第一部分 翻译（出处为PetroWiki）

1)The floating roof was developed in the 1920s to reduce product evaporation loss that occurred in the vapor space of fuels that were stored in fixed-roof tanks.

2）It has been demonstrated that evaporative emissions from a fixed-roof tank can be reduced by over 98% through the use of a properly designed and maintained external floating roof tank, assuming the same product and ambient conditions. Evaporative emissions, although greatly reduced, cannot be entirely eliminated. Normal practice is to use floating-roof tanks only to store products that are considered "stabilized" such that large quantities of vapor will not be introduced underneath the floating roof. In cases when the product entering the tank is at a condition that produces flashing conditions, vapors produced will be captured underneath the floating roof. Evaporation and associated product losses still occur from the rim space, standard roof deck fittings, product that remains on the tank shell, and tank operations that require the tank to be emptied and the floating roof landed on its supports.

第二部分 听力

播放mp3  3-5遍

第三部分

启动PetroWiki专题大作业（4人一组）