National Electrical Code Top Ten Tips: Article 515 -- Bulk Storage Plants
- Article 515 covers any portion of a property where flammable
liquids are received and subsequently stored in bulk [515.1]. That's the short version, and if you're unclear what is meant by "bulk" then here's some clarity.
How flammable liquids are received matters. They are received in bulk if recieved by tank vessels, pipelines, tank car, or tank vehicle. Notice pipeline is plural. It is possible to have a flammable liquid piped in, with flow upon demand, and that's not bulk delivery.
How flammable liquids are stored matters. If they are stored or blended in bulk for the purpose of distributing such liquids by tank vessel, pipeline, tank car, tank vehicle, portable tank, or container, then you have bulk storage.
- A property or portion thereof that qualifies for Article 515
requirements is a bulk plant or terminal.
- For any bulk plant or terminal that is also a Class I location,
you must apply Table 515.3 [515.3].
- Table 515.3 is slightly less than two pages long and consists of four columns:
Location, NEC Class I Division (1 or 2), Zone (0, 1, or 2), and
Extent of Classified Area. The point of this table is to tell you how big the classified area is based on the location (e.g. tank storage installations inside buildings), Division, and Zone. In the case of tank storage installations inside buildings, the classified area includes all equipment located below grade level if Divison 1, Zone 1. But if Division 2, Zone 2, the classified area for tank storage installations inside buildings is any equipment located at or above grade level.
- Wiring above a Class I location that is a bulk plant or terminal must be in metal raceways, Schedule 80 PVC, or in one of a few other approved raceways [515.7(A)].
- Any fixed equipment that might make arcs or sparks has to be of the totally enclosed type or be constructed so as to prevent sparks or hot metal particles from escaping [515.7(B)].
- Portable luminaires or other utilization equipment and their flexible cords must comply with the provisions of Article 501 or 505 for the class of location above which they are connected or used [515.7(C)].
- Underground wiring must run in threaded RMC or threaded IMC, but an exception applies [515.8(A)]. If the wiring is buried under at least 2 ft of covering, you can run it in Type PVC conduit, Type RTRC conduit, or a listed cable.
- Any gasoline dispensers in this area must comply with Article
- Ensure there are no differences of potential between metallic
objects. Per Article 250, don't ground metallic enclosures and
raceways; bond them [515.16]. Always check your bonding path and connections for mechanical integrity and electrical continuty.