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Industrial Systems: Redesign of Bellows-Type Helium Pump for the U.S. Navy

Client

Metal Bellows Corporation, Sharon, MA.

Problem

Client had contracted the delivery of this pump to the Naval Coastal Systems Laboratory, Panama City, FL. But the pump would not meet the required life specifications. The guide bearings for the bellows failed in 100 hours, instead of the 1000 hours required.

Solution

The bearings tried were made of teflon composites, among the best available for this application, but were much too short for proper guidance. They were functioning as guides in a slide-crank linkage to maintain the bellows moving in straight line and prevent fatigue failures. The design of the pump housing could not be changed much. And the guidance ratio L/D was much too small. The solution finally arrived at was to place the two opposing bellows collinearly instead of staggered and use one common slide rod for both bellows. The slide rod was then driven by a single crank and eccentric. By so doing, the guidance ratio L/D was increased almost twelve times. In addition to that, the bearings were replaced by pure carbon. Graphite sleeves of a special composition made to very exacting standards. Those bearings do not need lubrication in most cases. They also support high loads. In this case, the redesign allowed the pump to pass the required tests and it was still running way past the 1300 hours of operation when Professor Blanco last saw it.

Picture of the Bellows-Type Helium Pump for the U.S. Navy