In this paper we are designing two tube shell and tube type heat exchanger as per ASME Section VIII Div. 1, TEMA codes and IS 4503:1967. Main aim is to check the mechanical stability of the device by calculating parameters such as thickness of the equipment. ASME Section VIII Div. 1 is especially for designing of pressure vessels and boilers. Since heat exchanger is also a type of pressure vessel we used the codes.