I. Faults onouterrubber layer:

1. Cracks on external surface.

This is caused mainly by bending operation in cold conditions. Please do NOT handle the rubber hose or disassemble the hydraulic system in cold conditions, or have the operation done indoor where necessary.

2. Bubbles are found onexternalhose surface.

This is caused by defects in production or improper use.

3. Leakage is found in large volume but no fracture is located.

When pressurized fluid flows through the hose, theinnerrubber layer is washed out and scratched until large areas of wire layerareexposed to the liquid and cause leakage.

4. Severe deterioration is found onouterrubber layer with minor cracks onsurface.

This is caused by natural aging. As a result of aging and deterioration, theouterlayer is oxidized and covered with ozone layer which thickens as time goes, in which case even slight bending when the rubber hose is in use may cause small cracks. In this case, please replace the rubber hose.

 

II. Faults oninnerrubber layer:

1. Theinnerrubber layer becomes hard with cracks.

This is mainly because plasticizer is used in rubber products, to make the hoses flexible. But in overheat conditions, the plasticizer may overflow.

2. Severe deterioration and obvious expansion is found atinnerrubber layer.

This is causedby incompatibilitybetween theinnerrubber material and hydraulic oil used, which causeschemical reactions and deterioration. In such cases, inspections should be made to the physical and chemical indicators of hydraulic oil, to make sure compatible hydraulic oil with theinnerhose material is used within required temperature range.

3. Direct leakage is found atinnerhose layer.

This is caused by internal aging and fracturing, which may compromise the sealing effect. Please take actions according to the specific situations.

 

III.Faults at reinforcement layer:

1.Rubber hose fractures and rust is found on wires at the fracture location afterouterrubber layer is removed for inspection.

This is mainly caused by invasion of moisture or corrosive matters, which compromise the hose strength and lead to fracture at high pressure.

2.Rubber hose fractures and no rust but broken wires are found at the wire layer.

This is caused basically when the rubber hose is subject to high-frequency impacts.

 

IV. Faults at fracture area:

1. One or more clear-cut fractures are found on the rubber hose, but all other parts remain intact.

This is caused by excess system pressure that exceeds the pressure capacity of rubber hose.

2. Twist is found at fracture area.

This is caused by excess twisting during installation or use of the rubber hose.

 

V. Leakage at connectors:

1.Where ferrule-type connectorsare used, leakage is possibly caused by loosened connector or deformation of hose end as a result of large external forces or impacts, in which case inspection should be made to ferrule for deformation, to cutting knives fordamages,to hose end for damages and to tightness of ferrule nuts. Besides, external forces on the pipeline should be eliminated.

2.Whereflare-typeconnectorsare used, leakage is possibly caused by excess flaring, product defects or repeated assembly and disassembly, which lead to deformation or cracks at the flared area. In such cases, a section in suitable length may be cut off from the hose for re-flaring.

3.Where cones are used for sealing in pressurized conditions, leakage is mostly likely caused by damages to the cone surfaces, in which case abrasive sand may be used to polish the damaged surfaces.Leakage occurs in cases where O-ringis used on hose end or external surface for sealing purpose.