ERICO Practical Guide to Electrical Grounding - Manual (Page 99)

91 Chapter 6: Special Grounding Situations
AIRPORTS
Airports require special attention to grounding. They not
only handle fuel in close proximity to masses of people, but
the airport is usually on high ground and therefore subject
to lightning strikes. Static grounding is required whenever
an airplane is refueled. This is normally accomplished by
positioning a properly installed static grounding receptacle
in the tarmac near the location where the refueling takes
place. A static ground lead is attached to this receptacle
from both the refueling vehicle and from the aircraft before
the fuel hoses are attached to the aircraft. This equalizes any
potential difference between the two vehicles preventing a
static spark.
Static grounding receptacles are installed flush with the
finished tarmac (Fig. 6-1). The receptacle is welded to
either a ground rod or ground grid or both. Receptacles that
screw onto a threaded (sectional) rod are also available but
the threaded connection may increase in resistance with
time.
Static grounding receptacles have an internally cast ball
(also available with a removable ball) for attaching the
grounding clamp and are supplied with an attached cover.
Static grounding receptacles can be welded directly to a
ground rod. A ground conductor can be welded to the static
grounding receptacle at the same time the receptacle is
welded to a ground rod.
Lightning protection also should be installed on the airport
structures. Lightning protection is discussed in detail in
Chapter 2.
Anchor rods are also available for static grounding and tie
downs. Installation requires augering a hole, inserting the
assembly and backfilling. A large washer or steel plate with
nuts are also required to secure the rod (Fig. 6-2).
A combination static grounding receptacle / tie down is also
available. It may be welded to a rod and/or a conductor
(Fig. 6-3).
CORROSION AND CATHODIC
PROTECTION
Cathodic Protection. There are two general methods of
cathodic protection, the galvanic system and the impressed
current system. The galvanic system uses a sacrificial anode
of a material having a higher potential on the electromotive
series than the material to be protected (Fig. 6-4).
Magnesium, zinc or aluminum are typical sacrificial anode
materials. These anodes are designed to corrode and
“sacrifice” themselves to protect the pipe, tank, etc. The
anodes must be large enough to provide protection for a
reasonable length of time before they are dissipated. Then
they must be replaced for protection to continue.
Cover
Spring Clip, To Ball
Ball, 3/4" Dia.
B165
CADWELD Type
GB/GT Welded
Connection
Ground Rod
Fig. 6-1
A ground conductor can be weld-
ed to the static grounding recep-
tacle at the same time the recep-
tacle is welded to a ground rod.
Static grounding receptacles
can be welded directly to a
ground rod.
Static grounding receptacles have an
internally cast ball (also available
with a removable ball) for attaching
the grounding clamp and are
supplied with an attached cover.
Grounding Book 4/14/99 10/5/99 6:02 PM Page 91 (Black plate)