Appendix B 

 PIPE STRINGS 



STEEL PIPE 



High-grade steel is recommended for manufacturing pipe used to 

 support heavy loads. Steels of minimum yield strengths in the range of 

 1 10,000 to 150,000 psi are considered the most suitable for the purposes of 

 this project. Table 3 of this report summarizes the important properties of 

 two types of steel pipe which satisfy these requirements. 



Pipes manufactured from P-1 10 or V-150 steels have been made in 

 diameters of up to at least 10-3/4 inches. Table 4 of the report presents 

 some pertinent design parameters for a suitable range of pipe diameters. 



PIPE COUPLINGS 



The oil industry has developed couplings made of material which 

 possesses the same ultimate strength as the pipe itself. There has, in addition, 

 been extensive experience in designing pipe strings which are subjected to the 

 same type of loading and operational procedures encountered in deep-sea 

 heavy lift. Since there will be mi'ch making and breaking of the pipe string, 

 a special coupling should be used to provide the longest possible life for the 

 system. Table 5 of the report illustrates how the strengths of typical joints 

 compare with the strength of the pipe. It can be seen that the joints are about 

 90% efficient in most cases. 



Pipe couplings of up to 13-3/8-inch diameter have been successful in 

 oil field operations, suggesting that it will be fairly easy to make couplings 

 suitable for the needs of this project. Two basic pipe joint designs have been 

 extensively used in the oil industry (Figure B-1 ): shrink grip and flash-weld. 

 For a shrink-grip joint, the end of the pipe is threaded and a heated tool joint 

 is threaded onto the end of the drill pipe. For a flash-weld joint, a special 

 tool joint thread is fabricated and the connection is welded onto the pipe. 

 For reasons not stated, the project engineers for the FORDS chose the 

 shrink-grip method of coupling. It would appear that this approach is indeed 

 the best of the two. Since the pipe is made of high-grade steel and is 

 relatively large, any amount of welding would contribute to increasing costs 

 and inspection difficulties and should, therefore, be avoided. 



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