Questions about Double block and bleed valve and float needle valve

[tobebest]

1.for DBB valve, any difference between reduced bore one and full bore one?
2.is there float needle valve? its construction?
i need your advices,thank you in advance.

 

[LittleInch]

1) No, only size of the bore and cost
2) Not AFAIK, but may depend on size.

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