When you see its getting hot and beginning to flow, pull that flame back some. It takes less heat to keep it hot than to heat it up initially. i always sweat them in the closed position. Sweat ball valves are designed to be soldered, the internal parts can withstand the heat required for a complete solder joint.

Heat hurts valves To keep the heat from damaging the rubber or plastic parts inside, disassemble valves before soldering. Ball valves are a stubborn exception. Luckily, ball valves are not easily damaged by heat. Just be sure to open the valve and concentrate the heat at the fitting ends of the valve body.

The ball valve’s ease of operation, repair, and versatility lend it to extensive industrial use, supporting pressures up to 1,000 bar (100 MPa; 15,000 psi) and temperatures up to 752 °F (400 °C), depending on design and materials used.

Yes. Probably the easier way to do that would be to cut the existing valve off to virgin copper (it doesn’t need to be that long sticking out of the wall) and polish up the pipe, then install the new compression valve. A compression fitting needs in the order of an inch of clear pipe.

When soldering silver and using hard or soft solder, I often find the solder balls up – it just refuses to jump no matter how long it’s under the flame. This is because the flux has burnt out and there is no medium through which the solder will jump (or run as some would say).

6) Solder end ball valves should be installed with the valve in a closed position. Extreme care must be used to prevent overheating of the valve causing damage to seats and seals. Use care to prevent the flame from making contact with the valve body as damage can occur.

Limitations or Ball Valves Wet steam is damaging to all valve parts at the moment of opening and closing, or when throttling. Resilient seat materials in ball valves may be more susceptible to damage than metal or carbon graphite seats.