CASE CR6 - Galvanized Piping System for Hyperbaric Systems, R. Johnston
Problem with Galvanized Piping System.
Internal corrosion in piping system.
Collection of Facts: In the past, some L.P. air systems for hyperbaric
chambers have utilized galvanized piping while performance has been
satisfactory. The use of trisodium phosphate (TSP) as a cleaning agent could
potentially dissolve the zinc and leave the pipe vulnerable to corrosion.
Solution: Avoid galvanized piping on new systems.
On existing systems ensure
that TSP is not used to clean the system.
Case CR7 - Mariner Steel Fender Piling, J. Cecilio
Corrosion of Mariner Steel Fender Piling
Collection of Facts: The 132 H steel piles located at the Trident Wharf are
eighty feet long and conform to the HP 14x102 shape. The material specified
is of the ASTM A690 chemical composition and is commonly known as Mariner
Steel. These pilings were driven into clay bottom approximately twenty feet,
The remaining sixty feet includes forty feet in the immersed zone and the
final twenty feet above water. Tidal fluctuation in the basin causes about
four feet of the pile to be alternately wetted and dried twice daily. The
piles have been in place since the facility was built in 1975.
Portions of the piling subject to tidal fluctuations sustained the most
damage. Close observation revealed that 1arge sheets of corrosion product
were easily removed exposing pitted steel underneath.
Measurements were made to calculate percent reduction in thickness of
flange and corrosion rate of the H piling. The corrosion product was first
chipped off and then scraped to reveal the underlying steel for obtaining
accurate measurements. In addition to the uniform corrosion, many severe pits
were observed with depths estimated at 50 mils (0.050") or more. The pit
depth would be subtracted to determine the resulting thickness at the H piling
HP 14x102 AST, A690.
Flange thickness before corrosion
Flange thickness after corrosion
Decrease in thickness due to pitting
Resulting thickness at area of pit
Percent reduction due to corrosion (at area of pit):
Therefore, in four years of services, 29% of original material has been
lost due to corrosion.