What tests are required for hydraulic hoses before leaving the factory?
Salt spray test, blast test, low temperature bend test, pulse test.
1. Salt spray test
Test method:
The salt spray test is an accelerated test method. It first atomizes salt water of a certain concentration and then sprays it in a closed thermostat. By observing the changes of the hose joint after being placed in the thermostat for a period of time, it reflects the performance of the joint. The advantages and disadvantages of corrosion resistance.
Judging criteria:
The most common criterion is to compare the time it takes for oxides to appear on the joint to the design expectations to determine if the product is qualified.
For example, the qualification standard for Parker hose joints is that the time to produce white rust must be ≥120 hours, and the time to produce red rust must be ≥240 hours.
Of course, if you choose stainless steel connectors, you don’t have to worry too much about corrosion.
2. Explosion test test method:
The burst test is a destructive test that usually pressurizes a newly-withheld hydraulic hose assembly to 4 times the maximum working pressure at a constant speed within 30 days to determine the minimum burst pressure of the hose assembly.
Judging criteria:
If the test pressure is lower than the minimum burst pressure and the hose has phenomena such as leakage, bulges, pop-up joints or hose bursts, it will be deemed unqualified.
3. Low temperature bending test test method:
The low-temperature bending test is to place the hose assembly to be tested in a low-temperature box and keep the temperature of the low-temperature box constant at the minimum operating temperature specified for the hose. In addition, the hose needs to be kept in a straight state, and the test lasts for 24 hours. Then do a bending test on the mandrel. The diameter of the mandrel is twice the minimum bending radius of the hose. After the bending is completed, return it to room temperature. After visually checking that there are no cracks on the hose, do a pressure test. At this point, the entire low-temperature bending test is completed.
Judging criteria:
During the entire test process, the hose under test and related accessories should not rupture; when performing the pressure test after returning to room temperature, the hose under test should not leak or rupture. Conventional hydraulic hoses are rated to operate at a minimum temperature of –40°C, while Parker’s low-temperature hydraulic hoses can reach -57°C.
4. Pulse test test method:
Pulse testing of hydraulic hoses is a predictive test of hose life. The experimental steps are as follows:
First, bend the hose assembly to 90° or 180° and install it on the experimental device; feed the hose assembly with the corresponding test medium. During high-temperature testing, the medium temperature needs to be maintained at 100±3°C; feed the hose assembly with Pulse pressure is applied internally. The test pressure is 100%/125%/133% of the maximum working pressure of the hose assembly. The test frequency can be selected between 0.5Hz~1.3Hz. After completing the number of pulses specified by the corresponding standard (Parker 2,000,000 cycle pulse tests were conducted on its GlobalCore 787 and 797) and the experiment was completed.
There is also an upgraded version of the pulse test – the flexural pulse test. This test requires one end of the hydraulic hose assembly to be fixed, and the other end to be connected to a horizontal moving device. During the test, the movable end needs to move back and forth at a certain frequency.
Judging criteria:
After completing the required total number of pulses, the hose assembly is deemed to have passed the pulse test without any failure.