According to changing the type of oil in the process of transportation by the above ground pipeline, which may cause the pipe rack bending and thermal stress damage. The thermal expansion and thermal thrust of the compensator which has an important effect on the pipe rack bending were analyzed. Thereby, the axial horizontal displacement and horizontal thrust were determined. Clear and definite the reason for pipe rack bending. Combined with the type of medium transport in the pipe, the medium temperature, the pipe model, the pipe arrangement craft and other factors, the thermal stress of pipe and the allowable stress range were determined, To judged whether the pipe will produce destructive thermal stress and by the experience formula for further confirmation.

 

 

AutoCAD is an open computer aided design system. The system running environment is set through its system variables. When users need exploiting the system, some related system variables in application program should be set under the necessity of applications. In fact, it's difficult for users to master the commonly used system variables. By studying AutoCAD system variables, a technique of automatic tracking system variables in AutoCAD2006 is put forward, and a Visual LISP program of automatic tracking system variables was written. The experiment shows that the program can track all system variables in AutoCAD2006. The resource codes of Visual LISP were given, and its principle and usage were described in details. A applied tool was provided for AutoCAD exploitation users.