JANUARY 31 2003
isolated from ferrous pipe, or covered with a protective coating.
Metallic Ferrous Pipe. A metallic ferrous pipe passing through concrete
must not be in contact with the concrete. Provide a sleeve with waterproof dielectric
insulation between the pipe and the sleeve. Ferrous metal piping passing through a
concrete thrust block must be insulated from the concrete or cathodically protected.
Lightning and Fault Current.
The need for lightning and fault current
protection at isolating devices (dielectrically insulated flanges) should be considered.
Where a combustible atmosphere may be encountered, a sealed, weatherproof
lightning arrester must be installed across each isolating device. The arrester should be
the gapless, self-healing, solid-state type (metal oxide varistor). Cable connections
from arresters to isolating devices should be short, direct, and of a size suitable for
short-term, high-current loading.
SYSTEMS REQUIRING CATHODIC PROTECTION. Ensure both CP and
protective coatings are provided for the following buried/submerged metallic structures,
regardless of soil or water corrosivity:
Natural gas piping.
Liquid fuel piping.
Underground storage tank (UST) systems.
Fire protection piping.
Ductile iron pressurized piping under floor (slab on grade).
Underground heat distribution and chill water piping in metallic conduit.
Facilities with hazardous products as identified by the major commands,
major claimants, or other competent authorities.
Results of an economic analysis and recommendations by a qualified
corrosion engineer must govern the application of CP and protective coatings on gravity
sewer lines, regardless of soil resistivity, and the following facilities in soil resistivities
above 10,000 ohm-centimeters:
Potable water lines.
Other buried/submerged metallic facilities not covered above.