Effective Atmospheric Corrosion Management Using Coating Condition Inspection and Maintenance Programme
Authors: Shanmugam Jeevanandam 
Published: May 2016

A risk-based coating condition inspection programme is discussed, enumerating the approach taken to effectively qualify and quantify the level of external corrosion and the minimum level of maintenance re-work required to maintain facility integrity and reliability. Due to a very large and complex size of the facility, the inspection approach is based on "Block Inspection" philosophy utilising the SSPC-PA5, and industry best practice. The facility is broken down into inspectable and maintainable geographic blocks and inspected with ‘reporting-by-exception’ approach. A high quality of inspections coupled with optimising fabric maintenance costs by addressing high priority locations will ensure that the highest risk locations are mitigated at minimal cost using a long-term strategy instead of short term maintenance activities resulting in increased risk levels in multiple locations due to lack of planning and coordination.

Introduction

Onshore and offshore oil and gas installations around the world are subject to atmospheric corrosion on a continuous basis based on the prevailing conditions around the facility. External atmospheric corrosion occurs on equipment exposed to air, moisture and pollutants. The rate of atmospheric corrosion is determined by such factors as exposure to marine drift (airborne chlorides), airborne pollution and the time that surfaces remains wetted. This is a function of: rainfall or moisture,fallout from nearby equipment such as cooling towers, temperature and humidity andsweating conditions. Corrosion rates are also influenced by design features such as crevices which allow the entrapment of water and marine salts, the use of deluge systems, and the effectiveness of the protective coating systems.

The operating facility discussed in this paper covers approximately 4 million m2 of coated surfaces, including, but not restricted to structures, piping, equipment, tanks, vessels, columns, compressors, generators, supports, and other appurtenances. With such a large inventory, ad-hoc unplanned inspections followed by patch painting activities weren't adequate in maintaining it. Larger unplanned campaigns could not adequately and efficiently provide long-term corrosion protection. A more comprehensive and structured approach was needed.

In order to track and control corrosion on operation critical components, an effective long-term corrosion mitigation strategy and solution was required to overcome this challenge and to provide an effective and an optimal maintenance painting programme. Additionally, a condition-based monitoring and reporting programme was required in order for the inspection team to provide quantifiable data to translate this information into an effective maintenance programme and help track corrosion progression over the lifetime of the equipment.

Thus, an industry recognised structured approach undertaken to develop and execute a ‘block’ inspection and maintenance programme utilising the philosophy highlighted in SSPC PA-5 and risk- based inspection methodologies.