Bk 521-402BG Malleable Black Iron Pipe Cap 3/8 in

Product Description

The BK 521-402BG is a 3/8 inch malleable black iron pipe cap used to terminate threaded pipe ends in gas, air, and fluid piping systems. Manufactured from black malleable iron meeting ANSI/ASTM A-197 material standards, it features NPT threads conforming to ANSI B1.20.1 for a leak-resistant seal. Dimensions conform to ANSI/ASME B16.3, B16.14, and B16.39. Each fitting carries the Mueller logo cast directly into the body and is individually flag tagged for traceability. The fitting is 100% inspected and quality tested before leaving the factory. Plumbers, pipefitters, and gas service technicians install this cap to close off unused or temporary pipe openings.

This cap is suited for residential and light commercial piping applications where a 3/8 inch threaded pipe end requires a permanent or temporary closure. Common scenarios include capping unused gas line branches, closing off test points, and sealing idle ports on manifold systems. Sold individually, with a minimum order quantity of 5 units, making it practical for service trucks and shop stock alike.

Key Features

• Black malleable iron construction per ANSI/ASTM A-197 for durability in gas and fluid service
• NPT threads per ANSI B1.20.1 for reliable, leak-resistant engagement
• Dimensions per ANSI/ASME B16.3, B16.14, and B16.39 for consistent fitment
• Mueller logo cast into fitting body for brand and quality identification
• Individually flag tagged and 100% inspected for quality assurance

Compatibility

Designed as an OEM-style replacement and standard fitting for 3/8 inch NPT threaded pipe systems in residential and commercial gas, air, and fluid piping applications.

Installation Notes

Installation is performed by licensed plumbers or pipefitters in accordance with applicable local codes and IFGC or IPC requirements. Shut off and depressurize the line completely before removing or installing any threaded fitting. Apply thread sealant or PTFE tape appropriate for the service medium before threading the cap onto the pipe. Hand-tighten first, then use a pipe wrench to bring the fitting to proper engagement without over-tightening, which can crack the fitting body.

Technical Specifications

• Material: Malleable Black Iron
• Material Standard: ANSI/ASTM A-197
• Thread Standard: ANSI B1.20.1 NPT
• Dimension Standards: ANSI/ASME B16.3, B16.14, B16.39
• Pipe Size: 3/8 inch
• Weight: 0.085 pounds
• Unit of Measure: Each
• Minimum Order Quantity: 5

Standard Information

• Brand: BK
• Manufacturer Part Number: 521-402BG