Nut Stop Diameter of heavy barrel LWN flange 1

[HBMetals]

Dear engineer veterans,

I have a question about the LWN flange heavy barrel type. I am confused with the design which some manufacturers called "Nut Stop" and "Nut Relief". And they claim their default design is only "nut stop".

To my knowledge, Nut Stop O.D=Bolt Circle Diameter - Nut Across Flat Diameter. Could anyone here pls kindly explain for me how the 2 function be accomplished?

Thank u and regards!

 

[BobBartlett]

I have this for you from the FVC website.

FVC style HB necks have an automatic "nut stop" provided by the standard barrel OD. This eliminates the need for a second holding wrench. Optional "nut relief" in the barrel will allow two wrench operation.

To expand a little more, an HB (I always called it a "heavy barrel") has its barrel sized so that the barrel OD is the largest possible before the barrel OD MUST be undercut to allow for the nuts on flange back side. With the barrel OD as made, the nuts can fit on the studs, but the nuts cannot turn. We call that a "nut stop." The HB flanges are also available with the barrel undercut on the backside of the flange
so that the nut can turn. We call that a "nut relief."

The variable body (V1, V2, V3) and full body (FB) flanges must be undercut on their backsides to allow the nuts to fit. The under cut can either be just enough so that it acts as a "nut stop", or a little more so that the nut can turn, in which case it is a "nut relief."

This is the FVC (aka - Forged Vessel Connection) website:

http://www.fvc.cc/longweldneck_heavybarrel.htm

I am waiting for Google Translate to have an "engineer"-to-English setting.

 

[HBMetals]

Thank u Bob and I appreciate your explanation.