The pit cover should be sealed over with tarpaper or plastic.
顶盖必须用焦油纸或塑料封闭。
2
The paper analyzes the problem in separating oil tar by the mechanize trough. It raises the concrete transform plan, which gains the well economic efficiency in reality.
分析了机械化澄清槽分离焦油过程中存在的难题，提出了具体的改造方案，并且在实际中取得较好的经济效益。
3
This paper proposed to use coal tar and other processed products instead of partial heavy oil for float glass plants and analyzed related market supply, economic and technical feasibility.