BS ISO 4399:2019 pdf download – Fluid power systems and components — Connectors and associated components — Nominal pressures
This document specifies a selection of nominal pressures for hydraulic and pneumatic fluid power connectors and associated components.
NOTE There can be a need to provide a selection of nominal pressures for connectors and associated components used in applications where the external pressure on the components is greater than the internal pressure, for example vacuum service. A document that deals with this subject will be established in due course.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2944, Fluid power systems and components — Nominal pressures
ISO 5598, Fluid power systems and components — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at
— IEC Electropedia: available at
nominal pressure
pressure value assigned to a component, piping or a system for the purpose of convenient designation and indicating its belonging to a series
[SOURCE: ISO 2944:2000, 3.1]
4 Units
4.1 When used in a sentence, the nominal pressure shall be expressed in megapascals (MPa), with the equivalent value in bar 1) shown in parentheses.
4.2 The nominal pressure shall be assumed to be gauge pressure, i.e. the pressure above atmospheric pressure, when no modifier is given.
4.3 Nominal pressures other than those specified here shall be selected from ISO 2944.BS ISO 4399 pdf download.