Different lengths, different materials and different sizes of watertight enclosure compartments will have precise parameters of the rated pressure resistance depth, where the pressure resistance depth refers to the rated depth data obtained from product design and testing. Various components are installed inside and outside the watertight enclosures and are often modified, especially if the cable penetrators are well potted, which can have an impact on the sealing. There is a risk of seal failure every time the watertight enclosure is opened or changes are made to the unit, but hydrotesting the unit as a whole every time is not easy to do, and can increase the number of depth cycles and decrease the life expectancy.
Obvious check points for a good seal are:
- whether all O-rings are installed and whether the O-rings are worn, aged, deformed or cracked.
- whether there are scratches and impurities on the contact surface of the O-rings.
- whether the watertight enclosure is cracked and deformed.
- whether the cables in the cable penetrators have been pulled so that the gel is cracked and degummed.
- whether the locking caps of Enclosure Vents, Vacuum Plugs, Connectors, etc. are installed in place.
- whether all screws have been tightened.
The above items by visual inspection does not fully explain the equipment sealing good, so also need to carry out a quick and harmless sealing test.
Sealing test of underwater equipment is almost always vacuum airtight test, so that the equipment to maintain a slight internal vacuum is also often used for online monitoring of the state of the equipment, such as the equipment installed inside the temperature and humidity sensors, when the value of the change to a certain extent judged to be the equipment for the occurrence of liquid intrusion, and then through the setup program to disconnect the power, return or alarm prompts and so on. This vacuum test method is widely used for the following reasons: fast and convenient, non-destructive, requires less equipment, accurate results. This test method can only test the installation in place, sealing there is no problem, and can not show the water pressure resistance of the equipment.
Vacuuming also has other benefits, such as the existence of atmospheric pressure can also make the end cap and flange more tight, not easy to fall off and do not need additional locking, less air in the watertight enclosure can also reduce the moisture humidity in the air, less likely to produce condensation water droplets affecting the work of electronic components.
The following describes how to perform a vacuum test using a Vacuum Plug.
1. Install the self-sealing bulkhead onto the end cap.
2. Seal off the manual vacuum pump and check for any air leaks in the pump body.
3. Connect one end of the air hose to the manual vacuum pump and the other end to the copper plug.
4.
Insert the copper plug into the bulkhead and press the pump body multiple times until the plug does not detach due to the vacuum.
5. Continue pressing the vacuum pump until the reading reaches 15inHg and wait for a few minutes.
6. Check if the reading does not drop by more than 0.5inHg, indicating a good seal.
7. Remove the vacuum plug and screw on the lock cap.
See the video below: