Am currently working on a Gas plant, and the use of intrinsically safe cables are required. i want to know if there are any special characteristics and conditions that most be considered during the manufacturing of the intrinsically safe cables.

thanks.
Dyke.

 

Dyke,

Intrinsically safe cables are no different to other cables. It is common practice to use cables with a different coloured outer sheath (normally light blue) to Identify intrinsically safe circuits. (Check your local standards for requirements). The inductance and capacitance of the cable run must be taken into account when doing the calculations for your intrinsically safe circuits.

Regards.
Phil.

 

Phil,

Thanks for your reply.

Capacitance and Inductance would affect the impedance of the line and this is why those are important to take account. could you advise me a standard to state this issue?

Regards,
Vahid

 

Dyke... although the use of conventional cable is permitted in the USA, such is certainly not the case in countries following IEC Standards.

It is true that conductor materials and insulation of conventional and IS cables are virtually the same! However experience gained the hard way (explosions involving ordinary materials) led to subtle differences. For example, zinc and some plating materials can contribute energy to a spark. Also, galvanized iron is now considered unsafe. Still another is the use of copper, unless suitably protected, in an Acetylene atmosphere.

In conclusion, I strongly urge you to follow the mandated requirements for IS-certified cable in the Country or Locale in which the installation is located!

Regards, Phil Corso

 

See the European standard NF M 87-202 the characteristics given are Impedance less than 21.4 ohm/km and capacitance less than 160pF/meter.

 

what calculations are required in intrinsically safe circuits? Can you please explain.

suvo

 

May I know that it is a international standard to a local? Is it possible to give its complete title?

Regards,
Vahid