On the end cap of watertight enclosure of underwater equipment there are usually bulkhead penetrator devices such as underwater switches, depth sensors, indicator lights, temperature sensors, etc., which can not only be mounted on the end caps, but can also be wired externally to lead out.
These are the two methods of waterproofing the external devices: axial seal and external penetrator connecting tube.
1. Axial seal
If there is no location requirement for the bulkhead penetrator device, it is usually installed on the bulkhead of the watertight enclosure without connecting external cables. The bulkhead penetrator device must be axially sealed to be waterproof, rather than directly immersed in water as a whole, and the internal cables of the device are connected to the internal watertight enclosure.
Therefore, bulkhead penetrator devices are mostly threaded bolt shapes. The bottom is equipped with a sealing groove for the end face, and can be compressed by tightening the nut through the end cap to achieve waterproof within 1,000 meters.
The red frame of the above profile shows the position of the end face seal of the underwater indicator light, which can be sealed by simply tightening the bulkhead penetrator device to the end cap by nuts.
Points to note are:
- Ensure that the surface part of the end cap touching the O -ring is free of scratches and impurities.
- The O -ring is located in the sealing groove, you can evenly apply grease on the O -ring, because the grease has a certain viscosity can stick the O -ring is located in the sealing groove without falling off. Here the grease needs to be of a water-tight type that is insoluble in water.
- Tighten the nut properly. Do not add O -rings or other parts that reduce friction to the nut. However, anti-slip gaskets can be added to increase friction in the nut position.
- The opening hole can not be too large, can pass through the bolt, too large cause shaking and displacement. As shown below.
| Recommended Size | M6x1 Penetrator | M8x1 Penetrator | M10x1 Penetrator | M14x1.5 Penetrator | M16x1.5 Penetrator |
|---|---|---|---|---|---|
| Recommended Bulkhead Through Hole Size (A) | Ø6.1±0.1 / Threaded | Ø8.1±0.1 / Threaded | Ø10.1±0.1 / Threaded | Ø14.1±0.1 / Threaded | Ø16.1±0.1 / Threaded |
| Hatch Cover Thickness (B) | 6 | 14 | 13 | 18 | 17 |
| Surface Range (C) | 15 | 17 | 20 | 26 | 32 |
2. Penetrator Connecting Tube
One end of the watertight enclosure of the underwater equipment can not be touched by hand, so that the cable of the indicator light or switch has to be extended and placed in other positions. In this case, external penetrator connecting tube and underwater cable need to be extended and waterproof.
A penetrator connecting tube includes a connecting tube and a gran head locking nut. The underwater cable enters the connecting tube through the locking nut and is then filled with glue. The connecting tube acts as a fixing device and a storage device, and the locking nut acts as a fixing cable to prevent excessive bending and blocking the colloid.
Specific method (take underwater indicator light as an example):
- Select a underwater cable with an outer diameter of 7-8 for the M10x1 connecting tube, cut a underwater cable with a proper length and number of cores, and peel off the outer skin. (If the outer diameter of a cable is less than 7, the cable can also be used. Wrap tape or a heat shrink tube around the locking nut section of the cable to ensure that the cable touches the locking nut and is centered.)
- Cut the indicator cable to an appropriate length, and weld it with the extended underwater cable, and cover them with a heat shrink tube.
- Use alcohol to wipe the adhesive surface, such as the inside of the connecting tube and the suface of cables.
- Route the other end of the underwater cable through the connecting tube and tighten the indicator to the tube.
- Insert the end of the cable into the tube and pour glue. Screw on the locking nut.
- Wait for the glue to cure, do not move during curing.
Refer to the assembly relationship in the figure above. Cables must be fully in contact with the colloid and centered to ensure the sealing effect. After the above treatment, the bulkhead penetrator devices can be directly submerged and led to other locations.