DOUBLE PACKING AND LEAK-OFF A lantern ring and leak-off pipe provide for detection or removal of leakage, if any, from lower packing set (optional).是什么意思_DOUBLE PACKING AND LEAK-OFF A lantern ring and leak-off pipe provide for detection or removal of leakage, if any, from lower packing set (optional).在线翻译_英语_读音_用法_例句