reefer / tank aggregate是什么意思？

下面句子是出自"货主自备箱保函",不懂句子里的reefer / tank aggregate是什么意思： in the case of reefer / tank containers we further acknowledge that both you nor your agents or sub contractors are in any way responsible for the technical condition of the container, including reefer / tank aggregate, and we confirm setting the correct functioning of the aggregate and machinery itself as well as correct setting will fall under our exclusive responsibility. 有木有人知道啊，知道告诉偶拉，谢谢~