Evaluating the Resistance of Flexible Hoses to Repeated Flexing Under Pressure

Flexible hoses used in cars and motorcycles must accommodate the movement of the components to which they are connected while transferring fluids. In hoses installed between moving components, internal pressure and repeated flexing act together. Assessing hose performance therefore requires examining both its pressure-bearing capability and its durability during movement.

The Brake Hose Endurance Testing Machine is designed to simulate endurance testing conditions for flexible tubes and hoses used to convey hydraulic fluid or compressed air. During testing, the specimen undergoes repeated flexing while under pressure. This allows its ability to maintain structural integrity under the specified test conditions to be evaluated.

Four sets of clamps, an adjustable specimen length, a flexing speed of 800 rpm, and a pressure-controlled hydraulic system form the machine’s basic test configuration. A transparent protective cover and a shutdown function in the event of a burst support testing within a controlled working area.

Main Purpose of the Machine

The machine’s main purpose is to examine the resistance of flexible hoses to repeated mechanical movement under pressure. This assessment considers whether the specimen maintains its integrity throughout the test, how the connection areas behave, and what damage is present at the end of testing.

By comparing specimens tested under identical conditions, manufacturers can investigate how material selection, hose construction, and changes in the manufacturing process affect durability. This approach provides experimental data for new product development and quality control of existing production.

What Is a Brake Hose Endurance Test?

A brake hose endurance test evaluates the durability of a hose by subjecting it to repeated mechanical loading under specified pressure and movement conditions. The specimen is secured with clamps and subjected to flexing by a mechanical mechanism. The hydraulic system establishes the pressure applied to the specimen during this movement.

Specimen behaviour, applied conditions, and elapsed time are assessed together. Changes in the hose surface, problems observed at the connections, or events such as bursting provide the basis for evaluating the test.

The endurance assessment relates to the defined laboratory conditions. For meaningful comparisons between products, specimen preparation, clamping configuration, pressure, and test duration must remain consistent.

Importance and Purpose of the Test

The continued operation of hoses used in braking systems is important to the functionality of the system. Identifying a weakness that develops under repeated movement during production or development allows the product design to be reviewed.

Endurance testing is particularly useful for the following assessments:

• Material comparison: Examining the behaviour of different hose materials under identical test conditions.

• Structural evaluation: Investigating how changes in hose construction affect resistance to repeated flexing.

• Production consistency: Comparing the results of specimens taken from different production batches.

• Examination of connection areas: Evaluating the behaviour of hoses and fittings as they operate together.

• Design improvement: Using damage locations identified after testing to inform product development.

These assessments allow product performance to be evaluated using observations and documented test conditions.

Scientific Basis of the Test

The test is based on the combined mechanical loading produced by internal pressure and repeated bending. Pressure creates an internal load that stresses the hose wall, while flexing produces varying deformation along the hose.

Repeated flexing can cause fatigue damage to develop over time, particularly in the load-bearing structure of reinforced hoses. Damage development depends on hose construction, the severity of movement, and the applied pressure conditions. Engineering guidance from hose manufacturers also highlights the effect of continuous flexing on fatigue and service life.

Bend radius is another important variable when assessing mechanical loading. Excessively tight bends can increase stress in the hose reinforcement and adversely affect its pressure-bearing capability. Hose length and clamping geometry also influence how movement is distributed along the specimen.

Based on these principles, the machine’s flexing radius, specimen length, flexing speed, pressure, and test duration should be considered together. Tests conducted under identical conditions help interpret differences in durability between specimens.

Operating the Machine

Testing is performed in accordance with the manufacturer’s operating instructions and the test plan established for the product. The general operating sequence consists of the following stages:

1. Preparing the specimen: Identify the hose to be tested and record its length, material information, and connection details. Inspect the surface and connections before testing.

2. Mounting the specimen: Install the hose in the test assembly using suitable clamps and fittings. Ensure that the specimen is not unintentionally twisted during mounting and that the connections are suitable for the test movement.

3. Defining the test conditions: Specify the specimen length and test duration. Determine the pressure to be applied according to the test plan established for the product.

4. Closing the protective cover: Close the transparent protective cover to enable the hydraulic system. The cover also allows the test area to be observed from outside.

5. Performing the test: Subject the specimen to repeated flexing under pressure. Monitor elapsed time using the timer and observe specimen behaviour through the protective cover. If the specimen bursts, the hydraulic system’s shutdown function is activated.

6. Evaluating the result: After the test has ended and the system has been brought to a safe condition, inspect the specimen. The operator records the applied conditions, test duration, reason for termination, and any observed damage.

Technical Specifications

The adjustable specimen length allows hoses of different lengths to be mounted in the test assembly. Flexing radius and speed are the main parameters defining the mechanical movement applied to the specimen.

The pressure control system establishes the hydraulic loading conditions for the test. Test pressure, hydraulic system pressure, and maximum pressure describe different technical characteristics of the machine. Recording the actual pressure applied during testing makes the results easier to interpret.

The transparent cover allows the test area to be observed without approaching the specimen directly. Requiring the cover to be closed before enabling the hydraulic system, together with the shutdown function in the event of a burst, constitutes an important part of the machine’s safety arrangements.

Advantages

Technical Advantages

Combined application of pressure and flexing: The hose’s response to mechanical movement while internally pressurised can be examined within the same test setup.

Defined movement conditions: The specified flexing radius and speed provide a basis for comparing specimens using common test parameters.

Adjustable specimen length: The machine accommodates hose specimens prepared in different lengths.

Visible test area: The transparent cover allows specimen movement and visible changes to be observed without opening the test area.

Contribution to Quality Control

The machine supports batch comparisons by allowing production specimens to be tested under defined conditions. Consistent recording of results helps changes in durability to be assessed alongside production information.

For example, when a material formulation or hose construction is modified, specimens from before and after the change can be compared under identical test conditions. The effect of the modification on durability can then inform product development decisions.

Contribution to Export and Product Evaluation Processes

Records containing specimen identification, test conditions, duration, and observations can support product evaluation files submitted to export customers, supplier assessments, and technical reviews within certification processes. Consistent implementation of a test plan defined by the purchaser makes it easier for both parties to assess the results.

Applications

• Automotive hose manufacturers: Developing the durability of flexible hoses used in braking systems and other suitable fluid lines, and comparing production specimens.

• Motorcycle component manufacturers: Examining the response of hoses installed between moving connections to repeated flexing under pressure.

• Hose assembly manufacturers: Evaluating the combined behaviour of the hose body and end fittings.

• Research and development departments: Experimentally comparing changes in materials, reinforcement construction, or product design.

• Quality control and testing laboratories: Examining specimens under defined test conditions and documenting the results.

Use of the machine in these areas depends on the specimen’s compatibility with the connection arrangement and the machine’s pressure, length, and flexing characteristics.

Conclusion

The Brake Hose Endurance Testing Machine is a test system for examining the repeated flexing behaviour of flexible hoses under pressure. Its adjustable specimen length, defined flexing movement, and pressure-controlled hydraulic system allow hose durability to be compared.

Consistent application of test conditions and systematic recording of observations increase the value of the data obtained from the machine. These data can support material selection, product design, production consistency, and customer evaluations. Hose development and quality control activities can therefore be informed by experimental results obtained under defined conditions.