Vacuum Applications Beryllium Copper Bellows Nomenclature Bellows Movements Standard Tolerances Multiply or Laminated Bellows Neck Trims Explanation of Tabulated Data Ordering Instructions Vacuum Applications Series 7500 Bellows can be used for high-vacuum applications requiring leakage rates less than 1 x 10-10 STD ATM CC/SEC at base pressure of 1 x 10-6 TORR. Since most of these applications require extremely flexible bellows, Hyspan recommends materials thickness of 0.006" for inside diameters (I.D.) up to 4.5", 0.008"for I.D. up to 8.0", and 0.010" for I.D. up to 14". Any material Thickness can be used which has a maximum pressure (Column 7 on pages 6-17) exceeding 15 PSIG. Type 321 stainless steel is preferred because of its weldability and availability; however, other alloys can be substituted. Weld attachments for high-vacuum applications are very critical. Because of the thin bellows material that is normally used, the addition of filler rod is not practical. The illustrations show the Hyspan recommended weld joints for internal and external attachments. The bellows must be a tight fit to the band, and the materials compatible because they are fused together.