Test Method for Length Variation of Hydraulic Hose Assemblies

The purpose of the hydraulic hose assembly length change (elongation or shrinkage) test is to test the axial length change of the hydraulic hose assembly under the highest working pressure, the specific test method requirements are as follows:1. The measurement of elongation or shrinkage should be carried out on an unused and unaged hose assembly, and the free length of the hose between the hose joints should be at least 600mm.2, the hose assembly is connected to the pressure source, is not restricted state, if the natural bending of the hose is not straight state, can be fixed horizontally to make a straight state, pressure to the working pressure to maintain pressure 30s, and then release the pressure.3. After the pressure relief of the hose assembly is re-stabilized for 30 seconds, take a point in the middle of the hose joints at both ends and make an accurate reference mark at 125mm (l0) from each side.4. Repress the hose assembly to the specified maximum working pressure and maintain the pressure for 30s.5. During the pressure holding period of the hose, measure the distance between reference points on the hose and record it as l1.6. Determine the length change according to the following formula.△l= (l1-l0) /l0*100%In the formula: l0 -- After the hose assembly is initially pressurized, decompressed and re-stabilized, the distance between the marks is referred to in millimeters (mm).l1 - Hose assembly under pressure, distance between reference marks, in millimetres (mm).△l -- the percentage change in length is positive (+) when the length is extended and negative (-) when the length is shortened.7. The length change of the hydraulic hose assembly under the highest working pressure should comply with the following provisions.Wire braided hydraulic hose 1ST, 1SN, R1ATS type, 2ST, 2SN, R2ATS type length change -4%~+2%Wire wound hydraulic hoses 4SP, 4SH, R12, R13, R15 length variation ±2%