Industrial Cable & Connector Technology News: September 2012

Thursday, September 13, 2012

Crimping Technology for Industrial Connectors 101

How do you achieve the best-possible crimping in accordance with the industry safety standards?

The quality of an electrical connection depends to a great extent on the choice of suitable components in the respective nominal section widths and using recommended tools for processing.
Size differences between the cable and the connector (pipe-type cable lug/multicore cable end) are the result when only one crimp contact lead in class 5 und 6 - even with different structure (bunched conductor, stranded or compressed strand) could be compressed. Despite what appear visually to the sleeves, the correct combination of conductor, contact and tool can provide "gas-tight" crimping. The dimensional stability on the above-mentioned connecting points is guaranteed by, among other things, the following standards:

• DIN EN 60228 (VDE 0295), September 2005 "Conductors for cables and insulated lines"
The content of the standard includes among other things the maximum wire diameter and the maximum conductor resistance for the respective nominal cross sections (mm²), but not however, the number of wires or the structure. Improved technologies in the area of copper production mean that the conductor resistance specified in the standard can now be achieved with reduced cross sections.

• DIN 46228 – 4, September 1990 "Multicore cable ends – tube-type with plastic sleeve"

• Quality of crimping as per DIN 46228 – 1 and DIN EN 50027

Should connectors be crimped or soldered together?

The crimp connection is the best type of connection for all loaded applications. The advantage compared against all other connection contact cables is - 100% process-consistent fabrication and quality control in accordance with safety standards. Full compliance to safety standards will guarantee tensile strength, current load and forward resistance.

Solder connection on the other hand whether "soldered by hand" or automatically soldered" can affect the overall quality of the soldering points based on:

- the experience of the person doing the soldering
- temperature changes and movement, as the soldering point can deteriorate as time passes (problems that occur with the electronics/electrical system are often down to "dry solder joints" - in other words, poor contact)

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Wednesday, September 5, 2012

Industrial Wire & Cable Flammability Test Methods

Testing is a very critical aspect of Wire & Cable manufacturing. They are a very wide array of safety standards to comply with which can be very confusing. For example, flame resistance and fire propagation tests are often confused with one another on the basis of their very similar designations. However, the test methods employed are quite different:

IEC 60332-1-2: Test for vertical flame propagation for a single insulated wire or cable

This flame resistance test is passed by most cables constructed of flame-retardant materials, e.g. PVC and chloroprene rubber, or materials with special flame-retardant additives such as PUR. In the test, a single core or cable with a length of approx. 60 cm is mounted vertically using two clamps, after which a pre-defined flame is applied to the bottom end for a period of 60 seconds (or 120 seconds in the case of cable diameters > 25 mm). The test is deemed passed if, after the flame has been removed, the burning cable extinguishes itself and the fire damage is at least 50 mm from the upper mounting clamp. It is irrelevant how long the cable burns before extinguishing itself.

IEC 60332-3: Test for vertical flame spread of vertically-mounted bunched wires or cables

This fire propagation test is also known as the "bundle fire test" and is generally only passed by specially developed cables and wires with highly flame-retardant insulation and sheath material. In most cases, the flame resistance of the plastics used is greatly enhanced by the addition of aluminium or magnesium hydroxide. Multiple cables are bundled or layered in lengths of approx. 3.5 m and vertically affixed to a ladder-like metal structure, after which a flame is applied to the lower end of the cables using a propane burner. The cable volume and time of flame application is defined by the test method, since IEC 60332-3 comprises four different bundle fire tests:

• IEC 60332-3-22 Category A:    7 liters of combustible material per meter / flame application: 40 minutes
• IEC 60332-3-23 Category B: 3.5 liters of combustible material per meter / flame application: 40 minutes
• IEC 60332-3-24 Category C:   1.5 liters of combustible material per meter / flame application: 20 minutes / cable diameter > 12.0 mm
• IEC 60332-3-25 Category D:   0.5 liters of combustible material per meter / flame application: 20 minutes / cable diameter< 12.0 mm

IEC 60332-2-22 Category A is often used for maritime applications on oil rigs and ships, for example. The test is deemed passed if, after the burner has been switched off, the burning cables extinguish themselves and the fire damage does not cover more than 2.5 m measured from the bottom cable end. It is impossible to say which of the four test categories poses the most difficult challenge, since there are a range of different factors to consider.

IEC 60331: Functional integrity and fire resistance of electric cables

Unlike IEC 60332-1-2 and IEC 60332-3, this test does not assess the flame propagation but instead checks the electrical functioning of the cable in the event of a fire. In the test, a flame is applied across the entire horizontal length of a single, 120 cm cable for a period of 90 minutes. The test is deemed passed, if the cable continues to conduct electricity without shorting throughout the 90 minute flame application and for a subsequent 15 minute cooling period. This test is generally only passed by cables and wires with special, flame-retardant glass or mica wrapping enclosing the individual cores as well as the entire cable bundle.