ISO 3320:2013

Overview

ISO 3320:2013 specifies a metric series of cylinder bore (AL) and piston rod (MM) diameters and the corresponding standardized area ratios for hydraulic and pneumatic cylinders. The standard applies only to the dimensional criteria of cylinders and piston rods - it does not set or alter functional performance characteristics. This third edition consolidated and replaced earlier editions (ISO 3320:1987 and ISO 7181:1991).

Key Topics

• Metric diameter series: The standard provides preferred bore diameters (AL) from small to large sizes (examples in table series range up to 500 mm with some non-preferred values in parentheses). Piston rod diameters (MM) are given in a corresponding series (examples include values from small rods up to around 450 mm, with non-preferred entries in parentheses).
• Area ratios: For each bore/rod pair a corresponding ratio between the useful areas is given. Preferred area-ratio values include: 1.06, 1.12, 1.25, 1.33, 1.4, 1.6, 2, 2.5 and 5.
• Dimension tables and notes: Tables list AL and MM values and calculated areas A1 and A2 with effective value φ. Notes explain the use of preferred numbers (ISO 3) and the existence of non-preferred values for special applications.
• Normative references: Key referenced documents are ISO 3 (preferred numbers), ISO 5598 (fluid power vocabulary) and ISO 6099 (identification code for mounting dimensions and types).
• Identification recommendation: Manufacturers conforming to ISO 3320:2013 are recommended to use the identification statement in test reports, catalogues and sales literature.

Applications

ISO 3320:2013 is practical for:

• Design and specification of hydraulic and pneumatic cylinders where dimensional interchangeability matters.
• Component selection and procurement to ensure parts from different suppliers match common dimensional series.
• Catalogues and technical documentation, enabling clear, standard-based listings of bore and rod sizes and area ratios.
• Testing and reporting, where the recommended identification statement supports traceability and conformity claims.

Benefits include simplified inventory management, improved compatibility between components, and reduced design rework when selecting cylinder sizes.

Related Standards

• ISO 3 - Preferred numbers - Series of preferred numbers
• ISO 5598 - Fluid power systems and components - Vocabulary
• ISO 6099 - Cylinders - Identification code for mounting dimensions and types

Manufacturers and designers should note that ISO 3320:2013 addresses dimensional standards only; functional performance and application-specific requirements must be covered by other relevant specifications or testing. Recommended identification wording from the standard: "Cylinder bores, piston rod diameters and ratios selected in accordance with ISO 3320, Fluid power systems and components - Cylinder bores and piston rod diameters and area ratios - Metric series."