Allowable Contact Stresses of Jacking Gear Units Used in the Offshore Industry


An offshore jack-up drilling rig is a barge upon which a drilling 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 of the water providing a stable work platform from which to drill for oil and gas. 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. Lifetime number of cycles for these units are -- again, by gear industry standards - small, as 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.
ISBN: 978-1-55589-969-1 Pages: 8
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