Gap Observed Between
We have a customer that is concerned about a
stand-off on mating BX flanges. He has checked both the flange grooves
and the ring joint gasket and both are within tolerances.
enclosed a photo of the flange make up. I wonder if the flanges are
fully torqued this gap will be eliminated. Can you offer any advice or
recommendation to resolve this issue?
We don’t know your customers
experience, but the photos show two flanges stacked up with a gasket in
between without bolts. The gap shown is consistent with our experience on
our test rack when making assemblies for test. 6BX gaskets are designed
to compress radially before beginning to coin in the grooves as the bolts
are tightened. Without bolts, we would consider a 1/8” approx. stand-off
to be normal. Even with the bolts tightened to 50% of yield strength a
small gap will often remain (API mentions in Spec 6A that a “small” gap
is acceptable). API Spec 17D for subsea applications requires the flange
bolts be tightened to 70% of yield to remove any remaining gap (this
doesn’t always close the gap if you look closely).
customer has experience with flanges sealing with
R ring gaskets and has
not used BX gaskets before. If your customer is going to make a test, we
feel sure the experience of tightening the connection will relieve his
For more information about ring gasket seal performance and
flange make-up, see: