What is the difference between a heat-shrinkable tube and a common cambric sleeve?

They are both designed for the insulation of electrical connections. Cambric sleeve is made of PVC, KBT heat-shrinkable tubes are made of polyolefine- an ecology-friendly material. Heat shrinkable tubes are heat- and chemical-resistant due to its cross-linked structure. After shrinkage of a heat-shrinkable tube there are not overlaps between the tube and insulated surface. When you use cambric sleeve these overlaps are escapeless. So the advantages of the heat-shrinkable tube are comfortable, easy and quick installation. This is a choice of the modern electro-technical realm.

What does НГ mean in the names of some tubes?

These Russian letters mean that they are flame retardant.
The tubes with this kind of index in the name are self-extinguishing.
Among KBT range they are ТУТнг, ТТК(3:1), ТТК(4:1). There are antypirenes in the composite of polymers, they are responsible for flame retardance. Antypirens prevent oxygen supply, that makes burning impossible.
Recently fire safety requirements have become more strict- insulation of cables is required to be flame retardant, so the heat shrinkable tubing as well.

Can heat shrinkable tubing be used for the insulation of cable connections?

This is the main function of heat shrinkable tubing. Composite of polymer used for the production of KBT tubing performs significant electrical strength and can be used for insulation of cable connections for voltage up to 600 V.

What is the use of heat shrinkable tubing with adhesive layer? In what cases can a tube without an adhesive layer be used?

The adhesive layer works for leak-proof sealing of the connection. When heated the tube shrinks and the adhesive layer melts and spreads inside for perfect adhesion. Surplus of glue goes outside the tube and forms a sealing along its edges. So if you have special requirements for leak-proof connection, it is better to choose a tubing with an adhesive layer. Moreover, this kind of tubes have a higher shrinkage ratio (3:1, 4:1, 6:1) in comparison with a standard ration (2:1), and thicker walls for voltage up to 1 kV.

What are the steps of the correct shrinking of tubing?

Before choosing correct tubing you should know the exact diameter of the surface you want to insulate. If the tube has shrinkage ratio 2:1 you need to follow the rule 80:20, which means that the tube should be shrunk by no more than 80% and no less than 20% from its nominal range. In other words, the inner diameter of the tube before shrinkage should be 10-20% more than the diameter of the surface, and after shrinkage- 10-20% less than the diameter of the surface. If the reality will match these calculations you will have a good fitment of the tubing in the result.

I have always used tube ТУТ нг 6\3 made by KBT. The tube from my latest purchase failed to be stretched over a connector.

The tube should not be stretched! Before shrinkage, the tube should be easily put on the surface that needs to be insulated. The diameter of the connector or any other surface should be min 20% less than diameter of the tube. The sizes of the tubes indicated in the catalogue are nominal.
As a rule, KBT Tubes with shrinkage ratio 2:1 have a diameter from 6 to 6.5 mm.

Can I substitute a tube ТТШ with a common ТУТ made by KBT?

TTШ is a special type o tubing designed for the insulation of the busbar. It is made of special polymer composition with tracking-resistance, has a thicker wall ( 2.0 mm and 3.7 mm) and can work for bigger voltage -10 and 35 kV correspondingly. That is why these tubes can be sued for insulation of alum and copper busbar inside high voltage distributors and can also be installed outside. Common ТУТ tube made by KBT can't be sued for voltage more than 690 V.

Why is colorful tubing is more expensive than black tubing of the same size?

The difference in cost is explained by peculiarities in production technologies. In general heat shrinkable tubing goes through there stages: extrusion, sealing and blowing. When you start production of a tube that has a different color the remnants of the previous material should be taken out of the machine, so there are some non-recycled waste products that influence the price of the product.

What is the use of yellow and green heat shrinkable tubing?

In accordance with the international system green and yellow colors are used on earthing cables- green stripes of the yellow surface. So these colors are commonly used for systems of earthing.

What is the shrinkage ratio?

Shrink ratio is the correlation between the diameter of the tube before shrinkage and after shrinkage. In other words, a tube with shrink ratio 2:1 will be 2 times smaller after shrinkage, a tube with shrink ratio 3:1 will be three-time smaller and so on. The more the shrink ratio is the more complicated is the production process of this tube. The tube with a big shrink ratio is very useful in cases when you work with lots of different diameters.