With the ever-increasing spread of technology, it is now required for machinery to be present almost everywhere, including underwater. Underwater machinery means we also need underwater cables. The most common usage is, of course, for underwater pumps. Submersible cables actually have a wide usage, from marine exploration, shipping industry to irrigation.
One of the most commonly seen functions of a submersible cable is for underwater pumps. Among cables, the preferred cable is the submersible flat cable. Other than submersible cable, we also find underground feed cable where underwater pumps are installed. The function of the cable is to carry power underwater, while the feed cable lies between the wellhead the control panel.
Submersible cables have many applications. Some of these are:
- Deep boring wells
- Water supply plants
- Underground mining
- Sewage treatment plants
Selecting the right cable
It is extremely important that we select the cable carefully. The submersible cable protects the conductor within from the corrosion of the moisture outside while preventing any current from leaking outside. Failure to buy the right cable can be extremely dangerous. When selecting a cable there are three main components that we have to consider:
- The conductor, which is the wires that carry current.
- The insulation, which prevents the conductors from shorting. This cover ‘insulates’ the conductor, preventing it from coming into contact with other conductors.
- The jacket, which envelopes one or more conductors, providing them protection.
The selection of the right cable necessitates that we pay attention to all these factors and more. There are largely three types of cables available when it comes to submersible cables: submersible flat cable, twisted parallel and flat parallel. The most commonly found cables are the flat cables that can withstand abrasions, provide mechanical support and has the ability to weather the vibrations of the pump. The flat cable could also have a heavy-duty casing like steel where we have more chances of abrasions.
Flat cables are preferred here because of their flexibility and efficiency. The flat cable anatomy means that the conducting wires run parallel to each other, making it more flexible than twisted or round cables where the wires overlay each other. In the latter’s case, the contact between wires also gives rise to another problem — of overheating. In flat wires, conductors run parallel to each other and are well insulated. This means that there are no chances of contact. The higher surface to volume ration further lowers the risk of overheating.
Although aluminium could be used, the more common and preferred choice is copper. It is preferred because of its superior conductivity. Although aluminium is lighter, copper is far more efficient for our purposes.
Submersible cable conductors come in many sizes, from the very thin too much thicker wires. Usually, the size is specified in the manual for the pump. Selecting the right size is critical because the alternative can be dangerous, causing the shortage and even short circuit.
This means the number of copper conductor strands in the cable. This has a bigger importance than it appears. The more strands there are, the more is the flexibility of the cable. Cables with fewer strands are stiffer. Multiple strands also mean that we are looking for thin wires. Copper has an advantage where we need thinner conductors because its high conductivity means that it can be effectively used to make thin wires.
The proper choices here are rubber and PVC. Rubber is more expensive, so PVC is used more commonly. In some installations, the ability to withstand abrasions in very important, such as in case of deep good installations, where constant movement against the well can leave heavy abrasions. Steel casing can be added to make it more resistant to abrasions.
The best way to check for a cable’s safety is by checking the ISO certifications. ISO standards were confided to ensure that a cable’s manufacturing and construction met with well-defined safety parameters. A cable that carries the proper certification will at the very least be safe to use.
Submersible cables are used wherever we have underwater power requirement. The most preferred cables here are submersible flat cables. However, we must take care to choose the right size and standing.