When flux appears liquid and transparent on both tube and valve, start sweeping flame back and forth along axis of joint to maintain heat on parts to be joined, especially toward the base of the valve socket.

• 当管道和阀门上的焊剂都变成液状和透明时，则开始沿着连接轴向前后来会扫着火焰，保持连接部件的温度，特别是阀门承插口底部的温度。