12.5.3 Selection of Lifting Appliance
The choice of lifting appliance, e.g. hand chain hoist, electric power operated hoist or pneumatic power operated hoist, etc., will depend on the frequency of use, nature of load and working environment. Guidance on hand chain hoists will be found in section x-svn:///svn/leea/dita/xml/topics/TOP_00000000/TOP_00000048.html and on power operated hoists in section x-svn:///svn/leea/dita/xml/topics/TOP_00000000/TOP_00000157.html of this code. For some applications, fixed point lifting is desirable as a permanent feature. This can be achieved so that the operative is on the outside of the mobile supporting structure using built-in winch and pulley arrangements.
In all cases consideration must also be given to the means of connecting the lifting appliance to the runway beam. This may be achieved by the use of trolleys, beam clamps, fixed eyes or built-in pulleys dependent on the application, type of lifting appliance and design of the mobile supporting structure. It is important that such devices are compatible with the section of beam. Guidance on travelling girder trolleys will be found in section x-svn:///svn/leea/dita/xml/topics/TOP_00000000/TOP_00000323.html of this code and beam clamps in section SECTION 9 - BEAM CLAMPS.
In the case of power operated hoists, the type of power feed to be used must be taken into consideration together with the availability of a suitable power source. The power source must include provision for isolating the mobile supporting structure and hoist from the power supply and a ready means of disconnecting the supply when movement of the mobile supporting structure is necessary, e.g. plug and socket in the case of electrics or valve and quick release connector in the case of pneumatics. Electric power feeds must be provided with an integral earth line and under no circumstances should the mobile supporting structure itself be used for earthing purposes. Steps must be taken to avoid hazards that may exist or be caused by the selected power feed, e.g. trailing leads or hoses. Movement of the mobile supporting structure must be restricted so that no tension is placed on the power feed. (See section 12.11 SAFE USE OF MOBILE SUPPORTING STRUCTURES)
Careful consideration must be given to the capacity; both of the lifting appliance complete with its connecting device and of the mobile supporting structure. The marked capacity of the lifting appliance must not exceed that of the mobile supporting structure, so as to avoid confusion from differently marked SWLs. In the case of multi-point lifting using two or more appliances, the marked capacity of the mobile supporting structure is the maximum capacity and the total capacity of the appliances must not exceed this. For example, a mobile supporting structure marked 2 tonne SWL may be fitted with 1 x 2 tonne SWL hoist or 2 x 1 tonne SWL hoists.
Further consideration is necessary in the case of multi-point lifting. Steps must be taken to ensure that no one appliance carries more than its share of the total load.
Care must be taken if pulley block and winch arrangements, other than those built into the mobile supporting structure, are to be used. The mobile supporting structure capacity must take into account both the effects of the effort and of friction which will, in addition to the load, act on the mobile supporting structure. (See section 1 1.A4 APPENDIX 4 - STRUCTURES).