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A-28
IM 39J06B40-01EN 14th Edition: May 30, 2022
A4.5. Corrosive-gas Environment Compatibility
The DTSXL System employs modules which meet the ANSI/ISA G3 optional
environment requirements and are compatible with the corrosive gas-susceptible
environment.
SEE ALSO
Refer to the general specifications (GS 39J06B40-01EN) of each module to check whether each
module meets the G3 environment requirements.

Outline of G3 Environment Compatibility
The classification of the environment in which the process control equipment is installed
is determined by the ANSI/ISA S71.04 “Environmental Conditions for Process Control
Systems” standard. The environment having an atmosphere which contains steams and
mists (liquids, coded L), dusts (solids, coded S), or corrosive gases (gases, coded G) is
classified into four categories according to the levels of these substances determined.
The four categories of the corrosive gas environment are defined as follows:
- G1 (Mild)
：
A well-controlled environment in which corrosive gas is not the major cause
adversely affecting the reliability of plant equipment. The corrosion level on the
copper test piece is below 0.03 μ m (see note below).
- G2 (Moderate)
：
An environment in which corrosive gas can be detected and it could be determined
that the gas is the major cause adversely affecting the reliability of plant equipment.
The corrosion level on the copper test piece is below 0.1 μ m (see note below).
- G3 (Harsh)
：
An environment in which corrosive gas is frequently generated to cause corrosion
and that it is necessary to provide special measures or employ specially designed
or packaged plant equipment. The corrosion level on the copper test piece is below
0.2 μ m (see note below).
- GX (Severe)
：
An environment that demands special protective chassis for plant equipment,
specifications of which should be determined by a user and the manufacturer
through consultation. The corrosion level on the copper test piece is below 0.3 μ m
(see note below).
TIP
Copper test pieces are used to determine the level of corrosion for the classification of the plant
environment.
The test piece is an oxygen-free copper sheet, which is 15 cm
2
in area, 0.635 mm in thickness, 1/2 to
3/4H in hardness. The test piece is placed in the plant site for one month and checked for any change
before and after the test to determine the degree of corrosion (see table below). If the test period is
shorter than one month, the result is calculated to obtain equivalent data using an expression defined
by the standard.