Abstract
Most of the natural gas production is transported through pipelines that require periodic inspections to evaluate the structural integrity of the pipelines due to possible defects caused by degradation that can rupture causing leakage of the fluid causing major disasters. Based on this, the project presents a methodology for predicting cracks in pipe used in gas pipelines. The approximation is based on the principles of gamma densitometry to calculate the density of the pipe wall in order to investigate possible cracks. The natural gas fluid is found in such systems and interferes in the density calculations and therefore will be considered in the simulations. The detection system uses a narrow beam geometry appropriately, comprising gamma ray source (137Cs) and NaI(Tl) 3"x3" detectors for calculating transmitted and scattered photons. Different positioning angles of the detector are investigated. In this study, the MCNP-X code is used to perform the simulations, in order to develop a counting geometry. Simulations of different thicknesses of the crack were also used to determine the minimum thickness detected by the two NaI(Tl) detectors. Having equipment that can estimate cracks present in pipes used in gas pipelines, in addition to predicting their location can reduce costs and make a major contribution to this sector.
Highlights
Due to the growing demand, natural gas is a source of energy that has been showing growth in the Brazilian energy matrix for use in industry, homes, motor vehicles and the electric sector
Much of the natural gas production is transported by means of gas pipelines that require periodic inspections to evaluate the structural integrity of the pipelines due to possible defects caused by degradation that may rupture causing leakage of the fluid causing large-scale environmental disasters with population damage and the economy of the local region
In Brazil, there are a total of 9,700 km of gas pipelines, 7,107 km operated by TRANSPETRO (TRANSPETRO, 2014) and 2,593 km operated by TBG (TBG, 2015), through 443 municipalities, with a transportation capacity of 130 million m3/d natural gas, making the control of gas pipeline integrity important to predict abnormality that could cause future risk to people and the environment
Summary
Due to the growing demand, natural gas is a source of energy that has been showing growth in the Brazilian energy matrix for use in industry, homes, motor vehicles and the electric sector. The gamma-ray densitometry technique has been applied satisfactorily in many areas, such as: petrochemical, oil industry and mining It has been used for flow measurements (Salgado et al, 2009); prediction of density (Achmad et al, 2004); thickness measurements (Berman et al, 1954) and inspection of pipeline surfaces (Anjos et al, 1989). This method of absorbing gamma rays can provide reliable measurements of the density of the analyzed material, improving accuracy. These advantages make these density meters very important in the industry and for this reason have been investigated and improved by many researchers. Theoretical models were developed using the mathematical code MCNP-X based on simulations using the Monte Carlo method to develop a suitable counting geometry for crack detection by calculating density
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