2. Forged Fitting
Base on ANSI B16.11 standard, forged steel screwed and socketweld fittings become one of fittings in ANSI systems. These fittings perform the same function as the Butt-Weld fittings. There function is the same but the method of joining and the dimensioning is different. Normally these fittings are used in sizes 1-1/2" (or 2") and smaller. Welded fittings are specified the same as the pipe, by weight, schedule or wall thickness. Screwed and Socket-Weld fittings are specified per the pressure class. Thread engagements as well as the depths of the sockets for different pipe sizes are different and must be looked-up on an approved dimension table. These fittings are used for steam, water, oil, gas, and air. They are available in 2,000, 3,000 and 6,000-1b classes.
2.a Threaded Fitting For Pressure Classes
• 125# Cast Iron
• 250# Cast Iron
• 300# Malleable Iron
• 2000# Forged Steel *
• 3000# Forged Steel *
• 6000# Forged Steel
( * most common )

The Cast Iron and Malleable Iron fittings are basically used for air and water services at a low temperature and pressure. Forged fittings are normally used for higher pressures and temperatures as well as for the more complex commodities. The majority of the screwed fittings will have female (internal) threads per NPT (National Pipe Thread). The exception will be the swages and the plugs - they will have male (external) threads.

2.b Socket-Weld Fittings are Manufactured in Two Classes
• 3000# Forged Steel
• 6000# Forged Steel
Socket-Weld fittings have a deep socket into which the pipe slips and aligns itself. The weld is then made on the outer surface of the pipe and fitting. This eliminate the need for or use of special clamps or tack welding for alignment prior to the final fit-up welding. At the bottom of the socket a 1/16" gap is left to compensate for expansion when the weld is made. This gap is called a root-gap. The swage does not have an internal socket; it will fit into the socket of a fitting or be butt-welded to a pipe.