API Offshore Standards Activities: Wellhead And Christmas Tree Equipment
Authors: Schuh F.J. , Sampson T.R. 
Published: October 2008

This paper previews the content and application of the newly issued edition of API Spec 6A, Specification for Wellhead and Christmas Tree Equipment, which has an effective date of April 1, 1986. This document is significantly changed-from the previous (14th) Edition of Spec 6A. It introduces a concept of "Product Specification Levels" (PSL's) which represent different levels or aggregations of technical requirements for equipment manufactured in accord with the specification. Also described are temperature and retained-fluid requirements which equipment must meet. Included are design methods, more detailed material, and welding and quality control requirements. Appendices include suggestions for using service conditions and PSL's in ordering equipment.

The new specification is intended as a purchase document for a family of "standard" wellhead and Christmas tree equipment which would perform satisfactorily and safely in new installations (including most offshore installations) without supplemental requirements. Supplemental requirements would be required only for wells with very high pressures or unique combinations of operating conditions.

The new Spec 6A is a clear, easy-to-use document for purchasers and manufacturers of wellhead and Christmas tree equipment. It will be a commonly understood and used specification and will improve both the economics of well completion and safety and reliability in the field. It will also simplify the handling of equipment orders.

INTRODUCTION

API Spec 6A, Specification for Wellhead Equipment, a consolidation of six formerly separate publications, existed in more or less the same form for over 20 years after being adopted in 1961. Between 1961 and 1985 it was reissued in 14 successive editions. It related to items of equipment "utilized for pressure control systems required during the drilling and production life of a well." Its scope consisted primarily of dimensional and pressure-rating requirements with some materials requirements.

The latest edition of API Specification 6A, issued in December, 1985, and now titled Specification for Wellhead and Christmas Tree Equipment, differs significantly from earlier editions. Responding to needs for more rigorous requirements, this new specification includes equipment quality related provisions, provides for recognition of the environmental conditions in which Spec 6A equipment is to be placed in service, and contains more specific and detailed technical requirements. Guidelines for use of the specification should make ordering and manufacturing of equipment easier and less subject to error and misunderstanding. The new Spec 6A does not introduce any new requirements to the industry; rather, it is intended to encompass most of those requirements that industry is now using to meet existing operating needs. It is believed that 80 per cent of the industry's needs for new wellhead and Christmas tree equipment is covered in the new specification.

The fifteenth edition is limited to "a family of equipment for use at the wellhead in the production of oil and gas." It does not cover those specific items of drill through or subsea equipment (BOP's, hubs, etc.) which were covered in the fourteenth and earlier editions.