Monday, July 1, 2013

Harsh Environment Category 5e

Harsh Environment Category 5e.
First of all, what defines harsh environment?  Harsh environments for cabling typically have excessive levels of petrochemicals, acids, bases, direct impacts, torsional stress, tensile load, electro magnetic interference (EMI) or radio frequency interference (RFI).  Once these environmental stresses become higher than what a commercial grade category rated data cable can handle, application specific jackets, shielding, or special construction tactics must be used for ensure the life of the cable assembly.

11.)    Jacketing Material
All jackets have pros and cons.  The 3 primary choices are poly vinyl choloride or PVC (for commercial riser installations), polyvinylidene fluoride PVDF (for commercial plenum installations, thermoplastic elastomer TPE (more robust applications), and polyurethane PUR (normally the best choice for harsh environments).  Here is a simply breakdown of how commercial, TPE, and PUR jackets relate.

22.)    Shielding
Shielding comes in a few traditional flavors.  The first is overall foil shielding.  As the name implies it in a solid aluminum mylar wrap, typically grounded to an uninsulated ground wire that runs longitudinally thru the length of the wire and is ground to the foil throughout.  This wire is typically referred to as a drain wire.  Foil shielding is the best for stopping EMI ingress.  The second is overall braid shielding.  This type of shielding is a woven barrier of small gauge strands of metal that cover a percentage of the overall diameter of the wire.  Typical percentages range from 50% to 95%.  Because the braid shield has so much surface area, the need for a large ground conductor is required.  All of the braid should make contact with the point of ground on terminated ends, whether it be a shielded RJ45 plug/jack, or the braid could be twisted into a conductor and grounded to a telecommunications grounding busbar.  The third option is to combine the two options for maximum effectiveness.   Here is a simple drawing showing the different types of shielding.

33.)    Connectors come in a wide variety of configurations.  Both metal and plastic.  Coupling mechanisms that are threaded, bayonet latching, or push-pull.  Each can be custom configured to the application.  Here are a few examples.

M12 and M8 connectors can also used in industrial environments but are less popular than the more traditional RJ45 connectors (as seen above).

44.)    What should one consider when selecting the correct harsh environment category 5e solution?
1.)     Shielded or Unshielded?  EMI foil vs RF braid.
2.)     Solid or Stranded?  Flex cycling vs permanent install vs distance limitations
3.)     Installation Stress?  Pull force vs minimum bend radii
4.)     Oil Resistance?
5.)     UV Sunlight Resistance?
6.)     Weld Splatter Resistance?
7.)     CMX Outdoor UL Rating?  Drop cable vs permanent install
8.)     Burial?
9.)     Gasoline Reistance?
10.)   Low Smoke Zero Halogen?
11.)   MSHA?
12.)   Excessive Temperature Extremes?
13.)   600v UL AWM Rated?
14.)   PLTC (power limited tray cable) Rated?
15.)   Interlocking Armor?

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