Sigma 812508018 Ground Joint Pipe Union 1/2 in Fnpt 150 Lb

Product Description

The SIGMA 812508018 is a Figure 3463 ground joint pipe union designed for threaded pipe assemblies in gas, steam, and liquid piping systems. Manufactured from malleable iron with a black finish, this 1/2 inch nominal union allows piping runs to be disconnected and reconnected without disturbing the surrounding pipe layout. Rated at 150 lb, it uses female national pipe taper (FNPT) end connections on both halves, creating a metal-to-metal ground joint seat that maintains a reliable seal under pressure cycling and temperature variation. Licensed plumbers and pipefitters are the primary installers of this fitting in both new construction and retrofit work.

This union is suited for residential and light commercial piping applications including natural gas supply lines, steam distribution, hydronic heating systems, and water service runs where routine service access is required. The 1/2 inch nominal size fits standard Schedule 40 and Schedule 80 black iron pipe, making it a common stocking item for mechanical contractors, plumbing shops, and service technicians who work on boilers, unit heaters, and gas appliance connections.

Key Features

• Figure 3463 ground joint design with metal-to-metal seat for pressure-tight connections
• 150 lb pressure rating suitable for gas, steam, and liquid service
• FNPT end style on both halves for compatibility with standard threaded pipe
• Malleable iron construction resists impact and mechanical stress in service environments
• Black finish for use in gas and steam piping where galvanized fittings are not permitted

Compatibility

Designed as an OEM-style replacement fitting for standard 1/2 inch nominal threaded pipe assemblies in 150 lb malleable iron piping systems.

Installation Notes

Installation should be performed by a licensed plumber or pipefitter in accordance with applicable local mechanical and plumbing codes, including the IPC and IFGC where relevant. Shut off and depressurize the piping system completely before disassembling or installing any union. Apply appropriate pipe thread sealant or PTFE tape to the FNPT threads before assembly, and tighten the union nut by hand before final wrench make-up. Do not overtighten the union nut, as distortion of the ground joint seat will compromise the seal.

Technical Specifications

• Nominal Size: 1/2 inch
• End Style: FNPT (Female National Pipe Taper)
• Pressure Rating: 150 lb
• Material: Malleable Iron
• Finish: Black
• Figure Number: 3463

Standard Information

• Brand: SIGMA
• Manufacturer Part Number: 812508018