mikethecheme
New User
- Location
- New Jersey
- Occupation
- Process Safety Engineer
Hello all, new to the forum after lurking one some choice posts!
I am faced with a challenging air classification problem and I'm not feeling confident I have the right answer. Basically, I have a facility processing area that handles a bunch of flammable solvents up to Class IA with many different processing vessels.
Solvents are stored outdoors on racks and brought into the area using two material handling air locks. The airlocks are small - maybe 10' x 20' x 16' - and consist of a roll-up overhead door and man door into the process area and an roll-up overhead door and a man door into the process area. The practice is to (1) take material from outside and place it in the air lock via the roll-up door, (2) close the doors and then clean the drums, and (3) open the interior roll-up door and take the materials to their final destination. If they only use a partial skid, they move the material back outside in the reverse order. The airlocks lack positive pressure and/or exhaust ventilation. The roll-up doors (from what I can ascertain) are not gas-tight and make up a significant area of the wall between the locations.
The processing area is no-question C1D2 due to the nature of the facility. The outdoor area has some vessels/equipment with a radial classification. In the vicinity of the airlock roll-up door there is some overlap with with C1D2 <18" radii.
The problem - the air lock is treated as unclassified and contains unrated electrical equipment (roll-up door controls, the motors, some knife switch disconnects and outlets. All the electrical installations are more than 18" above the ground.
There are several scenarios to consider:
What do you think?
As you can tell from the novel I just wrote, I've been thinking a lot about this - probably overthinking it. I'm a ChemE by trade so forgive me if I'm lost in the sauce.
I am faced with a challenging air classification problem and I'm not feeling confident I have the right answer. Basically, I have a facility processing area that handles a bunch of flammable solvents up to Class IA with many different processing vessels.
Solvents are stored outdoors on racks and brought into the area using two material handling air locks. The airlocks are small - maybe 10' x 20' x 16' - and consist of a roll-up overhead door and man door into the process area and an roll-up overhead door and a man door into the process area. The practice is to (1) take material from outside and place it in the air lock via the roll-up door, (2) close the doors and then clean the drums, and (3) open the interior roll-up door and take the materials to their final destination. If they only use a partial skid, they move the material back outside in the reverse order. The airlocks lack positive pressure and/or exhaust ventilation. The roll-up doors (from what I can ascertain) are not gas-tight and make up a significant area of the wall between the locations.
The processing area is no-question C1D2 due to the nature of the facility. The outdoor area has some vessels/equipment with a radial classification. In the vicinity of the airlock roll-up door there is some overlap with with C1D2 <18" radii.
The problem - the air lock is treated as unclassified and contains unrated electrical equipment (roll-up door controls, the motors, some knife switch disconnects and outlets. All the electrical installations are more than 18" above the ground.
There are several scenarios to consider:
- Airlock is empty with doors closed. This should be permissible as there is no fuel to ignite. NFPA 497 5.10.1(e) most closely resembles this case if in the worst case you consider the roll-up door a "pierced wall". The exception is that the pierced wall is not to the outside but to an enclosed area without adequate ventilation. The entire footprint of the air lock is 5'-25' from potential leak sources so if it constitutes a pierced wall then its C1D2 up to 18" from grade. Worst case is it is 36" from grade if the lack of ventilation (natural or otherwise) disallows the reduction through the pierced wall.
- Airlock has material in it and is just sitting there. NFPA 497 5.5.1(3) would state that the area is not classified since the material is in "suitable containers" with no explicit ventilation requirement. "Acceptable containers" is fined in NFPA 30 9.4 which just states the container needs to meet DOT/UN specs - which they do - although some have been previously opened and resealed. NFPA 30 9.12.1 also states the area can be unclassified if the drums are sealed. NFPA 30 12.12 seems to contradict this by saying it shall meet the requirements of 9.12 and 7 if it meets the criteria of a "liquid storage room" (which it may not since its intended for that purpose at all times). NFPA 30 7 states that liquid storage rooms should be considered C1D2 (9.12.2 explicitly says this is true only if totally enclosed within the building).
- Airlock is open to the outside, closed to the inside. Its within the <18" radii of outdoor equipment so it should be C1D2 <18".
- Airlock is open to the inside, closed to the outside. The entire footprint within 5'-25' of leak points and would be C1D2 <36".
What do you think?
As you can tell from the novel I just wrote, I've been thinking a lot about this - probably overthinking it. I'm a ChemE by trade so forgive me if I'm lost in the sauce.
