limit switches limiting the travel of the crane on the track and stops or buffers at each end of the tracks. Overhead and gantry cranes The rated load capacity has to be plainly marked on each side of the crane, and if the crane has more than one hoisting unit, each hoist should have its rated load marked on it or its load block. The markings should be clearly and easily readable from ground level. Bridge trucks should have sweeps that extend below the top of the rail, and project in front of the truck wheels. Except for floor- operated cranes, any crane with a power traveling mechanism should have a gong, or another warning signal that is clearly audible over any other noise at the jobsite. Conclusion As discussed here and in other modules of the OSHA Safety Awareness courses for FDOT, the number of factors contributing to crane safety are myriad and critically important. These are large, heavy machines that at times seem to all but defy the laws 5
of physics in enabling projects to rise toward the sky, and a healthy respect for their mass and power will serve you well in staying safe on the job. Exam You are about to begin a 10 question exam on the material that was presented in this module. You must pass this exam with a score of 70% to receive credit for this course. You may take this exam as many times as necessary. Feel free to review the material if you feel you are not ready to proceed. You must agree to the following affidavit before you can begin to the exam. AFFIDAVIT By entering my name in the field below, I hereby declare, warrant and confirm, under penalty of perjury, that I have not misrepresented my identity, and I intend to personally take and complete the following exam. Please enter your name: ________________ Press the "next" button to begin after you have signed the affidavit.