ISO 11901-5:2021

Overview

ISO 11901-5:2021 - "Tools for pressing - Gas springs - Part 5: Safety instructions for gas springs" provides safety requirements and practical installation/operation guidance for nitrogen gas springs used in press tools and stamping dies. Aligned with ISO 11901-1, -3 and -4, this standard focuses on preventing failures and injuries by specifying protective design features (venting on fault), essential operating conditions and user instructions (Annex A) to maximize service life and safe operation.

Key topics and requirements

• Safety protections: Gas springs must include systems to vent gas to atmosphere in case of:
  • Uncontrolled return stroke (rod exceeding permitted speed after a jam is released).
  • Overstroke (rod pushed deeper than nominal stroke).
  • Overpressure (internal pressure rise from contamination or incorrect charging).
• Operating conditions (Annex A):
  • Designed for at least two million full strokes at maximum charging pressure and rated maximum temperature (where applicable).
  • Operating temperature range recommended: 0 °C to 80 °C.
  • Charging gas: only nitrogen (N2), commercial grade purity 5.0 (99.9990% vol) or better.
  • Maximum charging pressure: must not exceed manufacturer’s rating and shall be marked on the gas spring body.
  • Piston rod speed: a maximum permitted piston rod speed must be specified to avoid sudden high-speed returns.
• Mechanical requirements and mounting:
  • Force must be applied evenly; avoid lateral loads.
  • Safeguard gap (h): at least 10% of nominal stroke for strokes ≤ 50 mm, and at least 5 mm for strokes > 50 mm.
  • Multiple approved mounting options (lapped flange, two-part clamps, bottom flange, clamping flange, bolted-to-base, inserted into pockets) and strict cautions (e.g., do not use piston-rod threaded hole for mounting).
• Contaminants and maintenance:
  • Avoid permanent contact with fluids, swarf, abrasive dust and aggressive detergents.
  • Maintenance and servicing must be by authorised personnel only.
  • Typical maintenance intervals (per Table A.2) depend on stroke length (e.g., up to 1,000,000 strokes for s < 100 mm).

Practical applications and users

• Target users: press tool and die designers, toolmakers, maintenance engineers, safety managers, gas-spring manufacturers and suppliers, and conformity assessors.
• Applications: stamping dies, forming and pressing tools where nitrogen gas springs are used for energy storage, counterbalance or retaining functions.
• Practical benefits: reduces risk of catastrophic gas-spring failure, extends service life, eases compliance with machine safety regimes and manufacturer instructions.

Related standards

• ISO 11901 series (see parts 1, 3, 4) - provides dimensional, performance and testing context referenced by ISO 11901-5 for complete gas-spring specification and safety compliance.