备用密封件是阀帽(12)内主阀杆密封组件(20)的二级密封。
The backup seal is secondary to the main stem seal assembly (20) in the bonnet (12).
因此，二级密封价格招标是比一级密封价格招标更有效率的方式，对它的研究具有重要的理论与实践意义。
So we can say that the second-price sealed bidding is more efficient than the first-price sealed bidding. Therefore, it is important to research in this f…
近日，齐鲁石化炼油厂连续重整车间加氢裂化高速泵成功改用国产二级机械密封，改造后运行状况良好。
Recently, the CCR of Qilu Petrochemical refinery hydrocracking workshop successful switch to domestically produced high-speed secondary pump mechanical seals, modified to run in good condition.
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