Southwark Metal 55NC_18IN Duct End Cap 18 Inch Round

Product Description

The SOUTHWARK METAL 55NC_18IN is an 18-inch round sheet metal duct end cap designed to seal the open terminus of round duct runs in forced-air HVAC systems. Fabricated from hot-dipped galvanized steel, it provides corrosion resistance suited for both supply and return air applications. The plain, non-crimped design allows it to slip over or cap off duct sections cleanly without requiring a pre-formed crimp for fitment. HVAC sheet metal mechanics and duct installers typically specify this cap during new construction, renovation, or system modification work where a duct run must be capped, blanked, or temporarily sealed.

This end cap is used in residential and light commercial forced-air HVAC duct systems. It is well suited for capping unused branch takeoffs, sealing duct ends during construction phases, or terminating runs that are no longer in service. The round profile and 18-inch diameter make it appropriate for main trunk caps or larger branch duct terminations. It meets ACCA and SMACNA fabrication and installation standards, which are the governing specifications for sheet metal duct construction across most jurisdictions.

Key Features

• 18-inch diameter round profile for use on standard round duct
• Hot-dipped galvanized steel construction for corrosion resistance
• Plain end design without crimp for straightforward fitment
• Meets ACCA and SMACNA applicable standards
• Suitable for sealing, capping, or blanking round duct terminations

Compatibility

Designed as an OEM-style sheet metal fitting for use with 18-inch round galvanized duct systems installed and fabricated to ACCA and SMACNA standards.

Installation Notes

Installation is typically performed by licensed HVAC mechanics or sheet metal workers. Before capping any duct section, confirm the system is powered down and airflow to the affected branch is isolated. Secure the end cap with sheet metal screws and seal all joints with UL 181-rated duct sealant or foil tape per SMACNA guidelines to maintain system pressure integrity. Do not leave unsealed gaps that could allow conditioned air loss or contaminant ingress.

Technical Specifications

• Size: 18 inches diameter
• Shape: Round
• Material: Hot-Dipped Galvanized Steel
• End Type: Plain (no crimp)
• Applicable Standards: ACCA, SMACNA

Standard Information

• Brand: SOUTHWARK METAL
• Manufacturer Part Number: 55NC_18IN