Double Girder Over Head CraneOn a double girder crane, there are two girder beams that make up the bridge and they’re supported by an end truck on each side. In most instances, the trolley and hoist run on a rail installed on top of the bridge girders. With a double girder design, you gain the depth of the cross girder if the hoist is placed between or on top of the cross girders - providing an extra 18”-36” of hook height in most cases.
Double girder cranes can be either top running or under running in design. A top running double girder bridge crane will provide the most overhead room, as well as the greatest hook height.
Double girder cranes are recommended for heavy-duty applications where the crane has to handle heavier capacities and longer spans. Because of this, the components of the crane system, including the hoist and trolley, are more complex in design - making double girder cranes more expensive than a single girder crane.
They also require more material for the bridge beams and the runway system, so extra consideration should be given to the building’s support structure. Additional tie - backs or support columns may need to be added to handle the additional deadweight on the supports or building foundation.
Double girder bridge cranes are ideal for lifting heavy loads and can be used in more frequent operation than a single girder crane. They can also be used both indoors and outdoors, in a bridge or gantry setup, and are frequently used in mining, iron and steel production, railyards, and shipping ports.
» Above specifications are for Class II Duty Cranes as per IS-807 & ISS IS 3177 - 1977 (Revised) & 800.
» Dimensions detailed above are based on standard 10 metres height of lift.
» Specification for cranes above 25 ton capacity can be provied on request.
» The above specification are our standard. Exact specifications to suit customer requirement can be provided against specific enquiry.
» Due to continuous design improvements dimensions are subject to change without notice.
» We can supply central drive as per requirement.
» We can supply Class IV duty cranes.
CRANE PARTS ARRANGEMENTMOTOR : The motor is three phase squirrel cage, conical rotor type working on 440 volts, 3P,50 Hz A.C. supply. This motor is specially designed for hoist and crane and is insulated by class 'F' type of insulation according to B.S : 2613. The starting and stalling torques of this motor are 220 % and 290 % of the full load torque. The motor is rated at 40 % CDF.
BRAKE : The axial movement of the rotor is one of the characteristics of the conical rotor type of motor. This characteristic is taken advantage of in the actuation of the brake. When the motor is started the rotor is axially pulled into the magnetic centre of the stator and the brake is released. As soon as the current is cut off the brake spring presses the brake disc against the cover and the brake is applied. The braking torque is 100 % above the motor torque at the rated load. The maintenance and adjustment of the brake is very simple and can be done without removing any part. The brake disc and brake end cover are both made of high grade cast iron and the brake lining is of 'Ferrodo' type.
GEAR BOX : The gear box is made of high grade cast iron. The precision spur gears are machined from alloy steel and are fitted with ball / needle roller bearings. The gear box is filled with grease.
ROPE DRUM : The rope drum is rolled welded and precision machined. This rope drum is supported on large diameter roller bearings on both ends and the drive is through internal gears.
This rope guide moves on the drum like a nut and prevents the rope from overriding and loosening.
ROPE : Generally 6 x 37 / 6 x 36 construction fibre core preformed type, ungalvanised wire rope is supplied. (Galvanised and steel core wire ropes can also be supplied, if specifically asked for).
MAIN HOUSING : All hoist parts are enclosed in the main housing thus forming a better looking integral unit. The main housing like the rope drum is also of rolled and welded const
ruction, equipped with mounting bracket. LIMIT SWITCHES : Every hoist is provided with built in limit switches to control the top and bottom positions of the hook. Tappets can be adjusted on limit switch rod to any position in between the range provided. These limit switches are actuated by the rope guide.
CONTROL : The hoist is controlled by a pendant push button station. Supply to the pendant push button station i I s of 110 volts as per IS specifications.
MICROSPEED : All hoists can be fitted with a micro speed attachment which reduces the hoisting speed to 1/10th of the main hoisting speed. The micro speed attachment works independent of the load and main hoist. There is a separate control for the micro speed. This arrangement is invaluable in the handling of bulky, heavy and delicate loads.
TESTING : Every hoist unit is tested at 125 % of the rated load capacity on single fall of rope. Even the components pass through rigorous inspection tests before the hoist is approved for dispatch.