Ventilation in Class 1, Div 1 Location

[Corwin]

I have a question about a solvent storage room on site at our plant. First, here are some basic facts about the room:

• (2) 55 gallon metal drums of NMP (Class IIIA liquid) are stored in here. Both grounded
• (1) 55 gallon metal drum of waste material (NMP & MEK (Class IB liquid) mixed with epoxy resin). Also grounded
• (3) 30 gallon storage lockers (JustRite 893020) containing a mixture of 5 gal NMP & MEK in approved storage vessels. It can be assumed that these are all full and there is a 50/50 mix of the two solvents (not mixed in the same vessel)
• Overall room size is approximately 12? x 15?, and has a door on both the north side and the south side of the room (normally closed)
• The room has a drainage trench around it?s (interior) perimeter
• The room is enclosed by the rest of the building
• There is a suction vent (approximately 6? x 12?) on the south wall about 6? from the floor, as well as a 24? x 24? pressurized (I believe) vent on the ceiling very close to the south wall

My question is: is this room adequately ventilated? After some recent construction, we removed one vent/fan (not sure which) on the east side of the room, but did not replace it. The users of this room are currently holding open the south door to allow for better ventilation of the area, which does not seem right to me. My assumption is they leave this door open due to improper ventilation in the room.

After reading NFPA 30, it appears that we may be in violation.

It is my understanding from NFPA 30 that we?ll need to install a make-up inlet on the opposite side of our existing vent (north wall), discharge our exhaust ventilation outside the building (if not already being done), and provide 1 CFM of exhaust air for each square foot of floor area, or 150 CFM, whichever is greater. Can you please correct my assumption, or direct me down the right path?

Any advice you can provide would be helpful.

Thank you

 

[rbalex]

I apologize for the late response. Both my wife and I have been under the weather.

I appreciate that you tried to be as descriptive as possible, but there are still a few open items such as whether there are product transfer/mixing activities in the room. If it is strictly for storage, it is highly likely the room wouldn't be classified at all. That said, good ventilation is always recommended in enclosed, occupied spaces. Ask your HVAC expert, you will find the minimum ventilation isn't particularly difficult to achieve.

 

[Corwin]

Thanks very much for the reply. Drum pumps are in use in the room (specifically for the NMP 55 gallon drums). Also the waste drum ("witches brew", as they call it) is mixed in the room.

 

[rbalex]

Thanks very much for the reply. Drum pumps are in use in the room (specifically for the NMP 55 gallon drums). Also the waste drum ("witches brew", as they call it) is mixed in the room.

If you aren't already, you should become familiar with NFPA 497 as well as NFPA 30.

In absence of a high ambient temperature, I wouldn't be too concerned with NMP. Class IIIB materials can burn but with flashpoints above 200F they rarely create an explosive atmosphere.

The MEK could be a problem. It would depend on the processes and volume of product involved.

 

[bobgorno]

A few additional comments.

• Check with your architect. You noted that the room is "enclosed" by the rest of the building. Is this a cutoff room? If they removed one fan, it may have been the supply fan to stop the odors from moving thru the rest of the building from under the doors, etc. Not a good plan.
• MEK has an odor threshold of 2 PPM and PEL of 200 PPM. NMP PEL is 10 PPM; per some SDS (Safety Data Sheet) I have on hand. Check your SDS (fka MSDS).
• If the room is already considered to be Div 1, electrically you may be OK, but an Industrial Hygienist, or your EH&S Manager should be involved in the personnel protection methods utilized.
• It's pretty obvious why your employees are opening the door with the low odor threshold. I would make sure you spend some time researching the room location with regard to the rest of the building, IBC classification of room, personnel protection, including proper ventilation, and drum pump safe transfers.
• Even if you achieve adequate ventilation, 2PPM odor is hard to avoid, even with an elephant trunk, or "Nedermen".
• Check the gasketing of the doors, although it may not help with MEK odor.
• Watch your drum handling......bonding, bonding, bonding. I've seen drum lids blow off and into a suspended ceiling. Make sure the ground goes to ground. Check the integrity of the static grounding system.

 

[petersonra]

Make sure the ground goes to ground.

what exactly do you mean by this?

 

[bobgorno]

what exactly do you mean by this?

It did sound weird, didn't it?

What I've seen on multiple occasions, are overly helpful manufacturing techs, or otherwise non-qualified personnel, trying to play electrician in drum handling areas, or other solvent handling areas.

Upon inspection at the example I noted, where the drum lid went into the ceiling, I found a static ground clamp cable, attached to green painted unistrut, using a spring nut. The strut was anchored to a wall with standard wall anchors. The only thing conductive, or metallic, attached to the strut, was a copper pipe. The pipe clamp, attached to the strut, was isolated from the copper pipe with a rubber material. Possibly caused the static ignition that launched the lid in this case.

I have seen similar installations in other plants on painted strut, using spring nuts to connect the the static ground clamp bonding wire/terminal. At least these others seemed to try to keep the metal to metal connections to bldg steel, or conduit systems. Although spring nuts and paint might work if the paint was nicked, it surely would not be my choice.

BobG