By Gregory Havel
桥梁起重机通常在许多制造和设备维修设施中发现。Photo1显示了一个小型（10吨容量）的桥式起重机，该起重机在重型车辆组装厂中提供300英尺的服务和制造湾。
桥梁起重机的共同特征如下：
- Each end of the bridge is carried on a wheeled carriage supported on railroad rails that are bolted or welded to beams (photo 2). In the photo, the railroad rails are attached to the top flange of the beam with J-bolts.
- Each bridge carriage has one or more reversible electric drive motors (photo 3) to move the bridge along the rails.
- 提升机沿着桥的底部法兰在电动手推车上移动。它也是电力的。照片3显示了桥梁尽头的桥梁起重机。
- Electric power is carried to the bridge crane by way of exposed copper buss bars (as seen in photo 2 and at left in photo 1). Most of these cranes used three-phase electric power at 480 volts or higher and require three buss bars for electrical power and a fourth—often colored green—as an equipment ground.
- 电力通过弹簧杆的手臂和每个公交杆的接触鞋从公交杆转移到桥梁起重机（照片4、5）。
- Buss bars are connected to the power source at one end only. An electrical disconnect switch may be located on a column or wall supporting the track, or it may be located in a motor control center.
(1) Photos by author.
(2)
(3)
(4)
(5)
Small bridge cranes are often operated from the floor with pendant control boxes. More modern cranes like the one in the photo may use wireless remote control boxes that are carried by the operator on the shop floor. Very large bridge cranes, like those used in foundries and steel rolling mills, will carry the operator in an enclosed cab at the power end of the bridge.
Although the electrical buss bars are exposed and uninsulated, they are usually far out of reach of anyone working in the factory. Those in the photos are about 30 feet above the floor.
Some bridge cranes are designed so that when the crane is shut down, relays in the electrical system shut down the power to the buss bars. Other buss bars may remain energized unless manually disconnected at a switch or motor control center.
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Although the spacing of the buss bars for the contact shoes reduces the possibility of a short circuit or ground fault from a discharging fire sprinkler head, they are not far enough apart to prevent electric shock conducted by a solid hose or master stream device.
Notes on our preincident plan for a facility with one or more bridge cranes should include the location of the cranes, the location of the power source, whether the buss bars are deenergized when the crane is not in use, and any other information on the crane and its use that may affect firefighting operations.
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Gregory Havel是伯灵顿镇（WI）消防局的成员；退休的副局长兼培训官；以及一名35年的消防人员资深人士。他是威斯康星州认证的消防教练II，消防官II和消防检查员；Gateway技术学院消防计划的兼职讲师；Scherrer Construction Co. Inc.的安全总监Havel拥有圣诺伯特学院的学士学位；在设施管理和建筑建设方面拥有超过35年的经验；并已在FDIC介绍课程。
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