Abstract
Utilizing existing shipboard waterproof transition fittings (kickpipes) and existing ground adapters (GA) to protect cables routed between topside and below-deck or inter-compartmental spaces have created performance degradation of over 120 dB. These electromagnetic interference and electromagnetic pulse (EMI/EMP) protection devices are called ground adapters since they attempt to protect below-deck systems from various high level electromagnetic (EM) threats by shunting high level currents into the ground plane.
Specifically these shield and conduit ground adapters (SGA’s/CGA’s) are devices designed to establish a 360°, low impedance, wide band, long term electrical connection between either a cable’s shield or a shield conduit, and the ground structure through which the cable or conduit passes. This low impedance connection is designed to reduce and/or eliminate EMI and/or EMP problems by shunting undesired high level electromagnetic (EM) currents into the system's’ ground plane before reaching below deck spaces.
Several years ago two SGA’s were installed on the deck of a U.S. Naval ship for evaluation. A.C. and D.C. performance measurements were conducted on the SGAs prior to the installation, five months after installation and then one year later, after being exposed to 12 months of a harsh marine environment.
This paper will discuss: (1) the shipboard measured d.c. values of ground adapter degradation, (2) the laboratory measured d.c. & a.c. values of ground adapter degradation, (3) the corrosion related factors causing this degradation, (4) near and long term solutions to eliminate this degradation, and (5) the need for corrosion analysis and EM modelling in the development process.
