Historical SECO SEALS document – Post 2 is from Voi-Shan which introduces the “The Conical Seal” and includes the “Interim Report No. AN AN59MD3008-1, Flared Tubing – Survey of Concentricity” regarding the “Problem and leakage on High Pressure Lines” for sealing helium lines by Convair-Astronautics in August 1959.
Following is the abstract from the Convair-Astronautics report.
“The report describes an evaluation by Manufacturing Research and Development, Dept. 29A-2, assisted by Engineering, Pneumatics Design Group, to improve production tube flaring methods and equipment, for high pressure helium service. It was found, due to orange peel effects on the surface of the flared portion of the tube, and the material hardness of mating surfaces, leakage of helium was inevitable. The most effective and practical method of sealing the mating surface was accomplished by fitting a soft copper flared fitting seal, which has since become a standard production fitting.”
“Another cause for leakage was due to discrepancies existing in Military Standard Drawings involved. Until drawings have been revised in accordance with the recommendations of this report, fittings are not adequate for high pressure helium line assemblies.”
