An offshore jack-up driling rig is a barge upon which a driling platform is placed. The barge has legs which
can be lowered to the sea floor to support the rig. Then the barge can be“jacked-up’ out ofthe water providing
a stable work platform from which to drill for oil and gas. Jack-up drilling rigs were first introduced in the late
1950’s. Rack and pinion type jack-up units were introduced soon after that and have dominated the industry
ever since. The rack and pinion systems used to raise and lower the rig are enormous in terms of gear pitch, or
module, by gear industry standards. Quarter pitch (101.6 module) pinions are common, with both larger and
smaller teeth used. Lifetime number of cycles for these units are – again, by gear industry standards – tiny,
rack teeth typically have 25 year lifetime cycles measured in the low hundreds. That is off the charts for AGMA
(and ISO or DIN) design rules which draw a straight line to zero cycles for contact stress cycles less than
10,000. Use of any standards was abandoned from the start in the offshore industry for jacking applications.
The author presents methods, and experience of that industry and suggested allowable contact stresses in
such applications.