Area classification for VRU Class 1 div 2 ??

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buck2233

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Can someone help clarify a VRU setup for Natural gas processing and reclaiming Vapors off of our dumps from the plant. We have a new tank farm and have installed a VRU skid mounted unit. The VRU unit is rated as a class 1 Div 2 . How far away from tanks and or the containment wall must the unit be installed to be able to operate the VRU unit. The system will operate between 4 ounces and 8 ounces. The potential for release would be either the 150 series flange within 2 feet of the VRU skid or possibly the thief hatches on the tanks themselves spilling into the containment area. The tank farm is moved away from the plant processing area by more than 300 feet. My thoughts were that we should be at minimum of 50 feet before using Class 1 Div 2 otherwise if it is close to the tanks or a possible release we should have Class 1 Div 1 equipment.

Thank you
 
I?d like to clarify a few things first

Your mention of containment leads me to believe there may be something other than gaseous natural gas in the tanks. Is this correct; if so what is it?

What Standard was used to determine the electrical area classification?

I?m assuming the entire installation is outdoors in open air. Is this correct?
 
Your mention of containment leads me to believe there may be something other than gaseous natural gas in the tanks. Is this correct; if so what is it?
This is a mixture of water & hydrocarbon condensate from the plant dumps. It is seperated and half of the tank farm is for water and the other half is for Condensate (drip similiar to gasoline)

What Standard was used to determine the electrical area classification? NFPA is what the contract engineering used and we normally use API RP 500

I?m assuming the entire installation is outdoors in open air. Is this correct? Yes it is in the open air and is out in the middle of a field with no city or housing developement closer than 15 miles.
 
How has the consultant classified the area inside the containment basin? My understanding is they classified the containment area as Class 1 Div 1 but the spacing was done from the center of the tank and I wonder if it should be from the containment wall.
 
If they used API RP 500 or NFPA 497 it's hard to see where they got that much Division 1. It should have been based on Article 515. They still shouldn't find too much Division 1 unless you have an unsual dike system.

In any case, the VRU has no specific distance limitations from the tanks. Technically it could sit right next to a Division 1 location as long as it wasn't actually in the Division 1 location.
 
Thank you very much for your help. My concern is we were to close to the tanks and or containment wall and it sounds like we should be ok to continue with the VRU placement and try to get things running.

Thanks again for your time and help
 
I?m no expert but the Engineers that do the Area Class design also consider:
1) Vapor Pressure of the stabilized liquids
2) How much is Propane/Butane (heavier than air gas)
3) What happens to vapors when VRU goes down?
4) Vent and relief system on tanks

With all that they design for abnormal situations where the plant is dumping high VP liquids and the tanks are really cooking-off. That?s why they are 300ft from the plant.
 
rbalex said:
If they used API RP 500 or NFPA 497 it's hard to see where they got that much Division 1. It should have been based on Article 515. They still shouldn't find too much Division 1 unless you have an unsual dike system.

In any case, the VRU has no specific distance limitations from the tanks. Technically it could sit right next to a Division 1 location as long as it wasn't actually in the Division 1 location.
Click to expand...

"By the book", yes. However the NFPA is a suggested guideline and operational conditions can lead engineers to make judgement calls. It is hard to ascertain from the data supplied if it is correct or not, as usual.:)
 
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