The five main types of conduit seals used in hazardous locations are sealing fittings, explosion-proof sealants, flameproof cable glands, weatherproof gaskets, and threaded conduit seals. Each serves a specific purpose and is chosen based on the type of hazard present.
Why Hazardous Locations Require Conduit Seals
Sealing conduit in hazardous areas is not just a recommendation—it’s a legal requirement for safety. These seals prevent flammable gases, dust, or vapors from traveling through conduit runs and reaching ignition sources.
- Prevents explosions by stopping the spread of hazardous gases inside conduit systems.
- Blocks moisture intrusion, reducing the risk of short circuits and corrosion.
- Ensures NEC compliance for classified locations, avoiding penalties and shutdowns.
- Improves equipment lifespan by protecting electrical components from contamination.
- Maintains pressure barriers in environments with gas or vapor hazards.
Using the correct sealing method ensures long-term safety and reliability in hazardous locations.
Types of Conduit Seals for Hazardous Locations
You can use different types of electrical conduit seals depending on the location and situation at hand. Here are the five common types.
1. Sealing Fittings
Sealing fittings are one of the most effective ways to prevent hazardous gases from traveling through conduit systems. These fittings contain a chamber where a fire-resistant sealing compound is poured, creating a solid barrier inside the conduit.
These fittings are required in Class I, Division 1 locations, where flammable gases or vapors are present under normal operating conditions. NEC mandates that sealing fittings be installed within 18 inches of explosion-proof enclosures to prevent gas migration. Proper installation ensures a reliable seal, reducing the risk of explosions.
2. Explosion-Proof Sealants
Explosion-proof sealants are compounds specifically designed to create a gas-tight seal in conduit systems. These sealants harden to block the passage of hazardous materials, ensuring compliance with safety regulations.
These compounds are typically used inside sealing fittings and must be fire-resistant and rated for hazardous locations. Choosing the right sealant is essential, as standard caulks and adhesives do not provide the necessary protection. Following the manufacturer’s instructions ensures proper curing and long-term effectiveness.
3. Flameproof Cable Glands
Flameproof cable glands are used to seal the entry points of armored cables in hazardous areas. These glands prevent sparks or flames from escaping into the surrounding environment, reducing the risk of ignition.
Cable glands are commonly found in petrochemical plants, offshore platforms, and other explosive atmospheres. They must be rated for the specific hazard classification and installed according to manufacturer guidelines and NEC requirements to maintain their effectiveness.
4. Weatherproof Gaskets
Weatherproof gaskets provide additional protection against moisture and environmental contaminants. These gaskets are often used in outdoor or damp locations to prevent water from entering conduit systems.
While weatherproof gaskets do not provide explosion-proof protection, they are essential for maintaining electrical integrity in wet environments. Combining them with other sealing methods ensures a comprehensive approach to conduit sealing.
5. Threaded Conduit Seals
Threaded conduit seals use precision-machined threads to create a tight, leak-proof connection between conduit sections. These seals are ideal for locations where liquid-tight and dust-tight protection is necessary.
Threaded connections are often used in Class II and III hazardous locations, where combustible dust or fibers pose a risk. Ensuring proper installation and thread engagement is crucial for maintaining a secure seal.
How to Install Sealing Fittings in Hazardous Locations
Sealing fittings are essential for explosion-proof conduit systems. These fittings must be properly installed to ensure safety and compliance.
- Choose the correct fitting – Ensure the fitting is rated for the hazardous location.
- Position the fitting correctly – NEC requires sealing fittings within 18 inches of enclosures in Class I, Division 1 areas.
- Prepare the sealing compound – Mix the sealant according to the manufacturer's instructions.
- Pour the compound into the fitting – Fill the chamber completely, ensuring no air gaps.
- Allow the compound to cure – Wait the recommended time for it to harden before energizing the system.
Proper installation of sealing fittings is critical to maintaining explosion-proof integrity.
NEC Code Requirements for Conduit Sealing
The National Electrical Code (NEC) sets strict rules for sealing conduit in hazardous locations. These codes exist to prevent the spread of flammable gases, vapors, and dust through conduit runs.
For example, NEC requires sealing fittings to be installed within 18 inches of explosion-proof enclosures in Class I, Division 1 areas. It also mandates the use of approved sealing compounds and proper installation techniques. Following these rules ensures compliance and protects both workers and equipment.
Common Mistakes to Avoid When Sealing Conduit
Small errors during installation can lead to major safety risks. Avoiding these mistakes ensures your conduit system performs as intended.
- Using non-rated or incorrect sealing compounds
- Leaving air pockets or gaps inside the sealing chamber
- Placing sealing fittings too far from the required enclosures
- Over-tightening threaded conduit joints
- Skipping required gaskets or weatherproofing elements
- Ignoring curing times for sealants
- Using unapproved fittings in hazardous areas
Avoiding these common issues can make a big difference. Double-check your materials, placement, and technique to ensure a safe, code-compliant install.
