Stiffening Effects of Tubes in Heat Exchanger Tubesheet

Abstract

Strain-measuring tests were performed with strain gages on rectangular coupons taken from perforated plate with triangular pitch under both uniaxial tensile loads and pure bending loads. The effective Young’s modulus obtained from the tests have strong correlation with the values recommended by the ASME Code. Next, to evaluate the stiffening effects of tubes, similar strain-gage tests were performed for different types of perforated coupons. One type had the tubes strength welded into the penetration holes of the test coupons. Another type had the tubes both expanded and strength welded into the test coupons. Stiffening effects of tubes are clearly obtained from these tests. Judging from the effective Young’s modulus of triangular pitch obtained by the testing, the recommended minimum credit given to the tube wall is 50 percent under elastic load condition. In addition, for experimental tests on an actual large-sized shell-and-tube heat exchanger under hydraulic test condition, good correlation was obtained between calculated and measured stress when full credit was taken for the tube wall in the calculation.