Failure Analysis of Hydraulic Hoses

Introduction

Hydraulic hose is an important part of the concrete pump, excavator, loader and other construction machinery, however, it is often not paid attention to, in the use of leakage, cracks, rupture, loosening and other failures, often do not analyze the causes of failure and simply replace the hose, the same failure will be repeated shortly after use. The loosening or rupture of the hydraulic hose, not only wastes oil, pollution of the environment, and affect the efficiency of work, and even accidents, endangering human and machine safety.

The reason for the failure analysis of the pressure hose: improper use, unreasonable system design and unqualified hose manufacturing, etc.

First of all, the characteristics of the tube to analyze. Hose is divided into rubber and plastic hose, plastic hose is cheap, easy to install, but the bearing capacity is poor, easy to aging, only for oil return or drainage pipe; rubber hose is divided into two kinds of high pressure hose and low pressure hose, high pressure hose generally by the outer rubber layer, steel wire reinforced layer, rubber layer and inner rubber layer of four parts. The inner rubber layer is in direct contact with the hydraulic oil, one made of synthetic rubber. The load-bearing capacity of the hose depends on the reinforcement layer, which is the skeleton of the hose and is usually made of steel wire braid or winding. Most of the medium and high pressure hoses use steel wire braid as the skeleton, while high pressure and ultra high pressure hoses use steel wire winding skeleton. The outer rubber layer is generally made of rubber with good abrasion and corrosion resistance to ensure that the reinforcement layer is not subject to mechanical damage, chemical corrosion and moisture rusting.

Failure of the Outer Rubber Layer

Cracks in the Exterior of the Hose

(1) The main reason for cracks on the exterior of the hose is that the hose is bent in the cold environment. If a crack is found on the exterior of the hose, pay attention to observe whether the inner rubber of the hose is cracked and decide whether to replace the hose immediately. Therefore, do not move the hose or disassemble the hydraulic parts in the cold environment, if necessary, should be carried out indoors. If you need to work in a colder environment for a long time, you should replace the hose with a cold-resistant hose.

(2) bulging on the outer surface of the hose bulging on the outer surface of the hose is the reason for the production quality of the hose is not qualified, or improper use when working. If the bulge appears in the middle section of the hose, mostly for hose production quality problems, should be replaced in a timely manner qualified hose; if the bulge appears in the hose joint, it is likely that the joint is not properly installed. Hose joint number often has detachable, buckle type two. Detachable pipe joint in the jacket and joint number core made of hexagonal, easy to often disassemble the hose; buckle type pipe joint by the joint jacket and joint core, assembly shall be stripped of the outer rubber layer, and then buckle on special equipment, so that the hose to get a certain amount of compression.

(3) hose is not ruptured but a lot of oil seepage hose a lot of oil seepage but not found rupture, the reason is that the hose through the high-pressure liquid flow, the inner rubber is eroded, abrasion, until a large area of leakage out of the steel wire layer resulting in a lot of oil seepage. This failure generally occurs in the pipe bend, should check the replacement hose, and ensure that the hose in use bending radius in line with technical requirements.

(4) hose outer rubber layer is seriously deteriorated, the surface of the micro-crack this is the natural aging of the hose performance. Due to aging deterioration, the outer layer of continuous oxidation so that its surface is covered with a layer of ozone, thickened with the extension of time, the hose in use as long as the slight bending, it will produce tiny cracks. Encounter this situation, the hose should be replaced.

Failure of the Inner Glue Layer

(1) hose inside the rubber layer is hard and cracked: the main reason is that the rubber products due to the addition of plasticizers, making the hose flexible and plastic. But the hose is overheated, it will make the plasticizer overflow. In addition overheated oil through the system of hydraulic cylinders, hydraulic valves or other components, if a large pressure drop will make the oil decomposition, resulting in the hose inside the rubber layer oxidation and hardening. In this case, we should first check whether the system working temperature is normal, valve throttle, pump suction channel is smooth, etc., to exclude all factors that cause high oil temperature and make the oil decomposition after replacing the hose. If only the inner rubber below the hose rupture is hard, and the above remains good, it is because the hose rupture is overly flattened, bent too sharply or twisted and other phenomena lead to oil heating and accelerated oxidation, causing the inner rubber to be hard.

(2) hose inner rubber layer is seriously deteriorated, obviously swollen: hose inner rubber layer is seriously deteriorated, obviously swollen because the hose inner rubber material is not compatible with the hydraulic system oil, the hose is chemically deteriorated. If this phenomenon occurs, the oil tank should be checked, because it is possible to find broken rubber pieces at the oil return port. This should check the compatibility of the system oil and hose rubber material and the working temperature is in line with the standard.