If it is desired to reduce the required thickness of the tubesheet flanged Extension, then specify the ratio of the Required thicknesses of Tubesheet Flanged Ext. and the Tubesheet. This is used in TEMA RCB 7.1342 for U-tube tubesheet exchangers
This is an optional input and this ratio should be less than 1.0 and more than 0.2. The default value is 1.0.