Hazard Classification of PAX (KAX) 4

[alangh]

Hi,
I am doing a Hazardous Area Classification for a site that uses Potassium Amyl Xanthate (PAX or KAX). I have the MSDS sheet, but I can't determine which NFPA Group it should be listed in. I assume Group D, but I'd like to verify. I don't have NFPA 325, and it is no longer available. Could someone with this standard take a look for me and see if it is in there?

Thanks

Alan

 

[stookeyfpe]

It sounds like a fairly aggressive oxidizer that borders on an explosive. What is the formulation: powder, solid, in solution with a solvent?

Your material sounds challenging. We need more data.

 

[alangh]

Thanks for your reply.
The material is supplied in powder form, but it is dissolved in water for the process. I am only concerned about it when it is a liquid. It seems to be relatively safe unless it is heated, in which case it gives off carbon disulphide vapors which are highly flammable.

It is hard to get flashpoint data for the liquid in its normal state, but carbon disulphide has a flashpoint of about -30C.

I can't find out how much you have to heat the liquid to get the vapors.

Since the vapors are not normally present, can I just go with Div 2 for the whole area?

As you say - challenging.

 

[rbalex]

I can safely say I’m grateful never having had to work with carbon disulfide.

NFPA 497 generally covers the old NFPA 325 document for the materials of interest.

From NFPA 497[2004], Table 4.4.2 Note h:

Certain chemicals have characteristics that require safeguards beyond those required for any of the above groups. Carbon disulfide is one of these chemicals because of its low autoignition temperature and the small joint clearance necessary to arrest its flame propagation.

Carbon disulfide is what I call a “maverick.” Technically, it has no “Group” in the conventional NEC Division classification system. It is Group IIC in the Zone system. That puts it in the same category as acetylene. With respect to MIE, MIC and MESG, it’s even worse than acetylene. It does have a significantly lower %UFL but that’s about it.

The open question in my mind at the moment is, “Is it possible for the liquid to be heated to vaporization during the process under unusual but not necessarily upset conditions?” It is important to recognize that “normal” is not defined with respect to processes in the NEC and “normal” does not necessarily mean “often” or even “common.”

 

[cdafd]

alangh

Is the liquid form the final product form??

If so shouldn't there be a msds for it???

 

[alangh]

cdafd, there is an MSDS for it, but this doesn't cover the NFPA classification. And yes, liquid is the final product form.
rbalex, thanks for your information. The question I am wrestling with is whether to assume that carbon disulphide might be generated, or just to ignore it and deal only with the KAX 51 itself. Under "normal" conditions, there will be no carbon disulphide. And not knowing at what temperature KAX has to be heated to in order to generate CS2 is a concern. If the temp is not normally occurring in a process plant (say above 50C) then I can assume that there will be no CS2 even if there is a KAX leak. But if CS2 is generated at "normal" temperatures found in a plant, (say a hot motor or a light bulb globe) then I have a problem.
Agreed?

 

[rbalex]

Since I don't know the process involved, I can only speak in general terms. NFPA 497 is also the basic NFPA Recommended Practice for determining electrical area classification for chemical processes.

Again from NFPA 497 [2004]:

Section 1.1.4 This recommended practice does not apply to situations that could involve catastrophic failure of or catastrophic discharge from process vessels, pipelines, tanks, or systems.

My concerns would be how leaks may occur and whether those leaks may readily vaporize. If they are a common maintenance issue, then you may need to consider Division 1. If not, Division 2 would probably be acceptable. However, from the Table 4.4.2 note I cited earlier, I’d review a CS2 MDS and see what “…safeguards beyond those required for any of the above groups” just might be. This is nasty stuff we’re taking about; with issues well beyond electrical area classification.

 

[stookeyfpe]

Alangh,

I am traveling but everything Rbalex is telling you is true. I also have never had experience with CS2 but I havee though about it.

I have a reference to a peer reviewed article that was published in Chemical Engineering News in which one can calculate the evaporative flux of a liquid spill and following the Ideal Gas Law, estimate the required volume/area of mechanical ventilation to maintain the atmosphere < 25% LFL. As you are probably aware, CS2 has a low LFL value and a broad flammable range.

If someone can explain to me how to post a Adobe file of the paper, I'll be happy to share it with you.

I also am going to post the question on my alumni listserve to see if any of the graduates of my university have dealt with this material.

I don't know if this helps solve of your problems. It sounds like from an instrumentation or controls perspective, Z purge may be your only option.

 

[rbalex]

I'd be interested in seeing that paper myself.

In the entry pane below(Step 3 Attachment, right-hand side)you can upload your file and then "paste" a reference to it in your message.

 

[alangh]

I found out a bit more today. The solution is a 30% concentration and is not flammable, according to the supplier. They also said it did not have to be very hot to give off CS2, and they will confirm the actual temperature asap.

But since CS2 has a flashpoint of -30C, and an LEL of 1.25%, would not any vapors that are given off immediately ignite and burn off, without doing much harm? It seems to me it would be impossible to collect CS2 in sufficient quantities to cause a fire or explosion

 

[stookeyfpe]

Once your atmosphere exceeds the 1.25% LFL and the volume is less than the UFL, then any source of ignition with sufficent energy will result in a fire. Given the vapor pressure of CS2, I envision a very rapid fire, that could possibly produce a deflagration.

If any personnel are in that area, you are looking at burn victims. I don't have enough data to make an injury assessment - however, if you end up with partial depth or full depth burns over 9% of the human body, you should consider permanent skin damage and extended, long term, painful treatment.

You are dealing with a pretty nasty manufacturing by-product that offers little sympathy to anyone exposed to under fire exposure. A high degree of engineering control is warranted with CS2. Look at the vapor pressure - its damn near 2X that of acetone.

http://www.sciencestuff.com/msds/C1462.html

This degree of volatilty confirms to me why electrical equipment based on separation gaps for flame quenching verified using MESG won't work using more conventional methods of hazardous(classified) location electrical equipment.

 

[rbalex]

It appears Stookeyfpe and I agree on just about everything.

I would caution though that, while CS2 has terribly volatile fire properties, you can't count on it simply "burning off" as it is generated. Both its vapor density (2.6) and it AIT (90C) would lead me to believe that it would “cloud” until, as Stookyfpe said, it found “…any source of ignition with sufficent [sic] energy…” Given its exceptionally low MIE/MIC, it wouldn’t take much, but it would still probably take more than ambient temperature. In other words it would tend to collect until it found an ignition source. THEN the rapid and violent fire Stookyfpe described would occur.

Something else to consider: it is very toxic. This isn’t particularly unusual; most HVLs are toxic well below their LEL. From the MSDS Stookyfpe provided, it is 4ppm for CS2.

I would definitely want to understand the process and its safety mitigation far beyond the electrical area classification. I’d recommend having a serious “sit down” with the process, safety and operations management as a minimum.

 

[stookeyfpe]

I'm trying to locate the paper. But I know it's based on the US Airforce equation in the following Wikepedia reference (yes, I know its Wikepedia):

http://en.wikipedia.org/wiki/Accidental_release_source_terms

I'm still looking. Sorry I have a messy external hard drive. You can substitute CS2 empirical data for hydrazine and work the LFL calcs using LaChateliers equation.

 

[stookeyfpe]

Here is the paper

 

[rbalex]

Thanks for posting the paper; I sincerely appreciate it.

Since I'm an electrical engineer and not a true fire protection specialist, my own calculation skills are pretty much limited to that of the occasional fugitive emission for leaky valves and seals.

I was always sure "spills" had similar analytical tools but we tended to ignore the incidental ones and larger ones were considered “…catastrophes such as well blowouts or process vessel ruptures. Such extreme conditions require emergency measures at the time of occurrence.” [API RP 500 Section 2.2.1.b] I was an author/editor of the three previous RP 500 editions. I’m no longer on the technical committee, but I know they are gearing up for some major revisions this time.

 

[stookeyfpe]

rbalex,

As I fire protection engineer I always have a copy of API RP 500 on my shelf as I find it offers far more guidance that the NEC. I understand the NEC is the adopted code - however, RP 500 sure gives some really helpful options and beneficial information when dealing with hazardous locations. Its nice to know that I have helped an author of a very useful RP.

Let me know if you need anything else.

 

[alangh]

thanks very much for all the good advice.

Alan

 

[VBoris]

Can somebody advise me?
I am using IFM sensors IGC206 (24VDC) in Class I Div. 2 area.
I'm using double ended cord-set with built-in LED to connect these sensors to PLC card. The PLC is in non-hazardous area.
May I consider this system as a Nonincendive System or should I use other measures (IS barriers)?
Thanks.
Boris.

 

[alangh]

In case anyone else has this situation, the supplier of KAX 51 told me that it will generate CS2 above approximately 30C. Even though KAX 51 in liquid form is non-flammable, the factory is rated Class I, Div I. Scary stuff.

Alan

 

[stookeyfpe]

Alan,

That's a pretty freaky product. I went and searched for the product and its empirical formula - I now see how the CS2 is formed.

You get a star for one of the more interesting problems.