Compressed air lines - should they be grounded?

[WhoWhatNow]

I have my compressor in the basement and 3/4" black pipe running to my attached garage. Do I need to ground the air lines in the same way that the copper water lines are grounded? If so how?

 

[Warrenator]

I cannot imagine it would be necessary to ground them, it is possible that gas flowing through the pipe would cause it to build up a static charge but so what? If you ever get shocked (like a rubbing feet on carpet shock) it would be mild. No harm in grounding them, I suppose, but I would not bother.

 

[zkling]

Not in a standard home shop type setup. The only accessory lines that need to be grounded in a home shop would be for a dust collector.

 

[ddawg16]

I would ground them....only because if a hot wire were to touch them, then you could be creating a safety issue.

Same reason your plumbing is grounded...

 

[larry_g]

No down side in grounding and John gave you the upside.

lg
no neat sig line

 

[papasmirf]

If you value your health then by all means ground the black iron pipe. Go to your local electrical wholesaler or maybe a hardware store. You will be a 3/4" bonding clamp. She only copper wire. Ground with you air compressors ground will be ok or to the compressor motor base.


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[C96]

Your air lines should already be grounded through the compressor ground itself provided there are no rubber hose connections insulating the piping from the compressor. If you have used a rubber type hose or any other insulating material between the compressor tank and the ridged metal piping for vibration issues, then you should connect a bonding jumper of the same size wire used for the equipment ground running to your compressor across the section of rubber hose. This will effectively complete the ground-fault current path should the piping system become accidentally energized.

And yes, this is an NEC requirement. Article 250.4(A)(4)

And in my opinion, this should become a Sticky in the forums since most people use a rubber hose separating the metal piping system for vibration purposes.

 

[WhoWhatNow]

Thanks for the info guys. I do have a rubber hose between the compressor and pipe. I also have a solenoid valve just after the rubber hose but the valve is not grounded to the 110V line anywhere.

I think I will grab a ground strap next time I am at the store.

 

[Majordisorder]

Lightening does serious damage in a dwelling when it hits a piping system and it isn't grounded.

 

[ddawg16]

Lightening does serious damage in a dwelling when it hits a piping system and it isn't grounded.

Forgot about that one.....damned good point.....

 

[sberry]

Any metal that has any possibility of becoming energized should be grounded.

 

[compressornew]

If you want to grounded it then use copper pipe for under basements or machine connections.Connected copper pipes with proper valve fittings.

 

[Clik]

So, ....I should ground my toolbox? My steel rack? My steel vise bench? My Home Depot style metal shelving? My sheet metal brake? There are all sorts of large pieces of steel around my shop. What makes an airline anymore likely to become charged than any other long pieces of steel in my shop?

 

[BigE]

Air lines typically cover large areas and allow the voltage to travel far from where it originated. Your tool box is isolated and doesn't carry voltage outside of the "blast area" that would be affected if lightning struck it or if a hotline hit it.

Also, I believe grounding also affects the potential for corrosion.

 

[sberry]

Yes, your steel rack should be grounded. In the case of a tool box its almost impossible but benches yes. Many of the power sources like a drill are not fixed, bring their own ground or are gfci so using a power tool on an isolated bench isn't that big of a deal.

I went to a shop a while back, the guy is smart and a good machinist and the electric he has works but he doesn't understand grounding and got as shock and couldn't understand why, well,,, it kind of scares me, all that interconnected metal, circuits and not grounded.

It works so he doesn't get the problem? He does good looking wire work too.

Mine looks like spaghetti in a blender but I know the difference between the green or bare and the white wire though.

 

[Mattlt]

MOST hydraulic hoses are conductive. If you are using a hydraulic hose to connect the compressor to the air line, you should be OK. The wire reinforcing in the hose makes contact where the fittings are crimped on each end.

It's pretty easy to test continuity, and it certainly wouldn't hurt to add a separate ground strap.

 

[gungatim]

I grounded my copper airlines, figured it couldn't hurt. Just a saddle clamp and a couple feet of leftover ground wire from when I ran my main lines into the box, just like they did with my plumbing when my house was built. may not be necessary but again, sure can't hurt...

 

[larry4406]

Not air piping, but I build residential houses in MD with black pipe gas lines and black pipe sprinkler (fire suppression) piping. The AHJ requires both to be grounded. That said, I think your air lines would/should need same.

 

[Richard Cranium]

Thanks for the info. I will be putting a black pipe air system in my garage this summer and had never even though about grounding it...Richie

 

[Clik]

I would suppose that gas lines are required to be grounded because of the flammable gas they carry and sprinkler lines often build up hydrogen sulphide which is also flammable. Both could be ignited with static electricity. Why would I need to ground an airline that doesn't carry anything flammable. Yeah, it could be charged by lightning but only after lightning already blew through the walls or roof. I know, I know, it's not a big deal to do but if I go with that logic I'd have to ground every big chunk of metal in my shop.

 

[teamextreme]

I would suppose that gas lines are required to be grounded because of the flammable gas they carry and sprinkler lines often build up hydrogen sulphide which is also flammable. Both could be ignited with static electricity. Why would I need to ground an airline that doesn't carry anything flammable. Yeah, it could be charged by lightning but only after lightning already blew through the walls or roof. I know, I know, it's not a big deal to do but if I go with that logic I'd have to ground every big chunk of metal in my shop.

Large metal systems, such as air lines, plumbing, etc, are required to be grounded by NEC not due to flammability issues, but for electrical shock hazards. If an energized conductor were to touch a metal piping system that is not grounded, it would remain energized and pose a shock hazard to anyone who touched it.

 

[sberry]

if I go with that logic I'd have to ground every big chunk of metal in my shop.

In theory yes, as a practical matter it may be difficult.

 

[Stuart in MN]

This is from the 2008 NEC, my more recent copies of the NEC are in my office at work. Article 250.104(B) deals with grounding of metal piping systems other than water piping. It says that "where installed in or attached to a building or structure, a metal piping system(s), including gas piping, that is likely to become energized shall be bonded..." A compressed air system is probably not likely to become energized, so it's probably not required to ground it.

However, there is an FPN note at the end of the section that says, "Bonding all piping and metal air ducts within the premises will provide additional safety."

Since it's a simple enough thing to run a ground wire, I'd recommend doing it. It won't hurt anything and could possibly help.

edit: the NEC does specifically cover grounding the frames of metal buildings, so that's not debatable. It's probably a good idea to ground any substantial metal system that's permanently installed in, or is part of a building.

 

[Mattlt]

edit: the NEC does specifically cover grounding the frames of metal buildings, so that's not debatable. It's probably a good idea to ground any substantial metal system that's permanently installed in, or is part of a building.

Not to hijack the thread, something I've always wondered about. What about steel siding? Either steel siding on a house or sheet metal on a pole shed. How about steel on the inside of a shop? I guess that would be grounded just by the fact that the electrical panel and/or outlet boxes may be mounted to it. (Assuming steel boxes, or course.)

One of those things that I've never heard much discussion about.

 

[sberry]

Siding should be bonded.

 

[Mitheral]

Large metal systems, such as air lines, plumbing, etc, are required to be grounded by NEC not due to flammability issues, but for electrical shock hazards. If an energized conductor were to touch a metal piping system that is not grounded, it would remain energized and pose a shock hazard to anyone who touched it.

This is also a Canadian Code requirement (10-406). The risk is pretty real; people drape electrical cords on air piping all the time.

What about steel siding? Either steel siding on a house or sheet metal on a pole shed. How about steel on the inside of a shop? I guess that would be grounded just by the fact that the electrical panel and/or outlet boxes may be mounted to it. (Assuming steel boxes, or course.)

Yep, that too inside and out. While you maybe could rely on an incedental bond we usually bolt a servit post (basically a split bolt with an integral mounting stud) through the siding and a purlin and then run a bond wire over to our building bond point. A larger building will have several connections.