Research On The Reliability Of JJ160/41-K Type Derrick

Oil derrick is an important part of oil equipments. At present, the most common methods to do an safety evaluation for oil derricks is to do a field test for stress, displacement and structure dynamic characteristics of the derrick in engineering, base on the testing dates, the carrying capacity of the derricks is determined according to the method of linear extrapolation. But only limited dangerous positions can be made a test point arrangement in the loading test on site, and the test loads are far below the design loads. So, the comprehensive and reasonable evaluation results are difficult to be obtained. The safety assessment theory on oil derrick is the important theoretical basis for analyzing carrying capacity of derrick, its purpose is to analyze the actual working performance of the derricks and determine the carrying capacity and application conditions of the derricks in use by means of derrick assessment, to ensure safety operation of the derricks. The main methods to do a safety assessment is to combine testing data on loading test of the derricks in use during field with the numerical models of finite element analysis for derrick structure, and using field test datas to modify the computer numerical models for the derricks till it's close to real structure of the measured derricks, then the computer load simulation experiment for the derricks is carried out. At last, the reliability of the derricks in use is assessed by means of using reliability theory.Now a research program of mutual complementation and mutual coordination of testing research and analysis research of theoretical modeling is adopted. If only the research of testing technology is carried out, but analysis research of theoretical modeling for derricks is not carried out, such cases are certainly will appear: on the one hand, test content and target will lack of necessary theoretical guidance; on the other hand, the test results are difficult to be transformed into evidence assessment on safety and reliability of the derricks in use for popularizing. If only the analysis research of theoretical modeling is carried out, but the necessary testing research is not carried out at the same time, then the data informations which is necessary to safety and reliability evaluation for oil derricks can't be obtained, and the safety and reliability evaluation for derricks which accords with the actual science is difficult to be made out. The main contents which are studied in this paper are summarized as in the following aspects:1. Study on the reliability theory and method of JJ160/41-K type derrick in use. It includs:selecting applicable reliablity theory and methods.2. The determination and calculation of reliability index for k type oil derrick. It includs:determining reliability index; calculating and measuring the values of related indexes for new oil derricks.3. Reliability evaluation for JJ160/41-K type derrick in use. It includes: extracting stress measurement dates which are obtained from measuring during different service periods; building reliability models for oil derricks; calculating reliability for oil derricks in use by means of the determined reliability index; implementing reliability evaluation for oil derricks.Reliability study and stress measurement on site for derricks is carried out in this paper by taking JJ160/41-K type derrick for an example, and an evaluation method for derricks is put forward., it can be used for making a safe bearing capacity evaluation comparatively scientifically for JJ160/41-K type derrick.