STEMEC is a software for complete mechanical design of shell and tube heat exchangers according to ASME VIII div. 1 and TEMA, including tubesheet calculation to UHX part, calculation of weights and evaluation of material costs based on the material prices stored in the data base. The software includes also an optional module allowing the calculation of workshop hours by means of customizable tables providing times and prices for all the possible shop operations. Another option of the program allows the generation of a drawing (including setting plan, scantling drawing and tubesheet layout). The optional interface with the H.T.R.I. program Xist for thermal design of shell & tube heat exchangers permits to carry out complete mechanical design starting from the results of the thermal calculation