Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
(OP)
Currently the Crude Oil Storage Tanks at our facility have roof hatches that allow for inspection of the internal floating roofs. The hatch lid is made of Carbon Steel (not sure which type), however, it is very heavy for operators to lift regularly when inspecting the internal floating roof. We are interested in replacing the steel lid with possibly an aluminum lid. Due to the fact that this would be a corrosive atmosphere, would there be an excessive amount of galvanic corrosion between the aluminum lid and the carbon steel tank itself?





RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
I believe that you are going the wrong way, contemplating the material change in an area of personnel safety. Is nothing wrong with the relatively heavy manway lid, it is only lacking the good old davit to help swing the lid. Have you tried that?
cheers,
gr2vessels
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
I am going to ask the obvious, why don't you simply reduce the thickness of the hatches by making several new ones used for only inspection purposes (label them as such) to reduce weight and allow for easier entry? I would go the route of least resistance and use a thinner hatch plate, made of steel.
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
I'm obviously wondering IOT determine if it can be made thinner and lighter, and/or to propose an alternative material or design.
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
cheers,
gr2vessels
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
It appears that you have limited understanding of the galvanic corrosion;- both of the "non-compatible" materials have to be submerged in an electrolyte, not simply wetted by some condensate, in order to produce material loss due to galvanic corrosion. Even so, you can isolate electrically the hatch cover and the manway flange by using special isolator sleeves on the bolts. The corrosive atmosphere is not sufficient to produce galvanic corrosion.
However, your concern with the weight of the steel manway cover is still valid.
gr2vessels
RE: Galvanic Corrosion potential on roof hatch of Crude Oil Tank...
I don't think that you would have a problem with Al vs CS in you case. I like the idea of lightening the CS but if you go with AL make sure it is capable of supporting several people.
h
PS:
I like inspecting the large tank as there is a 8'x8'x6'deep sump that people fall into, Panic, even though you tell them it is there before you enter the tank.