Using isolation kits with Cathodic Protection

[Gorpomon]

Hi,

I have some quick questions about using isolation kits with Cathodic Protection. My web and forum searches didn't turn up what I needed so hopefully you all can help me.

1. Can someone link me to an article or briefly explain when to use a single and double washer set?

2. The sleeve just fits into flange hole, correct? it doesn't extend past that (I'm guessing so, otherwise how could you tighten the nuts) but I just want to make sure I'm not missing something.

3. Concerning an isolation kits use with cathodic protection. Since the current flows from the anode to the pipe in question though the electrolyte, what's to stop the CP current from hitting the pipe on both sides of the isolation kit? Am I correct in assuming its the electrical connection from the pipe to the DC source that completes the circuit and results in CP for the protected pipe? For a section of pipe that's not electrically connected wouldn't the CP current be considered stray current and thus cause corrosion?

 

[rustbuster]

Hello,

You are seach with incorrect wording. Google "cathodic protection insulation kit", you will find what you need.

2 You are correct

3 If you have good insulation the pipe is not part of the circuit and should recieve very little current.

Good Luck

 

[SJones]

3. You are correct in that it is the negative cable (drain line) that completes the electrical circuit and the connection should be on the protected side of the insulation joint. Stray current corrosion is caused by a foreign structure, i.e. not intended to be part of the protection circuit, picking up the CP current and then discharging it back to the protected circuit. The point of discharge is an anode and suffers rapid corrosion. The isolation joint should not be located where the external electrolyte contacts both sides otherwise you won't get isolation! It should be above ground or in a concrete pit, for example. That's dealt with the outside, now the inside. If you have a conducting electrolyte INSIDE the pipe and both sides of the isolation joint pick up CP current, say through pipe supports, current will try to return through the INSIDE electrolyte back to the circuit by 'jumping' the joint creating a nice hole in the adjacent pipe. In these cases, an insulating flange or a monolithic isolating joint is nigh on useless and an insulating spool piece has to be used of a sufficient length to create enough resistance to prevent current 'jumping'.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[grampi1]

Should check out

http://www.pikotek.com.

They make the only electrical isolation flange kits my company will use.

 

[SJones]

I'd go with that recommendation too.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04