Conclusions 



Assuming that the necessary precautions are tal<en in the design and 

 operation of the pipe string assembly, it is safe to conclude that by using 

 V-150 pipe, 10-3/4-inches in diameter, a 600-ton load could be lowered to 

 7,500 feet with a safety factor of two against failure. The most critical 

 factor is the dynamic loading which could very easily overstress the pipe at 

 the suspension point, if the support craft were heaving too much or if the 

 load were stopped too suddenly. However, the latter are problems which 

 are not unique to this project and serve to emphasize the importance of 

 accurately stating the limitations of a system and operating within prescribed 

 limits. 



PIPE HANDLING EQUIPMENT^! 



The equipment necessary to assemble and lower a pipe string for a 

 heavy-lift operation would be very similar to the standard equipment found 

 at any oil well. The major components are: (1 ) derrick, (2) crown block, 

 (3) traveling and hook block, (4) swivel, (5) pipe elevators, (6) tongs, 

 (7) links, (8) slips, (9) guidelines, (10) leads, (1 1 ) draw works and power 

 source, and (12) coupling devices. 



Recently there have been some important improvements in pipe 

 handling systems. Discoverer II, an offshore drilling vessel, has been outfitted 

 with a hydraulic system which enables only three men to make and break 

 drill pipe with the help of powered slips and tongs. The system is semi- 

 automatic and utilizes equipment which, at the time it was constructed, was 

 either available or required very little development. Other systems have 

 been designed to make and break drill pipe which is in motion. The pipe 

 handling system for MOHOLE was to be completely automated. 



Derricks 



The American Petroleum Institute has a set of standard specifications 

 which serves as a guideline for the design of derricks of various sizes and 

 load-handling capacities. Specifications for some of the largest "standard" 

 derricks are given in Table B-2. 



Atypical offshore derrick is approximately 150 feet tall and has a 

 load capacity of 500 tons. One of the largest derricks planned was that for 

 MOHOLE: it was to be 196 feet high and hoist a 500-ton load with a safety 

 factor of 1 .67 (the static rating of the derrick was 1 ,000 tons). 



113 



