Effective Management of Cathodically Protected Plant facilities in a Complex Gas Processing Plant

Abstract

Abstract Oil and Gas industries always have complex buried piping networks inside their plant facilities. Buried piping and other structures usually get multiplied due to frequent expansion of the plant facilities over years. Most of the buried piping is protected by dedicated impressed current Cathodic Protection (CP) systems installed during each expansion project. Furthermore, most of the buried piping is usually tied in with existing piping during the expansion projects, mostly without electrical isolation joints. No attempt is usually made by the CP designers to utilise the existing CP systems. Even though the buried piping is protected by distributed shallow groundbed anode systems, they are influenced by other CP systems and existing piping network due to shallow water table and associated low resistivity soil. Adding to the complexity of the piping network and the multiple CP systems, installation and commissioning of CP systems are usually handled by different personnel who usually are not fully aware of the importance of the CP systems, its installation, and proper commissioning. Experience shows that CP systems are not given its due importance during the project implementation, sometimes with improper design, installation and commissioning data. The scope of this paper is to brief the methodology used to ensure reliable operation of the cathodic protection system in order to protect the buried, immersed structures such as piping, tank bottoms, vessels and concrete structures exposed to marine atmosphere from external corrosion. Introduction Most of the oil & gas operating facilities consist of several main processing plants and support facilities such as utilities and offsite assets. Each of the assets will have buried piping, buried pipelines, aboveground storage tanks, buried vessels, etc. The facility in which the methodology adopted to effectively manage the cathodically protected structures discussed further in this paper includes reinforced concrete structures exposed to marine atmosphere and onshore injection well casings. Further, the operating facilities are expanded in phases by separate projects and tied into existing facilities. Each of these projects installed dedicated CP systems for the structures constructed under individual projects without considering the utilisation of existing CP systems installed to protect the structures to which it is tied-in. This is particularly applicable to plants, which have buried piping systems, especially the one related to firewater, potable and other utility water. Each of these CP systems were commissioned without considering the influence (interference) of the existing CP systems associated with each of these structures, mainly buried piping. Adding to these complexities, these CP systems were installed by general civil contractors without any supervision of experienced CP personnel and inspected by non-CP personnel. It is also important to note that the impressed current anode (ICCP) type of CP system was installed for all the buried facilities with the exception of few piping, which are buried under road crossings protected by the sacrificial anode (SACP) type. Hence, it is important first to understand the installed CP systems comprehensively to manage them effectively. In order to effectively manage such complex network of CP systems and to ensure corrosion protection of buried structure, a proper review of the installed CP systems, its components and the structures protected by each CP system was done. Below sections outline the methodology adopted to manage the cathodically protected structures in a natural gas processing plant.