Theoretical & Experimental Researches On A Novel Detecting Technology For Safety Valve

In order to solve the contradiction which the operation cycle of large-scale processing plant has been continually elongated, and on inspection cycle of safety relief devices are very restricted (one year a review), The safety valve online testing technology, a effective technical measures, is put forward to protecting safety and reliability of the long-term operation of processing plant. Britain's FURMANITE Corporation took the first lead to propose a kind of online testing equipment TREVITEST in the 1980s. So far the core of almost all commercial safety valves testing technology comes from this technology. That is using outside force to promote safety valve stem to force open the safety valve disc, in the same time, judging the open state and using computer data acquisition systems to test, to achieve non-demolition site calibration(setting pressure). There are some of disadvantages of this technology in that, the testing carried out in the open style of the implementation, randomness nature of the opened state judge, possibility to reduce the seal tightness after forcing opening, impossibility to take testing implementation for processing fluids belongs to toxic, hazardous, flammable, explosive, expensive media.A new testing technology which not forces open the safety valve is proposed in this paper. The operating characteristics of the component itself of the safety valve's internal structure is make fully used without changing the original internal structure and function. This new technology has been obtained the China national patent of invention authorization (ZL200510033124.0)It is shown that, the existing published literatures of safety valve testing technology on domestic and international research focus on two aspects of theoretical and application. Literatures of theory research are concentrated on the former Soviet Union, with emphasis on the over-pressure discharge principle and stability of structure and other basic theories. Literatures of applications research major on the inspect exchange of experience .there is a huge number literature. The basic research of domestic safety relief theory is behind abroad for many years. The most advanced research is also just stop at the flow field simulation. Abroad has begun to use chaos theory to research overpressure discharge mechanism of safety valve. But this study also limited to incompressible fluids. The most important for practical compressible fluid chaos theory research of valve discharge mechanism has not yet found in literature. There are a large number of domestic literatures in applied research of testing technology. But it is little theoretical research. Foreign public documents are less in practical technology.This research started from the technical concept of the foregoing patent and based on the literature investigation. In-depth studies on the theory and practical (laboratory and field trials) of patented technology are performed. Eventually, the concept of patent technology is changed into a reality and made a number of new analytical methods and techniques.The basic theory of modern design is used for innovative technology research in the theoretical investigation. By creating morphological matrix, building up several function solutions, some of feasible set are obtained. The simulation of safety valve spring which is the most important component is studied. Detailed analysis results are presented. The rationality of implementation of testing techniques is evaluated. In the theoretical studies of valve disc function extended the plate & shell theory is used to research valve disc film sensors. The analytical formula set on the thin-walled plate & shell combination sensor, withstanding linear distribution concentrated force, are solved on the base of new boundary conditions and solving equations. The formulas set are put forward for the structural strength, stiffness, sensitivity, etc. Progress in the theory also includes giving the new phenomenon demonstrated field trials a reasonable physical explanation, and a new method for test data treatment is provided.Some technology researches of the laboratory and field running tests in the application studies are completed. In the experiments aspect, a new calibration model is proposed to solve the parameters calibration problems of valve disc sensor. Then performances assessment is solved before running. In running test, two testing systems are used for a number of valve disc sensors, number of original data is obtained and the new phenomenon which was no mentioned before is discovered. In the search for a reasonable physical interpretation process, a new method to treat test data and new performance curves are proposed, so that the traditionally two performance description of spring force and lift curves are changed into a variety of rich, more comprehensive characterization are described, new understandings of the discharge mechanism is obtained. Specifically speak, they are:1,The mechanism of full-opening safety valve reflect disc helping open can be contributed to contact force of valve and reflect disc decline, and this reduced axial force is transferred to reflect disc, forming reflect (gas) axial force on discharge process. This is the basic cause of relief valve disc assist-open high, without pressure increases too much; the valve disc can get a sufficiently large open altitude and energy. According to this, we can calculate reflect force and evaluation of valve performance quantitatively.2,In the open process of the full-open safety relief valve, the mechanism of inertia force produced come from force unbalance of continue growing pressure-axial force below valve disc and the keep dropping contact axial force up the disc. force unbalance is then found, and the quantitatively calculation method is obtained。Unbalance force in the direction of opening, which the acceleration of the moving parts and inertia force are resulted from.Back-seat process can also be similar to understand. Accordingly, the quantitative evaluation of inertia force can be calculated and evaluated.