The Effects of Operating Parameters on the Geometry of a Measurement Section of a Pipeline
Abstract
This article deals with the effects of a temperature, pressure, gravity, pipe flanges and saddle supports of a measurement section of the pipeline on changes in the pipe geometry. The investigation was aimed, in particular, at examining changes in diameters of two pipeline sections relative to changes in their internal pressure, which ranged from 0 MPa to 6.0 MPa, and to changes in temperature, which ranged from 0 °C to 25 °C. As indicated by the results of a numerical simulation carried out within this research, a change in a diameter can be expressed most accurately if the effects of gravity, saddle supports and flanges are neglected. Changes in pipe diameters were examined merely as a function of changes in pressure and temperature. Gravity, flanges and saddle supports cause irregular pipe deformities that occur along the pipe circumference and length. These effects prevented identification of real values of changes in the pipe diameter on the measurement sections of the pipeline.
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Introduction
In investigation into changes in geometry of a measurement section of the pipeline, intended for natural gas transportation, two of the operating parameters play a significant role—a temperature and a pressure of transported gas. These two factors affect the pipe geometry, while their effects depend on particular combinations of pressure and temperature values; eventually, they determine a measured amount of transported gas. This article presents an analysis of the effects of pressure and temperature on the pipe geometry, which was carried out with four different pressure and four different temperature values. The results of the investigation are presented in the concluding section of the article in form of tables for two different types of pipes. Effects of pressure and temperature were evaluated using three calculation models while applying numerical methods: ProMechanika, ANSYS CFX and CosmosM [1-2]. The investigation was aimed at identifying the impact of identical boundary conditions on the results obtained by using the above listed software products. Another examined aspect was a possibility to apply simplified boundary conditions and their effects on the result.
Conclusion
The article presents results of investigation into two measurement sections of the natural gas pipeline. The analysis of the effects of pressure alone on pipe deformation revealed an interesting fact. The effect of any pressure at a pipe wall temperature of 0°C always results in a change in the pipe length in the negative direction (pipe length reduction); however, a change in the pipe diameter is positive.
The analysis of the effect of temperature alone on changes in the pipe length indicated that such changes never depend on the pipe diameter; however, they always depend only on a temperature of transported gas (i.e. the temperature inside the pipe). With an increase in the gas temperature, hence also in the temperature of the inner pipe wall, the pipe elongation increases too. The pipe elongation values, measured at identical temperatures, were identical for both pipe diameters.
A particular value of a difference in the pipe diameter, induced by a change in temperature, in the radial direction is directly proportional to the values of a pipe diameter and wall thickness.