2.6 INFORMATION TO BE EXCHANGED BETWEEN THE USER AND THE DESIGNER OR SUPPLIER
Bridge and gantry cranes may be used for closely defined applications or for more general applications. It is therefore not always possible to give the designer or supplier precise details of the task to be performed and in some cases the following information can only be provided in terms of maximum and minimum values. When purchasing a crane for a new building the crane designer will need to be intimately involved in the overall design of the facility.
When purchasing a crane for installation into an existing building or for use on an existing supporting structure or tracks, it is essential that the supplier surveys the site of the proposed installation.The required information should include, but is not limited to, the following:
The maximum load to be lifted or the SWL.
The nature of the loads to be lifted.
Whether the application involves multi-lifting.
Whether the application affects the load, e.g., hoisting out of water.
Details of the duty cycle.
The minimum required height of lift.
The required hoisting speed.
The required long travel speed.
The required cross-travel speed.
For an existing supporting structure or tracks, the span.
For an existing supporting structure or tracks, the permitted loadings (if known). If not known, a design check is necessary.
For an existing supporting structure, the available headroom and end clearances.
The preferred type of crane.
The available power supply.
The preferred power supply system.
The preferred crane control system.
The operating environment.
For portal and semi-portal bridge cranes, whether persons may be present in the operating area.
The crane operator's working conditions. For pendant-controlled cranes where the operator follows on foot, the travel motion speed must be limited. For single-speed motion where a clear walkway is available, limit the speed to a maximum of 1.0 m/s. If there are obstructions in the operator's path, it is recommended to have a selectable speed of 0.75 m/s or less. For pendant and remote-controlled cranes with two or more speeds, including stepless control, higher speeds are allowed, provided that the slowest selectable speed is 0.75 m/s or less.
For an existing supporting structures or tracks, it will be necessary at some stage to have the structure surveyed to determine its condition and accuracy of alignment. It may also be necessary to have the design checked for which purpose the end carriage wheel centers and maximum heel loadings of the intended crane are needed. A load test may also be required. As the costs of repair, strengthening, realignment and testing can be considerable, purchasers are advised to have the structure surveyed at an early stage before committing to purchasing the crane.