Rockwell Automation 1797-XXX FLEX Ex System Certification Reference Manual - Manual (Page 5)

1 Publication 1797-6.5.6 - June 2005
Preface
What Is Intrinsically Safe? According to Article 504 of the National Electrical Code, NFPA 70, an
intrinsically safe (I/S) product is defined as one in which no spark or thermal
effect generated during normal functioning and/or during specific fault
conditions is able to ignite a given explosive atmosphere.
One example of an I/S product is FLEX Ex distributed I/O control.
What are Product
Certifications? A product certification is a guarantee that the product has been designed and
manufactured with the required I/S specifications and protection. Considering
the potential danger in hazardous locations, product certification is required
for all I/S products.
Three Types of Product Certifications
In this reference manual, we describe three types of product certifications and
how they relate to FLEX Ex products:
• CENELEC - European Electrotechnical Committee for
Standardization. This is the standard in all European Union
countries.
• UL and C-UL - Underwriters Laboratories (UL in the United States
and C-UL in Canada)
• FM - Factory Mutual, another available certifying body in the United
States
FLEX Ex products are certified to the appropriate CENELEC, UL, C-UL and
FM standards, depending on the module.
What are Entity
Parameters?
Entity parameters provide a system of quantifying and matching safe levels for
voltage, current, inductance, and capacitance when connecting field devices
and system devices together.
FLEX Ex uses entity parameters to quantify safe levels when connecting I/O
modules to field devices. Inputs and outputs are specified with:
• open-circuit voltage (U
o
or V
oc
)
• short-circuit current (I
o
or I
sc
)
• allowed capacitance (C
o
or C
a
)
• allowed inductance (L
o
or L
a
)
Switched outputs are specified as if they were inputs.
Field devices using entity parameters are specified with:
• maximum input voltage (U
i
or V
max
)