Gaps in Socket Welds

The answer to the original question is quite simple and quite logical.

You have a Socket-Weld fitting or object (Ell, Tee, SW Flange, SW Valve, etc.) and you have a piece of pipe.

You insert the pipe into the socket of the fitting, flange or valve. Then you draw the pipe back out 1/16" from the bottom of the socket.

Now you make you proper fillet weld required for a Socket-Weld connection.

During the weld process the pipe is a thinner mass and will tend to heat-up hotter and faster than the other object. As the pipe heats up it will expand. The 1/16 inch gap is to allow for expansion. If there is no place for the pipe to expand away from the weld then the pipe will "Push" against the bottom of the socket and "expand out of the socket and in so doing will break the weld that is in the process of being made.