Abstract

This paper presents an analysis of the current approach to the design and testing of equipment used in subsea developments. The paper critically assesses the current equipment specification, design, manufacture and testing process. An essential part of the analysis is a review of the standards used by the industry and statutory regulations which impact on this process.

It raises significant questions about the efficacy of the design and testing procedures and the role of the regulating bodies in that process. It discusses the impact of poor specification and design procedures, and inadequate testing, of the safety and reliability of the equipment. As a consequence of the analysis it is suggested that the manner in which equipment is specified, designed and tested may need to be changed in order to meet future needs.

The above issues are focused, by considering the production of a subsea wellhead, from specification by the operator to delivery by the manufacturer.

National Mandatory Regulations and Industrial Specifications and Standards

Within the major petroleum producing nations, Governmental Mandatory regulations are combined with national and international standards and specifications to define the requirements by which the industry may operate. Some examples of these mandatory regulations are, the "Oil, Gas, Sulphur Operations in the Outer Continental Shelf, 30 CFR 250 Operating Regulations" in the U.S.A. and the Norwegian Petroleum Directorate published by "Acts, Regulations and Provisions for Petroleum Activity in Norway. On the 1st May 1974 the British Government published the Statutory Instrument Paper No. 289 which became "The Offshore Installation (Construction and Survey) Regulations 1974." These regulations have formed the basis of the United Kingdom Continental Shelf sector mandatory regulations regarding the design, construction and certification for Offshore Installations and equipment for the last 21 years. SI paper 289 gave rise to the guidance notes entitled "Offshore Installations. Guidance on Design, Construction and Certification."

These national mandatory regulations and guideline documents provide direction on a wide spectrum issues ranging from design criteria to engineering and operational practice. The level of design activity required by these documents vary. The British guidelines tend to be prescriptive, whereas the Norwegian regulations rely on both accountability and prescription. In general however, all of the documents call upon industrial standards and specifications to define the design criteria and engineering practice to be used in the development of a new product.

The most widely used international standards relating to engineering specifications and standards are those produced by the American Petroleum Institute (API). Although of USA origin the API documents are recognized and utilized on an international basis. The API specifications are produced and revised by committees comprised of operating companies and equipment or system manufacturers. In this way a consensus of views and experience may be utilized in producing a document with the appropriate design constraints and considerations.

In October 1992 the API published the API specification l7D "Specification on Subsea Wellhead and Christmas Tree Equipment", this document is the Subsea equivalent of API 6A "Wellhead Christmas tree Equipment". There is in fact extensive cross referencing of API 6A from API 17D. The API specifications reference other Industrial Standards extensively in specific areas of design, materials, manufacture and testing. The first edition of API 17D contains 53 references to related standards and specifications. Examples of the referenced standards include: "ASME Section VIII, Division 2: Pressure Vessels" for design;

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