Overview
EN ISO 228-2:2003 (ISO 228-2:1987) titled Pipe threads where pressure‑tight joints are not made on the threads - Part 2: Verification by means of limit gauges specifies the verification methods for cylindrical pipe threads using limit gauges. This European adoption cancels and replaces the first edition and complements EN/ISO 228‑1, which defines the thread dimensions and tolerances. The standard addresses the particular needs of the 55° thread profile used for non pressure‑tight pipe connections and requires multiple GO and NOT GO gauges to verify different profile elements.
Key topics
- Scope and purpose: Verification of cylindrical pipe threads (as defined in ISO 228‑1) by means of limit gauges rather than making pressure‑tight joints on the threads.
- Gauge types and function:
- GO threaded plug and ring gauges - check the maximum material limit (virtual pitch diameter) and ensure adequate flank/crest/root form.
- NOT GO threaded plug and ring gauges - check the minimum material limit and prevent oversize pitch diameters.
- Wear check plugs - confirm that GO/NOT GO gauges remain within allowable wear limits.
- Verification principles: Gauging follows established metrological practices (Taylor principle for GO checks), and includes checks for pitch diameter, major/minor diameters, flank form and rounding at crest/root.
- Multiple gauge requirements: Because the 55° thread profile has distinct elements to verify, several GO and several NOT GO gauges (and associated relief/clearance features) are required.
- Use and control: Procedures for using gauges by hand (number of turns allowed when gauging), periodic control of gauge wear, and acceptance criteria for threaded parts and gauges.
Applications
- Quality control and production inspection of threaded pipe fittings and connectors where sealing is achieved by a seal or gasket (not by the thread).
- Manufacturers of pipes, fittings and valves who must ensure interchangeability and dimensional conformance to ISO 228 series.
- Gauge manufacturers and calibration laboratories that produce and verify GO/NOT GO ring and plug gauges and wear check plugs.
- Industrial sectors using threaded pipe connections in non‑pressure sealing applications (machinery, instrumentation, general plumbing and assembly), referencing ISO 1179 where applicable.
Related standards
- EN/ISO 228‑1 - Designation, dimensions and tolerances for cylindrical pipe threads (complements Part 2).
- ISO 1502 - General-purpose metric screw thread gauging practices referenced for Taylor principle and symbols.
- ISO 1179 - Example industrial applications for pipe connections.
EN ISO 228‑2:2003 is essential for suppliers and inspectors who need consistent, repeatable verification of cylindrical pipe threads using limit gauges, ensuring interchangeability and compliance across international manufacturing and inspection processes.
