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#150926 - 02/01/06 09:01 AM Static electrical shock from vacuum hose
Becker Offline
Junior Member

Registered: 01/31/06
Posts: 1
Loc: Glenrock, Wyoming, USA
We work on the utility crew at a coal fired power plant, where we do a lot of work with large vacuum trucks. The issue is we are constantly getting shocks from static build up in the vacuum hoses, especially when vacuuming ash and coal. Adding to the problem is the fact that we are located in Wyoming, where it is high and dry. The low humidity adds to the static problem. The questions are as follows: 1. Are the static shocks we are recieving harmful to a persons health? 2. What is the absolute best way to keep from getting shocked and still get the job done safely?
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#150927 - 02/01/06 09:37 AM Re: Static electrical shock from vacuum hose
Dnkldorf Offline
Member

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
You are asking some pretty broad questions, but I try to answer them..hopefully not too broad.


1. Is it dangerous to a persons health?
yes and no

Static charges happens all the time, just by walking across the carpet, one can build up a charge, and then release it by touching a doorknob, or someone else for that matter. This happens all the time...
Does anyone die from this? Probably..if you look hard enough you can probalby find a report that states someone did. Does that mean I am not going to walk on carpet? No...

So that's tough to answer, sorry..

2. What is the absolute best way?

I don't the answer to that either. The absolute word would get you in trouble. There is probably alot of difference of opinions here.. maybe a multi-step approach would be good..
I know they make anti static mats, rubber gloves, and such.
Is the truck grounded when you do this?
Bascially, what I am saying, is without more details, it would be hard to give an absolute answer.. That word again..

Your particular job, how you do it, and what is causing it, would be out of my league on a computer in PA. It would have to be evaluated, by an expert where you are at.

Have you brought this issue up to your superiors?

Sorry for the run-around..

But hang in there, maybe someone else here has some better answers than I just gave you.

Dnk...


[This message has been edited by Dnkldorf (edited 02-01-2006).]

[This message has been edited by Dnkldorf (edited 02-01-2006).]

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#150928 - 02/01/06 06:23 PM Re: Static electrical shock from vacuum hose
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
If you are vacuuming coal dust the static can be very dangerous...it could result in an explosion. You need to use conductive hoses that will prevent the build up of static.
Don
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#150929 - 02/01/06 09:28 PM Re: Static electrical shock from vacuum hose
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
Don is right. Get grounded hoses and make sure there is a ground contact where it plugs in. We had that problem vacuuming up toner and developer around big laser printers. It is basically just coal dust in a plastic binder. Your hair would stand on end if you just used the garden variety vacuum. The data center found conductive hoses and sockets for the central vac system along with the hepa filters to stop toner.
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#150930 - 02/02/06 07:07 AM Re: Static electrical shock from vacuum hose
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Those type of trucks typically have a length of metal mesh hanging down from the frame, to the ground, for this reason. With time, the mesh abrades away, and needs replacing.

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#150931 - 02/02/06 08:25 AM Re: Static electrical shock from vacuum hose
Big Ed Offline
Member

Registered: 04/07/04
Posts: 56
Loc: Roxboro, NC, USA
Becker,
Have you tried using the the plant's ash handling system for a vacuum? Or are you sucking up stuff that is on the ground?

I also work at a power plant in the I&C dept. We have had similar problems using plastic hose. We switched to a concrete pumping hose. It is a green rubber outer sheath with an elastomer inner wall. There is a coil of metal that runs the length of the hose for rigidity, it grounds at the connection through the cam-lock fitting.

I believe that Goodall Rubber is where we get them.

Hope this helps.

For those who have never seen this done, it is a very impressive buildup of static. I have personally seen 1"-2" arcs from the plastic hose. It is nothing like sliding your feet and zapping the cat.
We had an operator get hung up between one of the plastic hoses and the ash hopper he was sucking out. It started to eat his lunch and he was having a heck of a time geting away from it. Fortunately for him there was someone there to see it and he closed the vacuum line.


Ed

[This message has been edited by Big Ed (edited 02-02-2006).]

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#150932 - 02/02/06 09:07 AM Re: Static electrical shock from vacuum hose
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
John
 Quote:
Those type of trucks typically have a length of metal mesh hanging down from the frame, to the ground, for this reason. With time, the mesh abrades away, and needs replacing.

That doesn't help if the hose is not a conductive hose.
Don
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#150933 - 02/02/06 09:09 AM Re: Static electrical shock from vacuum hose
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
Ed,
 Quote:
It is a green rubber outer sheath with an elastomer inner wall. There is a coil of metal that runs the length of the hose for rigidity, it grounds at the connection through the cam-lock fitting.

Unless the inner wall of the hose is conductive, you can still build up enough static to cause problems. The human shock hazard may be gone, but the dust ignition hazard is still there.
Don
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#150934 - 02/02/06 09:43 AM Re: Static electrical shock from vacuum hose
Dnkldorf Offline
Member

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
Ed, any idea what voltage range that would be?

What do these trucks look like? I am invisioning something like a "honey truck" with a vacuum system on it.


Dnk...

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#150935 - 02/02/06 12:25 PM Re: Static electrical shock from vacuum hose
Big Ed Offline
Member

Registered: 04/07/04
Posts: 56
Loc: Roxboro, NC, USA
I am not sure of the voltage, Dnk. I do know that it hurts like heck. I have gotten nail off of the old hoses once before. The closest comparison that I can come up with would be a precipitator, on the order of 10's of thousands volts. Low amperage, but a grunch of volts.

The trucks look a little like a honey wagon, only bigger. The back of the tank is usually hinged for cleaning. Try these links: http://www.goilm.com/pages/3/index.htm
The big blue truck, and http://teamgap.com/, click on wet/dry vac.

Don, I am not 100% sure if the elastomer is conductive. We only draw ash with these, so there is no ignition concern. I do know that you could hear the sparks in the old hose, there is no sound from the new. It is a bit thicker, so that could be why.

Ed

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