OT: Tension Brake in Hazardous Area

kamenges

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In the U.S. under the current standards is it allowable to use a friction brake for tension control in a hazardous area with a Group D gas with an auto-ignition temperature of 465 degrees C (acetone)? The web horsepower, which will define the brake dissipation horsepower, is only 0.03 HP. I will be using a brake that is rated many times that in rated power dissipation. Its a slow speed line. I haven't seen anything that specifically says I can't. I just want to make sure.

Thanks,
Keith
 
I dont know if you will find any ratings that allow it. Have you looked at any magnetic partical brakes. I think you could use a couple of RTDs to detect the internal temp.
I would have a hazard analysis done from a what if RTD 1 fails? Do you need 2 or 3 RTDs?

i say RTD because thermocouples could get noise from the magnet. I have seen guys key a mic on a radio calling for support and thermocouples go crazy.
 
Check out an oil-shear brake, like Force Controls. Since the discs are immersed in oul, and there is no contact between the friction surfaces, the design is inherently 'intrinsically safe'.
 
Originally posted by JeffKiper:

I dont know if you will find any ratings that allow it.

I think this may be more of a case where I need to know if it is specifically disallowed. This is basically a mechanical component. ATEX standards in Europe put restrictions on mechanical components used in explosive environments. To the best of my knowledge this has not made it to the U.S. yet.

The brake I will using is a pneumatic friction brake. I can easily get my hands on an I.S. E/P transducer. If I go mag particle the brake housing will need to be explosion proof since the driving current requirements will be well above the level of intrinsic safety

This really is more of a regulatory exercise than a true safety exercise. At it's maximum the brake will need to dissipate 21 watts. It is rated for well in excess of 200 watts. So I have no concerns about excessive heat build-up. It uses a brake pad against a disc to generate torque so sparking isn't a real issue. Even if you went metal on metal there isn't enough energy available to generate a spark. If this were an ATEX application I would have a methodology to prove that this is not a hazard. But that doesn't exist in the U.S. So as long as there isn't a specific "thou shalt not" rule I think I'm OK.

Originally posted by Gene Bond:

Check out an oil-shear brake, like Force Controls.

I like the technology but The torque is pretty high for what I am looking for, even in the smallest version. But I'll make sure I remembers these.

Keith
 
Just to close this out, I came across a guy who used a friction tension brake in an explosive environment a couple years back. As odd as it seems there really doesn't seem to be much restriction on mechanical components in explosive environments in the U.S. unless you are looking specifically at electrical elements of the mechanical device; for example static generation. So at this point I plan to go with the pneumatic friction brake.

Keith
 
To a large extent, what is allowed depends on the Class I hazardous area division 1 or 2. If ignitable concentrations of acetone can exist under normal operating conditions, then it is a Division 1 area, and it would be dangerous to use any type of equipment (including brake coils) that has not been tested and rated for use in a Class I, Division 1 area.

On the other hand, if it is an area where the vapors can only exist in the case of accidental breakdown or rupture of a container, then there is a little room for handling the problem with ventilation to reduce the hazard. Still your brake needs to be rated for that Class I, Division 2 area. If you use unrated equipment (any type of equipment, mechanical, electrical, or other) in a known hazardous area, then the company is asking for legal trouble in case of an accident, from its insurance company, and from the lawyers of the widows of the deceased workers.
 
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OK, let me approach this from the other direction. Does anyone know of any standards governing and sources for the following components for use in U.S hazardous areas:

Gear reducers
Gears
Chains
Friction materials
Pneumatic cylinders
Pneumatic brakes

If no standards exist then either none of these components can be used or they can be used without restriction. As of this date I have never come across standards that govern use of mechanical components in hazardous areas .

Keith
 
There is a European standard (Type EN) for non-electrical friction devices, EN-13463-5. There should be an equivalent Underwriters Laboratories (UL) standard, but I have not found it yet.

ASCO makes harzardous-area rated solenoids that could be used for a brake. If you could find a solenoid-operated brake with the EN-13463-5 rating, you would be in business combining the two devices.

Here is a link to the ASCO hazardous-area solenoid information.

http://www.asconumatics.eu/images/site/upload/_en/pdf1/00129gb.PDF

UL does have an electric brake listing for hazardous area brakes. Here is a page from Stearns-Rexrod that shows a UL Class I tag with code 22R5. It appears that the 87300-series of solenoid-oprated totally enclosed brakes would be rated for a Class I Division 1 Group D hazardous area (if used with the appropriatly-classifed hazardous-area motor).

http://stearns.rexnord.com/pdf/cat_200/feb_2010/26-27_Div1_HAZLOC.pdf
 
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OK, let me approach this from the other direction. Does anyone know of any standards governing and sources for the following components for use in U.S hazardous areas:

Gear reducers
Gears
Chains
Friction materials
Pneumatic cylinders
Pneumatic brakes

If no standards exist then either none of these components can be used or they can be used without restriction. As of this date I have never come across standards that govern use of mechanical components in hazardous areas . Keith

I was wondering the same thing. Have never seen a gearbox with any kind of hazard labeling on it.

In post 4 you mentioned there are European standards. I would look at them and copy if possible or needed or even apply to your situation. That should do to ensure you have done due diligence and all the legal burokrat mumbo jumbo

Dan Bentler
 
Originally posted by Lancie1:

UL does have an electric brake listing for hazardous area brakes.

These look like on/off design brakes. I need something with continuously variable torque. I am using this for a web tension application to unwind a roll of polyester. I had considered magnetic particle brakes. But the whole concept of introducing an electrical explosive hazard just so I can procure a component with rating and construction to mitigate the hazard I'm intentionally and unnecessarily introducing seems a bit crazy to me.


Originally posted by leitmotif:

In post 4 you mentioned there are European standards.

This is EN-13463-5, as mentioned above. We are currently building a machine for a company in Ireland that needs to meet the ATEX directive. So we have some internal knowledge of what is required to meet that. However, there is no U.S. equivalent. As of today it seems that it is the Wild West where mechanical components are concerned in the U.S. I do like the idea of at least evaluating the brake relative to the ATEX directive, though. It would show that I didn't just throw the thing in there without considering the consequences.

Keith
 
So we have some internal knowledge of what is required to meet that. However, there is no U.S. equivalent.
For a product to be used in Ireland, you should be using European standards and European parts. The US standards will not be relevent.
 
Originally posted by Lancie1:

For a product to be used in Ireland, you should be using European standards and European parts. The US standards will not be relevent.

I understand that. What I said was that the company I work for has designed and manufactured equipment according to the ATEX directive for use in Ireland. The ATEX directive has a section that deals with mechanical components in explosive environments. As a result, there are device designed and manufactured for use in ATEX environments. We have specified and selected such components.

However, there is no analog to EN-13463-5 in the U.S., at least as far as I can tell. If that is the case then I am by exclusion able to use ANY mechanical device I choose in an explosive environment in the U.S. as long as it is not designed as a source of ignition, like a torch or a piezoelectric igniter. So my brake, while it may get warm, doesn't fall under the umbrella of any HazLoc standard.

Keith
 

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