Overview
ISO 11926-2:1995 - "Connections for general use and fluid power - Ports and stud ends with ISO 725 threads and O-ring sealing - Part 2: Heavy‑duty (S series) stud ends" - specifies dimensional, performance and testing requirements for heavy‑duty (S series) stud ends with ISO 725 threads and O‑ring sealing for general use and fluid power (hydraulic/pneumatic) systems. The standard covers both adjustable and non‑adjustable stud ends, their related O‑rings, and the formal designation format for these fittings.
Key topics and technical requirements
- Scope and components: Dimensions and hex tolerances (see ISO 4759‑1), flatness and fit of adjustable stud end washers, and designation rules.
- Working pressure: Designed for working pressures up to 63 MPa (630 bar) for non‑adjustable stud ends and up to 40 MPa (400 bar) for adjustable stud ends (actual permissible pressure depends on size, material and application).
- Materials and O‑rings: Stud ends are made from low‑carbon steel (plated) and O‑rings are specified as nitrile (NBR) conforming to the dimensional and quality criteria of the standard (specific IRHD hardness and dimensions are provided).
- Performance testing:
- Burst pressure test: Minimum ratio of burst-to-working pressure of 4:1; test blocks and procedures are defined and test report forms are provided (Annex A).
- Cyclic endurance (impulse) test: Six samples tested to 1,000,000 cycles at specified impulse pressures with defined cycle rates and pressure rise rates.
- Torque and assembly: Qualification torque values for testing are specified by thread size; assembly torque depends on lubrication, coating and surface finish and should follow manufacturer guidance.
- Designation: Standardized naming format (example: Stud end ISO 11926‑2 - 1/2 - 20) for cataloguing and traceability.
Applications and practical use
- Used in hydraulic and pneumatic systems, hose fittings, pipe and tube connections where robust O‑ring sealed threaded connections are required.
- Typical applications: hydraulic manifolds, industrial machinery, mobile equipment, and fluid conductor fittings subject to high pressure and cyclic loading.
- Practical value: ensures interchangeability, defined test methods (burst/impulse), and documented quality acceptance - critical for safety‑critical fluid power designs.
Who should use this standard
- Hydraulic equipment designers, fluid power component manufacturers, test laboratories, quality engineers and procurement teams specifying heavy‑duty stud ends with O‑ring seals.
- Useful for compliance, product qualification, and clear specification in technical documentation and catalogs.
Related standards
- ISO 725 (inch screw threads - basic dimensions)
- ISO 3601‑3 (O‑ring quality acceptance)
- ISO 11926 (other parts: ports, L series stud ends)
- ISO 6149 and SAE J1453 referenced for related hydraulic port designs
Keywords: ISO 11926-2:1995, heavy-duty (S series) stud ends, ISO 725 threads, O‑ring sealing, fluid power, hydraulic fittings, burst pressure, cyclic endurance, nitrile NBR O‑rings.
