Foreword

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This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee SC 8, Product testing.

This first edition of ISO 8426-2 cancels and replaces the second edition ( ISO 8426:2008 ), which has been technically revised.

A list of all parts in the ISO 8426 series can be found on the ISO website.

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Introduction

In hydraulic fluid power systems, power is transmitted and controlled through a liquid under pressure within an enclosed circuit. Two types of components of such systems are the positive displacement pumps and motors. One of the technical parameters of these components is the derived displacement, also known as derived capacity. This document is intended to describe the zero-pressure intercept method for determining the derived displacement of hydraulic fluid power positive displacement pumps and motors. The term derived displacement is preferred over derived capacity.

1 Scope

This document specifies the zero-pressure intercept method for the determination of the derived displacement of hydraulic fluid power positive displacement pumps and motors under steady state conditions. A single value for the derived displacement is determined from measurements at a single shaft speed.

2 Normative references

3 Terms and definitions

4 Symbols and units

5 Test procedure

5.1 General requirements

5.2 Number of steady-state differential pressures

5.3 Variable displacement unit

5.4 Reverse flow unit

5.5 Unit used as pump or motor

6 Calculation of derived displacement

7 Test report

Bibliography