| With the rapid development of drilling technology, the demand for much advanced, reliable and economically applicable drilling equipment becomes more and more stronger. The complexity in structure and un-satisfying properties make old drilling rigs hard to meet the demand of new drilling technology and process. So it is utterly necessary for the industry to find a new type of oil drilling rig to replace the old ones. ZJ50/ 3150LDB, a new type of electromechanical combination driven oil drilling rig, is developed based on solid market survey and users'demand. Crown block, an integral component of the hoisting system, is one of the most critical parts of the rig. Trip in or out of the hole, well-site failure handling and normal penetration can be conducted by combining it with drawworks and traveling blocks of the hoisting system. Strict requirements can be found in API Spec 4F"Specification for Drilling and Well Servicing Structures", 8A and 8C"Specification for Drilling and Production Hoisting Equipment"in term of designing main structure and parts of this critical component. The parameters and configuration of the crown block described in this article are made in accordance of relative API standards and are the results of extensive perusing and search of documents published at home and abroad. The crown block has its reliability and rigidity greatly improved by adopting I-beam weldment for its platform and new materials such as Q345-B, 40CrNiMoA and 35CrMoA for its parts. I-beam weldment quality can be guaranteed by automated welding machine. New ring forging process is used for crown sheaves with secured milling quality and new structures like crown-o-matic, anti-falling device and crown protection add more safety factors to better meet HSE requirements. Shafts, sheaves and platform of the crown blocks are all go through computation on mechanics and by ANSYS finite element analysis. The results prove that this new type of AJ50LDB crown block can fully meet design requirements.
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