Failure mechanism of a coil type crude oil heater and optimization method

Wax deposition reduces the transportation capacity of oil pipelines and brings major safety hazards to oil production. Heating crude oil with a coil type heater can prevent wax deposition. To study the failure mechanism of the connection between the coil pipe and the gathering pipe and then find optimization methods, the microstructures of the welded joint are observed by scanning electron microscopy, and the mechanical properties of the materials are tested. A mechanical model of the interaction between crude oil and coil pipe is constructed for simulation calculations. The relations between mechanical properties and structural parameters are obtained, and the influence of inclination angle of coil pipe on heat transfer performance is found opposite to that on static performance. Based on the comprehensive analysis of heat transfer rate and stress-strain of multi groups of coil pipes, the methods to optimize the overall performance of the coil heater from the aspects of material, structure and processing technology are proposed. The maximum equivalent (von-Mises) stress and shear stress of bell end coil pipe are reduced by 14.81% and 3.22% respectively, and the heat transfer rate is increased by 7.36 kW compared with that of the original structure under the same working condition.