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Failure Modes and Effects
Engineering Consulting
Two sets of hydrodynamic journal bearings were designed to spin a detector and associated electronic signal processing circuits in an enclosure that provided a hard vacuum operating environment. These journal bearings generated pressure as they rotated and lifted an eight pound rotor one-tenth of a micro-inch for extremely smooth operation in any orientation. These bearings failed to operate in the hard vacuum environment, leaking the lubricating oil past the seal. The failure modes and their effects were analyzed and the consultant provided a solution to the failure. This required eliminating some internal parts and machining a lubricant flow path in each of the $40,000 bearings. The modified bearings were installed into the sensor instrument and the instrument failure was eliminated.
A neodymium-Yag laser rod was used in an elliptical flash lamp cavity with the laser rod aligned to one focus and a gas filled flash lamp aligned along the other focus. A liquid coolant was pumped through the cavity to keep the rod cool so that dimensional changes in the rod would not change the lasing modes of the laser. This unit was used in a range finder and failure reports mounted just after a few months of use. Failure mode diagnosis suspected and proved through engineering analysis that the flash lamp produced a particular wavelength of light that was absorbed by the hydrocarbon cooling fluid. The energy contained in this wavelength was sufficient to break the bonds of the hydrocarbon producing carbon particles in the cooling fluid. After sufficient firings of the laser, enough carbon particles were produced to absorb the remaining energy from the flash lamp to render the range finder useless. The effects of this failure mechanism were understood and the consultant recommended a redesign of the laser to operate without cooling fluid in the cavity; however, the rod was machined to a particular shape and bonded to an aluminum pedestal so that as heat flowed through the rod and pedestal the rod became round and emitted the correct mode.
Two companies were issued different contracts that used the same circuits in the end article; however, one contract required the interface circuits to be radiation hard to 10 milli-joules while the other company's contract had no requirement other than available technology. The interfaces were incompatible and neither company could use the other's design. Failure modes and effects analysis was used to determine if a new circuit could be developed that would provide the 10 milli-joule radiation hard requirement but be minimally disruptive to the other company's circuit design. The consultant innovated a new radiation hard circuit that solved the problem and provided 20 milli-joules of radiation hardness.
Forty years of experience with failure modes and effects analysis along with solutions to solve the failures is available to you in a wide range of fields that include: radar signal processing, image processing, control systems, sensing, and more...
Customers include the U.S. National Laboratories, Military, and commercial clients.
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