Document 91b3YMrQrLKpvGr6dag72o9kD

Hoisting Apparatus and Conveyors mg beneath the boom Otherwise, if the truck wheels should roll into a low spot m the pavement, the boom might suddenly crash through a car roof If not disassembled, a crane being trans ported should have the crane engine running and the operator in the cab to swing the boom when necessary to avoid fouling trees, poles, or buildings when the vehicle turns comers Before heavy, slow-moving equipment, or heavy equipment on a low-slung trailer, is moved over any public or private railroad grade crossing, a responsible representative of the railroad company should be notified The railroad then can provide flag protec tion to guard against a train's striking the equipment while it is moving over the cross ing, or if the equipment becomes stalled or "hung up" on die crossing This is an im portant precaution for the benefit of both the equipment owner and the railroad company Electric wires. The boom and cables of a crane should be kept away from all electnc wires, regardless of their voltage Equip ment should be operated m such a manner that no part of it, including the load, can come within 6 ft of electnc lines or apparatus unless the power in the lines is shut off Local laws may specify distances greater than 6 ft In such a case, the local law shall prevail The U S Army Corps of Engineers has established the following minimum required clearances and requires a notice of them to be posted at the operator's position Power Lines Nomina! System kv Minimum Required Clearance Feet Under 69 69 115-161 230-285 3-15 500 10 12 15 20 25 35 Electronic devices are available that can be attached to the boom and will sound an alarm if the boom comes within a predeter mined distance from a live wire This equip ment is subject to failure and should be used only when it is absolutely impossible to main tain minimum clearances, barricade, or de energize power lines One state has a law allowing the prosecu tion of employers and equipment operators who permit crane booms to come within 6 ft of high-voltage lines or who operate at any location without a sign, "Unlawful To Operate This Equipment Within Six Feet of High-Voltage Lines" posted on the ng Boom guards of wood or of pipe mounted on 15-kv insulators provide mechanical pro tection against contact If a crane boom contacts a conductor, the hazard is greatest to the hook-on man and others who may touch the load or the sling To protect these men, a commercially avail able load hook with an insulated link can be used If the boom or cables accidentally come into contact with a wire, the operator should swing the crane to get clear If the wire has been broken and the boom cannot be cleared from it, the operator should stay on the crane and remain calm A crawler crane, if the ground is wet or damp, will be electrically grounded, and when the boom touches a power line, the wire will, m turn, be grounded and the power company circuit breaker will open Some arcing may occur After a few seconds, how ever, the circuit breaker will automatically close and reenergize the wire Again the circuit breaker may open, and again it will close Thus the wire may be "dead" at one instant, but live a few seconds later On the other hand, if the boom of an auto motive crane on rubber tires should become tangled with a "hot" electnc wire, the entire crane will be energized, for the rubber tires will insulate the crane and truck from the ground Hence, the circuit breaker may not open, and the wire and the crane may remain energized Stepping from the crane to the ground is often fatal, for one hand and one foot may be in contact with the crane when the other foot touches the ground Therefore, the op erator should remain on the crane until tbe emergency crew from the electnc company amves and frees the crane from the live wire If the gasoline tank should become ignited or if for any other reason it is impossible for the operator to remain on the crane, he should jump, making sure that all parts of his body 560