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| Re: Fourth Rails and Safety (832243) | |||
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Re: Fourth Rails and Safety |
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Posted by SelkirkTMO on Fri Sep 11 21:48:50 2009, in response to Re: Fourth Rails and Safety, posted by Jackson park B Train on Fri Sep 11 21:33:01 2009. They're actually talking about galvanic protection, normally done with a sacrificial anode made of zinc or other metals which are sacrificed instead of the steel and piping. The "grounding and bonding" requirements are to ensure that no stray currents flow from pipes to ground or other metallic surfaces by tying them all together to ground so as to eliminate any potential stray current.AC power isn't so much of a problem at all since the polarity reverses 60 times a second. The real problem for galvanic corrosion is the result of DC flow only such as in electric railway systems and of course, subways. |
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