Abstract

This case study details the retrofit installation of a replaceable linear anode based impressed current cathodic protection for a critical service double wall cryogenic Ethylene Storage Tank in Kuwait. The ground bed underneath the tank bottom has been provided with the heaters to maintain the temperature of soil, preventing the ice film formation below the tank bottom. This critical service tank could not be taken out of service and the existing CP system consisting of discreet anodes around the perimeter of the tank proved ineffective in meeting NACE criteria for cathodic protection. Utilizing Horizontal Directional Drilling (HDD) to bore under the tank, offered the opportunity to install directly below the tank linear anodes and a portable reference electrode profile tube while remaining in service. This novel approach to installing cathodic protection on existing tanks offers several critical benefits but had not previously been attempted in the Middle East Region. This paper will discuss the lessons learned in bringing this technology to the Middle East Region and focus on the design process, the installation works including the use of advanced electronic tracking technology for the HDD bore, and the commissioning results.

Introduction

Corrosion has long been recognized as an extremely costly naturally occurring phenomenon that can be controlled through the proper application of corrosion prevention and control methods protecting public safety, extending the service life of assets and preventing damage to property and the environment. The landmark Cost of Corrosion Study published by the U.S. Federal Highway Administration estimated that corrosion costs were approximately 3.1% of the nation's GDP. Within the study, several key sectors of the US economy were studied. This paper is focused on one of those areas – the corrosion risks associated with storage tanks that contain hazardous materials. The study determined that the annual direct cost of corrosion for above ground hazardous material storage tanks (ASTs) in the US was ∼$4.5 billion.

Cathodic protection be applied to prevent corrosion of external tank bottom plates for above ground storage tanks (ASTs) that are exposed to soil or sand foundations. API Recommended Practice 651 notes that "cathodic protection for new aboveground storage tanks should be included in the initial design."1

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