What is recommended for connecting copper tube and copper fittings in severe low temperature service?

For connecting copper tube and copper fittings in severe low temperature service, using brazing alloys is recommended due to their specific properties that make them suitable for such extreme conditions. Brazing creates a strong, durable joint that withstands the thermal stresses that can occur at low temperatures.

The brazing process involves melting a filler metal that has a lower melting point than that of the copper components being joined but higher than that of soft solder. This results in a strong bond that can also resist the possibility of joint failure due to thermal contraction.

In contrast, soft solder is generally not recommended for low temperature service because it can become brittle and lose its strength under such conditions. Welding, while creating a very strong joint, can also introduce stress risers and is not typically used for joining copper in similar applications due to its complexity. Compression fittings may provide a convenient and effective solution but do not achieve the same level of durability and reliability as brazed connections when exposed to severe low temperatures.