Bk 521-202BG 3/8 in Malleable Black Iron Coupling

Product Description

The BK 521-202BG is a 3/8-inch malleable black iron coupling designed for threaded pipe connections in gas, air, and general-purpose piping systems. Manufactured from malleable iron conforming to ANSI/ASTM A-197, this coupling provides reliable joining of same-diameter pipe runs. Dimensions conform to ANSI/ASME B16.3, B16.14, and B16.39 standards, and threads are cut to ANSI B1.20.1 NPT specification. Each fitting is individually flag tagged and 100% inspected and quality tested before leaving the factory. The Mueller logo is cast into the body of each fitting. Licensed plumbers and pipefitters are the typical installers for this type of fitting.

This coupling is suited for residential and light commercial piping installations where a straight, threaded union between two pipe sections is required. Common applications include gas distribution piping, compressed air lines, and general black iron pipe assemblies. The black iron finish makes it appropriate for gas service where coating or galvanizing is not required. Sold individually, with a minimum order quantity of 5 units.

Key Features

• Malleable black iron construction per ANSI/ASTM A-197 for durability in threaded piping systems
• 3/8-inch NPT threads conforming to ANSI B1.20.1 for reliable, leak-resistant connections
• Dimensional compliance with ANSI/ASME B16.3, B16.14, and B16.39
• 100% inspected and quality tested at the factory
• Individually flag tagged for easy identification on the job
• Mueller logo cast into the fitting body for manufacturer traceability

Compatibility

Designed as an OEM-style replacement or new-installation fitting for standard 3/8-inch NPT threaded black iron pipe systems.

Installation Notes

Installation should be performed by a licensed plumber or pipefitter in accordance with applicable local codes and the International Fuel Gas Code (IFGC) or International Plumbing Code (IPC) where applicable. Shut off and depressurize the pipe system fully before disassembling any threaded connections. Apply an approved pipe thread sealant or PTFE tape rated for the intended service medium before making up the joint. Do not over-tighten threaded malleable iron fittings, as this can crack the fitting body.

Technical Specifications

• Material: Malleable Black Iron, ANSI/ASTM A-197
• Thread Standard: ANSI B1.20.1 NPT
• Dimensional Standard: ANSI/ASME B16.3, B16.14, B16.39
• Pipe Size: 3/8 inches
• Weight: 0.131 pounds
• Sold As: Each
• Minimum Order Quantity: 5

Standard Information

• Brand: BK
• Manufacturer Part Number: 521-202BG