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| Which material is used for insulation of sheet metal terminals? |
| Special PVC provides excellent insulating property as well as its colour does not faint after crimping |
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Why the colour of insulation is different? |
As per international practice in use, Red colour is for terminals of 1.5 Sq.mm, Blue colour is for terminals of 2.5 Sq.mm & Yellow colour is for terminals of 4-6 Sq.mm, |
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| Can insulted terminals be crimped with the tools meant for non insulated terminals? |
NO. The tools designed for Non insulated terminals will not properly crimp the terminals. It will also damage the insulating sleeve. |
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What are the Indian standard specifications for our products? |
Indian standard specifications are formulated for Aluminium terminals only. At present specifications for copper or sheet metal terminals are not formulated.
IS 8308 - 1993 covers Aluminium In Line Connectors & IS 8309 - 1993 covers Aluminium Tubular Terminal Ends. |
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How do we know the purity of copper or Aluminium used in our products? |
Purity of these metals are determined on the basis of its conductivity, which can be measured by special meters. Conductivity of Electrical grade of copper should be minimum 99% IACS (International Annealed Copper Standard) and that of aluminium should be minimum 60% IACS. |
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| Does 99% copper content guarantee 99% IACS conductivity? |
No. Conductivity is affected by the type of impurities content in balance 1%. It has been observed that 0.5% arsenic may bring down the conductivity to the tune of 50% to 60% |
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| What is O.F.H.C. Copper? |
In practice electrical wires and cable terminals are made out of electrolytic tough pitch copper (ETP grade copper). This grade of copper contains 150 ppm to 400 ppm oxygen through out the metal. In addition to that wire bars of ETP grade also have 8 to 10 mm thick set layer containing copper oxide particles.
Oxygen free high conductivity copper contains less than 30 ppm oxygen in the metal and is completely free from copper oxide particles. Lower oxygen content in oxygen free high conductivity copper has many advantages over ETP grade of copper. |
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| How to check the cable size? |
Measure diameter of one strand = d
Radius of one strand = r (d/2)
No. of strands = n
Cross section of cable = n x 22/7 x r².
Say for 240 Sq.mm. cable
d = 2.9 mm
r (d/2) = 1.45 mm
n = 37
Cross section = (37 x 22 x 1.45 x 1.45)/7 i.e. 244.49 (Say 240 Sq.mm.) |
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| How can we know that the crimped joint is proper or not? |
It can be ascertained by:
Pull Off Load Test - Crimped joint should withstand the pull off load of 4Kg./Sq.mm. Say for 240 Sq.mm. cable, it should withstand 240 X 4 = 960 Kg.
Joint Resistance - As per IS 8337 the resistance of crimped joint on aluminium wire should not be more than the resistance across the length of the conductor equal to the length of barrel of the terminal. |
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| What is bi metallic corrosion? |
Corrosion takes place when i) two different metals are connected together ii) electrical current passes through the joint iii) Moisture is present. |
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| How the corrosion can be reduced or prevented? |
It can be prevented or reduced by applying special corrosion inhibiting compounds between the surfaces of different material being used in electrical circuit. |
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| How Corrosion Inhibiting Compound should be used? |
Compound should be freely applied over the stripped portion of wire and also on the inside surface of barrel. Excess compound will seal the barrel mouth after crimping and in turn prevent the ingress of moisture or other contaminated substances present in the surrounding atmosphere.
Compound is recommended to be used when aluminium is used with aluminium also. |
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| Cable tail can not go easily into the barrel? |
Barrel inner diameter is designed just to receive the conductor. Where sector (triangular) shape of cable tail is used, it becomes difficult to insert the stripped conductor into the barrel. It is recommended to use special forming dies to form sector shape conductor into round shape before crimping.
Never try to insert the wire into the barrel by hammering. This will damage the terminal and or wire. |
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| Flexible wire does not go into the barrel of the same size of terminal? |
Outer diameter of flexible wire is maximum compared to the other (stranded or solid} shape. Our terminals are designed to easily receive stranded wires. It becomes difficult to insert the flexible wire into the barrel. Best practice is to form the wire with forming dies or use one higher size of terminal and crimp with “D” type of dies.
Use of terminals having easy entry barrels will also provide ease of insertion. |
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| What is serrations? |
Serration is roughening of inside wall of the barrel, which looks as if the inside wall is threaded. It should be uniform and should not hurt if the finger is pushed inside the barrel. |
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| Why serrations are provided? |
| Serration help in cutting oxide film formed over the conductor. (In case of aluminium the oxide film is formed at normal temperature or humidity). Serrations also help in providing better grip of the joint. However, we have taken the pull off test over the same size of crimped terminal, with and without serrations. Though the terminals without serrations withstand lesser pull off load, it is will within the limits of 4Kg./Sq.mm. |
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| In some of the terminals palm length is shorter than other brands? |
| It has been observed that when the terminal is bolted on the equipment, the maximum effective contact surface will be equal to the outer diameter of the washer of the bolt. If the palm length is more than the outer diameter of the washer, it does not provide extra contact surface. In some cases the longer lengths of the palm are obstructing the bolting of the terminal on equipment.
However, care has been taken while designing that the barrel length is maintained and most of the cases the total length is also maintained. |
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| Which terminals are recommended for XLPE cables which have higher current rating compared to other type of insulation? |
| The metal content of XLPE cable or the other cable is same because the cross section is same. Current carrying capacity of XLPE cable is higher only because the insulation withstands higher temperature rise. It is recommended to use long barrel terminals so as to accommodate maximum number of crimps on the barrel, which will help to withstand higher short circuit currents also. |
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| What should be the stripping length of conductor? |
| It should be slightly more than the barrel length, which will give the rough idea whether the conductor has been fully inserted or not. However, wherever possible, it is recommended to use the terminals having inspection vent, which will show if the conductor is fully inserted or not. |
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| Terminals having bigger stud hole (say 16-mm) can be used with smaller bolt (say 12-mm)? |
NO. When the smaller bolt is used with the terminal having higher stud hole, the bolt washer starts forming dish shape while tightening and does not exert proper pressure on the palm. This results in improper contact.
The rule of big hole for big as well as small cat does not apply here. |
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| What is the importance of spring washer in any bolted connections? |
| When the current flows through any conductive metal, heat is generated. The conducting metal expands when the heat is generated and contracts when the current stops flowing. Spring washer helps in maintaining proper pressure on bolted joints during expansion and contraction. |
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