DNV GL launches regulatory roadmap for US floaters  

Raja Roy

September 1, 2014

Raja Roy examines DNV GL’s first comprehensive overview on how to properly comply with US Coast Guard requirements to operate FOIs, FSOs and FPSOs in US waters.

The roadmap document called “Verification for compliance with United States regulations on the outer continental shelf” follows from the US Coast Guard’s (USCG) policy letter last year, accepting approval plans and inspections from the class societies DNV GL, Lloyd’s Register, and ABS as basis of USCG approval. However, differences in the accepted rules and standards, and the subsequent variety in the complementing requirements from the CFRs (code of federal regulations) led to uncertainties among operators, both about requirements and final approvals.

This roadmap removes the uncertainty factor. By including all the relevant information in a single document, it is a clear path for compliance.

The BW Pioneer FPSO, currently in Petrobras’ Cascade/Chinook development in the Gulf of Mexico, can process 80,000bo/d. Image from Petrobras.


The USCG, within the Department of Homeland Security, has broad authority under the Outer Continental Shelf Lands Act to regulate safety of life and property on US Outer Continental Shelf (OCS) facilities and vessels engaged in OCS activities, and the safety of navigation. The USCG is also responsible for security regulations on OCS facilities, as specified under the Maritime Transportation Security Act. Other regulatory agencies, such as the Bureau of Safety and Environmental Enforcement (BSEE) also share jurisdiction over OCS activities.

Commercial vessel safety standards for US-flagged vessels, Mobile Offshore Drilling Units (MODU), undocumented floating facilities, and fixed facilities are published in chapter 1 of Titles 33 and 46, CFR. The regulations provide detailed guidance for the design, construction and operation of these units.

However, USCG has recognized that the design and technology of offshore facilities continues to advance at a rapid pace, and that existing US regulations (CFRs mentioned above) do not address the current state of technology. Under 33 CFR 143.120, the USCG has the authority to accept alternative design and engineering standards if an equivalent level of safety is provided.

Accordingly, the USCG published CG-ENG Policy Letter No. 01-13, which prescribes alternate design and equipment standards for floating offshore installations (FOI) and floating production, storage, and offloading offshore units (FPSO) located on the US OCS. In general, the policy letter requires the floating unit to be classed by a classification society (DNV GL, ABS and Lloyd’s Register) that is accepted by the USCG, and establishes requirements to be met in addition to the classification society’s rules.

A floating facility meeting the design and construction requirements of this policy letter is considered meet a level of safety equivalent to that prescribed by 33 CFR 143.

Objective of the regulatory roadmap

As there are differences in the class society rules, which form the basis of the equivalencies, and the complementing requirements from the CFR, there remained an uncertainty on the requirements and the final approvals. To remove this uncertainty factor and in order to establish a clear path of compliance, DNV GL created a roadmap and a class notation (US) in the interest of the operators and engineering houses.

The BW Pioneer FPSO. Image from Petrobras.

A matrix of requirements

The document titled DNV GL SE-003, outlines a regulatory roadmap for owners and operators of FOI, FPSO and FSO units wishing to engage in OCS activities in the US Gulf of Mexico. The roadmap uses DNV GL classification rules and services as a building block, and identifies additional USCG design and equipment requirements for these units that are not otherwise covered by the rules.

Compliance with the appropriate DNV GL classification notations and supplemental USCG design and equipment requirements described in this service specification provides an equivalent level of safety to the USCG’s design and equipment requirements prescribed in the CFR.

Contents of the document

The document outlines a DNV GL class-based verification scheme for US compliance for offshore objects of the following types: FOI, FSO, and FPSOs.The document is divided into two main chapters and an appendix:

USCG acceptance of the DNV GL plan review and inspections is predicated on the basis that such actions are in accordance with the relevant class notations and additional USCG requirements described in CG-ENG Policy Letter No. 01-13. The USCG will make decisions concerning equivalencies, or resolutions of apparent conflicts in or among the applicable requirements.

DNV GL main class and additional US notation for an FPSO:

Normally for an FPSO (with US flag or foreign flag), the following minimum class notations will be proposed under DNV GL class.

1A1 production and storage Unit POSMOOR offloading

USCG’s and the Bureau of Safety and Environmental Enforcement’s (BSEE) main concerns for FPSOs operating in the OCS are for evacuation and seeking shelter during a hurricane. Therefore the FPSO will require a valid tanker certificate for evacuation during a hurricane situation. Therefore such FPSOs /FSOs require a detachable/disconnectable turret that can be relatively quickly disconnected in the event of a hurricane or extreme weather.In such situations, the vessel will adopt the tanker mode and move out to seek shelter. Therefore, the 1A1 notation (typically for mobile offshore units as opposed to permanent offshore installations) is the mandatory notation together with POSMOOR for passive mooring. Double hull requirements in 33 CFR 157.10d(c)(1)(i) and 33 CFR 157.10d(c)(2)(i), and the requirements in 33 CFR 157.10d(c)(3) and 33 CFR 157.11(g)(2) must be met. DNV GL- classed FPSOs complying with the relevant sections of the OSS document for meeting the class notation, together with the supplemental USCG requirement as documented in the compliance matrix, will be awarded the additional notation of Production and Storage Unit (US).

Supplemental USCG Requirement for FPSO

Chapter 2 contains supplemental requirements by the USCG that are otherwise not required under normal DNV GL class rules for the relevant FPSO notations.

These have been arranged by discipline in a tabular format noting the area of discipline, a description of the requirement for clearer understanding and the item number in the policy letter for easy reference.

The main areas that have been documented for USCG supplemental requirement for FPSOs are as follows:

  1. Stability: highlighting USCG’s requirement for intact and damage stability and MARPOL annex 1 requirement; MODU CODE requirements; demonstration of safe disconnection procedure for severe weather, etc.
  2. Piping systems: on arrangements; pollution prevention; ballast piping; and transfer system
  3. Hazardous locations: Zone 1 and 2 definitions
  4. Electrical and instrumentations: requirements on emergency generator loads, detection of conditions of disconnection, non-acceptance of ATEX certification, etc.
  5. Fire and safety: USCG requirements on fire extinguishing, detection and wellhead protection.

BSEE requirements:

The other regulatory agency that share jurisdiction on OCS activities is BSEE, which has its own requirements. BSEE requirements that are related to structures, mooring and foundation are covered under a platform verification program as defined in 30 CFR 250 sub-chapter I. The verification program needs to be performed by a nominated CVA (DNV GL has such authorization). The CVAs responsibilities during design, fabrication and installation are defined in 250.915, 250.916, and 250.917.

As specified in 250.916 for design verification for floating facilities (FOIs and FPSOs) the CVA needs to ensure that the requirements of the USCG for structural integrity and stability have been met. Besides the structural integrity and stability requirements, BSEE mandates specified independent assessments for the following:

Therefore, for these units with DNV GL class including the US notation, most of the BSEE requirement for the structural integrity and stability inclusive of mooring, turret and hull interfaces will be satisfied. Of these, the mooring component of particular interest to both BSEE and USCG is the usage of polyester ropes in the OCS. DNV GL have an extensive qualification program for polyester ropes and components as well as for the suppliers of that component, and standards which meet BSEE NTL requirements. Both DNV GL’s standard and its qualification procedure have been used in recent projects for the mooring verification program.

The above assessments can be performed under the CVA scheme using the applicable international standards mentioned in 250.901, 2007 NTL G14 and equivalent DNV GL standards (which have been accepted by BSEE under the scheme for previous GOM projects).

DNV GL’s work in the Gulf of Mexico

In 2008, DNV was the classification society and CVA for the first FPSO (BW Pioneer) in the US GOM, for the Cascade and Chinook field and is currently working on a classification and CVA project for a floater in the GOM for Delta House.

Raja Roy
is a principal engineer at DNV GL. He has 22 years of relevant experience in structural engineering for fixed and floating offshore platforms and vessels. His expertise includes regulatory coordination for coastal and shelf state requirements for offshore projects and project management for multidisciplinary classification/verification projects.