Cathodic protection of LPG mounded vessels - Specific solutions for particular problems

摘要

Corrosion of LPG Tanks is, among others, a long term risk for safety. Apart the many rules implemented, also by learned lessons from past accidents, corrosion protection of LPG Tanks is quite a special application. Our experience in new large capacity Mounded LPG Systems has led to focus specific "HOT SPOTS" in the various phases of design, installation, commissioning and operation of such systems. In order to be successful, the design, materials selection, site erection procedures and operation of a Cathodic Protection system should come alongside the above said phases, thus making aware the CP specialists of the peculiarities that can influence the implementation of such type of installation. The complex various phases of site erection of two 2000 m3 LPG mounded tanks in Madinah (KSA) area, and the subsequent positive commissioning results, together with the development of a new modular CP Equipment devoted to such type of Complex Structures, including an "in-built" specific Monitoring System are presented and discussed. The implementation of the CP System involved many kinds of specific competences in various fields such as mechanical installation, choice of soil and proper compaction, careful verification of coating damages and the relevant repair, design of the installation of groundbeds and permanent reference electrodes, wiring of the whole system up to the Control Room. Commissioning has confirmed that in such complex structure the unavoidable presence of hidden "hot spots" can be healed thanks to the preventative measures taken in the various phases of the CP design and installation.