The publication of the 19th Edition of API Spec 6A /
ISO 10423 effective February 1, 2005, presents a standardized uppermost
union connection for the top of Well Head Christmas Trees. Past names for this
equipment include: Wellhead Flange Adapter, Tree Top, Tree Cap, Lubricator Adapter, Bottom Hole
Test Adapter, and Well Bore Access Flange. This union or “collar secured
connection”, offers operators a convenient way to attach well service
equipment to the Well Head.
API Spec 6A presents this equipment in an
“informative annex” meaning the details of the specification do not yet
constitute a requirement. This Annex K provides detailed specifications
for a collar secured connection as one piece with a body having a
specific API flange or hub lower connection. This first version of Annex K shows this equipment
with many bore sizes below the full bore necessary to pass the drift
test required for Christmas Trees, and API makes no mention of 2-1/16"
nominal size Top Connectors.
Top connectors specified in API Spec 6A have
designated uppermost collar
connections implied for specific Flange and Hub sizes and working pressures. API
Spec 6A does not mention cross adaptation, but Operators may specify
"Adapting Top Connectors" just as they may specify Adapter Flanges or
Adapter Spools; however, following the exact Flange /
Hub top connection specification allows Operators to always know the
connection if they know the Run connections of the
Christmas Tree. If
adapting to connect differing Lubricator Connections proves necessary,
operators should use care in properly identifying and specifying both
the male and female halves of the adapter, including the necessary
Annex K omits any mention of an
internal “lift” thread. Internal lift threads provide a means of
connecting a commonly available tubing or casing joint to the top of the
assembled Christmas Tree to make a straight vertical lift of the Christmas Tree for
installation on the Well Head assembly. Operators desiring these threads
for lifting should not use these
internal threads as a pressure holding connection.
CAUTION: WOODCO USA
recommends only API 8 round tubing or casing threads for use as Lift
Threads inside the bore of API Top Connectors. Standard API 8 round
tubing and casing threads allow full bores within the Top Connectors so
as to assure the passage of a standard “Back Pressure Valve.” Operators
sometimes specify a proprietary “premium” tubing thread as a lift thread
inside a top connector. Often “premium” threads require an I.D. bore
that will not pass the drift test required for Christmas Trees, and this
may prevent the later installation of a tree removal "Back Pressure Valve".
As an option, WOODCO USA can provide a Bonnet with a
lug to accept a Lifting Shackle.
WOODCO USA provides Top Connectors in all the sizes
and pressures specified in API Spec 6A / ISO 10423. Our design follows the
necessary dimensions specified in Annex K to assure the full
interchangeability of all components/parts for the uppermost “collar”
connector, while adopting the other necessary dimensions
specified elsewhere in API Spec 6A for interchangeability and function
as part of a Christmas Tree. 2-1/16" Top Connectors manufactured by
WOODCO USA will have the uppermost collar connection specified for the
same pressure 2-9/16" size. All WOODCO USA Top Connectors meet all API
Spec 6A design requirements.
The illustrations below display the configurations of
Top Connectors manufactured by WOODCO USA.