LNG dispensers

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My understanding is that the entire LNG dispenser enclosure and the surrounding area for 5' in all directions from it is a Class 1, Division 1 location. If a lighting conduit emerges from grade (1"RMC) located about 12" from the dispenser and extends to 10 feet above grade, and the dispenser is 6 feet tall, that places the end (top) of that conduit in the Division 1 location (4' above dispenser). If a light fixture is installed at the top of that conduit and is listed for Class 1, Division 2, that is a violation. If that same conduit was extended to place the light above the 5 foot boundry, (let's say - 10' above the top of the dispenser), placing it in the Division 2 location, and assuming there is a coupling somewhere in the Division 1 area, would a seal be required since the conduit is leaving a Division 1 location and running to a Division 2 location? These are all meant as questions, not statements, since I am trying to make sense of it. Any help would be appreciated. The part that is the most fuzzy to me concerns seals when leaving a division 1 location and entering a division 2 location. Thank you
 

GoldDigger

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To which I would add the question of whether the conduit emerging from underground and going unbroken until it is in the Division 2 region has ever entered the Division 1 region in the first place and if so at what point? Would you need one seal as it emerges from the underground and another where it passes from 1 to 2?
You hypothesize a coupling somewhere inside Division 1, in which case would you need two seals, one on each side of the coupling.??? :)

Tapatalk!
 
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I was thinking that the conduit emerging from the ground is passing through the division 1 area since it will be running vertically about 12" from the face of the LNG dispenser. I'm basing that on an area 5' in all directions from the enclosure being division 1. For the contractor to get the light to 12 or 13 feet in the air, he will probably be using a coupling somewhere in that division 1 area unless he can get a 20 foot piece of RMC.

So my two main questions are:
1. Is my thinking correct about the Division 1 boundary for the LNG dispenser?
2. If passing from a div 1 to a div 2, will a seal be required?

Note: the specified light fixtures are listed for class 1, division 2.
 

nhee2

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NFPA 52 (2013 version) defines the Div 1 area for outdoor vehicle/cargo transfer areas as 'within 5' in all directions from the point of transfer' and the Div 2 area as 'Beyond 5 ft but within 15 ft in all directions from the point of transfer. It does define anything relative to inside/outside of the dispenser enclosure.
 

rbalex

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I was thinking that the conduit emerging from the ground is passing through the division 1 area since it will be running vertically about 12" from the face of the LNG dispenser. I'm basing that on an area 5' in all directions from the enclosure being division 1. For the contractor to get the light to 12 or 13 feet in the air, he will probably be using a coupling somewhere in that division 1 area unless he can get a 20 foot piece of RMC.

So my two main questions are:
1. Is my thinking correct about the Division 1 boundary for the LNG dispenser?
2. If passing from a div 1 to a div 2, will a seal be required?

Note: the specified light fixtures are listed for class 1, division 2.
1. You have defined the Division 1 envelope correctly.

2. You have two boundaries to deal with: at grade and at the Division 1/Division 2 boundary. Note both are a Division 1 boundary and within the scope of Section 501.15(A)(4). In addition, the boundary at grade requires a seal no matter what.[Section 514.8]

There is no way to avoid a seal in this installation even where the conduit passes entirely through the Division 1 location. Section 501.15(A) Exception No. 1 requires both ends of the raceway to be in unclassified locations.

All that said, you could judiciously select the location of a single seal to do "double duty". It would have to be within 10' (conduit feet) of both boundaries with no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Division 1 location.
 

nhee2

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NFPA 52 is the code for LNG/CNG fueling facilities, and table 10.2.2.4 applies to fueling facilities. I am surprised that it differs from the classification table in NEC 514.

I would go conservative and classify the dispenser as Cl I Div 1 as called for in the NEC 514. But I would also include the area around the fueling connection to vehicles in the Div 1 area as specified in NFPA 52.
 

rbalex

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NFPA 52 is the code for LNG/CNG fueling facilities, and table 10.2.2.4 applies to fueling facilities. I am surprised that it differs from the classification table in NEC 514.

I would go conservative and classify the dispenser as Cl I Div 1 as called for in the NEC 514. But I would also include the area around the fueling connection to vehicles in the Div 1 area as specified in NFPA 52.
I sincerely appreciate the reference to NFPA 52. Adopting a more conservative approach is fine if it's economically justified.

It's a tough enough job coordinating the NEC internally; it's nearly impossible to coordinate between NFPA Standards. As it stands now, Art 514 only references NFPA 30A [2012] and while NFPA 30A references NFPA 52 it's the 2010 Edition.

First, NFPA 52 declares itself superior to any document in conflict with it. [1.1.6] Fortunately, of the two, only the NEC is likely to be specifically adopted legally
.
Second, with modern vapor recovery requirements, creating a Division 1 or 2 envelope around the "point of delivery" is philosophically unnecessary, which is why it isn't required in either Table 514.3(B)(1) or (2).

Last even if the NFPA 52 envelopes were adopted, it wouldn't change the sealing requirements of the OP.
 

nhee2

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I am not certain there is any vapor recovery on an LNG fueling dispenser connection, but I could be wrong.

Many times the electrical inspector will reference NEC, but the fire marshall uses the NFPA 52 standard. From a practical standpoint, there are probably are electrical components within 5' of the dispensing point anyway (other than an overhead light, maybe) so drawing a slightly larger Div 1 area on the classification dwg has not resulted in additional cost. I agree that either way it does not impact the question (or answer) regarding the seal fitting.

I am surprised that the NFPA 52 table does not call out the dispenser internals as a Div 1 area, like it does for the CNG dispenser.
 

rbalex

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Methane is a "greenhouse" gas and vapor recovery is an EPA requirement. The dispenser manufacturer is responsible for compliance.
 

nhee2

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I assumed for LNG there was no vapor to recover - I thought the vapor bubble is collapsed as the cold liquid is dispensed into the vehicle tank. As opposed to gasoline vapors which are displaced by liquid during a fill.

However, I agree - 1 seal fitting strategically located....
 

GoldDigger

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I assumed for LNG there was no vapor to recover - I thought the vapor bubble is collapsed as the cold liquid is dispensed into the vehicle tank. As opposed to gasoline vapors which are displaced by liquid during a fill.

However, I agree - 1 seal fitting strategically located....
With LNG, I would guess that it would be similar to LPG in that:
1. An open try cock at the bottom of the required air space inside the tank would be part of the normal fill procedure for safety against overfilling.
2. There would be some unavoidable spillage/venting of liquid when disconnecting the fill hose unless vapor recovery equipment was used.
 

rbalex

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I assumed for LNG there was no vapor to recover - I thought the vapor bubble is collapsed as the cold liquid is dispensed into the vehicle tank. As opposed to gasoline vapors which are displaced by liquid during a fill ...
Also true - so what is the "source" for the Division 1 envelope in normal operation?

The NFPA 52 envelopes appear to be based on catastrophic failures which is philosophically opposed to to basic area classification practices such as NFPA 497, Section 1.1.4 or API RP 500, Section 1.2.1b.
 

nhee2

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LNG is cryogenic while LPG is not. They would not be the same. The cold liquid condenses the vapor in the tank. There is no vapor flow back to the dispenser.
 

nhee2

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Rbalex, I assume the classification criteria is a holdover from bulk trailer filling/offloading stations which generally use ball valves and open ended hoses and not the vehicle fueling nozzles which are designed to be leak proof. Although in the fueling I have watched, some leakage during connection or disconnection of the nozzle during fueling was not uncommon.
 
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