ISO 5171:2019

Overview

ISO 5171:2019 - Gas welding equipment: Pressure gauges used in welding, cutting and allied processes specifies requirements for Bourdon-tube pressure gauges used with compressed gas systems at pressures up to 30 MPa (300 bar). The standard covers gauges for welding and cutting applications, including use with dissolved acetylene and liquefied gases under pressure, but excludes gauges for acetylene in acetylene-manufacturing plants. It is the fourth edition (2019) and updates the 2009 version.

Key topics and technical requirements

• Scope and units: All pressures are gauge pressures in MPa (and bar).
• Gauge type and accuracy: Applies to Bourdon-tube gauges with a minimum accuracy of class 2.5 (±2.5 % of full-scale).
• Maximum scale and marking: Maximum operating pressure must be marked on the dial and shall not exceed 3/4 of the maximum scale reading; preferred scale values follow ISO 497.
• Materials and oxygen compatibility: Parts in contact with gases must resist chemical action of the gas. Oxygen service requires non‑flammable materials and oxygen‑compatible lubricants and sealants (see ISO 9539).
• Design, dimensions and threads: Nominal case sizes (40, 50, 63 mm) and connection threads conform to ISO 228-1 (parallel), ISO 7-1 (tapered R) or ANSI/ASME B1.20.1 (NPT).
• Safety features: Gauges must include a vent/blowout safety device to safely dissipate internal pressure and prevent parts being ejected toward the user.
• Mechanical and performance tests:
  • Overpressure/leakage tests: Test A - 24 h at 60 °C, leakage ≤ 0.306 mbar·L/min; Test B (supplementary) - leakage ≤ 0.0612 mbar·L/min under specified conditions.
  • Torsion: Torque tests at 10 Nm (accuracy retained) and 25 Nm (leak-tightness).
  • Bending: Load 1 kN - gauge must remain leak-tight at maximum scale pressure.
  • Case vent, flammability, and other tests: Requirements to ensure safe venting and non-flammability for oxygen service.
• Marking and testing procedures: Clauses define required markings, test sample quantities and test methods.

Applications and users

ISO 5171:2019 is intended for:

• Manufacturers of gas welding, cutting and allied equipment and pressure gauges (design, production and QA).
• Procurement and specification engineers selecting gauges for oxygen, acetylene, CO and other compressed gas systems.
• Safety and maintenance personnel who install, inspect or service regulators, manifolds and cylinders.
• Testing laboratories and conformity assessors performing leakage, torsion and overpressure tests. Practical benefits include safer gauge selection, compliance with international safety and performance expectations, and clear criteria for design, testing and marking.

Related standards

Commonly referenced with: ISO 9539, ISO 14114, ISO 2503, ISO 15296, ISO 497, ISO 7-1, ISO 228-1, ANSI/ASME B1.20.1. These cover material requirements, manifold systems, regulators, terminology and thread specifications.