Detail of GB/T 7939.3-2023

Introduction of GB/T 7939.3-2023

GB/T 7939.3-2023 Connections for hydraulic fluid power - Test methods - Part 3: Hose assemblies 1 Scope This document specifies the test methods for evaluating the performance of hoses and hose assemblies used in hydraulic fluid power systems. This document is applicable to the test and performance evaluation of hoses and hose assemblies according to relevant technical requirements. 2 Normative references The following referenced documents are indispensable for the application 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. ISO 1402 Rubber and plastics hoses and hose assemblies - Hydrostatic testing Note: GB/T 5563-2013 Rubber and plastics hoses and hose assemblies - Hydrostatic testing (ISO 1402 : 2009 ,IDT) ISO 3448 Industrial liquid lubricants - ISO viscosity classification Note: GB/T 3141-1994 Industrial liquid lubricants - ISO viscosity classification (eqv ISO 3448:1992) ISO 4671 Rubber and plastics hoses and hose assemblies- Methods of measurement of the dimensions of hoses and the lengths of hose assemblies Note: GB/T 9573-2013 Rubber and plastics hoses and hose assemblies - Methods of measurement of the dimensions of hoses and the lengths of hose assemblies (ISO 4671:2007, IDT) ISO 5598 Fluid power systems and components - Vocabulary Note: GB/T 17446-2012 Fluid power systems and components - Vocabulary (ISO 5598:2008, IDT) ISO 5893 Rubber and plastics test equipment - Tensile, flexural and compression types (constant rate of traverse) - Specification Note: GB/T 25270-2010 Rubber and plastics test equipment - Tensile flexural and compression types (constant rate of traverse) - Specification (ISO 5893:2002, IDT) ISO 6133 Rubber and plastics - Analysis of multi- peak traces obtained in determinations of tear strength and adhesion strength Note: GB/T 12833-2006 Rubber and plastics - Analysis of multipeak traces obtained in determinations of tear strength and adhesion strength (ISO6133:1998, IDT) ISO 8033 Rubber and plastics hoses - Determination of adhesion between components Note: GB/T 14905-2020 Rubber and plastics hoses - Determination of adhesion between components (ISO 8033:2016, IDT) ISO/TR 11340 Rubber and rubber products - Hydraulic hose assemblies - External leakage classification for hydraulic systems Note: GB/Z 18427-2001 Hydraulic hose assemblies - External leakage classification for hydraulic systems (idt ISO/TR 11340 :1994) ISO/TS 17165-2 Hydraulic fluid power- Hose assemblies - Part 2 : Practices for hydraulic hose assemblies ISO 23529 Rubber - General procedures for preparing and conditioning test pieces for physical test methods Note: GB/T2941-2006 Rubber - General procedures for preparing and conditioning test pieces for physical test methods (ISO 23529:2004, IDT) 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply. 3.1 change-in-length elongation or contraction of the hose or hose assembly due to pressurization 3.2 minimum burst pressure minimum pressure at which failure of the hose or hose assembly occurs Note: This failure can be a hose burst, leakage or separation of the hose from the hose fitting. 3.3 cyclic endurance (impulse) test fatigue test conducted between a lower cyclic test pressure and an upper cyclic test pressure to determine performance of a hose assembly under pressure cycling conditions 4 Visual examination of product Hose assemblies shall be visually inspected in accordance with ISO/TS 17165-2, to determine that the correct hose and hose fittings are properly installed. 5 Standard tests 5.1 Dimensional check test 5.1.1 General The hoses shall be inspected for conformity with all the dimensions of the relevant hose specification. Note: These test methods are technically equivalent to those specified in ISO 4671. 5.1.2 Measurement of outside and reinforcement diameters 5.1.2.1 Determine finished outside diameter and reinforcement diameter by calculation from measurement of the respective circumference. 5.1.2.2 Take outside diameter measurements at a minimum of 25 mm from the hose ends. 5.1.3 Measurement of inside diameter 5.1.3.1 Measure the inside diameter by means of a suitable expanding ball or telescoping gauge in accordance with method 2 given in ISO 4671. 5.1.3.2 Take inside diameter measurements at a minimum of 25 mm from the hose ends. 5.1.4 Measurement of concentricity 5.1.4.1 Measure concentricity over both the reinforcement and the finished outside diameters using either a dial indicator gauge or a micrometre. 5.1.4.2 Take concentricity measurements at a minimum of 15 mm from the hose ends. 5.1.4.3 Round the foot of the measuring instrument to conform to the inside diameter of the hose. 5.1.4.4 Take readings at 90° intervals around the hose. Acceptability is based on the total variation between the highest and lowest readings. 5.2 Proof test 5.2.1 Test the hose assemblies in accordance with the relevant product specification using the method specified in ISO 1402, for a period of between 30 s and 60 s for all sizes. The proof pressure shall be twice the maximum working pressure, unless otherwise specified. 5.2.2 Hose assemblies that exhibit no leakage or other evidence of failure after being subjected to the proof test shall be deemed to have passed the test. 5.3 Change-in-length test 5.3.1 Conduct measurements for the determination of elongation or contraction on a previously unused, unaged hose assembly having a free length between hose fittings of at least 600 mm. 5.3.2 Attach the hose assembly to the pressure source in an unrestricted straight position. If the hose is not straight due to its natural curvature, it may be fastened laterally to achieve a straight position. Pressurize to the maximum working pressure for a period of 30 s, then release the pressure. 5.3.3 Place accurate reference marks 500 mm (lo) apart on the outer cover of the hose, midway between hose fittings, after allowing the hose assembly to restabilize for a period of 30 s following pressure release. 5.3.4 Repressurize the hose assembly to the specified maximum working pressure for a period of 30 s. 5.3.5 Measure the distance between reference marks while the hose is pressurized and record this as l₁ . 5.3.6 Determine the change in length using the following formula in accordance with ISO 1402: 5.4 Burst test 5.4.1 General This is a destructive test. Hose or hose assemblies that have been subjected to this test should be destroyed. 5.4.2 Procedure 5.4.2.1 Subject unaged hose or hose assemblies, on which the hose fittings have been attached for less than 30 d, to a hydrostatic pressure. Increase the pressure at a rate in accordance with ISO 1402 until the hose or hose assembly fails. The minimum burst pressure shall be four times the maximum working pressure, unless otherwise specified in the pertinent hose product standard. 5.4.2.2 Reject hose assemblies showing leakage, hose burst or indication of failure below the specified minimum burst pressure.

Contents of GB/T 7939.3-2023