Shunted Non-rated Equipment in Class 1 Div 2 Area

[Sumo]

I am installing a roll-up door operator in the compressor building of a natural gas pipeline. The area was deemed to be class 1 division 2. The building has hazardous gas detection which I will use to shunt trip the power feed from the control building if the gas level reaches 40% LEL.

2 questions:
1. Can I purchase a standard (non-rated) industrial roll-up door opener for this application?
2. Does the push button switch to operate the door opener (mounted inside the compressor building) need to be explosionproof?

My gut feel is that a non-rated piece of equipment may be installed in that environment (if shunt tripped) but that all conduit fittings and wiring methods must still meet class 1 div 2 requirements, including an explosionproof switch although there will be no power provide ignition to the explosive atmosphere (i.e. there is no provision in 501.115(B)(1) to allow non-rated switch when used in a shunt trip protection scenario).

What are your thoughts?

 

[GoldDigger]

I understand your concern on getting the specification correct, given that the typical electrician will not have experience in this area.

As a side note, I wonder if it is possible to install the roll-up opener with the motor on the outside?

 

[RWC/NC.]

Trying remember years ago, on project facility w/a large chemical storage blding, on the facility grounds, where we wired an electrical roll-up door, for the chemicals storage area. It was when Article 504 was new addition to the NFPA 70. (1996 era?)
*During this time, having a AHJ that would cause most supervision literally "throw up in fear" knowing he'd be one, showing up. (RTP/NC)

The door controls were intrinsically safe (Art.504) installed in EMT to controller location above. Apparatus controls above, was mounted in/explosion proof enclosure. I can't remember (trying) if actual door motor, was mounted inside or outside environment.

But it seems remembering the door motor itself, was quite possibly mounted outside of the environment. (.oh well..)

 

[rbalex]

I am installing a roll-up door operator in the compressor building of a natural gas pipeline. The area was deemed to be class 1 division 2. The building has hazardous gas detection which I will use to shunt trip the power feed from the control building if the gas level reaches 40% LEL.

2 questions:
1. Can I purchase a standard (non-rated) industrial roll-up door opener for this application?
2. Does the push button switch to operate the door opener (mounted inside the compressor building) need to be explosionproof?

My gut feel is that a non-rated piece of equipment may be installed in that environment (if shunt tripped) but that all conduit fittings and wiring methods must still meet class 1 div 2 requirements, including an explosionproof switch although there will be no power provide ignition to the explosive atmosphere (i.e. there is no provision in 501.115(B)(1) to allow non-rated switch when used in a shunt trip protection scenario).

What are your thoughts?

In the interest of full disclosure, I do not like gas detection protection techniques. That said, there are only three applications permitted by the NEC. They are listed in sections 500.7(K)(2) through (4). [See Section 500.7(K)(1)(e)] Which one is being used?

 

[Sumo]

I understand your concern on getting the specification correct, given that the typical electrician will not have experience in this area.

As a side note, I wonder if it is possible to install the roll-up opener with the motor on the outside?

I like the idea; however, according to the as-built construction documents, the div 2 extends 25 feet out around the building.

In the interest of full disclosure, I do not like gas detection protection techniques. That said, there are only three applications permitted by the NEC. They are listed in sections 500.7(K)(2) through (4). [See Section 500.7(K)(1)(e)] Which one is being used?

Thanks for pointing me there. Our compressor station design appears to utilize 500.7(K)(2) to "re-classify" the interior from class 1 div 1 down to class 1 div 2 which dictates our wiring methods. It seems to me that we designed to the requirements of 500.7(K)(3) to handle the equipment that is not safe to operate if gas is present. So if the door opener itself is shunted because it cannot be run if gas is present, I can't see why the electrical control box (contactor) at the opener motor and the switch that is fed from the box would need to be explosionproof. But I have not seen as yet a clear statement in the NEC that says that. I seem to be missing the connect between 501.115(B) and 500.7(K).

 

[don_resqcapt19]

I like the idea; however, according to the as-built construction documents, the div 2 extends 25 feet out around the building.


....

Given the vapor density of natural gas, 25' seems extensive.

 

[Sumo]

Given the vapor density of natural gas, 25' seems extensive.

Agreed. 25 feet is the recommendation of the API 500 "Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities" for div 2 boundary around source of gas release. We used that for years until a contract design firm referenced AGA XL1001 which uses 15 feet for the radius of the div 2 area around the same points plus around bolted flanges and such. So we use that for our new facilities. The div 1 area is 5 feet around point sources that release under normal operating conditions.

 

[rbalex]

Thanks for pointing me there. Our compressor station design appears to utilize 500.7(K)(2) to "re-classify" the interior from class 1 div 1 down to class 1 div 2 which dictates our wiring methods. It seems to me that we designed to the requirements of 500.7(K)(3) to handle the equipment that is not safe to operate if gas is present. So if the door opener itself is shunted because it cannot be run if gas is present, I can't see why the electrical control box (contactor) at the opener motor and the switch that is fed from the box would need to be explosionproof. But I have not seen as yet a clear statement in the NEC that says that. I seem to be missing the connect between 501.115(B) and 500.7(K).

It’s important to recognize, no matter what you do, under Section 500.7 (K) you will still have an active Class I, Division 2 location. In other words, no amount of gas detection will effectively reduce a location to unclassified. (This is why I don’t like gas detection systems - no matter what level they activate)

That said, depending on the nature of the motor (Section 501.125) it may not need to be explosionproof. If the controls are in the classified envelope, they will still need to be suitable for Division 2. [Section 501.115(B)]

BTW AGA XL1001 is a fine Standard - it just isn’t recognized by FedOSHA.

 

[Sumo]

It’s important to recognize, no matter what you do, under Section 500.7 (K) you will still have an active Class I, Division 2 location. In other words, no amount of gas detection will effectively reduce a location to unclassified. (This is why I don’t like gas detection systems - no matter what level they activate)

That said, depending on the nature of the motor (Section 501.125) it may not need to be explosionproof. If the controls are in the classified envelope, they will still need to be suitable for Division 2. [Section 501.115(B)]

BTW AGA XL1001 is a fine Standard - it just isn’t recognized by FedOSHA.

That is very good information. Thank you for your insight!

 

[rbalex]

That is very good information. Thank you for your insight!

Think about it, a gas detector implies you believe flammable gases/vapors could be in the location under some abnormal condition, which is practically the definition of Division 2. [Section 500.5(B)(2)]