Quick Hits

Episode 2: Classified Locations & Storage Tanks (515.5)

SLIDE 1 (HOOK / COVER)

⚡ NEC Quick Hit: Bulk Storage Tank Classifications (Part 2) ⚡

How far do hazardous boundaries extend around fixed-roof tanks, floating-roof tanks, and drum filling stations? Let's check Table 515.5! 👇

SLIDE 2 (ABOVEGROUND STORAGE TANKS)

Fixed & Floating Roof Boundaries:

• Fixed Roof Tanks: The entire inside of a fixed-roof tank is classified as Class I, Division 1 (or Zone 0). The area within 3.0 m (10 ft) from the shell, ends, or roof is Class I, Division 2 (or Zone 2).

• Floating Roof Tanks: For floating roofs with a fixed outer roof, the space between the floating and fixed roof sections is Division 1 / Zone 0. With no fixed outer roof, the area above the floating roof and within the shell is Division 1 / Zone 1.

• Vents: Open ends of tank vents feature a Division 1 / Zone 1 boundary within 1.5 m (5 ft), extending to Division 2 / Zone 2 between 1.5 m and 3.0 m (5 ft and 10 ft).

SLIDE 3 (DRUM AND CONTAINER FILLING)

Indoor & Outdoor Filling Stations:

• Inside Containers: The interior area of drums and containers being filled is Class I, Division 1 / Zone 0.

• Filling Openings: The space within 900 mm (3 ft) of vent and fill openings is Class I, Division 1 / Zone 1.

• Extended Boundaries: An outer zone extending between 900 mm and 1.5 m (3 ft and 5 ft), plus up to 450 mm (18 in.) above grade within a 3.0 m (10 ft) horizontal radius, is Class I, Division 2 / Zone 2.

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Table 515.5 area classifications are directly extracted from NFPA 30 (Chapter 5), meaning they assume all facility construction and ventilation requirements have been fully met!

💬 Save this post for your next industrial tank farm design!

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