Overview
ISO 3662:1976 - "Hydraulic fluid power - Pumps and motors - Geometric displacements" standardizes the geometric displacement values for hydraulic pumps and motors with rotating or oscillating drives. It covers fixed and variable displacement units (for variable units, the values refer to the maximum displacement) and provides a table of nominal displacements from 0.1 to 9 000 millilitres per revolution (ml/rev). These nominal values are intended for convenient designation and can be used to derive other basic design criteria and normal ratings.
Key topics
- Definition of geometric displacement: the calculated total of all volume changes in pressure chambers caused by movement of displacement elements during one shaft revolution or one double stroke of an oscillating drive. Tolerances, clearances, distortions and deformations are not included.
- Nominal displacement table: preferred values (R10 series recommended) from 0.1 ml/rev up to 9 000 ml/rev; values printed in parentheses are non-preferred.
- Application to variable displacement units: displacement values in the standard refer to maximum displacement for such units.
- Designation and identification: provides a standardized identification statement for test reports, catalogues and sales literature to declare conformity.
- Guidance on extended ranges: for displacements above 9 000 ml/rev, specify values using R20 series numbers; R10 is the preferred series.
Applications
ISO 3662 is practical for:
- Hydraulic pump and motor design - selecting and specifying nominal geometric displacements for performance and sizing calculations.
- Manufacturer catalogs and product identification - using standardized displacement denominations for marketing and procurement.
- Test reports and certification - declaring compliance with a recognized international displacement series.
- System engineering - deriving pump/motor ratings and matching components in hydraulic fluid power systems (positive displacement devices).
Keywords: ISO 3662, geometric displacement, hydraulic fluid power, hydraulic pumps, hydraulic motors, nominal displacement, ml/rev, variable displacement.
Who should use this standard
- Hydraulic equipment designers and OEMs specifying pump and motor displacements.
- Technical writers and catalog managers producing product literature or datasheets.
- Test laboratories and certification bodies preparing reports.
- Purchasing and maintenance engineers selecting replacement components or matching system elements.
Related standards
- ISO 5598 - Fluid power vocabulary (definitions referenced by ISO 3662).
- ISO 497 - Guide to choice of series of preferred numbers (R-series guidance used for nominal values).
Identification statement example for documentation:
"Geometric displacements conform to ISO 3662, Hydraulic fluid power - Pumps and motors - Geometric displacements."
