9.4　Cradle

9.4.1　The cradle supplied by individual parts should be assembled on the platform or the rail chair.The assembly shall comply with the requirement of the design technical document or the written technical instruction of the supplier's site representative.In case of no requirement in the design technical document，comply with the written technical instruction of the supplier's field representative or that of Articles 9.4.2-9.4.9 of the code.

9.4.2　In case of cradle pairing，they shall be assembled at"0"position for smelting and firmly supported.

9.4.3　Prior to cradle welding，the corresponding WPQ shall be carried out and the operation instruction for welding shall be prepared based on the WPQ report.The welding shall be carried out in strict accordance with the instruction.

9.4.4　The cradles shall be assembled according to the equipment drawings and the marks by the manufacturer，with the allowable deviation of dimensions conforming to the following requirements:

1　The central distance of two curved plates shall be with the allowable deviation of±2.0mm，and the measurement by ruler should be carried out.

2　The end teeth，end post or diagonal's relative difference marked by manufacturer of two curved plates shall be with the allowable deviation of 3.0mm，and the measurement by ruler should be carried out.

3　The verticality of the curved plates shall be with the allowable deviation of 0.5/1000，and its upper end should be inclined away from the furnace core，which should be measured by suspension wire.

4　The corresponding teeth（posts）of two curved plates shall be at the same horizontal plane and with the allowable deviation of 1.0mm，which should be measured by optical instrument.

5　In case that the furnace cover and electrode rotating mechanism（portal frame）is installed on the cradle，the central distance between the cradle and it shall be with the allowable deviation of±2.0mm，which should be measured by ruler.

9.4.5　The length，thickness and distance of tack welds shall ensure that the weld cannot get cracked during formal welding operation.

9.4.6　The deformation during welding shall be monitored and controlled.

9.4.7　The appearance quality of welds shall conform to related requirements of current national standard Code for Installation Acceptance of Steel-making Mechanical Equipment GB 50403.

9.4.8　The internal quality of welds shall conform to related requirements of current national standard Code for Installation Acceptance of Steel-making Mechanical Equipment GB 50403.

9.4.9　The cradles shall be installed according to the following requirements:

1　The cradles shall be lifted on the rail chair and adjusted to"0"position，and finally firmly supported.

2　The longitudinal and horizontal center lines shall be adjusted，and the measurement by plumb wire should be carried out，with the allowable deviation of 2.0mm.

3　Shake the cradles and check that the mesh of curved plates'teeth（posts）and rail chairs'teeth（holes）shall comply with the requirement of the design technical document.

4　In case that the furnace cover and electrode rotating mechanism are installed on the cradle，the levelness of their bearing surface shall be inspected，and the measurement by leveler should be carried out，with the allowable deviation of 0.20/1000 and the direction of furnace core over its external side.