E.F. Johnson Company 5100 Series, Service Manual

Page: 12 / 173

GENERAL INFORMATION
1-7
cient electrical and thermal energy under normal oper-
ation or specified fault conditions per the testing
standard to cause ignition of a specific flammable or
combustible atmosphere in its most easily ignited con-
centration. In other words, this transceiver should not
cause a fire or explosion when used in certain flamma-
ble atmospheres.
Fault - A defect or electrical breakdown of any compo-
nent, spacing, or insulation which alone or in combina-
tion with other faults may adversely affect the electrical
or thermal characteristics of the intrinsically safe circuit
(for example, a shorted transistor).
1.11.3 POSSIBLE IGNITION SOURCES
When a transceiver is evaluated by Factory
Mutual, possible sources of ignition are checked.
These sources may be electrical (spark) or thermal
(heat). The following could be sources of spark
ignition:
•
Discharge of a capacitive circuit by a fault such as a
short circuit.
•
Interruption of an inductive circuit.
•
Intermittent making or breaking of a resistive
circuit.
•
Hot-wire fusing.
The following could be sources of thermal
ignition:
•
Heating of a small-gauge wire or PC board trace.
•
High surface temperature of components.
1.11.4 INTRINSICALLY SAFE AND
NONINCENDIVE RATINGS
This transceiver is rated intrinsically safe for
some types of hazards and nonincendive for other
types of hazards. An intrinsically safe rating applies to
operation in Division 1 areas, and a nonincendive
rating applies to operation in Division 2 areas (see
next section). The difference between these ratings is
as follows:
The intrinsically safe rating is a higher rating
because more severe conditions must be met. To be
approved for this rating, the transceiver must not cause
ignition of a particular atmosphere if two of the faults
specified in the testing procedure occur. In other
words, it must be able to withstand two simultaneous
unrelated breakdowns without causing ignition. To
receive a nonincendive rating, the transceiver needs to
withstand only a single fault without causing ignition
of a particular atmosphere.
1.11.5 CLASSIFICATION OF HAZARDOUS
AREAS AND ATMOSPHERES
Introduction
This transceiver has been submitted for approval
to operate in the following hazardous atmospheres and
areas. Contact your sales representative or refer to the
label on the back of the transceiver to determine the
specific atmospheres and areas for which approval was
obtained.
Intrinsically Safe - Class I, II, and III, Division 1,
Groups C, D, E, F, and G. NOTE: Models with the UCM
module (P.N. 242-51xx-xxx-xx 3 ) are not approved for
Group C operation (see Section 1.12).
Nonincendive - Class I, Division 2, Groups A, B, C,
and D.
Temperature Code - T3C
The meanings of these Class, Division, and
Group designations are as follows.
Classification of Hazardous Areas (Division)
Hazardous areas are classified as Division 1 or 2
as shown in Table 1-2. Since a Division 1 area is con-
sidered most hazardous, a transceiver approved for a
specific Division 1 atmosphere can also be used in the
same Division 2 atmosphere. The intrinsically safe rat-
ing applies to Division 1 areas and the nonincendive
rating applies to Division 2 areas.
Atmosphere Classification (Class/Group)
For the purposes of testing and approval, various
atmospheric mixtures have been grouped on the basis
of their hazardous characteristics. Equipment is
approved for a class of material and also for the spe-
cific group of gas, vapor, or dust in that class. Class I
materials include gases and vapors, Class II materials