Yamatake Corporation Safety
ST3000 Smart Transmitter Series 900 Electronic Differential Pressure/Pressure Transmitter 15
6. If the associated apparatus is a type of shunt diode barriers, supplementary
bonding to the grounding electrode is needed. And the grounding path resistance
from the farthest barrier to the grounding electrode shall not exceed 1W.
In practice, the bonding to the grounding electrode is achieved by connecting the
grounding terminals of the barriers to the intrinsically safe ground bus which is
connected to the grounding electrode with an insulated conductor not smaller than
No.12 AWG (2.05 mm in dia.).
7. In hazardous locations, non-current-carrying metal parts of the apparatus,
raceways, and other enclosures of the intrinsically safe system shall be bonded to
ensure the electrical continuity.
8. In non-hazardous locations, where metal raceways are used for the intrinsi-
cally safe system wiring in hazardous locations, all intervening raceways, fit-
tings, boxes, enclosures, etc. between the hazardous locations and the point of
grounding for the power supply system or point of grounding of a separately
derived system, shall be grounded by using bonding jumpers with proper fittings
or other approved means of bonding.
9. Where conduits and cables are used to protect the intrinsically safe wiring against
environments, the conduits and cables must be sealed so that they do not transmit
gases, vapors, or dust from a hazardous location to a non-hazardous location. Seal-
ing fittings should be installed in each conduit run leaving the hazardous location,
on either side of the boundary within 10 ft (3.05 m) of the boundary. Such seals
need not be explosionproof.
10.
The grounding electrode
usually available on premises is specified in a), b), c) or d):
a) Metal underground water pipe in direct contact with the earth for 10 ft (3.05
m) or more.
b) Metal frame of the building, where effectively grounded.
c) Concrete-encased electrode. An electrode encased by at least 2 inches (50.8
mm) of concrete, located within and near the bottom of a concrete foundation
or footing that is in direct contact with the earth, consisting of at least 20 ft (6.1
m) of one or more bare or zinc galvanized or other electrically conductive
coated steel reinforcing bars or rods not less than 1/2 inch (12.7 mm) diameter,
or consisting of at least 20 ft (6.1 m) of bare copper conductor not smaller than
No.2 AWG (6.54 mm in dia.).
d) Ground ring. A ground ring encircling the building or structure, in direct con-
tact with the earth at a depth below earth surface not less than 2 1/2 ft (762
mm), consisting of at least 20 ft (6.1 m) of bare copper conductor not smaller
than No.2 AWG.
Where none of the above electrodes is available, made electrodes should be used:
To Next Page
Loading...
