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NBBI NB 23 (NBIC) National Board Inspection Code - Part 4 Pressure Relief Devices

NBBI NB 23 (NBIC) National Board Inspection Code - Part 4 Pressure Relief Devices by The National Board of Boiler and Pressure Vessel Inspectors (25th) — ava...

The National Board of Boiler and Pressure Vessel Inspectors 25th

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NBBI NB 23 (NBIC) Part 4 – Pressure Relief Devices is the volume of the National Board Inspection Code dedicated to the installation, in‑service inspection, testing, and repair of pressure relief devices that protect pressure‑retaining items from overpressure. It provides a complete framework to ensure these devices operate reliably for the life of the equipment. Purpose and scope Part 4 focuses specifically on pressure relief devices used on boilers, pressure vessels, and pressure piping, such as safety valves, relief valves, and rupture discs. It addresses how these devices are selected, installed, inspected, tested, maintained, repaired, and documented so that they continue to provide adequate overpressure protection under all expected operating conditions. Major topics covered NBIC Part 4 typically includes: Device types and definitions Describes the different kinds of pressure relief devices, their basic operating principles, and terminology used throughout the code. Installation requirements Sets rules for inlet and outlet piping, valve orientation, drain arrangements, discharge locations, and isolation, ensuring devices can relieve pressure without undue restriction or interference. In‑service inspection and testing Provides guidance on inspection intervals, visual checks, functional testing (including shop and field testing), acceptable tolerances, and criteria for continued service or removal. Repair, adjustment, and recalibration Establishes requirements for organizations that repair and set pressure relief valves, including procedures, qualification of personnel, use of proper parts, seal management, and post‑repair testing. Documentation and certification Specifies the records, tags, reports, and, where applicable, application of National Board “VR” or similar marking to demonstrate that repairs and testing meet recognized standards. Typical users and applications NBIC Part 4 is used by: Valve repair and service organizations, especially those holding appropriate National Board certifications. Authorized inspectors and jurisdictional authorities overseeing overpressure protection systems. Owner‑users, plant engineers, and reliability/integrity teams managing fleets of safety and relief valves. Engineering firms designing or modifying pressure relief systems associated with boilers and pressure vessels. Role within the NBIC set Within the NB 23 NBIC 4‑volume set, Part 4 complements: Part 1 – Installation requirements for initial placement and connection of pressure relief devices. Part 2 – Inspection practices that include evaluation of overpressure protection. Part 3 – Repairs and alterations affecting pressure boundaries, which often trigger review or changes to pressure relief devices. Together, NBIC Part 4 ensures that the last line of defense—pressure relief devices—remains effective, traceable, and compliant throughout the life of pressure‑retaining equipment.