Several highly publicized refinery piping failures around injection points have made apparent the need for more detailed inspection requirements in these areas. This need was addressed by the American Petroleum Institute (API) with the first edition of the API 570 Piping Inspection Code. This paper discusses implementation of an inspection program that complies with API 570 injection point inspections and improves the overall reliability of injection systems. Four case histories are presented to illustrate the benefits of increased inspection efforts and to provide experiences to help improve existing inspection programs.
Many different types of process additives are used to maintain reliability and to ensure optimum performance of refinery operations. An additive may be a proprietary chemical such as a corrosion inhibitor, antifoulant, antifoam, oxygen scavenger, or as simple as a water stream to dissolve salt deposition or dilute corrosive process components. Typically, these process additives are injected into refinery piping systems through small branch connections either directly or through a quill or spray nozzle. These locations are commonly referred to as injection points.
Several types of unique corrosion mechanisms associated with injection points have become apparent to refinery personnel over the years. Problems include impingement opposite the injection point or at downstream changes in pipe direction, corrosivity of the additive itself, and insufficient or excessive injection rates. Many of these problems result in highly localized deterioration.
In recent years, several well publicized piping failures associated with injection points have been discussed at industry forums such as NACE, API, etc. Probably the most widely known was the failure and resulting fire at the Shell Norco refinery. Upon discussion, it became apparent that existing piping inspection programs were not sufficient to detect localized corrosion problems at injection points and that more thorough programs specifically designed to identify the unique problems of injection points were required.