For example, a furnace may require relining after a specified number of hours of usage, or aircraft fixtures such as seats and galleys may require replacement several times during the life of the airframe.
例如，熔炉可能需要在使用了特定数目的小时以后更换衬里，飞机的座位和备餐间等固定设备可能需要在使用同一机身期间处置数次。