Learnings From Incidents in Steam Systems

Abstract

In Oil & Gas plants, steam is supplied to different process units such as turbines & reboilers through piping and is routed on pipe racks. The steam system is encountered with typical problems such as condensate accumulation, hammering, vibrations, condensate discharge, etc. These can cause serious damages to the piping and supporting systems. Such operational and design issues related to steam service can affect the integrity of Plant structures. This paper presents the improvements that are considered in steam lines and their supporting structures which assures high safety and integrity of the system. Steam traps are provided to filter out condensate and non-condensable gases without letting steam escape from steam pipes. Faulty working of steam traps causes accumulation of condensate resulting in hammering which induces heavy vibration and impulsive loads. The impact loads are not accounted in structure design as their magnitude can't be precisely computed due to its complexity and dynamic nature. These accidental loads can have destabilizing effects on the system such as failure of pipe supports, supporting structure, consequential damage of neighboring pipes etc. Conventional practice of open discharge of steam trap condensate on concrete substructure is another cause of concern. Comprehensive study of failure of piping & structural systems at different plants was undertaken to identify possible root causes and realize mitigation measures. To address the deficiencies identified and to further enhance safety, various improvement options were studied and optimal solutions to steam system design were finalized. Some of the improvements proposed included positive isolation / blinding of steam lines to avoid condensate build up, removal of abandoned steam lines, periodic condition monitoring of steam traps, installation of automatic Wireless Acoustic Monitoring system for steam traps, design prerequisites for cantilever supports, sampling and testing of supplied structural bolts as a part of QA/QC, routing of condensate drain discharge to plant drainage system. Suggested improvements and recommendations were implemented and no further issues were reported until this time.