Classification trichloroethylene

[augie47]

I understand it is not an inspectors duty to Classify areas, but it is nice not to be completely "in the dark". I have a facility that stores trichloroethylene in enclosed but vented tanks.
They are installing lighting over these storage tanks and, so far, classification data is scarce,
Does any one have any experience with such installations.

 

[don_resqcapt19]

A MSDS shows a "1" in the red part of the NFPA 704 diamond indicating a low fire hazard. The DOT class is 6.1 for poison and not 3 for flammable liquid. I don't think it needs to be a classified area.

 

[rbalex]

From NFPA 497 (the "Bible" for classifying materials themselves):

5.4.5 Experience has shown that some halogenated liquid hydrocarbons, such as trichloroethylene; 1,1,1-trichloroethane; methylene chloride; and 1,1-dichloro-1-fluoroethane (HCFC-141b), which do not have flash points, but do have a flammable range, are for practical purposes nonflammable and do not require special electrical equipment for hazardous (classified) locations.
[Underline mine]

 

[augie47]

Thanks

 

[don_resqcapt19]

Bob,
What am I missing? The product is a liquid that can burn, but it does not have a flash point so how does it burn? My understanding from hazmat and fire service training is that only vapors burn. The flash point is defined as the temperature at which a liquid gives off enough vapors to support a "flash" fire. If a product does not have a flash point, how is it still flammable.

 

[rbalex]

Bob,
What am I missing? The product is a liquid that can burn, but it does not have a flash point so how does it burn? My understanding from hazmat and fire service training is that only vapors burn. The flash point is defined as the temperature at which a liquid gives off enough vapors to support a "flash" fire. If a product does not have a flash point, how is it still flammable.

Don,

Thanks for asking. This one made me do a bit of research. It isn't even listed in NFPA 497 Table 4.4.2.

Basically, it is because the flammable range is both very low and extremely narrow (8.0 to 10.5% @ 77F) as indicated by the MSDS you provided. Essentially, it becomes too "rich" quickly and, if ignition does occur, it becomes self extinquising.

 

[don_resqcapt19]

Thanks Bob. I guess that is somewhat like the DOT classification of non-flammable gas for ammonia because its LEL (15%) is above the normal range for a flammable product.

 

[rbalex]

Thanks Bob. I guess that is somewhat like the DOT classification of non-flammable gas for ammonia because its LEL (15%) is above the normal range for a flammable product.

Don,

Thanks again; it looks like I need to retract part of my original statement. Compared to other flammable materials in NFPA 497, Table 4.4.2 the LEL is fairly high, but the flammability limits are still very narrow. Most Table 4.4.2 materials range 8 to 10% minimum and have relatively lower flashpoints.

This MSDS says the flashpoint is 90F. It indicates the same flammability range. Most MSDS seem more concerned with toxicity.

One of the primary principles in NFPA 497 is the use of experience as a basis; e.g., 5.4.1 and 5.5.4. (One of my favorites):

5.5.4 When classifying buildings, careful evaluation of prior experience with the same or similar installations should be made.It is not enough to identify only a potential source of the combustible material within the building and proceed immediately to defining the extent of either the Class I, Division 1 or Division 2; or Class I, Zone 1 or Zone 2 classified areas. Where experience indicates that a particular design concept is sound, a more hazardous classification for similar installations may not be justified. Furthermore, it is conceivable that an area be reclassified from either Class I, Division 1 to Class I Division 2, or from Class I, Division 2 to unclassified, or from Class I, Zone 1 to Class I, Zone 2, or from Class I, Zone 2 to unclassified, based on experience.

 

[don_resqcapt19]

Thanks Bob,
The two MSDS I looked at did not show a flash point and as I understand it, if the liquid does not have a flash point, it is not flammable. So to me, having a fire rating of 1 and no flash point is a contradiction.
it is a toxic product, but as I recall that was what was used on the cleaning wipes in high voltage termination kits a number of years ago. I think it replaced carbon tetrachloride when they decided that was too toxic to use for that purpose.