Table B-2. Characteristics of Typical Derricks 



Manufacturer 



Height 

 (ft) 



Weight 

 (tons) 



Gross Nominal 



Capacity 



(tons) 



Continental Emsco 

 IDECO, Presser Industries 

 Lee C. More Corp. 



142 

 143 

 189 



52.9 

 45.7 

 61.8 



526.5 

 407.5 

 696.0 



For the project under consideration, it is estimated that the derrick 

 should be able to hoist 800 tons with a safety factor of two. This requirement 

 is certainly within the state-of-the-art, but such a derrick would probably be 

 one of special design. 



Sheaves and Hoisting Equipment 



Crown Blocks. The crown block provides a means of transferring the 

 load to the derrick while, at the same time, providing mechanical advantage. 

 Crown blocks usually consist of six or seven sheaves grooved to accommodate 

 the wire cable. Specifications for some of the largest crown blocks are 

 presented in Table B-3. 



Table B-3. Characteristics of Standard Crown Blocks 



Manufacturer 



Maximum 



Working Load 



(tons) 



Length 

 (ft) 



Height 

 (in.) 



Width 

 (in.) 



Weight 

 (tons) 



ALCO 



Continental-Emsco 

 IDECO 



National Supply 

 Oilwell Supply 

 Regan Forge 



600 

 600 

 560 

 583 

 580 

 600 



9 

 9 

 8 



63 

 59 



46 



49-1/2 



50 



5.0 - 5.4 



7.0 



6.3 

 7.5-8.0 



114 



