ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
What does your work place look like?
by HotLine1 - 11/23/20 03:35 PM
Where is Everyone?
by Lostazhell - 11/21/20 04:17 AM
Ground fault remover :-)
by dsk - 11/21/20 02:47 AM
Work Gloves?
by gfretwell - 11/20/20 10:17 PM
Reverse-feeding transformer in PV system?
by winnie - 11/19/20 06:49 AM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 17 guests, and 14 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Electric Current in Gas Pipes? #38781 06/01/04 11:28 PM
Joined: Aug 2002
Posts: 1,081
T
ThinkGood Offline OP
Member
From an insert included with the latest gas/electric bill:

Quote

Keep Metal Objects Away From Your Gas Meter

It is important to keep metal away from your gas meter. PSE&G uses metal pipes that are protected from corrosion by a small electrical current running through them. This makes the pipes stronger and more efficient. If attached to these pipes, metal objects (such as a dog's leash or an antenna) strip the corrosion protection and cause problems with the electricity running through the pipes. When pipes become damaged, they may not work as well, and we may need to fix them.

Work Gear for Electricians and the Trades
Re: Electric Current in Gas Pipes? #38782 06/01/04 11:51 PM
Joined: Feb 2003
Posts: 939
F
frenchelectrican Offline
Member
Thinkgood:

i dont know what to say but that is very odd but i did heard some kind of protection by injecting small DC not AC current with very low votage too.

myself i did see one on major petroleum pipeline it have small power device to inject the dc power to prevent corrosion on pipe line.

i know this is kinda of odd item to see it but if anyone else know about this please do pitch in here.

merci, marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Re: Electric Current in Gas Pipes? #38783 06/02/04 12:25 AM
Joined: Jun 2001
Posts: 642
N
nesparky Offline
Member
This is called cathodic protection. It is a way of preventing corrosion on metals. It is a specilized circuit that some where has a sacrifical metal that is supposed to corrod (rust away) before the metal bieng protected.
It's an intersting subject, but expensive to install and requires regular testing.


ed
Re: Electric Current in Gas Pipes? #38784 06/02/04 01:28 AM
Joined: Feb 2004
Posts: 1,434
Lostazhell Offline
Member
Ahhh... This reminds me of something... A few AHJ's out here want gas to be bonded back to the panel, along with the normal things... I have (had... I gotta look for it again,) a formal letter from So Cal Gas Co. stating they DO NOT want their system bonded to the electrical grounding system... I get fun looks when I pull this out during inspections! [Linked Image] A couple places want it anyways... Could this have something to do with that?? I always thought it was better if a hot wire hit a gas line that it didn't spark! [Linked Image]

-Randy

Re: Electric Current in Gas Pipes? #38785 06/02/04 05:09 AM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Randy while the NEC does not allow gas lines as a grounding electrode the NEC requires the gas piping in the house to be bonded. Around here gas lines are threaded or welded black iron pipe.

So in the structure the gas lines are bonded.

I imagine they install a dielectric coupling at the meter in order to provide the cathodic protection.

Quote
250.104(B) Other Metal Piping. Where installed in or attached to a building or structure, metal piping system(s), including gas piping, that may become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as the bonding means. The points of attachment of the bonding jumper(s) shall be accessible.

Unless you are installing dielectric fittings on the gas line at the hot water heater the gas line ends up bonded anyway. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: Electric Current in Gas Pipes? #38786 06/02/04 05:59 AM
Joined: Sep 2003
Posts: 650
W
winnie Offline
Member
This goes to different authorities with different (and conflicting) requirements. Metal piping systems in the house should be bonded, both IMHO and by NEC. But plumbers hate underground water pipe as the grounding electrode, the NEC prohibits the use of underground gas pipe as a grounding electrode, and clearly the gas company doesn't like it either.

IMHO the 'best' way to balance all of this is to have dielectric couplings in any underground metal piping systems where they enter structures, to bond this piping internally, but to explicitly not use this piping as a grounding electrode. This would help eliminate the problems of neutral currents flowing on metal piping, something that happens in urban areas where houses that use the same water pipes all bond them to neutral in their main panels; net result is multiple bonds between neutral and a continuous metallic system, and thus significant parallel paths.

This would require a change in the NEC, since an underground water pipe of sufficient length is _required_ to be used as a grounding electrode.

-Jon

Re: Electric Current in Gas Pipes? #38787 06/02/04 06:17 AM
Joined: Aug 2002
Posts: 1,081
T
ThinkGood Offline OP
Member
OK, a dielectric at the meter makes sense. However, the pipe that enters the meter is coming from under the ground.

How do they keep the electric current on the pipe if it's in contact with the ground? I know for certain that under the street the pipe is in direct contact with the earth, based on some emergency digging once done around here.

Maybe this should be moved to theory...can somebody explain the cathodic protection in terms of how the current doesn't just go to ground?

Thanks.

Re: Electric Current in Gas Pipes? #38788 06/02/04 07:35 AM
Joined: Sep 2002
Posts: 1,497
C
C-H Offline
Member
Isn't the whole point that the current goes to ground? (Low voltage = not much current)

I like Winnies idea!

Re: Electric Current in Gas Pipes? #38789 06/02/04 11:17 AM
Joined: Oct 2003
Posts: 152
M
Mean Gene Offline
Member
A very interesting topic. In my area, everyone gets flexible plastic pipe, yellow in color, with a stranded yellow tracer wire of about 8 gauge from the main to the building. The wire isn't connected to anything. It's just there to aid in locating the pipe underground.

Re: Electric Current in Gas Pipes? #38790 06/02/04 03:15 PM
Joined: Dec 2003
Posts: 886
H
hbiss Offline
Member
Around here all new and recent gas services are poly pipe. AND I have noticed rectifiers in cabinets mounted on poles apparently for cathodic protection but this seems to be for the larger distribution lines. Don't know if it would still energize the smaller mains.

-Hal

Page 1 of 2 1 2

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
JoeKP
JoeKP
Berkley, MA
Posts: 144
Joined: March 2008
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 9
Popular Topics(Views)
271,887 Are you busy
205,750 Re: Forum
193,861 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3