Dear JWS,
Though your question is a general one,for you didn't specify the (INCIDENT ,or mal operation,or Off specification)..
The function of any surge or hold up drum,tank,or vessel is to allow enough time for ,separation of phases e.g gases and water from crude oil or naphtha stream for further processing..etc..
A good residence time will ensure,an on spec.feed stream..
Too hort residence time,will give you an off spec product..
Whereas too long residence time ,will make the vessel to large and uneconomical..
These are only examples,coming to mind..if you have a specific design problem..let me know.
Regards,
Waiel Hasan