ISO 8426-2-2025 PDF

Full title and description

St ISO 8426-2-2025 — Hydraulic fluid power — Determination of derived displacement of positive displacement pumps and motors — Part 2: Zero-pressure intercept method. This part specifies the zero-pressure intercept procedure to determine a single value of derived displacement from measurements at a single shaft speed for positive displacement pumps and motors.

Abstract

This international standard specifies the zero-pressure intercept method for determination of the derived displacement of hydraulic fluid power positive displacement pumps and motors under steady-state conditions. The method produces a single derived-displacement value determined from measurements at a single shaft speed and defines the measurement and calculation approach required for reporting that value.

General information

• Status: Published
• Publication date: August 2025 (2025-08)
• Publisher: International Organization for Standardization (ISO)
• ICS / categories: 23.100.10 (Pumps and motors; hydraulic fluid power)
• Edition / version: Edition 1 (2025)
• Number of pages: 6

Key bibliographic and status data per ISO record for ISO 8426-2:2025.

Scope

ISO 8426-2:2025 applies to positive displacement pumps and motors used in hydraulic fluid power systems and covers the zero-pressure intercept test method for determining the derived displacement under steady-state conditions. It is intended to provide a standardized single-value test method (single shaft speed) as an alternative method within the revised ISO 8426 series. The standard focuses on test arrangements, measurement procedure, calculation of derived displacement and minimum reporting requirements.

Key topics and requirements

• Definition of derived displacement for positive displacement pumps and motors.
• Zero-pressure intercept test method — procedure to obtain a derived-displacement value from measurements at a single, defined shaft speed.
• Required steady-state test conditions and measurement instrumentation considerations.
• Calculation method for converting measured flow/shaft data into derived displacement.
• Minimum reporting content (test conditions, measured values, calculated displacement, uncertainty/commentary).

Typical use and users

Used by hydraulic component manufacturers, independent test laboratories, quality and R&D engineers, certification bodies and procurement/specification teams to verify and report the derived displacement of positive-displacement pumps and motors. The standard is suitable for type testing, verification, and comparative performance assessment where a single-point derived displacement is required.

Related standards

ISO 8426-2:2025 is published alongside ISO 8426-1:2025 (Two-step Toet method) as the two-part revision of the withdrawn ISO 8426:2008. Users often consult ISO 8426-1:2025 when multi-speed or two-step measurement methods are preferred; ISO 8426:2008 has been withdrawn and superseded by the 2025 two-part series.

Keywords

derived displacement; positive displacement pump; hydraulic motor; hydraulic fluid power; zero-pressure intercept; pump testing; measurement method; ISO 8426.

FAQ

Q: What is this standard?

A: ISO 8426-2:2025 is an international standard that defines the zero-pressure intercept method to determine a single-value derived displacement of positive displacement pumps and motors in hydraulic fluid power applications.

Q: What does it cover?

A: It covers the test procedure, required steady-state conditions, measurement and calculation steps to obtain the derived displacement from measurements taken at a single shaft speed, and the minimum reporting requirements for the result.

Q: Who typically uses it?

A: Manufacturers, independent test laboratories, R&D and QA engineers, certification and conformity-assessment bodies, and specification/procurement teams working with hydraulic pumps and motors. These users rely on the standard for consistent single-point displacement reporting and comparison.

Q: Is it current or superseded?

A: ISO 8426-2:2025 is current (published August 2025) and supersedes the withdrawn ISO 8426:2008 as part of the new two-part series.

Q: Is it part of a series?

A: Yes — it is Part 2 of the revised ISO 8426 series published in 2025; Part 1 (ISO 8426-1:2025) specifies the two-step Toet method and the two parts together replace ISO 8426:2008.

Q: What are the key keywords?

A: Derived displacement, zero-pressure intercept, positive displacement pumps, hydraulic motors, hydraulic fluid power, pump testing, ISO 8426.