Can anyone provide more information on "2*" hazard/risk category designation in table 5? Thanks in advance!

What do you need that's not in Table 5?

Any reason why they set "2*" category? Is it just an alternative to use faceshield?

HRC 2* provides better face protection than HRC 2. You have the choice of either a faceshield with balaclava (sock hood), or an FR hood.

In HRC 2, you can choose to use a faceshield without a balaclava underneath, or an FR hood.

Rating must be at least 8 cal/cm^2 in every case, and safety glasses are required.

HRC 2* is typically referenced in Table 4 when the working distance is expected to be closer than operating a switch (voltage measurement, etc.).

So how do we put the category on the labels? There is no "2*" available from the software (PTW32) we have for now. Usually how do you explain it to the electricians if they ask what kind of PPE they should wear based on category shown on the Labels? Just ask them to refer to the table 4? It is hard to give the instruction if you are doing a big project.

Noah:

Have you completed detailed engineering based Arc Flash Hazard Analysis or just the Table Method?

If you have completed detailed AFHA you cannot put HRC values on the detailed label.

You can only call arc rated protective clothing by an HRC if you have used the Table Method.

Regards;
Terry Becker, P.Eng., CSA Z462 Technical Committee Voting Member
ESPS Electrical Safety Program Solutions INC.
Calgary, AB
terry.becker@espsi.ca

Terry,

In Annex Q, there are label samples. I clearly remember one (the secone one, but maybe the fourth) with both a IE of 18 cal/cm^2 and a HRC 3.

I know that Annex is not normative but informative, but I concluded that it's possible to do calcs (4.3.3.3.3 I think) and list a HRC based on the calculated IE (and using Table 6 reversed).

Annex B also has the same type of info (alongside the TCC, with the one-line).

Have you put any labels on equipments with the category 2* shown on it? If not, what's the usage of this special category?

Vincent:

Annex Q indicates that you can either put the incident energy level on OR the HRC, engineering calculations or Table Method for the CSA Z462 (or 70E)mandatory label, but not both.

The CSA Z462 TC will be changing the sample detailed label (not mandatory) removing the HRC information, this was a mistake and is now recognized as not technically correct.

In fact and unfortunately the Table Method originally in 70E has created a real problem with everyone calling the clothing by HRC when it reality ASTM F 1959 tests for arc rating (e.g. ATPV or EBT).

You can only use the HRC designation for arc rated clothing if you use the Table Method of AFHA.

Regards;
Terry Becker, P.Eng.
Owner
ESPS Electrical Safety Program Solution INC.

Hello Terry,

CSAZ462 says that we can use methhod 1 or method 2 for the selection of PPE. From method 1," the incident energy exposure level shall be based on the working distance of the worker's face and the chest ares from a prospective arc source for the taks to be performed". So normally the incident energy that we get from study is based on working on exposed life parts of the energized electrical equipment. I really don't think that incident energy will be the same level as when you just switch the breaker when the cover is on. We have been asked by clients many times why they have to wear PPE3 or PPE4 to switch the breakers based on Arc flash labels. Since that (operating breaker) is a different task to what described in Method 1, can we use method 2 to decide PPE level based on Table 4? I think that task (operating breaker when cover is on) is not done from detailed analysis, we can use method 2 in lieu of the incident energy analysis as said under 4.3.7.3.9.

Please help to clarify. Thanks!

Never assume that the door or cover is going to protect you from an Arc Flash Hazard. There have been many documented accidents where the covers or doors have been blown off completely. The door or cover may momentarily reduce the energy...until it blows off.

I didn't say there would be no hazard when the cover is on. I just said the hazard level will be different with cover is on or off. It is very clearly indicated in table 4 that the HRC for operating breakers with covers on is less than working on exposed parts. I spoke to SKM as well, they also confirmed that their software can only give the incident energy based on working on exposed life part, they can't provide incident engery level for other task like operating breaker when cover is on. If the detailed analysis can't provide exact category for this task, we then should be able to use table 4 for this task.

There have not been any studies or experimentation that I am aware of that gives us the ability to reduce the energy level when there is a cover or closed door. Maybe after the IEEE 1584 committee finishes their testing we will have a better idea. The problem is that each manufacturer has different door and cover attachment means. There would be an huge number of experimentation that would have to be done.

So if we look at the table 4 from CSA Z462 again, how can we get different HRC based on different specific tasks which to me it could be the same equipment? There must be some tests done in order to give these info in CSA.

On two of the sites I work at regularly, the MCC doors are rarely latched, nor can they be latched due to the state of disrepair and unavailible sapre parts. One is due to be replaced in 2013... Needless to say that I always "step it up a notch" when I work on either site, and am aware of additional potential hazzards.. Even though they have changed some settings of the main breaker and got the AF to around 10.3, I always wear more gear than is needed, and treat each operation as a chance of failure...

At least they have done the study.. Other clients with WAY older equipment haven't done a study, but have done a bit more maintenance.....

You cannot use Method 1 and Method 2 together. The HRC doesn't have anything to do with a calculated incident energy level. Unfortunately the software ETAP, SKM, and Easypower all include HRCs when the incident energy is calculated which is not correct.

An employer needs to establsh an Electrical Safety Program and it will provide direction on arc flash protective clothing when incident energy calculations are completed.

A two level arc rated clothing system is then defined in the Electrical Safety Program.

Unfortunately PPE vendors are marketing their arc rated clothing in HRCs when they should be marketing it for the arc rating. An HRC is an imaginary value created by the NFPA 70E TC, it is not the arc rating of arc flash protective clothing.

I keep seeing these discussions about how Cals/cm2 and HRC should not be intermixed and used together. If a person calculates the arc flash energy (cals/cm2) and then looks up the HRC, what harm will be done? How would a person be under-protected by using the HRC once the energy level is known?

I believe using the HRC 0, 1, 2, & 4 is an extremely easy way for people to understand this very confusing subject. We as industry leaders need to make things easier...not more complicated for the end user.

Mixing Tables with IE Calculations





I think I have example of both good and bad mixing… feedback appreciated.

Example: the IE for a 600V Class Switchgear is calculated at 2.1 cal/cm^2 (including main) and the company safety policy dictates PPE is now required for operating all breakers or fused switches on switchgear. So the FR clothing required to operate a breaker on this service must have at least this ATPV or higher. (IE calculated excluding main is the required PPE for operation of the service’s main breaker; 2 separate labels are applied.)

What I believe is not allowed with the whole mixing of HRC & IE calcs is for someone to then reference T130.(C)(9) and say, "it says here that for 600V class switchgear cb or fused switch operation with covers on is only HRC 0" while we now know the IE calculation actually comes out at 2.1 cal/cm^2 which is higher than HRC 0.

HRC 0 = 0 - 1.1 cal/cm^2
HRC 1 = 1.2 - 4 cal/cm^2

All the NFPA-70E says in 130.7(C)(3) and 130.7(C)(13)(b) about selecting arc flash protective equipment for the head is that it shall be worn where there is danger of contact with energized objects, flashes or flying objects and shall have a suitable rating for the arc flash exposure. So, if my IE is 2.1 cal/cm^2 does that require just a face shield, a face shield + balacava or a flash suit hood?

So then the calculated IE of 2.1 cal/cm^2 was equated to a HRC in order to reference T130.7(C)(10) for guidance in determining the company's policy on required FR protective equipment. 2.1 cal/cm^2 would fall into HRC 1 and therefore the minimum requirement is for a face shield & hard hat. In EasyPower the PPE levels for each HRC were then edited to provide a more inclusive description.

I’m guessing the software companies include both the IE and the HRC to cover both the protective clothing and the protective equipment because at some point you have to create levels, categories or ranges in order to determine things such as, is the face shield still required at 1.9 cal/cm^2 what about at 1.3 cal/cm^2? So why not use the HRC that are already in existence for this determination?

Not sure I want to stir this one up again but much of it was discussed in the following thread:

[url="http://arcflashforum.com/showthread.php?t=655"]HRC / Ei discussion[/url]

The 2012 Edition of 70E continues to discourage linking Ei to a category or level. Like you and most others, I have not found a logical reason.

The only thing I can think of is perhaps it is because of 11/12 cal/cm^2 arc ratings that are becoming more widely used. If you have Level 2 = 8 cal and Level 3 = 25 cal, where does 12 cal fit in?

By not using levels and just providing an arc rating, you can use 12 cal more effectively in recommendations. I'm not sure if that is the reason but it makes sense.

Other's thoughts?