where triple offset butterfly valve can be used and what the benefits to use it instead of ball and gate valve , and where in mostly needed in tank farms projects?
I have seen Triple Offset and even Double Offset in client specifications for non-utility service with sometimes only Triple being accepted in sour service. The benefit is that a butterfly valve is considerably dimensionally smaller than gate or ball therefore lighter, cheaper more easy installation option and typically used instead of gate/ball block valves in sizes above NPS 8. I know that manufacturers state them as been able to regulate flow but have never seen them selected on this basis. They come in wafer, lug and double flanged style and I seen used in tank farm for MOV and Manual but only flanged allowed directly on to nozzles and do not insert spacer/blind/Fig 8 directly to butterfly valve as disc when open protrudes beyond valve body even in double flange type.
alhnaity:
Since you are listed as a petroleum engineer, and mention tank farms, I presume your question probably is specific for 'petroleum area'.
Please be adviced that you will always get a better answer by giving as much detailed information as possible, sharpening your queryand questions, and that perhaps a preliminary search of this forum or site in general could help you, checking out what is discussed earlier (search bar at top of page).
I would also advice you (if allowed or possible from your position) to contact suppliers directly, or search of comments from suppliers for the different valvetypes.
Never recommend or specify a valve from a supplier that cannot give you a live reference for the valve beeing used for a longer periode (several years) in an equal application.
Apart from this: some highly qualified manufacturors offer high pressure double and triple offset valves that can compete in performance/price ratio with other valves, also ball-valves.
Regulating is another question, to be seen apart from on/off duty, where you always have to specify all needed flow conditions exactly.
(Comment : triple butterflys can regulate within limits, or be supplied with disc constructions adapted for the exact regulation needed, but will not necessarily be able to cover all regulations needed, and not necessarily be best choice.)
