Barge Dock Classification

[kerickson]

My question is regarding the extent of the classified area (Class 1, Div 2) in NEC Figure 515.3, which is for a marine terminal handling flammable liquids.

In the situation in question, there is a barge dock with hard piping and loading hoses to load/offload gasoline and diesel fuels. There is hard piping to a certain point, and then 50' hoses are connected, which reach to the barges.

Note 1 of Figure 515.3 defines the "source of vapor" as the "operating envelope and stored position of the outboard flange connection of the loading arm or house." Is the "source of vapor" the point where the hose connects to the hard piping, or is it the point where the hose connects to the barge? Additionally, a blind flange is secured on the loading end of the hose when it is detached from the barge. Would the loading end of the hose be considered the "source of vapor" in the stowed position as well, or would the "source of vapor" be the connection point between the hard piping and the hose in this situation?

In Figure 515.3 it appears that the classified area extends 50' inland from the "source of vapor" point, and at a height of 25'+ from the surface of the dock structure. (The height of the classified area is not the primary concern in this application, but rather the horizontal distance toward land.) Additionally, the classified area extends another 50' inland at a height of 2' from the surface of the dock structure. Is this a correct interpretation of this code?

Also, is there a radius of classified area around the "source of vapor"? How far along the water edge of the dock does it extend? Since the entire hull of the barge is a tank, according to Note 2 the classified area extends inland 25' from the hull for the entire length of the barge. Where does the larger classified area (of my previous paragraph) end, and the classified area becomes only the 25' from the barge hull?

Thanks in advance for any help you can give!

 

[rbalex]

If the products are handled in separate lines, the diesel lines can generally be ignored; the gasoline lines cannot.

• The starting point is the shore to ship connector (the “outboard flange”).
• All locations where connector may be present between active use and storage create a “source of vapor” operating envelope. This will also include the hose to hard pipe connection, in your case.
• The blind flange is irrelevant since once a location is classified it is always classified for the purposes of equipment installations. A “Hot Work” permit may act as a temporary reclassification document for some work activities but no permanent installations.
• Once the “source of vapor” operating envelope is established, a Division 2 location is created as follows:
  1. 25’ above and 25’ in any horizontal direction from the envelope down to water surface.
  2. 25’ above the pier and 50’ in any horizontal direction from the envelope down to water surface.
  3. 2’ above the pier and 100’ in the direction of the pier from the envelope down to water surface.

If you have NFPA 497 available to you, it is somewhat analogous to Figures 5.9.1 (g) & (h) except the “source” is mobile.