ISO 6149-4:2017

Overview

ISO 6149-4:2017 - Connections for fluid power and general use - Part 4 specifies dimensions, design, test methods and requirements for external hex and internal hex port plugs used with ISO 6149‑1 ports. The standard covers metric screw threads (ISO 261) with O‑ring sealing for fluid power and general hydraulic applications. Port plugs conforming to ISO 6149-4:2017 are intended for working pressures up to 63 MPa (630 bar), with allowable pressure depending on plug size, material, design and application.

Key topics and technical requirements

• Dimensions and tolerances: Detailed external-hex and internal-hex plug dimensions, hex tolerances (per ISO 4759‑1), and metric screw thread class 6g (ISO 261).
• Seal and O‑ring requirements: Default O‑rings are NBR (nitrile) at 90 ± 5 IRHD, meeting ISO 3601‑3 quality criteria; O‑ring dimensions and tolerances are specified.
• Performance limits: Rated for use at temperatures −40 °C to +120 °C (with petroleum-based hydraulic fluids unless otherwise specified). Burst, impulse (cyclic) and vacuum test requirements are defined.
• Test methods: Burst, cyclic endurance and vacuum tests are performed per ISO 19879 using qualification torques in the standard; manufacturers must test to verify performance - dimensional conformance alone does not guarantee rated performance.
• Materials, manufacture and finish: Guidance on materials (e.g., low‑carbon steel), workmanship, surface finish (Ra ≤ 6.3 µm default) and corrosion protection (salt spray performance per ISO 9227). Cadmium plating is disallowed.
• Identification and designation: Standardized ordering codes (e.g., Plug ISO 6149‑4‑PLEH‑M12‑NBR) and marking requirements (manufacturer name/trademark).
• Safety warning: Intermixing stud ends conforming to this document with ports to ISO 1179, ISO 9974 or ISO 11926 can create hazardous situations - consult standards and manufacturers.

Applications

• Sealing unused hydraulic ports on valves, manifolds, pumps and actuators.
• Closing ports in fluid power systems where O‑ring sealing and metric thread compatibility are required.
• Use in high‑pressure hydraulic circuits, mobile equipment, industrial machinery and general fluid handling where ISO 6149‑1 ports are employed.

Who uses this standard

• Hydraulic component designers and system engineers specifying port plugs.
• Manufacturers of plugs, fittings, valves and hydraulic components for conformity and quality assurance.
• Test laboratories and procurement/specification teams verifying performance, compatibility and marking.
• Maintenance and reliability engineers selecting correct plugs, materials and sealing options.

Related standards

• ISO 6149‑1 (ports for O‑ring seal), ISO 6149‑2 (stud ends), ISO 261 (metric threads), ISO 19879 (test methods), ISO 3601‑3 (O‑ring quality), ISO 9227 (salt spray), ISO 4042 / ISO 10683 (coatings).

Keywords: ISO 6149-4:2017, port plugs, external hex, internal hex, O‑ring sealing, ISO 6149‑1 ports, metric threads, fluid power, hydraulic fittings, test methods.