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 Post subject: Arc Flash Acessment and Catagory Ratings
PostPosted: Sat Feb 14, 2015 6:30 pm 

Joined: Fri Feb 13, 2015 9:16 pm
Posts: 2
I have looked thru the last few 70E versions and the 1910 OSHA for information regarding Arch Flash Acessment required. I do find where if you have one it must be upgraded every 5 years or any time some type of expansion or major changes have been made. What I want to know is where can I find the documented answer to: a Arch FLash Hazard Acessment is required and where it is located.
I am also looking for the information about the Cat. rating and does both the current and cycle time need to be met. Example 70E says Cat is for 35KA with 15 cycle time. What if the current is 55KA and 7 cycles. Employer is requesting to put in infrared windows for infrared viewing. I agree this is the best way but putting these windows in on the run is not safe. I am in need of documented code that says I am correct. IEEE1584 is close but most feel this is above and beyond 70E and could be considered overkill. My self I dont see any reason for putting employees in harms way. Looking for feedback and location for documentation.


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 Post subject: Re: Arch Flash Acessment and Catagory Ratings
PostPosted: Sun Feb 15, 2015 1:04 pm 
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Location: North Carolina
tmwhitwo wrote:
I have looked thru the last few 70E versions and the 1910 OSHA for information regarding Arch Flash Acessment required. I do find where if you have one it must be upgraded every 5 years or any time some type of expansion or major changes have been made. What I want to know is where can I find the documented answer to: a Arch FLash Hazard Acessment is required and where it is located.
I am also looking for the information about the Cat. rating and does both the current and cycle time need to be met. Example 70E says Cat is for 35KA with 15 cycle time. What if the current is 55KA and 7 cycles. Employer is requesting to put in infrared windows for infrared viewing. I agree this is the best way but putting these windows in on the run is not safe. I am in need of documented code that says I am correct. IEEE1584 is close but most feel this is above and beyond 70E and could be considered overkill. My self I dont see any reason for putting employees in harms way. Looking for feedback and location for documentation.

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Lots of questions. Arc flash protection arises out of the general duty clause. Employers have a general duty to protect employees against recognized hazards. 70E exists, so it is recognized. They first issued fines in 2006. The timing info is in 70E.

The tables in 70E are maximum combined values. Must meet both parameters to use the tables. BUT watch out. The opening time is dependent on the arcing current. There is no straightforward forward (easy) way to determine this. For bolted fault considerations, it is trivially easy to estimate a conservative value. But at low currents, arc flash skyrockets so a miss on arcing current leaves employees exposed. Using the tables works about 50% of the time based on incident data collected by Doan. It increases to 100% based on the same report.

As to putting in windows, first look at 130 in 70E. Depending on the equipment it may not be energized work. But a case has happened both in North Carolina where I work now and one case reported by CBS Sales where vibration of employees working in one area of some equipment induced an arc flash in an unrelated area. Second IR windows are not a panacea. In practice I have had a lot of problems seeing everything that needs to be imaged. IR scanning is diagnostic work so EEWP does not apply. We do it all the time with a 2 man crew. The door opener/closer wears arc flash PPE. The camera man does not. The doors get opened in groups, then closed again in groups.


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 Post subject: Re: Arch Flash Acessment and Catagory Ratings
PostPosted: Sun Feb 15, 2015 2:10 pm 

Joined: Fri Feb 13, 2015 9:16 pm
Posts: 2
First let me say thank you for your feedback. Also look forward to using this source in the future.
I noticed you did not mention the requirement for a company to have completed a Arch Flash study by a certain time frame. I do understand the the 1910 standard duty clause about employees will be protected from a flash hazard no greater than a second degree Sun Burn. With 2006 mention, I can assume all data that needs to be collected for any type of flash hazard would need to be on file and updated as required by time and or equipment upgrade.
The work we are needing to get done is no doubt cat 4. We will be exposing the secondary side of a 480vac 1500kva transformer connection. These covers are bolted in place and will be removed then the IR inspection will be done. At the say time we will be adding windows for the IR camera.
I have watched several safety films about Flash hazard studies. The one thing that sticks in my mind is the metal material that is discharged from the explosion at the time of the arch. According to several studies, the material could be at super sonic speed. If the melted metal is discharged at this same rate, is it not fair to say no PPE will protect you from the metal penetrating clothing or any material in its path. Also the force of the blast on a persons body and ears will be subjected to extreme pressures.
I understand what you are saying about your location and the work and how your group gets it done. What I am looking at is the liability involved if or when there is a issue. Adding the values up for cat 4 protection and knowing what is the minimal protection 70E says needs to be done, I just feel we would be crossing the line on the Cat4 rating. Not even considering motor contribution we will exceed 55ka easliy. The primary switch (13.8KV) is not fused. We are protected from the main source with relay protection.
Look forward to your feedback.


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 Post subject: Re: Arc Flash Acessment and Catagory Ratings
PostPosted: Mon Feb 16, 2015 6:27 am 

Joined: Mon Jun 09, 2014 9:19 am
Posts: 43
The answer to your first question is in OSHA 1910.132(d)(2). "The employer shall verify that the required workplace hazard assessment has been performed through a written certification that identifies the workplace evaluated; the person certifying that the evaluation has been performed; the date(s) of the hazard assessment; and, which identifies the document as a certification of hazard assessment." This is also the same standard that says you as an employer will provide the PPE required to protect your workers from all hazards once you have performed the assessments.

The answer to your second question is yes, you have to meet both requirements to use the tables in NFPA 70E. 35ka AND 15 cycles. If you have either of those higher than what is stated you cannot go by the tables for your PPE selection, you must do an analysis.

If you are going to install arc flash windows I recommend you have an engineered study done to determine the correct placement. I am a thermographer and have seen several installed where you cannot see the energized equipment ans still need to take the covers off the perform the IR study. We installed hundreds of windows at a customers facitlity several years ago and the engineered study was worth the money spent for them. We can open the windows and get a clear picture of their equipment.


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 Post subject: Re: Arc Flash Acessment and Catagory Ratings
PostPosted: Mon Feb 16, 2015 9:17 am 

Joined: Mon Feb 22, 2010 10:24 am
Posts: 21
The section that requires updating when major changes occur and must be reviewed at least every five years is NPFA 70E-2012 130.5, page 26 and NFPA 70E-2015 130.5 (2), page 26. Note that 2012 uses the term Arc Flash Hazard Analysis and 2015 uses the term Arc Flash Risk Assessment.


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 Post subject: Re: Arc Flash Acessment and Catagory Ratings
PostPosted: Mon Feb 16, 2015 9:02 pm 

Joined: Mon Feb 16, 2015 8:34 pm
Posts: 2
In response to your question the OSHA standard 29CFR 1910.269 and appendix E have the answer to your questions.

• 29CFR1910.269(I)(3)(i)The employer shall establish minimum approach
distances for ac and dc systems.

• 29CFR1910.269(l)(8)(i)The employer shall assess the workplace to identify
employees exposed to hazards from flames or from electric arcs.

• 29CFR1910 (l)(8)(ii) For each employee exposed to hazards from electric arcs,
the employer shall make a reasonable estimate of the incident heat energy to
which the employee would be exposed using the calculating methods in
appendix E Protection From Flames and Electric Arcs.

• 29CFR1910 Appendix E Protection From Flames and Electric Arcs Table 2

TABLE 2-METHODS OF CALCULATING INCIDENT HEAT ENERGY FROM AN
ELECTRIC ARC

1. Standard for Electrical Safety Requirements for Employee Workplaces, NFPA
70E-2012, Annex D, "Sample Calculation of Flash Protection Boundary."
2. Doughty, T.E., Neal, T.E., and Floyd II, H.L., "Predicting Incident Energy to
Better Manage the Electric Arc Hazard on 600 V Power Distribution Systems,"
Record of Conference Papers IEEE IAS 45th Annual Petroleum and Chemical
Industry Conference, September 28-30, 1998.
3. Guide for Performing Arc-Flash Hazard Calculations, IEEE Std 1584-2002,
1584a-2004 (Amendment 1 to IEEE Std 1584-2002), and 1584b-2011
(Amendment 2: Changes to Clause 4 of IEEE Std 1584-2002).*
4. ARCPRO, a commercially available software program developed by Kinectrics,
Toronto, ON, CA.

• 29CFR1910.269(I)(8)(v)The employer shall ensure that each employee
exposed to hazards from electric arcs wears protective clothing and other
protective equipment with an arc rating greater than or equal to the heat
energy estimated under paragraph (I)(8)(ii) of this section whenever that
estimate exceeds 2.0 cal/cm2 the employer shall make a reasonable estimate
of the incident heat energy to which the employee would be exposed.

In the standard revision OSHA references the 2000 edition of the NFPA 70E as
can be seen in the reference for calculations they reference the 2012 edition of
the NFPA 70E.

In the question about the short circuit current and cycles it either change the
incident energy will change. If the current increases the incident energy will
increase or if the fault clearing time increases in cycles the incident energy will
increase. The same goes for the working distance if the working distance
decreases the incident energy goes up. If the working distance increases the
incident energy goes down.

The NFPA 70E is not referenced in the OSHA standard but is used under the General Duty Clause.


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 Post subject: Re: Arc Flash Acessment and Catagory Ratings
PostPosted: Mon Feb 16, 2015 10:23 pm 
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The quoted sections of 1910.269 are subchapter R for generation, transmission, and distribution...mostly utilities but cogen facilities and some private companies that have distribution gear fall under 1910.269. Utilization equipment falls under wubchapter S. OSHA issued a final ruling on doing an arc flash study and implementing it in phases over the course of the first half of 2015 for subchapter R. For subchapter S the general duty clause and 1910.132 have been applied for close to 10 years now. Utilities only got a pass because the research took longer.

As to a 1500 kVA, 480 secondary transformer, this comes up a lot in my plant. Generally this is the breakpoint where it is tough to get incident energy below 40 cal/cm2 with primary side protection only. I just did one on Friday and I ended up having to recommend either current limiters or fuses on the secondary side, or cranking down the breaker on the primary side to the point that it will trip from transformer inrush (maintenance switch), or installing bushing CT's and using a primary side breaker to trip on secondary faults. I would not trust the 70E tables for this particular scenario.

As to molten metal, etc. do not forget that force=mass x acceleration. Any welder can give you lots of stories about being hit with slag and as a former iron foundry worker I can too. If you wear a fire retardant shirt or jacket, it does not do further damage because it does not sustain a flame but only welding leathers offer any degree of protection at all from slag. The bigger danger is the door itself. There is a considerable amount of pressure built up in the first 1-2 cycles and the doors often fly off. The only real protection is to stand to the side. I have not seen 'bullet holes' ever so the sheet metal sides probably offer enough protection as long as they are not the 'shrapnel'. The pressure wave gets up to a few PSI which is more than enough to rupture an ear drum (1 PSI) but these grow back. It takes at least 20-30 PSI to cause a lethal concussive shock wave and there is no credible evidence outside of a thoroughly discredited formula from Lee that the arc blast approaches those pressures.

As to any liability claims, these are based on the idea that lawyers always win. It is an affirmative defense to say that one is following industry consensus safety standards. No safety standard ever written offers a 100% guarantee. Modern safety management relies on probability and offering comparable risk. The risk of a serious injury from an arc flash is about 1 in 100,000 per worker per year in the U.S. currently, about half the rate of shock injuries, and 50 times less like than major auto accidents. Specific tasks can definitely increase or decrease this likelihood however, so a risk assessment is not only required but a necessity. Just using PPE as a solution is not acceptable either.


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 Post subject: Re: Arc Flash Acessment and Catagory Ratings
PostPosted: Tue Feb 17, 2015 4:43 am 
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Location: Swanton, Vermont
I second loavetacycle's comments on the IR windows. I am an infrared inspection contractor. I had a customer buy windows and install them. It appeared to be another case of a salesperson convincing maintenance or safety management to buy and install something they know nothing about, thinking it was simple. It's just like a window, right? The windows were made from a material that was not the best match for the camera's wavelength, but was one of the most expensive. The sizes and position of the window installation were completely arbitrary. The windows thus provide zero value for the cost and effort. There are a number of factors that need to be considered when choosing and installing these devices otherwise one is wasting their time and money. I highly suggest trying one or two windows before completing the total project. Often times the window manufacturer's installation dimensions are optimistic. For example, looking through a window or view port at an angle, you may not be able to see what you expected to see.


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