Choosing clean cabling for cleanrooms

| Cleanrooms and Contamination Control

Specifying the right cabling for the cleanroom environment
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Jonathan Newell talks to Aerco about its range of specialist cabling designed to be used in FED STD 209E Class 1 cleanrooms.

UK based Aerco is stocking the Xtra-Guard cable range from Alpha Wire, which includes the top-of-the-range Xtra-Guard 5 cabling that’s designed to be used in a wide variety of highly-demanding applications, including Class 1 cleanroom environments, medical grade applications when sterilised and chemical processing as well as food and beverage wash-down applications.

I spoke to David Cairns of Aerco to understand what makes this cable suitable for use in cleanrooms and discovered that it’s all about the jacketing.

Instead of using the usual PVC, Polyurethane or Polyethylene coating, Xtra-Guard 5 uses Fluorinated Ethylene Propylene (FEP), a Dupont material similar to Teflon but which is able to be extruded into forms such as cable jackets.

The benefit of this material is that it’s chemically inert. According to Cairns, it is important for materials which are used for cleanroom cables to have a number of vital properties. “They must be resistant to harsh cleaning agents, as every now and again the cleanroom itself has to be cleaned.  PVC is not suitable as it will break down and small particles may flake off and contaminate the cleanroom,” he explained.

Similarly, Xtra-Guard 5 cabling contains no materials that can migrate anywhere else, there is no shedding or outgassing. Also, Alpha-Wire Xtra-Guard 5 doesn’t absorb contaminants in the way that PVC does. PVC is hydroscopic and will absorb water and other particles.

Wide applicability  

I asked Cairns if the Xtra-Guard 5 is a Cat 5 data cable or whether there are other applications that it can be used for. He told me it’s available in 16-24 gauge multi-core or 18-24 gauge multi-pair depending on the application. It’s also available unshielded or with 1.5mm Aluminium / Polyester shielding for EMC protection. There’s also the option to have increased EMI shielding with the Alpha Supra-Shield system, which uses a combination of aluminium foil, polyester and copper braid to provide high levels of shielding both from interference and emissions.

According to Cairns, there is also an advantage in terms of cable size which results from the use of FEP. Due to its excellent dielectric strength, the material enables the cables to be made typically 20-30% smaller than the equivalent conventional cable.

Changing environments

With the greener cleanroom environment that now exists with the banning of fluorocarbon cleaning agents, I asked Cairns whether or not the absence of such aggressive chemicals provided a continued need for cabling that is chemically inert. “It’s important in such environments to have materials that aren’t going to chemically change when cleaned using whatever cleaning agent. For example, PVC can be affected even by soap and water.”

He went on to say that there are other environmental factors that are often encountered in cleanrooms which can have a bad effect on polymers. The example he used was UV light, which doesn’t affect FEP.

Cleanroom cables available with different levels of EMI shieldingColour

The cores of the Xtra-Guard 5 cable are coloured but have no exposure to the outside world and the colouring eases the task of wiring. The outer jacket is uncoloured and although colours are available, Cairns recommends the use of cable tags to identify cables rather than risking outgassing of the pigment in harsh environments.

Cost

There is a premium to pay for the Xtra-Guard 5 cable when compared to other cables in the same range, something which Cairns says can be avoided in some less stringent applications by knowing what the cable is for and what environment it will be placed in.

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