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137 VAC U U M C U P S & F I T T I N G S 6 For more information or for additional configurations, please contact us at NASInsideSales@imi-precision.com VACUUM CUPS Leakage Flow - Porous Leakage Flow - Uneven Surface Large bore fitting and vacuum line Extra large bore fitting and vacuum line Atmospheric Pressure Atmospheric Pressure Atmospheric Pressure Atmospheric Pressure Porous Materials: corrugated, woven materials, or objects with extremely rough or uneven surfaces When handling porous materials, it is important that the flow path between the object and the vacuum generator is as large as necessary to allow the generator to draw away the air that leaks through the surface or from gaps between the cup and the surface. Pay close attention to the bore size of the fitting in the cup, as well as the size of the vacuum lines. To confirm vacuum lines are sized properly, see the Operating and Installation Instructions section for each generator. When calculating the holding force for porous materials, the vacuum level that will be achieved is not normally known because the leak rate of the material is unknown. To move forward and determine the diameter of the vacuum cups, assume that system will reach a vacuum level of 8 PSI [16"Hg, 0.542 bar]. Norgren recommends the "M" series vacuum generators to maximize flow and minimize compressed air usage when handling porous materials. To ensure that the vacuum level of 8 PSI [16"Hg, .542 bar] is achieved, contact Norgren Tech Support for a generator recommendation. Vacuum Cup Selection Guide Example: Holding Force Calculation for Porous Materials or Uneven Surfaces Application: lift a 100 lb [45.36 kg]corrugated box with vacuum cups in the horizontal plane. Remember the safety factor and the equation F = P * A. 200 lbs [90.72 kg] = 8 PSI [.542 bar] x A - Solve for A – the total vacuum cup(s) area. A = 200 [90.72]/8 [.542 bar] = 25 in 2 [164.35 cm 2 ] of combined cup area. Assume the number of cups used will be 4. Determine the Number of Cups Needed to Determine the Diameter of each Cup Divide the total area by the number of cups (25/4)[164.35/4] – area of each cup is 6.25 in 2 [41.09 cm 2 ]. Solve for the diameter (d 2 ) using the equation: A = p * d 2 /4, 6.25 = 3.14 (d 2 )/4 [A = p * d 2 /4 , 41.09 = 3.14 (d 2 /4)] d = square root of (6.25 * 4/3.14) = 2.82 [d = square root of (41.09 * 4/3.14) = 72.3 mm] Solution: Choose a flat cup with cleats or bellows cups with a diameter of 3" [76.2mm] or greater. (Dimensions have been rounded up.) In this situation, Norgren recommends a NVP80-250M vacuum generator.