Class 1 div 2 installation help : cable type and open cable tray

[tomleleu]

I’m working on a automation project in the tank storage sector which consists of automating 70 automatic pneumatic valves which are located in a class 1 div 2 area.
The way we would like to execute it is drawn below :

View attachment 16308


We had following questions :
1) Does the marshaling panel have to be explosion-proof ? If will only contain terminals.
It might be that the customer wants us to pressurize the panel as it gets really hot and humid in the summer. What kind of panel do we need to use than ?
2) Do I need cable seals on the marshaling panel for my TC-ER cables coming from the MCC building ? According to art 501.15(E) not if we use cables that are not transmitting gases or vapors. How do we know that ? Does the cable supplier deliver us a certificate ?
In case it’s a pressurized panel, what is the impact for the cable seals ?
3) According to 501.10(B)(1)(5) we can use MC cable in a cable tray in class 1 div 2. Just to be sure about the terminology, cable trays does mean open cable trays (like in cable ladders) and not just conduits ?
Is this way of execution common in the oil and gas sector in the US ? We really want to avoid using conduits as much as we can (for pricing and execution speed reasons).
4) The TC-ER cables from the MCC building to the marshaling panel will be laying in an existing cable tray. The customer told me that this tray has a mixture of instrumentation cables and power cable. Do we need to take any precautions here for this type of cable ?

Best regards,

Tom Leleu

 

[rbalex]

I see from your sketch that Division 1 was crossed out and replaced with Division 2. Before I answer any other questions, I have to ask the all-important question, "Who made that decision and on what basis?" Otherwise, this is about as close to a DYI as I've seen for an engineering question.

 

[tomleleu]

I see from your sketch that Division 1 was crossed out and replaced with Division 2. Before I answer any other questions, I have to ask the all-important question, "Who made that decision and on what basis?" Otherwise, this is about as close to a DYI as I've seen for an engineering question.

This is based on the NFPA 497: Recommended Practice for the Classification of Flammable Liquids, Gases or Vapors of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.
A loading bay is considered class 1 div 2. Everything below the scales (in the sumps) is div 1.

 

[Ragin Cajun]

Don't need seals, don't need pressurization. Don't waste the funds.

Nothing "sparking" in the cabinet.

RC

 

[petersonra]

Just off the top of my head.

We had following questions :
1) Does the marshaling panel have to be explosion-proof ? If will only contain terminals.
probably not if it is in a division 2 area.

It might be that the customer wants us to pressurize the panel as it gets really hot and humid in the summer. What kind of panel do we need to use than ?
Why would you pressurize a cabinet that contains only terminals in a division 2 area?


2) Do I need cable seals on the marshaling panel for my TC-ER cables coming from the MCC building ? According to art 501.15(E) not if we use cables that are not transmitting gases or vapors. How do we know that ? Does the cable supplier deliver us a certificate ?
I always have to look this up because the sealing rules are not as obvious as I would like.

In case it’s a pressurized panel, what is the impact for the cable seals ?
Most people seal up pressurized panels because otherwise it uses a lot of very expensive air.

3) According to 501.10(B)(1)(5) we can use MC cable in a cable tray in class 1 div 2. Just to be sure about the terminology, cable trays does mean open cable trays (like in cable ladders) and not just conduits ?
Conduit is not a cable tray. You are starting to ask scary questions.

Is this way of execution common in the oil and gas sector in the US ? We really want to avoid using conduits as much as we can (for pricing and execution speed reasons).
Is this off shore? If so it is more common. For refineries, less so.

4) The TC-ER cables from the MCC building to the marshaling panel will be laying in an existing cable tray. The customer told me that this tray has a mixture of instrumentation cables and power cable. Do we need to take any precautions here for this type of cable ?

You may have to put in some kind of separator. The manufacturer of the cable tray probably has something suitable.

Best regards,

Tom Leleu

It seems to me that you are asking people to help you design stuff with little in the way of information. It seems more appropriate that you acquire the help of a professional with experience in this field rather than random people on the Internet.