Quick Hits

Episode 4: Sealing, Process Seals & Bonding (505.16 – 505.30)

SLIDE 1 (HOOK / COVER)

⚡ NEC Quick Hit: Zone Sealing & Bonding (Part 4 - Article 505) ⚡

When are conduit seals required in Zone 1 vs. Zone 2? What are the rules for process-connected instruments? Let's finish Article 505! 👇

SLIDE 2 (CONDUIT & BOUNDARY SEALS)

Minimizing Gas Migration:

• Enclosure Seals: Conduit seals must be provided within 50 mm (2 in.) of enclosures with protection types "d", "db", "e", or "eb".

• Boundary Seals: Conduit runs leaving a Zone 1 or Zone 2 location into an unclassified area require a seal within 3.05 m (10 ft) of the boundary. These seals do not need to be explosionproof, but they must be identified to minimize gas passage.

SLIDE 3 (PROCESS SEALS & BONDING)

Preventing Fluid Migration:

• Process Sealing: Instruments (like pressure transmitters or canned pumps) with a single process seal must feature an additional means of mitigation, such as a vented secondary barrier, secondary seal, or listed Type MI cable assembly.

• Bonding: Metal raceways and enclosures in hazardous locations must be bonded through wrenchtight threaded connections or listed bonding devices.

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Always verify whether process-connected equipment is marked "single seal" or "dual seal" to determine if an external conduit seal or secondary barrier is legally required on your process loops!

💬 Save this post for your final code review on Zone Classification Systems!

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