Corrosion-resistant universal joints withstand undersea environment

Using machines and components in marine or underwater applications requires exceptionally high resistance to corrosive elements, a recent undersea oil pipeline system installation illustrates.

Stainless steel universal joint assembly from Belden Inc., used in underwater oil field equipment, is made of corrosion-resistant 316L stainless steel to withstand harsh corrosive sea elements.

Universal joint manufacturer Belden Inc . faced just such a harsh environment when it provided actuator connection shafts for an undersea oil valve actuator. The installation was located on the sea floor some 330 ft below sea level. Valves are opened and closed by small submarines. To allow the submarines to operate the valves from a safe distance, the valves are fitted with articulated shafts, which also transfer actuation movement and force to other parts of the system. The shafts are constructed like telescopes to allow change in length to adapt to small movements and relocation of the equipment’s position. Shaft assemblies must be easy to disassemble for transportation and reassemble for refitting.

Because of the harsh underwater environment, all components must have exceptional corrosion resistance. The universal joints use a high-grade stainless steel. Yokes are made of 316L stainless steel. Their contact surfaces are PTFE-coated to prevent galling and improve friction properties. Pins and blocks are also made of 316L stainless and protected with grease-packed boots.

AISI 303 stainless steel yokes and AISI 416 steel pins and blocks are also available to provide higher strength and better wear resistance. Standard single joints can be modified with a variety of stainless steel grades, including 304, 316, 17-4, and 15-5 to meet specific requirements. Diameters range from 1/2 to 6 in. (13 to 153 mm) with a standard operating angle of 35°.

— Jeanine Katzel, senior editor, Control Engineering, jkatzel@reedbusiness.com

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