Offshore Platform Fabrication Specification Requirements
Authors: Peterson M.L. , Hein N.W. 
Published: October 2008

The offshore petroleum industry requirements for fabrication of offshore platforms, generally in all areas outside of the North Sea, are normally based on the requirements of API RP 2A which refers to the AWS welding code, D1. 1 for detailed welding requirements. These documents have been proven to be highly useful to address minimum design and construction practices. However, there are a number of unresolved technical and contractual issues not specifically covered by these documents due to their original scope. Thus, a significant number of producing companies often supplement these references to clarify and augment the requirements. This paper will discuss some of the main paragraphs and points in these referenced documents that require technical and contractual clarification. Additionally, new work on the development of an joint industry, specific fabrication specification for offshore petroleum platforms will be presented.

Introduction

The design and construction of offshore platforms for use in the drilling, completion, development, processing, etc. of an offshore petroleum reservoir should follow normal industry recommended practices (RP) as described by the American Petroleum Institute (API). Historically, the main document that has been used is API RP 2A1. However, reliability based, load and resistance factor design (LRFD) practices also can be used2. The main requirements for welding, fabrication, and inspection of platforms designed to either practice are exactly the same in these two documents. Thus, this paper will discuss the applicable fabrication requirements from only RP 2A, knowing the discussion will also apply to RP 2A-LRFD; but, the sections are numbered differently.

The welding code referenced in the design and fabrication RPs is the American Welding Society (AWS) structural welding code for steel3. This general document covers the welding requirements, weld procedure and welder qualification requirements, and weld quality (accept/reject) criteria. This code used to be applied to all structural fabrication, whether it was a bridge, building, or offshore platform. However, recently, a new code was issued to cover welding related specifically to highway bridge structures4.

It should be noted that the eleventh edition (1988) of the code is the one that is currently required by the API RP 2A. However, there is an API task group that is reviewing these RPs and will probably refer to the current, thirteenth edition. This AWS D1. 1-92 was approved on December 24, 1991. An additional supplement to the welding code is the API RP 2X5. This document covers the ultrasonic examination and inspector qualification specifically related to tubular members.

Although these referenced documents are very useful for designing, welding, and inspecting offshore platforms, there are a number of problem areas in these documents. An example of the potential problem is that the 1992 AWS code has over 70 paragraphs that refers to the "Engineer" for possible approval, acceptance, or clarification. In paragraph 1.1.2 of the AWS welding code it defines the "Engineer" as the "duly designated person who acts for and in behalf of the owner on all matters within the scope of the Code. "