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Keystone Engineering’s Wayne Tuttle has been granted United States Patent 9,840,752 for a new method for performing Post Weld Heat Treatment (PWHT) on the company’s line of spacecraft propellant tanks and related products.  This new method allows welds to be heat retreated while protecting sensitive internal components such as elastomeric bladders from exposure to excessive temperatures.  Prior art required heavier weld lands to make up for the reduced strength of a non-treated weld.  Utilizing this new technology, Keystone can provide elastomeric bladder and diaphragm tanks that are lighter than those of its competitors.