One of the problems of working with electrical devices in underground or underwater conditions is the possibility of an electric leakage, which can be fatal. There is also the risk that comes from the corrosion caused by a highly moist environment. This is why we need specially constructed cables like submersible flat cable.
Submersible cables are often found with submersible pumps. These are also suitable for the underground application. A submersible cable is constructed so that it can withstand the highly corrosive nature of its environment while staying efficient in carrying electricity.
These cables are found in a wide range of applications, such as:
- Sewage treatment plants
- Waste management
- Water supply plants
- Irrigation industry
- Gas drilling
- Deep well boring
- Marine industry
Based on their application there are two broad classifications of submersible flat cable underground feed cable and submersible pump cable. The difference in the two lies in their positioning. The submersible pump cable is placed between the wellhead and the pump, while the underground feed cable is placed between the wellhead and the control panel. Both are equipped to carry electricity while submerged in water. However, the underground feed cable can also be buried underground.
Choosing a submersible cable:
Given the demanding nature of its environment, it is important that the cable is chosen carefully. Any fault here will not just impact the functioning of the pump, it can also be dangerous.
Type of cable
Submersible cables are available in three types: twisted, heavy-duty flat jacketed and flat twisted. The heavy-duty submersible flat cable is suitable for the very demanding operations of submersible cables. Not only the installation process, where the cable is twisted and turned, it must also waistband vibrations and the torque force that accompanies the pump’s functioning.
The flat cables — both twisted and parallel were considered expensive. The steel casing that was required for its demanding environment, made the cable more expensive than other alternatives. But PVC insulation has made the cable more affordable, although it is not as strong in mechanical strength as a steel jacketed cable.
Submersible cable conductors come in all kind of sizes. The size of the cable is decided according to multiple criteria. The length of the cable is important here since it will decide the ampacity. When calculating the ampacity, you must take into account the cable location in free air, in water or in conduit. Voltage drop is another factor that must be taken into account when measuring the length. It is not unusual to find a submersible pump with multiple sized cables. This usually happens when the pump is already installed and we need extra cabling. Different sized cables can be used only after carefully calculating requirements.
This term is meant for the copper strands that form the conductor of the cable. Stranding is important because the finer it is, the more flexible is the cable. Today you can get cables with different flexibilities. Depending on the functioning and the operating temperature, you can select the flexibility of a cable.
The insulation is an important factor in the submersible cable because the cable has to resist the corrosion caused by water, chemicals while withstanding demanding installations. Some cables are required to move around and withstand the torque movement of a pump. In some cases, like in an STP, the cables are working in extremely toxic and corrosive environment. The insulation becomes critical because of such conditions. Steel jacketed, rubber, PVC — all these have been used as insulating material. Steel lacks flexibility and is expensive. Rubber is flexible but quite expensive. PVC is both flexible and affordable. It is also quite light, making its installation easier.
Most submersible pumps also require grounding so as to ensure safety. In some cases, this is extremely critical. So, you may require the cable for grounding.
As explained above, flexibility can be a major requirement. Some pumps have movement, some are used in the extremely cold environment. In the first case, a cable will need the flexibility to cope with movement caused by pump’s vibration and torque pull when it is switched on. In the second case, an extremely cold environment can make cable maneuvering difficult. A rigid cable will only make it worse.
Submersible flat cables are used all around us. When selecting a submersible cable, check its type, decide the size, standing, and insulation.