Parameter of medium pressure Pcp is required, for example, to estimate the mass of natural gas involved in the formation of a fiery torch in case of emergency destruction of the main pipeline. However, the methodology for a systematic calculation of this parameter in the current methodological and normative documents, the author has not found. Despite the apparent simplicity of the problem, the analysis has shown that the parameter Pcp depends primarily on the performance QTU of pipeline, the pressure PH at the beginning of the emergency area and the pressure P0 at the point of the destruction of the pipeline, which in turn are determined by the dependencies from the pressure PK in the end of emergency site, the relationship of the lengths L1/L emergency areas, inner diameter dBH of the pipeline, it's the roughness k0, the hydraulic resistance coefficient X, the gas flow velocity w, it's the density in the working p in the normal pH and in the standard conditions pc, and more than twenty parameters characterizing the state of a gas in terms of its transport and depressurization of the pipeline. In some cases there is no justification of the calculated transitions, for example, to calculate the final pressure Рк2 gas at the second site crash in the presence of data for the initial pressure Ph1 first site crash. Calculations of these parameters regulated in several normative documents, which introduces uncertainty in the choice of the calculation scheme and is accompanied by the production of different calculation results. Calculations of other parameters recommended by the standard methods are complex, three-dimensional routine, require access to specialized software products that are not available in the current engineering activities. The subjects of this article are refinement of these problems, the rationale for the recommended design solutions and adapting them in a simple, systematic methodology for calculating the average pressure at different sections of the main pipeline.