There are many ways to test the tightness of hydraulic tubes. The following are some common test methods and specific operations:
Pressure test method
1. Test preparation
Install the hydraulic tube on the test bench and connect relevant test
equipment, such as pressure pump, pressure gauge, etc. Make sure that the test
system is firmly connected to the hydraulic tube without leakage risk.
According to the working pressure range of the hydraulic tube, select a
pressure gauge and pressure pump with a suitable range. Generally, the pressure
gauge range should be 1.5-2 times the test pressure.
2. Test steps
Start the pressure pump and slowly fill the hydraulic tube with
pressure medium (usually hydraulic oil or water) to gradually increase the
pressure to the specified test pressure. During the pressure increase process,
observe whether there is leakage in the hydraulic tube and each connection.
After reaching the test pressure, keep the pressure stable for a period of
time, usually 10-15 minutes, and pay close attention to the changes in the
pressure gauge reading during this period. If the pressure drops by more than
the specified value, it means that there is a sealing problem with the hydraulic
tube.
3. Judgment criteria
Generally speaking, during the pressure maintenance period, the
pressure drop should not exceed 5% of the test pressure. If it exceeds this
range, the hydraulic tube needs to be inspected, the leak point needs to be
found and repaired.
Bubble test method
1. Test preparation
Close one end of the hydraulic tube and connect the other end to the
air source, such as a compressed air bottle. Prepare a basin of water or other
suitable liquid to observe the bubble generation.
2. Test steps
Open the air source and slowly fill the hydraulic tube with a certain
pressure of air, generally 0.3 - 0.5MPa. Immerse the hydraulic tube in water
and carefully observe whether there are bubbles on the surface and connection
parts of the hydraulic tube. If bubbles are generated, it indicates that there
is a leak in that part.
3. Judgment criteria
If continuous bubbles are found during the test, regardless of the size
of the bubbles, it means that the hydraulic tube is not sealed. The leaking
part needs to be marked for subsequent repair.
Applying test fluid method
1. Test preparation
Prepare special sealing test fluid, such as soapy water, leak detection
agent, etc., as well as application tools, such as brushes or sprayers.
2. Test steps
Apply or spray the test liquid evenly on the surface and connection
parts of the hydraulic tube to ensure that all possible leaking parts are
covered. Observe the part after applying the test liquid to see if there are
bubbles or flow marks of the test liquid. If bubbles appear or the test liquid
has obvious signs of flow, it means that there is a leak in this part.
3. Judgment criteria
The judgment is based on whether there are bubbles or abnormal flow of
the test liquid. As long as the above phenomenon occurs, it means that there is
a sealing problem in the hydraulic tube and it needs to be repaired.
Helium mass spectrometer leak detection method
1. Test preparation
A professional helium mass spectrometer leak detector and supporting
equipment are required to place the hydraulic tube in a sealed test cavity to
ensure that the cavity is well sealed.
2. Test steps
Fill a certain amount of helium into the hydraulic tube, and then scan
and detect the test cavity with a helium mass spectrometer leak detector. The
helium mass spectrometer leak detector can detect extremely small amounts of
helium leakage, and judge the sealing of the hydraulic tube by detecting the
amount of helium leakage.
3. Judgment criteria
According to the test results of the helium mass spectrometer leak
detector, if the detected helium leakage exceeds the specified allowable
leakage rate, the hydraulic tube is judged to be unsealed. Generally, for
high-precision hydraulic systems, the allowable helium leakage rate is very
low, usually below 10⁻⁹Pa・m³/s.
Summary
Pressure testing, bubble testing, smearing detection fluid, helium mass
spectrometer leak detection and other methods have their own advantages and
disadvantages. In practice, it is necessary to reasonably select the test
method according to the use scenario, accuracy and budget of the hydraulic tube
to ensure its sealing and ensure the stable operation of the hydraulic system.