Undergournd conduit runs, Class I Division 2 and Articles 300.10, 300.12 & 514.8

[Dale001289]

Construction wants to install an short, intermediate PVC conduit of approximately 8-12" long between the underground RGS long radius elbow and vertical RGS conduit where it 'stubs-up' through the concrete slab to above grade equipment. This was done to save money. The environment is a Class I, Division 2, LNG plant expansion and I see this as a violation of articles, 300.10, 300.12 and 514.8.
Comments?

 

[nhee2]

Is this a motor fueling LNG facility? If not then I don't believe 514 applies.

Does the hazardous area actually extend below grade?

Although I would question the cost savings, I believe what you are describing would be allowed by 501.10(B)(1), which references 501.10(A)(1), if you are 24" below grade and encased in 2" concrete. Proper bonding would be required per 501.30.

 

[Dale001289]

Is this a motor fueling LNG facility? If not then I don't believe 514 applies.

Does the hazardous area actually extend below grade?

Although I would question the cost savings, I believe what you are describing would be allowed by 501.10(B)(1), which references 501.10(A)(1), if you are 24" below grade and encased in 2" concrete. Proper bonding would be required per 501.30.[/QUOTE

Prior to the 2005 code, the ground was classified as Division 1 for the first two feet underground. Now its shown as nonhazardous.
Even though the installation wouldn't be described as motor fueling per se, I believe article 514.3(B)(1) still applies. This plant has many outdoor pumps, some installed near LNG storage tanks (see table 514.3 (B)(1). Also if I'm reading correctly, 501.10(A)(1) requires threaded rigid metal conduit for the last 24 inches of underground run or the point of connection to the aboveground raceway. Even though the conduit will be almost entirely buried (except at the stub-up) its still electrically discontinuous, i.e. below grade the RGS elbow will be floating, which in real-world terms probably isn't a big deal but I still see it as a code violation.

 

[nhee2]

514.3 relates to classification of motor fueling facilities. It sounds like you are at a storage/peak shaving facility. That would be classified per NFPA 59A and not 514.

Proper bonding per 501.30 would provide electrical continuity.

 

[Dale001289]

514.3 relates to classification of motor fueling facilities. It sounds like you are at a storage/peak shaving facility. That would be classified per NFPA 59A and not 514.

Proper bonding per 501.30 would provide electrical continuity.

I assume you mean bond the below grade RGS elbow with the above grade RGS stubup?
Remember there's a PVC coupling in between the two.

 

[nhee2]

Still not certain why they would want to do this.

But how would it be any different from any other UG conduit run that transitions from steel aboveground to PVC below?

 

[Dale001289]

Still not certain why they would want to do this.

But how would it be any different from any other UG conduit run that transitions from steel aboveground to PVC below?

Stub-ups (i.e. long radius elbows/sweeps) are normally RGS even though the underground runs, in concrete duct bank are PVC. Reasons: RGS elbows have less side-wall friction, PVC elbows may fracture during concrete pour, and lastly Article 514 (even though may not directly apply) requires last two feet to be metallic conduit.

A coupling has to be added to the long radius elbow above grade in order to attach the vertical RGS conduit - here's where construction has elected to use PCV in lieu of Steel.

 

[nhee2]

Stub-ups (i.e. long radius elbows/sweeps) are normally RGS even though the underground runs, in concrete duct bank are PVC. Reasons: RGS elbows have less side-wall friction, PVC elbows may fracture during concrete pour, and lastly Article 514 (even though may not directly apply) requires last two feet to be metallic conduit.

A coupling has to be added to the long radius elbow above grade in order to attach the vertical RGS conduit - here's where construction has elected to use PCV in lieu of Steel.

I missed that the PVC is located above grade. I thought it was a transition piece below grade.

Unless there is some reason it meets the conditions of 501.10(B)(6), what you describe would not be correct for a Div 2 location.