API 682 containment seal
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Based on the 2014 version as a starting point for discussion, I still haven’t understood this concept. According to the definition in 3.1.20, it refers to an external seal of Type 2 arrangement; per Note 2 in 4.1.4, if the external seal is of the dry type, it is defined as a containment seal. Then does a wet-type seal, namely 2CW-CW, not qualify as a containment seal?
2CW-CW is contact wet seal-contact wet seal, not 2CW-CS
The containment seal is defined as a secondary protection seal, which is usually contactless
The contradiction lies in the following: Section 3.1.21 defines the containment seal chamber, and according to this definition, the sealing mechanism within this chamber is the containment seal. Figure 1 on page 16 describes arrangement 2 as “two seals per cartridge assembly with a containment seal chamber...”; based on this description, 2CW-CW is also considered to be installed within the containment seal chamber. Therefore, according to the definition in 3.1.21, the outer sealing mechanism of 2CW-CW would be the containment seal. Overall, Figure 1’s description of arrangement 2 is incorrect, or at least not precise. Article 4.1.4.1 defines arrangement 2 in terms of pressure, without mentioning a “containment seal chamber”. The question that arises then is: why is it necessary to define a “containment seal chamber”?