ISO 3968:2017 油圧作動油の動力—フィルター—差圧と流量の評価 | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee SC 6, Contamination control.

This third edition cancels and replaces the second edition (ISO 3968:2001), which has been technically revised. It also incorporates the Technical Corrigendum ISO 3968:2001/Cor1:2002.

Introduction

In hydraulic fluid power systems, power is transmitted and controlled through a fluid under pressure circulating within a closed circuit. Filters maintain the cleanliness of the fluid by retaining the insoluble contaminants.

Hydraulic filters normally include a housing that serves as the pressure-containing vessel to direct the flow of fluid through a filter element that separates contaminants from the test fluid.

This document foresees the possibility to test spin-on filters in which the replaceable unit does or does not include a filter head.

In operation, fluid flowing through a filter meets resistance due to kinetic and viscous effects. The pressure required to overcome this resistance and to maintain flow is known as the differential pressure. The differential pressure is the total pressure difference observed between the filter inlet port and outlet port and represents the sum of the losses recorded in the housing and filter element.

Factors which affect clean filter differential pressure are fluid viscosity, fluid specific gravity, flow rate, filter element media type and construction, as well as housing design.

1 Scope

This document specifies a procedure for evaluating differential pressure versus flow characteristics of hydraulic filters and constitutes a basis for agreement between the filter manufacturer and user.

It also specifies a method for measurement of the differential pressure generated at different flow rates and viscosities by the relevant parts of a filter assembly, spin-on and any valves contained within the filter which are in the flow stream. The typical types of filter to be tested are as follows:

Type 1: which are spin-on filters in which the replaceable unit does not include a filter head (it might or might not include the element by-pass valve);

Type 2: which are spin-on filters in which the replaceable element is tested together with a filter head (it might or might not include the element by-pass valve);

Type 3: which are filter assembly, usually of the replacement element type, that is the housing (head and bowl) and element.

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.

3 Terms and definitions

For the purposes of this document, the definitions given in ISO 5598 and the following apply:

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Bibliography