Understanding Submersible Cables: Powering South African Industries Underwater

Introduction

Submersible cables are specialised electrical cables engineered to operate fully or partially submerged in water or other liquids, making them indispensable in industries where reliable power delivery in wet environments is critical. In South Africa, where mining, agriculture, and water management are economic cornerstones, submersible cables play a pivotal role in ensuring operational efficiency and safety. From powering deep well pumps in rural irrigation systems to supporting drainage operations in flooded mines, these cables are designed to withstand harsh underwater conditions while delivering consistent performance.

This article provides an in-depth analysis of submersible cables, exploring their design, applications, technical specifications, and advantages. It also addresses common questions and highlights their relevance to South African industries, such as the mining sector in Gauteng and the agricultural heartlands of the Western Cape. By understanding the unique characteristics of submersible cables, stakeholders can make informed decisions to optimise performance and reduce costs in water-intensive applications.

What Are Submersible Cables?

Submersible cables, often referred to as submersible pump cables or well pump wires, are electrical cables specifically designed for continuous or partial submersion in water or other liquids. Unlike standard cables, which may fail in wet conditions due to water ingress or insulation degradation, submersible cables are built with robust waterproof insulation, durable sheathing, and high-conductivity conductors to ensure reliable power transmission in challenging environments.

The key differences between submersible cables and standard cables lie in their construction. Submersible cables feature superior water resistance, enhanced mechanical protection, and materials tailored to withstand abrasion, chemicals, and pressure. These attributes make them ideal for applications such as submersible pumps, underwater motors, irrigation systems, and marine installations. In South Africa, submersible cables are critical in scenarios ranging from municipal water supply systems in Johannesburg to deep borehole irrigation in the Free State.

Design and Construction of Submersible Cables

The design of submersible cables is a testament to engineering precision, combining materials and configurations to ensure durability and performance underwater. Below are the key components of their construction:

Waterproof Insulation

Submersible cables are insulated with materials like cross-linked polyethylene (XLPE), ethylene propylene rubber (EPR), or specialised polyvinyl chloride (PVC). These materials offer excellent moisture resistance and thermal stability, ensuring the cable remains functional even under prolonged submersion. For example, XLPE insulation, commonly used in cables like the ZR-YJV22-0.6/1kV, provides superior resistance to water ingress and high temperatures, making it suitable for deep well applications.

Durable Sheathing

The outer sheath of a submersible cable is typically made of PVC, rubber, or high-density polyethylene (HDPE). This layer protects the cable from abrasion, chemicals, oils, and water pressure. In heavy-duty applications, such as mining operations in South Africa’s Witwatersrand Basin, an additional heavy-duty PVC jacket may be applied to enhance protection against mechanical stress.

Conductor Materials

The core of submersible cables is usually made of high-conductivity copper, often stranded (e.g., 19 strands per conductor) to improve flexibility and durability. In saline or corrosive environments, such as offshore oil platforms near Cape Town, tinned copper conductors are used to prevent corrosion, ensuring long-term reliability.

Optional Armoring

For applications in high-pressure or rocky environments, such as underground mining shafts, submersible cables may include steel wire or tape armoring. This additional layer provides mechanical protection, preventing damage from abrasion or crushing. Armored submersible cables, like the ZR-YJV22-0.6/1kV 3CX95+1CX50, are widely used in South African mining operations.

Configurations

Submersible cables are available in flat or round configurations:

• Flat Submersible Cables: These have a ribbon-like profile, with conductors arranged in a row, making them ideal for narrow borewells where space is limited. Their single-axis flexibility simplifies installation and enhances durability.

• Round Submersible Cables: These have conductors twisted like a rope, offering greater flexibility for deeper or more complex installations. They are suited for applications requiring cables to navigate tight or irregular spaces.

Types of Submersible Cables

Submersible cables come in various types, each tailored to specific applications and environmental conditions. The following are the most common configurations:

Flat Submersible Cables

Flat cables are designed for space-efficient installation in narrow borewells, such as those used in agricultural irrigation systems in South Africa’s Northern Cape. Their thin profile allows them to fit snugly within tight casings, reducing the risk of damage during installation.

Round Submersible Cables

Round cables are preferred for deeper installations or applications requiring greater flexibility, such as municipal water pumps in Durban. Their twisted construction allows them to navigate complex routes and withstand twisting forces during installation.

Armored Submersible Cables

Armored cables, equipped with steel wire or tape, are built for high mechanical stress environments. In South African gold and platinum mines, armored submersible cables like the (N)TSCGECEWOU are used to power drainage pumps in flooded shafts, where rocky surfaces and high pressure pose significant risks.

Specialised Cables

Several specialised submersible cables cater to specific depth and application requirements:

• H07RN-8-F: Suitable for shallow depths up to 10 meters, commonly used in swimming pool lighting or small-scale water features.

• 300m Pump Cables: Standard cables for moderate-depth applications, such as residential water wells.

• Drincable 800: Designed for depths up to 800 meters, ideal for deep borehole irrigation or offshore oil wells.

• Mining-Specific Cables: Cables like (N)TSCGEWOU are tailored for submersible applications in open-cast and sub-surface mining environments, offering enhanced chemical and abrasion resistance.

Applications of Submersible Cables

Submersible cables are critical in industries where electrical equipment must operate reliably in wet or submerged conditions. Below are key applications, with a focus on South African contexts:

Water and Wastewater Management

In South Africa, where water scarcity is a growing concern, submersible cables power pumps in municipal water supply systems, sewage treatment plants, and stormwater management facilities. For example, in Cape Town’s wastewater treatment plants, submersible cables ensure uninterrupted operation of pumps handling large volumes of effluent.

Agricultural Irrigation

South Africa’s agricultural sector relies heavily on deep well submersible pump cables to power irrigation systems. In regions like the Free State, where boreholes can reach depths of hundreds of meters, flat submersible cables are used to deliver power efficiently to pumps, supporting crop production in arid areas.

Oil and Gas

Electrical submersible pump (ESP) cables are used in South Africa’s offshore oil and gas operations, such as those along the Mossel Bay coast. These cables power pumps located deep underground, with marine-grade sheathing and tinned copper conductors to resist corrosion in saline environments.

Mining

South Africa’s mining industry, particularly in Gauteng and Mpumalanga, depends on heavy-duty submersible cables to power drainage and ventilation systems in flooded mines. Armored cables like the (N)TSCGECEWOU are critical for ensuring safety and operational continuity in these harsh environments.

Marine and Offshore

Marine-grade submersible cables are used in sub-sea lighting, remotely operated vehicle (ROV) systems, and offshore platform power connections. In South African ports like Durban, these cables support critical infrastructure in corrosive saltwater environments.

Fountains and Pools

Low-voltage submersible cables power submerged lighting and water features in architectural installations, such as those found in Johannesburg’s urban parks or Cape Town’s waterfront developments.

Technical Specifications and Standards

Submersible cables are subject to stringent technical standards to ensure safety and performance. Key specifications include:

Voltage Ratings

Submersible cables are available in voltage ratings such as 450/750V for low-voltage applications and 600/1000V for more demanding systems. Higher voltage ratings, such as 3.3kV to 6.6kV, are used for powerful pumps or long-distance runs.

Depth Ratings

Cables are rated for specific depths, ranging from 10 meters (H07RN-8-F) for shallow applications to 800 meters (Drincable 800) for deep installations. In South Africa, deep borehole irrigation systems often require cables rated for 300–800 meters.

Standards

Submersible cables comply with standards like UL 83 Type THW, which specifies thermoplastic-insulated, heat- and water-resistant cables. They are also AD8 classified, meeting IPX8 requirements for continuous submersion. These standards ensure the cables can withstand operating temperatures from -40°C to 75°C and resist flames, acids, oils, abrasion, and UV exposure.

Conductor Sizes

Conductor sizes range from 14 AWG to 2 AWG for well pump wires, accommodating various power requirements. For heavy-duty applications, larger cross-sections (e.g., 3Cx95mm² + 1Cx50mm²) are used to minimise voltage drop over long distances.

Environmental Resistance

Submersible cables are designed to resist harsh environmental conditions, including acids, alkalis, oils, and sunlight. This is particularly important in South African mining and agricultural settings, where cables may be exposed to corrosive chemicals or intense UV radiation.

Submersible Cables vs. Water-Resistant Cables

While both submersible and water-resistant cables offer some level of moisture protection, their applications differ significantly:

• Submersible Cables: Designed for permanent submersion, these cables use waterproof materials like EPR or specialised PVC to prevent water ingress. They are built to withstand continuous exposure to water pressure and harsh chemicals, making them ideal for deep wells and underwater motors.

• Water-Resistant Cables: These are designed for temporary submersion, such as in flooded cable ducts. They may use swellable tapes or AL/PET layers for water resistance but lack the robust construction required for permanent submersion.

In South African mining operations, using water-resistant cables in place of submersible cables could lead to conductor damage and system failures, highlighting the importance of selecting cables tailored for the intended application.

Advantages of Submersible Cables

Submersible cables offer several advantages that make them indispensable in water-intensive industries:

Unmatched Water Resistance

Their waterproof insulation and sheathing ensure reliable operation underwater, preventing current leakage and insulation degradation. This is critical for applications like sewage treatment in South African municipalities.

Enhanced Durability

With materials designed to resist abrasion, chemicals, oils, and UV exposure, submersible cables can last 10–15 years in harsh environments, reducing replacement costs. In South African mines, this durability translates to fewer operational disruptions.

Flexible Installation

Flat and round configurations allow submersible cables to be installed in tight or irregular spaces, such as narrow borewells or complex marine installations. This flexibility is particularly valuable in South Africa’s diverse agricultural and industrial landscapes.

Safe and Reliable Power Transmission

Submersible cables prevent short circuits and electric shocks, ensuring safety in residential, commercial, and industrial applications. This is crucial in South African water management systems, where reliable power delivery is essential.

Reduced Maintenance Costs

Their rugged construction minimises the need for frequent replacements, lowering long-term maintenance costs. For example, in South African irrigation systems, high-quality submersible cables reduce downtime and maintenance expenses.

Choosing the Right Submersible Cable

Selecting the appropriate submersible cable requires careful consideration of several factors:

Voltage and Current Ratings

Choose a cable with a voltage rating that matches the application, such as 0.6/1kV for low-voltage pumps or 3.3kV for high-power systems. Ensure the current rating supports the load without excessive voltage drop.

Conductor Size

Select a conductor size (e.g., 3Cx95mm² + 1Cx50mm²) based on the load current and installation length to minimise power loss. In South African boreholes, larger conductors are often required for deep installations.

Temperature and Depth Ratings

Ensure the cable can withstand the operating temperature and hydrostatic pressure at the required depth. For deep borehole irrigation in the Northern Cape, cables like the Drincable 800 are ideal.

Environmental Conditions

In corrosive environments, such as offshore oil platforms or mining operations, use tinned copper conductors and chemical-resistant sheathing to enhance durability.

Cost Considerations

Avoid over-specifying depth ratings to optimise costs. For example, using a Drincable 800 for a 10-meter application is unnecessarily expensive. Consulting technical experts, such as Feichun Cables, can help identify the most cost-effective solution.

FAQs About Submersible Cables

What is the difference between submersible pump cable and standard cable?

Submersible pump cables are designed for permanent submersion, with waterproof insulation and sheathing to prevent water ingress. Standard cables lack these features and are unsuitable for wet environments.

Can submersible cables be used in saline water?

Yes, cables with tinned copper conductors and marine-grade sheathing are corrosion-resistant and suitable for saline environments, such as offshore installations near Durban.

What depth can submersible cables operate at?

Depth ratings range from 10 meters (H07RN-8-F) for shallow applications to 800 meters (Drincable 800) for deep installations, depending on the cable type.

Are flat or round cables better for borewells?

Flat cables are ideal for narrow borewells due to their space-efficient design, while round cables offer greater flexibility for deeper or more complex installations.

How long do submersible cables last?

High-quality submersible cables can last 10–15 years in harsh environments with minimal maintenance, making them a cost-effective choice for South African industries.

Conclusion

Submersible cables are the backbone of water-intensive industries in South Africa, enabling reliable power delivery in challenging environments like deep wells, flooded mines, and offshore platforms. Their robust construction—featuring waterproof insulation, durable sheathing, and high-conductivity conductors—ensures safety, efficiency, and durability in applications ranging from municipal water management to agricultural irrigation and mining operations.

Selecting the right submersible cable requires careful consideration of voltage, depth, conductor size, and environmental conditions. By choosing cables tailored to specific applications, stakeholders can optimise performance, reduce maintenance costs, and ensure long-term reliability. In South Africa’s dynamic industrial landscape, consulting technical experts, such as Feichun Cables, can provide valuable guidance for project-specific cable selection, ensuring success in water management, agriculture, mining, and beyond.