Boundary Seals

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ramayeux

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Lafayette Louisiana
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Electrical Inspector
I am currently on a project where we have several different interpretations of 501.15 Sealing and Drainage4) Class I, Division 1 Boundary. We are leaving a Class 1 Div 2 location going under ground about 200' and coming back up to a cable tray 18' high. We have equipment seals and boundary seals on one side. We are not sealed where our conduit comes back up form the ground. My question would be if we are required to have boundary seals on both sides.
 
Well, depending on the definition of sealing you are talking about, and I assume Chico and an appropriate fitting, I don't think so but any outside buried raceway entering a building structure must be sealed off (think ductseal) , so for the cable tray side you need to put duct seal .
 
ramayeux said:
I am currently on a project where we have several different interpretations of 501.15 Sealing and Drainage4) Class I, Division 1 Boundary. We are leaving a Class 1 Div 2 location going under ground about 200' and coming back up to a cable tray 18' high. We have equipment seals and boundary seals on one side. We are not sealed where our conduit comes back up form the ground. My question would be if we are required to have boundary seals on both sides.
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How about clarifying where the Division 1 location is within your scenario first. There is a whole other Section for Class I, Division 2/unclassified boundaries. [Section 501.15(B)(2)]
 
We leave a Class 1 Div 2 area at a pipeline tie in point and go into the ground. Our equipment is on this side and consist of pressure transmitters, valve actuators, and gas detectors. All of this equipment has EYS's installed. Where we go into the ground on this side there are boundary seals about 18 inches above grade. There are no other fittings below the seal. The conduit crosses the facility and comes back up also in a class 1 Div 2 area. It dead ends about 18' in the air at a cable tray. It is open to atmosphere at the tray.
 
ramayeux said:
We leave a Class 1 Div 2 area at a pipeline tie in point and go into the ground. Our equipment is on this side and consist of pressure transmitters, valve actuators, and gas detectors. All of this equipment has EYS's installed. Where we go into the ground on this side there are boundary seals about 18 inches above grade. There are no other fittings below the seal. The conduit crosses the facility and comes back up also in a class 1 Div 2 area. It dead ends about 18' in the air at a cable tray. It is open to atmosphere at the tray.
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That 18' run could be a bit of a problem.

To start see Section 501.15(B)(2). The boundary seals at either end don't need to be explosionproof. See the last two sentences in Section 501.15(B)(2). That takes care of the process end.

Let's look at the cable tray end. This is where the 18' could be iffy. Technically, the "real" boundary is at grade and the seal belongs within 10' of it. The conduit to tray transition is covered by Exception No. 2 so you don't need two [edit add:] boundary seals on that end. I personally wouldn't worry about the coupling needed between the two (or more) conduit sections, especially if I used a single continuous 18' section - but the Code is the Code and 10' is the limit.

Just curious, which Application, Section 500.7(K)(2), (K)(3), or (K)(4) are you using to justify the gas detection system?
 
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It's actually H2S gas detection and required due to a crude line running next to the NGL line we are tying into. I'm not sure what the engineer's argument was for the installation.
 
ramayeux said:
It's actually H2S gas detection and required due to a crude line running next to the NGL line we are tying into. I'm not sure what the engineer's argument was for the installation.
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That's a pretty good reason especially since it has nothing to do with "downgrading" a classified location. Besides being highly flammable, it is also highly toxic.
 
ramayeux said:
I am currently on a project where we have several different interpretations of 501.15 Sealing and Drainage4) Class I, Division 1 Boundary. We are leaving a Class 1 Div 2 location going under ground about 200' and coming back up to a cable tray 18' high. We have equipment seals and boundary seals on one side. We are not sealed where our conduit comes back up form the ground. My question would be if we are required to have boundary seals on both sides.
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Is the cable tray installation located outdoors? Are the conduits stubbing up directly to the tray and open air? Is the cable tray elevated above the C1D2 sphere of influence?
You probably do not need a conduit a seal. Reference 501.15(B)(2) Exception No. 2. Make sure you meet the requirements of both 1) and 2) of this exception. It's rather common in industrial settings to skip the seals on conduits that stub-up to tray in C1D2 areas since the tray elevations are normally higher than the sphere of influence of the C1D2 zone.
 
ramayeux said:
We leave a Class 1 Div 2 area at a pipeline tie in point and go into the ground. Our equipment is on this side and consist of pressure transmitters, valve actuators, and gas detectors. All of this equipment has EYS's installed. Where we go into the ground on this side there are boundary seals about 18 inches above grade. There are no other fittings below the seal. The conduit crosses the facility and comes back up also in a class 1 Div 2 area. It dead ends about 18' in the air at a cable tray. It is open to atmosphere at the tray.
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See my comment above. The transmitters are not ignition sources to my knowledge and based on the rest of the information here, you appear to meet both requirements 1) and 2) of 501.15(B)(2) Exception No. 2.
 
We are in West Texas building an NGL pump station. The site we are referencing is all outdoors. The cable tray goes back to an MCC building about 40' away. Where we stub up to the tray is in a Class 1 Div2 location. There is a fitting where we stub up that was used as a pull point. The conduit is open to atmosphere. I'm not sure what the height of the C1D2 is.
 
ramayeux said:
We are in West Texas building an NGL pump station. The site we are referencing is all outdoors. The cable tray goes back to an MCC building about 40' away. Where we stub up to the tray is in a Class 1 Div2 location. There is a fitting where we stub up that was used as a pull point. The conduit is open to atmosphere. I'm not sure what the height of the C1D2 is.
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Typically 15ft from the source for C1D2 boundaries. Did the plan set include any side profiles of the hazardous zones?
 
ramayeux said:
We are in West Texas building an NGL pump station. The site we are referencing is all outdoors. The cable tray goes back to an MCC building about 40' away. Where we stub up to the tray is in a Class 1 Div2 location. There is a fitting where we stub up that was used as a pull point. The conduit is open to atmosphere. I'm not sure what the height of the C1D2 is.
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If you don't know the height of the envelope, someone has overlooked Section 500.4 which makes it an OSHA violation as well.
 
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