Norwegian consultant and valve instructor, Ingolf Fra Holmslet, continues his bi-monthly series of informative articles. There are a lot of misunderstandings with regards to the meaning of the phrases 'double block & bleed', 'double isolation', 'double active seal' and 'double barrier'. Double block and bleed, in accordance with API, means that there is pressure on both sides of the valve but nothing in the cavity. This is a good way of testing the seat's integrity as an up stream seat. But when it comes back to using the valve in connection with planned work on the down stream side of the valve the double block & bleed, as in the API interpretation of the phrase, has to be changed to something else such as double isolation or double barrier.
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机译：挪威顾问兼阀门讲师Ingolf Fra Holmslet继续其双月刊的系列文章。关于“双重阻隔和渗出”，“双重隔离”，“双重有效密封”和“双重屏障”等词组的含义存在很多误解。根据API的规定，双重阻塞和放气意味着在阀的两侧都存在压力，但腔体内没有压力。这是测试座椅作为上游座椅完整性的好方法。但是，当重新使用阀门与阀门下游侧的计划工作相关联时，如该短语的API解释那样，必须将双重阻塞和放气更改为其他形式，例如双重隔离或双重屏障。
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