The publication of the 19th Edition of API Spec 6A / 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 uppermost 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 (see below), including the necessary working pressure.

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. 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.


API Hub Top Connector

Certain sizes and pressures of Top Connectors require a back-up ring as part of the sealing means of the collar secured connection. WOODCO USA can supply, as parts, the seals and back-up rings for all Top Connectors manufactured in compliance with dimensions shown in API Spec 6A, Annex K. WOODCO USA recommends replacement of the seals each time the operator opens the uppermost collar connection for the purpose of servicing the well. The table below lists, by bottom connection, all of the sizes of Top Connectors currently manufactured by WOODCO USA, and identifies the seals as replacement parts.

Operators may order various adapters using combinations of these Collar Connectors and Flanges, Hubs, and other forms of Hammer Union connectors, either Male or Female.

2-1/16″ 5M*92-3/8″ 8R EUE5-3/4**4.000568-342-90 FKM 
2-1/16″ 10M*92-3/8″ 8R EUE5-3/4**4.000568-342-90 FKM 
2-1/16″ 15M*92-3/8″ 8R EUE5-3/4**4.000568-342-90 FKM 
2-1/16″ 20M*102-3/8″ 8R EUE6-1/4**4.000568-342-90 FKM 568-153-80 FKMYES
2-9/16″ 5M92-7/8″ 8R EUE5-3/4**4.000568-342-90 FKM 
2-9/16″ 10M92-7/8″ 8R EUE5-3/4**4.000568-342-90 FKM 
2-9/16″ 15M92-7/8″ 8R EUE5-3/4**4.000568-342-90 FKM 
2-9/16″ 20M102-7/8″ 8R EUE6-1/4**4.000568-342-90 FKM 568-153-80 FKMYES
3-1/8″ 5M103-1/2″ 8R EUE5-3/4**4.000568-342-90 FKM 
3-1/16″ 10M103-1/2″ 8R EUE5-3/4**4.000568-342-90 FKM 
3-1/16″ 15M103-1/2″ 8R EUE7-1/2**5.500568-354-90 FKM 568-159-80 FKMYES
4-1/16″ 5M114-1/2″ 8R EUE8-3/8**5.250568-427-90 FKM 
4-1/16″ 10M114-1/2″ 8R EUE8-3/8**5.250568-427-90 FKM 
4-1/16″ 15M124-1/2″ 8R EUE9-1/2**6.250568-436-90 FKM 568-161-80 FKMYES
5-1/8″ 5M125-1/2″ 8R LCT9**6.750568-438-90 FKM 
5-1/8″ 10M125-1/2″ 8R LCT9**6.750568-438-90 FKM 
5-1/8″ 15M145-1/2″ 8R LCT12-1/4**7.000568-439-90 FKM 568-166-80 FKMYES
7-1/16″ 5M127″ 8R LCT9-1/2**8.000568-443-90 FKM 
7-1/16″ 10M137″ 8R LCT11-1/2**8.250568-444-90 FKM 568-168-80 FKMYES
*2-1/16″ nominal size Top Connectors do not appear in API Spec. 6A, WOODCO USA offers these sizes with the collar type upper connection also used on 2-9/16″ sizes with the same pressure rating.

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