Profile: Harold Potter Ltd. is a supplier of a variety of cranes including overhead, bridge, portal, Goliath, semi Goliath and swing jib cranes. We also manufacture lifting gear including runway systems, lifting beams and spreader beams. We are buyers and sellers of used lifting gear. All bridge cranes have the same basic structure. A crane cross girder supports a moving trolley with a hoist attached. The crane cross girder can be a single girder or a double girder - with varying advantages. Single girders are typically less expensive and use simpler trolley systems, whereas the double girder allows for greater hook height. The entire bridge crane is supported by runway beams, allowing it to travel along the length of a factory. There are two distinct types of bridge cranes: top running bridge cranes, and under running bridge cranes. For top running bridge cranes, the bridge crane structure rides on top of runway beams. This system allows greater loads to be lifted, and is a more efficient use of headroom. Bridge cranes are widely used in heavy-duty industrial plants including train construction and cement processing plants.