Uninterrupted power supply is possible only with a reliable connection of electrical wires. Often, twisting technology is used for this purpose. But wires connected in this way are prone to overheating and oxidation. Due to the incompatible electrochemical properties of metals, it is undesirable to twist aluminum and copper wires. In such cases, crimping with sleeves is recommended.
GML - what is it?
Copper sleeves are used to connect copper electrical wires by twisting. The abbreviation GM denotes an ordinary, without any coating, copper sleeve. GML is a copper sleeve that has undergone a tinning procedure. A special tin-bismuth layer is applied to it. This is especially necessary for products made of copper, as this material is prone to oxidation.
Due to this coating, tinned copper sleeves are not subject to corrosive processes and do not react with cveins. These products are not recommended for use in electrical work in conjunction with aluminum wires. This is explained by the fact that during compression, the protective coating may collapse, and the GML sleeve will enter into a chemical reaction with aluminum.
Case types
Connecting sleeves can be of the following types:
- GA. Under this abbreviation is a sleeve made of aluminum. This type is used exclusively for connecting aluminum wires.
- GAM. This is a combined type. Often such guides are also called aluminum-copper. Used for butt joints of aluminum and copper wires (building in old electrical wiring). Since aluminum has a higher resistance than copper, in GAM products the aluminum part is produced with an increased diameter.
- GSI. The isolated connecting sleeves represent tinned products on which PVC isolation is applied. Are applied to connection of stranded copper wires. During crimping, the insulation is not removed. Pressing with special pincers can be done directly through the cover.
Tubes for connecting power cables
Cable sleeves are used for cable installation in instrumentation, switchboards and mechanical engineering. They provide good contact during installation and prevent cable separation during use.
Cable sleeves are highly resistant to deformation and protect the wire from mechanical damage. This issignificantly extends the life of the product.
Types of end sleeves
Depending on the installation method, the sleeves are intended for:
- For crimping. Installation is carried out using cable presses.
- For soldering. Compared to crimping, this connection method is more labor-intensive.
- For connection with bolts. Work is carried out without the use of a special tool.
GML sleeve section
Sizes and range of sections are shown in the table. The standard minimum cross section is 1.5 square meters. mm. Next comes in ascending order: 2.5 square meters. mm, 4-6-10 sq. mm. Tinned copper sleeves with their parameters correspond to the wire section. Professional electricians use simplified names: “fours”, “tens”, etc. “Six” is a tinned copper sleeve having a 6-mm minimum section. GML-6 - this designation can be seen in the technical documentation.
When is the "six" used?
According to its characteristics, the sleeve GML-6 can freely pass through itself four electrical wires with a minimum cross section of 1.5 square meters. mm. With a cross section of 2.5 sq. mm, no more than three such wires will enter this sleeve. The fourth can be used as a sealant. The minimum cross section of this wire should be 1.5 square meters. mm. In addition, the "six" can be used to crimp two wires with a cross section of 2.5 square meters. mm.
Sleeve device
Depending on the design, the GML sleeve can be:
- Through. Such a sleeve is a hollow tube.
- Containing a baffle in the middle of the tube. This type is used for butt joint. You can adjust the depth of entry of the connected cables using the data of the GML sleeve. Extended (extended) wires are recommended to be connected using tubes equipped with partitions.
Product characteristics (GOST 23469.3-79)
- Product type – tinned copper sleeve. Designed for crimping wires and cables made of copper. The product is processed by tin-bismuth tinning. As a result, the sleeve acquires a white tint. Designed for voltages not exceeding 10 kV
- The design of the sleeve is through. In terms of inner and outer diameter, the product corresponds to the tips of GOST 7386.
- GML are designed to connect cables and wires (flexibility classes 5 and 6). In order to carry out electrical wiring of copper conductors of class 2 or 3, you will need a tinned copper sleeve, the size of which can be selected using a special table.
Crimping principle
Crimping is a process in which electrical wires are connected using special sleeves. The functions of the connecting mechanisms are performed by metal tubes (sleeves), into which wires are inserted from both sides.
The principle of crimping is to compress the sleeve with the wires in it using press tongs. In everyday life, this special tool can be replaced with pliers orhammer. Compression takes place in several places. After that, the sleeves are insulated with a heat shrink tube or insulating PVC tape. This step can be skipped if a ready-made insulated connection sleeve is used.
Steps
Crimping with sleeves is easy if you follow the step by step instructions:
- You need to decide what type of sleeves will be used. The material of the wire must match the material of the sleeve. It is undesirable to use copper connectors for cables made of aluminum, since their chemical interaction can occur, which will lead to oxidation and a decrease in electrical conductivity.
- Make the inside of the case using quartz-vaseline pastes.
- Prepare the cores of the cables to be connected. To do this, the insulation is removed from the wires. The length of such a section must correspond to the length of the sleeve. If the crimping procedure is used for wires of shaped type (their cross-section is oval or rectangular), then such cores must be rounded to fit the geometry of the connecting sleeve.
- After removing the insulation, the cores must be cleaned. At the end of this step, the surface of the wire should acquire a metallic sheen.
- Treat the stripped surface of the wire with quartz-vaseline paste.
- Put the connecting sleeve on the prepared wires. During this work, it is important to ensure that the ends of the wires to be connected are joined to each other incenter of sleeve.
- Perform pressure testing. The work is carried out by reciprocating movement of the upper handle of a special press. The action should be performed until the matrices are in full contact. It is important that the working area of the pliers matches the size of the sleeve.
- Insulate the junction. You can use electrical tape for this. Heat shrink tubing will also do the job. In this case, the connected wires are passed through it at the very beginning of work. Soldering the tube is easy using a building dryer.
When is crimping used?
This technology using GML can be used:
- for connecting wires in a high load line.
- When connecting large gauge wires.
- In cases where it is not possible to apply any other type of connection.
The most common crimping mistakes
Often, some craftsmen, not having special crimping pliers at hand, use ordinary pliers, a chisel and a hammer for crimping. This is not recommended, since the pliers are equipped with special dies, punches and sponges that provide high-quality crimping. It is not uncommon for wires connected in a tinned copper sleeve with pliers to fall out of it after some time. There is a wide range of manual or electric crimpers available on the tooling market today.
In the absence of a tinned copper connection sleeve of the required size, there may becopper tube used. The free space left between the core and the wall of the copper tube is filled by the craftsmen with pieces of other cores. It is important that these pieces are of the same metal as the tube. This requirement applies to both copper and aluminum pipes. However, there is a big difference between the electrical material in a real sleeve and the material in a homemade one made from a tube. Therefore, for crimping, it is best to purchase a connecting tool made of a special grade of metal. In the case of GML, this will be electrical copper.
Often, having bought GML with an unsuitable cross-section, some consumers cut off part of the conductor. This mainly occurs in cases where the cross section of the tinned copper sleeve is smaller than that of the core. Cutting is not recommended as the reduced cross section in the wire will create a mechanical weak spot on the wire where breakage can occur.
After an unsuccessfully chosen too large GML, during the connection of stranded wires, they cannot be folded in half and thrust into the sleeve. It will not add mechanical strength to the joint. The contact will still remain unreliable. To connect the wires using crimping, you do not need to use a soldering iron or welding machine. For work, you need only special pliers. They are easy to work in the most inaccessible places. Tinned copper sleeves, as well as similar products of other types, are becoming increasingly popular.
