API RP 583

Abstract

This recommended practice covers the design, maintenance, inspection, and mitigation practices to address external corrosion under insulation (CUI) and corrosion under fireproofing (CUF). The document discusses the external corrosion of carbon and low alloy steels under insulation and fireproofing and the external chloride stress corrosion cracking (ECSCC) of austenitic and duplex stainless steels under insulation. The document does not cover atmospheric corrosion or corrosion at uninsulated pipe supports but does discuss corrosion at insulated pipe supports. The purpose of this recommended practice is to: — help owner-operators understand the complexity of the many CUI/CUF issues; — provide owner-operators with an understanding on the capabilities and limitations of the various nondestructive examination methods used to identify CUI and CUF damage; — provide owner-operators with an approach to likelihood assessment for CUI and CUF damage; and — provide owner-operators guidance on how to design, install, and maintain insulation systems to avoid CUI and CUF damage. The practices described in this document apply to pressure vessels, piping, and storage tanks and spheres. The document discusses the factors impacting damage mechanisms, the guidelines to prevent external corrosion/ cracking under insulation, the maintenance practices to avoid damage, the inspection practices to detect/assess damage, and the guidelines for likelihood assessments of equipment or structural steel subject to CUI and CUF damage.