Molly Ayala
Splicing submersible electrical cables is a critical aspect of submersible pump and motor installations. A good splice should be watertight, electrically conductive, and mechanically strong. There are various methods and kits available for creating a proper splice, such as the tape method, heat shrink splice kits, and cold shrink splice kits. The process involves stripping insulation from the cables, connecting the conductors, and applying heat shrink tubing or adhesive to create a secure and watertight joint. Proper splicing techniques ensure long-lasting and trouble-free installations while preventing damage or failure of the entire pumping system.
| Characteristics | Values |
|---|---|
| Splicing methods | Tape method, heat shrink splice kits, cold shrink splice kits, adhesive-based splice kits |
| Tape method | The original method for splicing, now superseded by heat shrink kits |
| Heat shrink splice kits | The most common method, using heat to shrink tubing around the splice |
| Cold shrink splice kits | Kits that do not require heat, such as the 3M product |
| Adhesive-based splice kits | Kits that require the user to mix and pour urethane potting compound into a mould and wait for it to cure |
| Splice kit contents | Stake-ons for electrical connections, and shrink tubes to make the splice watertight |
| Splicing process | Strip insulation, slide heat shrink onto cable, crimp connector to conductor, heat with heat gun, key outer insulation with sandpaper |
| Splicing considerations | Compactness, physical and electrical strength, continuity, and water resistance |
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What You'll Learn
Splicing kit options
There are several kits available for splicing submersible electrical cables. The type of kit you use will depend on the type of submersible pump cable you are using and the depth of the application.
The tape method was the traditional way to splice cables, but now there are shrink-tube splice kits available. These kits consist of stake-ons, which make the electrical connection, and shrink tubes, which make the splice watertight. The shrink tube is heated with a hot air gun or torch, causing it to shrink to about a third of its expanded size, bonding to the wire insulation and creating a strong, watertight joint. The kits are sized for the particular pump cable size you are using, with kits for smaller sizes of cable being designed to handle several sizes of pump cable.
For instance, one kit will work for #10, #12 and #14 cables. If you are splicing a large size wire to a small wire, you can crimp a #10/14 stake-on to the small wire and then crimp the larger stake-on over the small stake-on. This technique can also be used when installing the shrink tube in a transition splice.
There are also adhesive-based splice kits available, such as the 3M™ Scotchcast™ Cable Splicing Kit, which requires you to mix and pour urethane potting compound into a mould and wait for it to cure. A similar alternative is the Shake N' Seal underground wire splice kit, which provides a permanent watertight seal and can be buried immediately.
If you are looking for a quicker solution, the WetLink Cable Splice Kit is a revolutionary alternative to adhesive-based kits. It does not require any potting compounds, moulds, or curing time, and can handle a water depth of 500 metres. This kit includes a small box, made with high-strength polycarbonate plastic, with holes on either end for the WetLink Penetrators, which seal to almost any cable with a compression gland seal.
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Preparing the cables
Firstly, you must strip the insulation from the cables. The amount you strip will depend on the type of cable you are using. For the submersible drop cable, strip back about 25mm of the outer black insulation and 10mm of insulation from each conductor. As for the motor cable, strip back about 80mm of the blue insulation and 10mm of insulation from its conductor.
Next, you will need to prepare the heat shrink tubing. Slide a large heat shrink piece onto the cable, followed by a small heat shrink piece onto each conductor. Ensure that the heat shrink tubing is of the appropriate size and type for your cable. It should be heavy-duty, thick-walled, flame-retardant, and rated for continuous submersion in water.
After preparing the heat shrink tubing, you can proceed to crimp the connectors. Crimp one end of a crimp connector to each conductor, ensuring a secure connection. This step involves joining the individual conductors physically.
Before moving on to the next step, it is important to key the outer insulation of the cables with sandpaper. This process involves roughening the surface of the insulation to improve the adhesion of the sealing tapes and heat shrink tubing. Apply the sandpaper included in the kit to the black and blue insulators, being careful not to sand along the length of the cables.
By following these steps, you will have successfully prepared the cables for splicing. The next steps will involve applying heat to the heat shrink tubing and completing the splice, ensuring that it is watertight and secure.
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Connecting the cables
There are two main ways to make a splice: the tape method and the heat shrink-tube splice kit method. The tape method was the original way to make a splice, but now the heat shrink-tube splice kit method is almost universal in the pump industry.
The heat shrink-tube splice kit method involves using a kit with a small box, made with high-strength polycarbonate plastic, and holes on either end for the WetLink Penetrators, which seal to almost any cable with a compression gland seal. The kit also includes a Molykote Pillow Pack. To use this kit, you will need two WetLink Penetrators sized for your cable diameter. The splice can handle a depth of 500 meters of water.
To connect the cables, first, strip back the insulation from the submersible drop cable and the motor cable. Then, slide a large heat shrink onto the cable and crimp one end of a crimp connector to each conductor. Next, slide a small heat shrink onto each conductor and crimp the connector to the matching conductor of the other cable. Heat the heat shrinks with a heat gun, starting from one end.
If you are using the tape method, you will need to make sure the splice is kept as compact as possible, while retaining the needed mechanical and electrical strength and continuity. One way to provide a compact splice is by staggering the individual splices.
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Applying heat
First, prepare the cables by stripping back the insulation on both the submersible drop cable and the motor cable. For the drop cable, strip back about 25mm of the black insulation and 10mm of insulation from each conductor. For the motor cable, strip back about 80mm of the blue insulation and 10mm of insulation from its conductor.
Next, slide the heat shrink tubing onto the cables. Start by sliding the large heat shrink over both cables, ensuring it is centred between them. Then, slide a small heat shrink onto each individual conductor. The heat shrink tubing is a polyolefin-based plastic tubing with an adhesive coating on the inside. When heated, it will shrink in diameter, creating a strong and watertight joint.
Now, it's time to apply heat. Use a heat gun and start from one end of the heat shrink, gradually moving towards the centre. You can also use a hot air gun or a torch for this step. As the tubing heats up, it will shrink in size, forming a secure connection. Make sure all the heat shrinks are heated evenly and simultaneously.
After heating, use sandpaper to key the outer insulation of the cables. This process will create a rough surface, removing the shine from the rubber. It helps the sealing tapes and heat shrink to bond effectively. Be careful not to key the rubber along the length of the cables.
Finally, let the assembly cool down. This step is crucial in expelling air bubbles and ensuring a strong joint. Once cooled, you can test the completed cable splice joint with a multimeter or appliance tester to ensure proper electrical connections and continuity.
By following these detailed instructions for applying heat, you can create a secure and watertight splice when splicing submersible electrical cables.
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Testing the splice
Visual Inspection:
Begin by visually inspecting the splice. Ensure that the heat shrink tubing has contracted adequately and securely covers the splice. Look for any signs of damage, such as charring or melting, which could indicate a problem with the connection or the heating process.
Electrical Conductivity:
Check the electrical conductivity of the splice. Use a multimeter or an ohmmeter to test for continuity between the spliced wires. Set the device to measure resistance or continuity, and touch the probes to the corresponding wires on each side of the splice. The device should indicate a complete circuit, showing that the splice is electrically sound.
Watertightness:
To test the watertight integrity of the splice, you can perform a simple immersion test. Submerge the spliced section of the cable in a container of water. Ensure that the water covers the splice completely and observe for any signs of air bubbles escaping or water seeping into the splice. If the splice is properly sealed, there should be no movement of air or water.
Pull Test:
Perform a pull test to ensure the mechanical strength of the splice. Grip the cable on either side of the splice and apply gentle tension in opposite directions. The splice should hold firmly, and there should be no signs of the wires slipping or the splice coming apart.
Advanced Testing:
For more advanced testing, you may consider using a Time Domain Reflectometer (TDR) to detect the splice. A TDR is a sophisticated instrument that can pinpoint the exact location of a splice or any faults along the cable. However, it is an expensive tool, and you may need to rent one or consult a professional with the necessary expertise to operate it effectively.
Remember, a proper splice is crucial to the long-term performance of your submersible electrical cable. If you have any doubts about the quality of the splice or the testing process, it is always best to seek advice from a qualified electrician or cable splicing specialist.
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