ISO 4399:2019

Overview

ISO 4399:2019 - "Fluid power systems and components - Connectors and associated components - Nominal pressures" provides a standardized selection of nominal pressures for hydraulic and pneumatic connectors and their associated components. The third edition updates common pressure values and clarifies how nominal pressures are expressed and used for component designation. It applies to designers, manufacturers, test laboratories, procurement specialists and anyone specifying fluid power connectors for hydraulic and pneumatic systems.

Key Topics

• Selection of nominal pressures: Nominal pressures for connectors and associated components are specified in a reference table (Table 1). These values are intended for convenient designation and series classification.
• Units and expression: Nominal pressures shall be expressed in megapascals (MPa) in text, with the equivalent value in bar shown in parentheses (e.g., 10 MPa (100 bar)).
• Gauge pressure assumption: Unless otherwise specified, nominal pressures are assumed to be gauge pressure (pressure above atmospheric).
• Preferred vs non-preferred values: Some values are shown in square brackets in Table 1 and are non-preferred; these bracketed values shall not be used for new designs.
• Normative references: The standard refers to ISO 2944 (Nominal pressures) and ISO 5598 (Vocabulary), ensuring consistent terminology and broader pressure-selection rules.
• Future considerations: The document notes potential need for nominal pressure selections where external pressure exceeds internal pressure (e.g., vacuum service) and that a dedicated document will be developed.

Applications

ISO 4399:2019 is used in practical tasks such as:

• Specifying pressure ratings for hydraulic connectors, pneumatic connectors, fittings and associated components in product catalogs and procurement documents.
• Ensuring consistent interoperability and safety across components from different manufacturers by using standardized nominal pressures.
• Supporting test reports, quality control and conformity statements for fluid power components.
• Guiding system designers when selecting connectors for hydraulic systems (e.g., mobile equipment, industrial hydraulics) and pneumatic systems (e.g., automation, process control).

Who uses it:

• Component manufacturers and suppliers
• Design and R&D engineers in fluid power systems
• Test laboratories and certification bodies
• Procurement and maintenance teams

Related Standards

• ISO 2944 - Fluid power systems and components - Nominal pressures
• ISO 5598 - Fluid power systems and components - Vocabulary
• Prepared by ISO/TC 131 (Fluid power systems), Subcommittee SC 4 (Connectors)

Identification statement for use in literature: "Nominal pressures for connectors and associated components are selected from ISO 4399, Fluid power systems and components - Connectors and associated components - Nominal pressures."

Keywords: ISO 4399:2019, fluid power, nominal pressures, hydraulic connectors, pneumatic connectors, pressure ratings, MPa, bar.