The choice of girder type in an overhead crane should be based upon application and building envelope considerations rather than price. Even though single girder cranes are generally less expensive than double girder cranes, each is the best tool for their designed application.
SINGLE GIRDER CRANES
Single girder cranes are great for light to moderate duty applications for normal production or maintenance applications. Single Girder Cranes have one girder attached to end trucks of the crane with the end trucks running on runway rail that runs the desired length of the building. With single girder cranes, the hoist is underrunning with the cross travel trolley generally running on the lower flange of the bridge girder. Single girder cranes are generally limited to 20 ton capacity with the bridge girder construction of wide flange beams under 65’ span and fabricated single box girder over 65’ span. The overall span is limited to about 130’.
Single girder cranes typically require less space over the top of the runway beam to the lowest obstruction of the building since the hoist in below the girder. In many existing buildings, the runways have been installed at a high position within the building limiting available clearance for use of only single girder cranes.
A single girder crane should suffice if the duty requirement is light to heavy and the application is simple production or maintenance.
DOUBLE GIRDER CRANE
Double Girder Cranes are great for larger capacities, higher duty cycles, and longer bridge spans. Double girder cranes have two girders attached to end trucks of the crane with the end trucks running on runway rail that runs the desired length of the building. With double girder cranes, the hoist is top running on rails installed on the tops of the girders with the hoist spanning the gage of the two girders. Double girder cranes are generally used for heavier loads, longer bridge spans, and for improved hook height since the hoisting machinery is on top of the girders rather than below. The capacity of double girder crane can be over 100 tons and with spans reaching well over 150’.
Double girder cranes typically require more space over the top of the runway beam to the lowest obstruction of the building since the hoisting machinery runs above the bridge girder. Therefore, where a double girder crane is desired there must be 4’ or more of clearance over the runway to the lowest obstruction. This over the runway clearance requirement increases with the capacity of the crane unless the hoist is dropped in between the girders, which is generally costly.
Many special applications such as heavy production, coil handling, and turning of loads with dual hoists are best served through the use of double girder cranes.
CRANE 1 has application professionals in each of our offices that can assist you in determining the correct crane and hoist type for your application. We design, fabricate, and install single and double girder cranes out of our regional fabrication facilities that ensure efficient delivery and high-quality control. When ready to specify your next crane, give your local CRANE 1 branch office a call.