A crane beam is a preformed metal beam on which the crab or lifting head of a mobile overhead crane slides. It can feature different crane girder layouts such as single girders, double girders or bridge girders. Crane beams are subjected to severe stresses during hoisting operations and require regular inspection and maintenance. Crane girders provide a stable track on which overhead cranes travel and can have one to three crane girders depending on the installation. Single crane beam installations are useful in applications where no transverse movement is required, while bridge and double girder cranes allow three-dimensional movement of the hook. Crane beams are constantly subjected to numerous stress loads during operation and must be properly graded and regularly inspected for signs of damage.
A crane beam is a preformed metal beam on which the crab or lifting head of a mobile overhead crane slides. Such beams are typically “I” profile beams which can be reinforced at various points depending on the loads and configuration of the crane in question. They can feature different crane girder layouts such as single girders, double girders or bridge girders. The configuration depends largely on the headroom in the building and the loads the crane is designed to lift. A crane beam is subjected to a variety of often severe stresses during hoisting operations and special attention should be paid to assessment, reinforcement and periodic inspection and maintenance.
Crane girders are usually heavy I-beam steel elements that provide a stable track on which overhead cranes travel. Depending on the type of installation, gantries typically have one to three crane girders. The crab or movable crane head features a series of rollers that ride on the top or bottom cross member of the I-beam. In single-beam installations, only one crab beam is used. In double girder or bridge cranes, the crab girder is equipped with bogies at either end and travels up and down the cargo space on two additional crane girders.
Single crane beam installations are useful in applications where no transverse movement is required. Also known as monorail cranes, these machines can travel the length of the girder and only lift or lower loads. This type of crane is useful in confined spaces where movement of the load is limited to the length of the space. These cranes generally run on the bottom of the girder which is typically supported at several points along its top girder. A disadvantage is the low hook height because the crab and hook are usually located under the crane beam.
Bridge and double girder cranes are much more flexible and allow three-dimensional movement of the hook. In these installations, the crab can move across the crane beam to cover the width of the space. Additionally, the crane beam assembly can travel along the length of the space covering a much larger area than a monorail. This type of crane has the added benefit of sliding the crab beam over the side support beams or being raised to slide between them. This allows for extended hook heights and greater flexibility.
Crane beams, especially the crab beam, are constantly subjected to numerous stress loads during operation. These include vertical stresses caused by the load, lateral stresses caused by acceleration and braking of the crab, and transverse stresses caused by swinging the load. Crane girders are often reinforced with flat plates or channels along the mounting cross sections to resist these stresses. To ensure the safety of operating personnel and loads carried by the crane, crane beams must be properly graded and regularly inspected for signs of damage.
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