Security is one of the main requirements for electrical wiring. Overheating, fire, contact disturbance most often occur in the joints. Therefore, isolation of connections is important for reliable and safe operation of electrical networks. Regular insulation tape does not protect against prolonged exposure to moisture, the material of the fabric tape may deteriorate over time, the joint does not look very neat. Therefore, today an alternative to electrical tape is shrink tube.
- 1 Heat shrink tubing
- 2 Properties and characteristics of heat shrink tubing
- 3 How to use shrink tubing
- 4 Heat shrink tubing dimensions
Heat shrink tubing
Shrinking before other methods of insulation have several advantages:
- tight fit eliminates the isolation of the insulation, even under mechanical action;
- easy installation;
- additional mechanical strength;
The heat shrink is made of a polymeric material, which is compressed by high temperature. After shrinkage, the tube tightly fits the junction, accurately repeating its relief, and forms a durable hermetic coating. Therefore, the main, but not its only purpose is to ensure reliable insulation of current-carrying wire connections. In addition, heat shrink tubing serves
- sealing and moisture protection;
- protection against mechanical damage, dirt and chemical corrosion;
- protection of places of excesses and protection from deformation;
- restoration of damaged insulation and sheaths of wires and cables;
- binding strands;
- color marking.
Using colored tubes for marking is very convenient, a small ring of the corresponding color sits on top of the insulating layer on the end of the wire. For example, in wires of DC circuits they use red on plus and black on minus, in wires grounding - yellow-green combined color, and in a three-phase circuit - red, yellow and green colors for corresponding phases.
Large color range allows the use of heat shrinkage and as a decorative material.
In everyday life, heat shrinking is used to repair home appliances and to isolate electrical wiring. Due to its durability, variety of sizes and ability to work at high temperatures, it is very convenient when repair of onboard electrical network and installation in the car alarms, radio, car audio and onboard computers. On foreign car brands rigid heat shrinkable tubes are used for mechanical and anti-corrosion protection of fuel lines and brake hoses.
Properties and characteristics of heat shrink tubing
Heat shrink properties:
- The main property of the tube is the ability to change the diameter and thickness, shrink under the influence of temperatures from 80 ° C to 120 ° C. In radio electronics, products with a lower initial heating temperature of 70 ° C are used;
- The operating temperature range is from -45 ° С to +125 ° С. In the automotive industry, tubes with a temperature of 135 ° C are used to isolate compounds under the hood;
- Standard color - black, non-standard - red, white, blue, green, yellow. In places where you need to monitor the quality of the connection, transparent shrink tubing is used.
- Shrinkage ratio from 2: 1 to 6: 1, that is, the ability to shrink 2 to 6 times;
- The presence of the adhesive layer, if you need reliable sealing, waterproofing and corrosion protection of contact joints. Hot melt adhesive layer on the inner surface of the tube gives the joint additional strength and resistance to mechanical stress;
- Resistance to aggressive environment. Thermal shrinkings are chemically resistant, oil-resistant, heat-resistant, light-stabilized, with the effect of photoluminescence;
- The composition of the polymer. These can be polyolefins, PVC, elastomers and other materials on which the resistance to fire, the action of ultraviolet rays, color solutions;
- The color scheme, in which the most common standard and combined versions of two colors. Often tubes with similar characteristics are made of transparent polyolefin and in black with different connection requirements.
How to use shrink tubing
The installation process shrink is quite simple, and in everyday life you can do without special tools. It is possible to heat a tube and a usual lighter or a gas torch. Although, of course, industrial dryer allows shrinkage neatly and evenly.
The whole difficulty lies in the correct selection of the sizes of the heat shrink tubing.
The initial internal diameter is always known, and the thickness of the tube and its shrinkage coefficient, i.e. independently determine the diameter after shrinkage, although usually the geometrical parameters before and after shrinkage are indicated by the manufacturer. Initial dimensions need to know that the tube is placed on the wire or connector without tension. And in order to ensure reliable hermetic protection, the diameter of the heat shrinkage after heating must be less than the diameter of the connection of wires or the product that it protects. The greater the shrinkage of the tube, the greater its thickness after heating and the higher the strength.
Choosing a heat shrinkable diameter, it is necessary to cut a piece from it in such a way that it overlaps the section along the length that needs to be insulated with a margin for longitudinal shrinkage of the tube. This indicator is also set by the manufacturer, and is usually 5–10%.
The cut must be smooth and the surface without deep scratches so that the tube does not break due to high temperature in places where there are burrs and external damage.
When the tube is worn on a section of wire that is insulated, it is heated by a heat gun or a lighter from the middle to the edges, if it is long or with an adhesive layer, or from one edge to the other, in case it is necessary to avoid large longitudinal shrinkage. If you start warming up immediately from both sides, air bubbles will remain at the junction and wrinkles will appear on the tube itself. You need to warm up the entire area evenly without overheating, so that there are no gaps, charring or bubbles in the heat shrinkage.
Important is also correct choose the heating temperature, but this is already determined empirically. The main thing is not to rush, the high temperature will increase the speed of shrinkage only slightly, and will lead to marriage necessarily, especially if the installer does not have experience of similar works.
If it is necessary to insulate the joints with shrinkable tubes with an adhesive layer, the sharp edges on the product are cleaned, the surface is cleaned and degreased, and then heated.
Heat shrink tubing dimensions
Manufacturers always label heat-shrinkable tubes. The main parameter is always the internal diameter before shrinkage. Sometimes the fraction after shrinkage is indicated through a fraction, and sometimes the coefficient by which the final diameter is calculated.
Standard and most 2: 1 ratio is common.
European manufacturers indicate the dimensions of the tubes in inches, and when converted to millimeters (1 inch = 2.54 mm), diameters of the type 1.6 mm, 12.7 mm are obtained.
Products of Asian and Russian manufacturers are available in multiples of 0.5 or 1 mm.
As a rule, the tubes are supplied in 1000 mm cutting (one meter each). Although there are types of shrinkable, which are supplied in bays of 50, 100 or 200 meters.
Almost always you can pick up two tubes of similar sizes, in this case it is better to use a product of larger diameter.
The thickness of the heat shrink is divided into two types:
- thin-walled with wall thickness after shrinkage is not more than 1 mm. These are colored, black and transparent tubes with a shrinkage ratio from 2: 1 to 4: 1 without adhesive layer. Used for marking wires and as insulation, and may have additional properties: heat-resistant, low-temperature shrinkage, self-extinguishing, with increased resistance to UV rays;
- thick-walled and srednestenny with a wall thickness after shrinkage from 1.5 to 4.5 mm and a shrinkage ratio from 2: 1 to 6: 1, as a rule, with an adhesive layer. They are used to insulate power cables, including for street mounting, for bandaging wiring harnesses, to protect steel pipes from corrosion.
If you learn (and it is not difficult) to isolate connections in electrical circuits using heat shrinkable tubes, you can quickly and reliably not only repair household appliances, but also carry out more complicated network laying works in a house or apartment.