Cracking Failure Analysis And Countermeasures Of A Tee On Residual Oil Hydrogenation Unit

Hydrogenation technology is to improve the quality of products in petroleum refining to meet the requirements of environmental protection and to reduce the sulfur content of products plays an important role.Hydrogenation technology in petroleum refining industry to improve the crude oil processing deficiency and optimize product distribution and environmental protection have a very important role.In recent years,because of the lack of domestic oil resources,a large number of high sulfur crude oil have been imported from abroad.As the processing of high sulfur crude oil,hydrogenation unit has been gradually recognized and valued in refinery sectors.The development of hydrogenation unit is also more widely used in all aspects.Because of the poor nature of the crude oil,the corrosion of the hydrogenation unit is aggravated,especially the corrosion of the residual oil hydrogenation unit which is provided with low residual carbon is more serious.Due to residue hydrogen processing device belongs to the high temperature,high pressure and hydrogen condition,and also the process of flammable and explosive medium,once corrosion failure occurred,an extremely serious accident would occurred.Therefore corrosion problem of residue hydrogen processing unit might cause the industry great loss.The design pressure of residue hydrogenation unit reaction system is very high,so the product's quality of the pressure pipeline of high pressure pipe fittings(tee)quality also should be be addressed.This attract much attention of the technician and researchers.This paper mainly presents the failure analysis of tee in the residue oil hydrogenation unit,which leads to the emergency shutdown of the unit.In order to avoid the repeated failure of the familiar tee,the counter measures for safe and stable production of residual oil hydrogenation unit are further provided.The main contents of this paper include:(1)A brief description of the main device about the residual oil hydrogenation unit in the process of refining,and description of the the main process of residual oil hydrogenation unit process together with corrosion mechanisms.(2)Description of manufacturing process of the tee.Variety of methodologies to the analyze the failure of the tee.The macro and micro,the mechanical properties testing,hardness analysis,chemical composition analysis,metallurgigraphic analysis and other means of comprehensive analysis of failure causes have been adopted to find out the cause of the failure.According to the cause of failure,the corresponding measures are put forward to ensure the safe operation of the unit.(3)ANSYS software has been applied to analyze the failure of the tee in the normal operating conditions of cracking stress situation,and corresponding measures are put forwarded.Based on comprehensive analysis,it is found that the hardness of the tee exceeds the standard's value.The initial cracking source is located at the bottom of the tube surface,along the wall thickness wall extending outward and plasticity index is lower than the standard.The results show that heat treatment of tee is not proper.Therefore the quality of the tee should be assured during the construction and installation stages.