The Inspection of Hydraulic Hose
Brake hose is an important part of the car, the improper normal use and maintenance will cause damage to the hose. So how do we know that the brake hose has failed? What are the causes of the brake hose failure?
1.Amount of inner hole passing after reduction
After reducing the diameter of the inner hole through is to examine the joint pressure, the influence of the hole through the hose tube body, according to the requirements of GB16897-2010, nylon (plastic) brake hose is not suitable for this test. According to the research, if the brake hose fails to meet the requirements in this test, it will have a serious impact on the flow of brake fluid and the transfer of braking force. The common inner diameter passing quantity after reduction is not up to standard, which is mainly reflected in improper selection of inner diameter specification of joint pipe core and improper riveting of joint and hose.
2 Maximum expansion
Because the volume change of gas under pressure is greater than that of liquid, and the hydraulic brake hose has almost no effect on braking force when the volume changes, so the requirements for this test in the national standard are mainly aimed at the hydraulic brake hose. At present, the common hydraulic brake hose diameter ψ3.2, ψ4.8, ψ6.3, specified in the GB16897-2010 different inner diameter of the hydraulic brake hose respectively under Pa 6.9 M and 10.3 MPa expansion amount (per unit length of brake hose under pressure to produce volume variation).
The maximum expansion evaluates the hydraulic brake hose’s ability to transfer brake fluid under emergency braking conditions. If it fails to meet the standard requirements, the brake may be delayed and even the hose may burst.
3 Bursting strength
Brake hose is an important part of automobile brake system, so the burst strength requirement of brake hose is the key concern of inspection organizations and brake hose enterprises. Hydraulic brake hose structure is divided into single-layer and multi-layer. Multi-layer is composed of external rubber layer, reinforcement layer and internal rubber layer. The reinforcing layer plays a role in strengthening the pressure resistance. If the quality of the reinforcing layer is not up to the standard or inappropriate material is chosen, the bursting strength of the brake hose will be affected.
4 Tensile strength
The brake hose may fall off or break the hose due to excessive turning or continuous turning in the process of running the car, leading to brake failure. For hydraulic brake hose, its tensile strength value should be ≥ 1446n. The reason for the substandard tensile strength is generally that the pipe joint falls off due to the infirm clamping or improper design of the pipe joint in the processing process of the enterprise, resulting in the failure of the brake.
5 Ozone resistance
Ozone is easy to react with unsaturated bonds in rubber, resulting in rubber degradation. The brake fluid leakage in the process of using the automobile hose is mostly caused by the poor ozone resistance and durability of the brake hose coating. According to the requirements of GB16897-2010, the automobile brake hose shall be kept in the ozone aging test box with ozone concentration (50±5) ×10-8 and the temperature inside the box (40±2℃) for 70±2h, and then the external surface shall be observed under 7 times magnifying glass to see whether cracks or cracks occur. Improper selection of materials or problems in the production process will affect the ozone resistance of the outer rubber layer and lead to leakage, thus resulting in brake failure.
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