Macy 



AOO MORE WATER 

 IN COLUMNS TO 

 BRING TO 70'ORAFT 



FILL B TANKS 



FILL "a" tanks 



FILL COLUMNS TO 

 10' ABOVE DECK 



FILL COLUMNS TO 

 DECK LEVEL 



FILL COLUMNS TO 

 9.9' LEVEL- DECK 

 AWASH 



Fig. 18 - Variation in the metacentric height (GM) of 

 a colunin stabilized platform during submerging 



to effect a movement of the center of flotation in a more favorable direction, 

 there are two outriggers at one end which contain cylinders to provide additional 

 water plane area at a considerable lever arm in both directions. 



Drilling platforms which are designed for resting on the bottom in a partic- 

 ular water depth do not need as thorough a stability investigation as those which 

 are intended for drilling semisubmerged. The reason for this is that the tre- 

 mendous length and width of these platforms is such that in a fixed water depth 

 for which a platform is specially designed, it would heel over to the point where 

 one edge of it was aground long before the rig could capsize. On the other hand 

 platforms designed for drilling semisubmerged could conceivable be in water 

 much deeper than the width of the platform. Fortunately, the range of righting 

 levers of column stabilized platforms is very large — 50 to 70 degrees being 

 usual. 



As a safety factor, intact buoyancy above the water line is desirable. One 

 form of this buoyancy is horizontal subdivision in the columns. Some of the 

 compartments are occasionally filled with foamed-in-place plastic or empty oil 



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