Mechanical integrity for piping and vessels in industrial refrigeration systems.

The vast majority of industrial refrigeration systems in operation today use anhydrous ammonia as the refrigerant. Because of the hazards associated with ammonia, managing this infrastructure to avoid accidental releases is essential to protect the safety of on-site personnel and the surrounding public. Past incidents and accidents have provided overwhelming evidence that the loss of mechanical integrity due to external corrosion of piping and pressure vessels represents one of the primary failure modes. Since the principal material of construction for piping and pressure vessels is carbon steel, they are particularly susceptible to external corrosion. In this paper, we discuss the underlying factors that degrade the mechanical integrity of the piping and pressure vessels used in ammonia refrigeration systems. Effective strategies for inspections and tests to ensure the ongoing mechanical integrity of piping and vessels throughout the life of the system are presented. Recommendations for classifying corrosion and subsequent remediation are provided.