An offshore jack-up drilling rig is a barge upon which adrilling platform is placed. The barge has legs which can belowered to the sea floor to support the rig. Then the barge can be”jacked-up” out of thewater providing a stable work platform fromwhich to drill for oil and gas. Jack-up drilling rigs were firstintroduced in the late 1950’s. Rack and pinion type jack-up unitswere introduced soon after that and have dominated the industryever since. The rack and pinion systems used to raise and lower therig are enormous in terms of gear pitch, or module, by gearindustry standards. Quarter pitch (101.6module) pinions are common,with both larger and smaller teeth used. Lifetime number of cyclesfor these units are – again, by gear industry standards -tiny, rack teeth typically have 25 year lifetime cycles measured inthe low hundreds. That is off the charts forAGMA (and ISO or DIN)design rules which draw a straight line to zero cycles for contactstress cycles less than 10,000. Use of any standards was abandonedfrom the start in the offshore industry for jacking applications.The author presents methods, and experience of that industry andsuggested allowable contact stresses in such applications.
- Edition:
- 09
- Published:
- 09/01/2009
- Number of Pages:
- 8
- File Size:
- 1 file , 220 KB
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