Common methods for checking rubber tubes

Many countries' rubber universal test standards stipulate a set of methods for verifying the reliability of various types of rubber tubes. In addition, many test methods are gradually being widely adopted. These methods are:

1. Hose size measurement:

Inner diameter, outer diameter, outer diameter of the reinforcing layer, wall thickness, concentricity, inner and outer layer thickness, inner diameter of the assembly, new national standard and ISO increase the length and measuring point mark, specifying the pipe joint and various pipe joints The method of measuring the length of the hose.

2. Hydraulic test:

Verify Pressure Test: Verify that hoses and assemblies are leaking, deformed, and damaged for 30 s to 60 s at verified pressure.

Pressure deformation test: Hold the specified pressure (working pressure verification pressure or other pressure below the verification pressure) for 1 minute, measure the length and outer diameter of the hose and the torsion angle and bending.

Burst pressure test: Determines the pressure at which the hose blasts at a specified boost rate.

 Leak test: Store at a static pressure of 70% of the minimum burst pressure for 5 min, repeat once to check for leaks or damage. Since the test often uses water, unlike the viscosity of the actual use liquid, the burst pressure and leakage pressure measured at normal temperature may be slightly lower.

3. Low temperature bending test

Low temperature rigidity: The ratio of the torque measured by the hose to the torsion wheel with a diameter of 12 times the inner diameter of the hose and the torque measured at the standard temperature after being held at a low temperature for 6 hours and twisted by 180° within 12 s.

Low temperature bending: The hose is clamped on a torsion wheel with a diameter of 12 times the inner diameter of the hose. After being parked for 24 hours at low temperature, it is twisted by 180° within 10s to check whether the inner and outer rubbers are brittle and damaged.

The simplest test for measuring the low-temperature brittleness of a hose is to bend the specimen at a low temperature of 90°, or to compress a section of the hose and compress it to see if it is brittle. Another method is to use a weight of a weight to fall freely. See if the sample is brittle.

4. Bending test: 

After bending the hose to a certain extent, the ratio of the minimum outer diameter of the curved portion to the outer diameter before bending, the passing ability of the steel ball and the bending force when pressurized in the tube are measured.

5. Sucking test: 

After vacuuming for 1 min, hold for 10 min, roll with a steel ball with a diameter of 0.9 times the inner diameter of the hose to check the degree of collapse of the hose. Some standards use the change rate of the outer diameter of the hose to indicate the degree of deformation of the hose.

6. Interlayer adhesion strength test: 

Most automotive hoses are braided hoses with a diameter of less than 50mm. The test is usually used for strips with a width of 10mm or 25mm. It is also a ring with a width of 25mm. It is peeled at 90° and the tensile speed is 25mm. /min.

7. Liquid wall penetration test:

Under normal pressure, the hose is connected to a container filled with a certain liquid and the container nozzle is sealed, the test device is placed horizontally, and then the entire test device due to the outward penetration of the liquid through the hose is periodically weighed. The mass changes to determine the penetration rate of the liquid.

8. Volume expansion test: 

The hose should not produce obvious volume change under the pressure of transferring liquid. The method of measuring volume expansion is to connect the hose to a hydraulic source, the other end and a measuring tube for measuring the volume of the liquid after expansion of the hose. Connected. The pressure in the hose is raised to the test pressure to expand the hose, then the hydraulic source is closed, and the valve connected to the measuring tube is opened. At this time, the liquid in the volume expansion portion rises into the measuring tube, and the volume of expansion can be measured.

9. Cleanliness and extraction test: 

Inject the C liquid into the hose for the fuel hose, vent it after 24 hours, and clean the inner wall with C liquid. Collecting and rinsing the C liquid, filtering out the insoluble impurities, drying and weighing to obtain the weight of the insoluble impurities, indicating the cleanliness by the amount of impurities on the inner surface area of the unit hose or the maximum size of the impurities; evaporating and drying the filtered solution Weigh to the weight of the soluble substance. The wax was extracted from the filtrate by evaporation from the filtrate, and the obtained methanol extract was evaporated to dryness to give a weight of the wax.

10. Salt spray test: 

The hose assembly was placed in a salt spray formed by a 35 ° C 5% sodium chloride aqueous solution. After 24 hours, the joint metal was inspected for corrosion.