17D Blind Flanges Without raised faces
My company is assembling some 17D
equipment for subsea use, and one of the lines has a studded tee serving
as an elbow with a blind flange closing the run to provide a fluid
cushion. I observed on the assembly drawings, that neither the studded
tee or the connecting blind flange have a raised face, but my experience
with 6A 6BX flanges suggests to me that at least one of the mating flange
connectors must have a raised face.
Am I correct in my assessment?
You will find the following answer
to your question contained within the information at
API Spec 17D specifically states, “All Flanges used on Subsea
completions equipment shall be of the ring joint type designed for
face-to-face make-up. The connection make-up force and external loads
shall react primarily on the raised face of the flange. Therefore, at
least one of the Flanges in a connection shall have a raised face.” API
Spec 17D specifies an optional raised face on 17D Type SS Blind Flanges.
WOODCO USA recommends that API 17D SS Blind
Flanges always have raised faces.
API Spec 17D makes no mention of
Studded Flange connectors as specified in API Spec 6A, but does not
prohibit them. The implication of acceptance of API Spec 6A connections,
and the fact that API Spec 6A permits the omission of raised faces on
studded face 6BX Flanges will surely result in operators attempting to
install a 17D SS Blind Flange without a raised face onto an API 6A
studded face connection, also without a raised face. Without using
technical terms, any kind of damage to, or coating on, the face of
either of the joining full face flange connectors with BX ring grooves
will prevent the face to face contact intended and explained in API Spec