English to Russian Tech/Engineering Chemistry; Chem Sci/Eng Polymerisation

The volume of the reactor and attached settling domes is 117.2 m3
The reactor (excluding the stirrer, any settling domes and any internals) typically has an internal volume of between 50 and 250 m3.
Typically, one or more, such as one or two settling domes are mounted on the top of the reactor.

Речь идет о газофазном реакторе для полимеризации пропилена. Вопрос: что такое эти settling domes и как их перевести?