Development Of Professional Software For Design And Numeric Analysis On Mechanical Properties Of The Combined Fittings

The combined piping fittings is two or more adjacent on-site welding pressure pipes which are regarded designed and machininged as a whole. which acquired national patent, patent number ZL 2004 20110038.6. Tubes play an important role in connecting pressure pipeline system as accessory. The carrying capacity of tubes will affected the integrity and safte operation to the whole piping system directly. But few research is report home and abroad in this area. So far, there are no one combined fittings manufacturers who products combined tubes. Therefore, it is necessary to develop a general research in design method, standard specification and mechanical properties, which will provide technical guarantee to promote the new product's engineering application.The main works and achievements in this paper were shown as below:(1) Study on types of typical combinationAccording to tubes which were used in piping systems in petrochemical industry, fuel gas, steam and so on, the relation of different tubes appeared in the same node of pipeline was studied. Types of combined fittings were most generality or similarity were found and separated, and then structural optimization were needed and not simple combination. These types were used as typical combinations for further modular design.(2) Study on development of professional software for design of combined fittingsThe design idea is based on Object-oriented VB programming environment and SQL data base management system ,to developed the professional software for design by using self-bring interface in AutoCAD.(3) Study on mechanical properties of combined fittingsUsing numerical value analysis method, studied on mechanical properties and security of two typical types combined fittings: long radius double elbows and equal diameter tees with long radius elbow.The limit loads of long radius double elbows combination were calculated under internal pressure, pure bending and combined effect of pressure and bending moment, its influencing factors were gained by analyzing, The simplified estimation formulas for plastic limit load of combined fittings were established by the method of Marquardt. Meanwhile, by calculating the mechanical properties of the isometric equal diameter tees with long radius elbow in different knuckle radius, the impact of the knuckle radius to the limit load of combined fittings was gained and got the best knuckle radius of Tees.The research findings of this paper have important values in ensuring the normal operation of the pressure piping system, reducing the cost and improving the progress of the project.