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Offshore guidelines

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DNV GL technical guidelines are developed and based on the competence and experience of our global network of engineers, extensive research, development programs and through close cooperation with our customers worldwide. We meet a changing business environment with regulatory foresight and industry insights and continuously develop our standards and guidelines in order to be in the forefront. We ensure that offshore units are safe, efficient and reliable whilst secure that our customers stay at the competitive edge.

DNV-OTG-01 OFFSHORE CLASSIFICATION

This document provides an introduction to the system of offshore classification, how it works, conditions of validity and its interaction with maritime and coastal state control.

DNV-OTG-02 OFFSHORE GAS EXPORT AND RECEIVING TERMINALS 

In this guideline we present services with respect to risk based verification, certification and classification of offshore gas terminals. It also clarifies the role of risk assessment and qualification of technology within these services.
In addition, this document addresses a number of key technical areas related to offshore terminals and discusses some of the challenges associated with them.

DNV-OTG-03 STRUCTURAL STRENGTH 

The purpose of this document is to provide an introduction to offshore classification service related to structural strength, including a brief description of early phase services as well as full classification services related to structural strength.

DNV-OTG-05 TEMPORARY EQUIPMENT ON OFFSHORE INSTALLATIONS

This guidance has been developed to enable enhanced control of temporary equipment being delivered to fix and mobile offshore units. This document aid service companies, drilling contractors, oil companies, vessel owners, and guide them in certifying and controlling the temporary equipment being sent offshore.

DNV-OTG-06 RECERTIFICATION OF WELL CONTROL EQUIPMENT – SERVICE DESCRIPTION

This document describes our recommendations for recertification of well control equipment, in addition to outline our understanding of the requirement for recertification of well control equipment specified by Petroleum Safety Authority Norway (PSA).

DNV-OTG-07 GUIDANCE ON DNV’S DRILL NOTATION

This guideline boost the understanding of our DRILL notation, its scope, objective, procedures and requirements in the operational phase of a drilling unit. Knowledge provided will ensure an efficient and effective follow up process to maximize the benefits of the notation.  
The guidelines are to be used in conjunction with DNVGL Rules for classification of Drilling units and the technical standard DNVGL-OS-E101 Drilling Systems together, as a supplementary guidance document.

DNVGL- OTG-08 UNDER WATER INSPECTIONS IN LIEU OF DRYDOCK’ (UWILD)

UWILD clarify to owners and Flag State Administrations the DNV GL conditions required accepting and supporting in-water bottom survey of Mobile Offshore Units (MOUs) as an alternative to dry docking. The guideline is applicable for the units covered by DNV GL Offshore Classification, including but not limited to drilling units, FPSO’s, FSO and LNG production and storage units and it is aligned with the relevant unified requirements of the International Association of Class Societies (IACS). Additional, UWILD provides regulators with a transparent background documentation of the in - water inspections replacing the traditional dry docking.

DNVGL-OTG-09 REGULATORY COMPLIANCE OF OFFSHORE UNITS - OPERATION OFFSHORE ATLANTIC CANADA REGIONS 

In this publication we provide an overview of the regulatory regime for Mobile Offshore Units (MOU) intended to operate in regions off  the eastern coast of Canada. Furthermore, the document outlines the processes by which the requirements of the administrations for the relevant Canadian regions can be met through application of Class systematics.

DNVGL-OTG-10 DP-CLASSED VESSELS WITH CLOSED BUS-TIE(S) 

Advanced dynamic positioning (DP) vessels can now meet critical safety regulations while gaining operational flexibility, efficiency and cost savings through new design and monitoring methods.
Our  guidelines provides guidance on how systems based on closed bus-ties configuration can be designed and verified with additional protection and monitoring facilities, ensuring integrity and robustness. We address the critical issue of testing by recommending test requirements that safeguard equipment from damage during testing, while at the same time obtaining sufficient evidence of robustness.

DNVGL-OTG-11 WELL TEST EQUIPMENT SURVEY  

Well tests often happen at relatively short notice and in many cases it is an activity arranged by the operator with little input from the rig owner.
Notwithstanding, the owner is responsible for the installation and compliance with applicable classification requirements. Furthermore, the design and installation is usually performed by a 3rd party “well test company” likely utilizing temporary equipment for (a large share of) the well test installation. Conclusively, a well test installation involves many different disciplines and applicable classification rules.
The above described situation can in many cases lead to an inefficient process and in some cases confusion with regards to requirements (as included in DNVGL Rules for classification), roles and responsibilities. This underlines the need for guidance assisting the well test companies and the rig owners to get the design prepared appropriately.

DNVGL- OTG-12 MOBILE OFFSHORE UNITS – LIGHTWEIGHT MONITORING AND CONTROL DURING THE OPERATIONAL LIFE-CYCLE   

To ensure units are being operated in compliance with the applicable rules and requirements, a rig owner need to know the exact lightweight and centre of gravity at all times. The vertical centre of gravity (VCG) of the unit directly influences stability and, therefore, safety and the unit needs to be operated within limiting VCG curves. Apart from complying with various regulators’ specific requirements, correct lightweight parameters are directly linked to the variable deck load (VDL) capacity of the unit and hence have an economical value as well.
This guideline provides an overview of the various requirements relating to lightweight determination and advices on follow up during the lifetime for the various types of offshore units.

DNVGL- OTG-13 PREDICTION OF AIR GAP FOR COLUMN-STABILISED UNITS (New edition - March 2017)

The air gap of a column-stabilised unit is defined as the vertical distance between the underside of the deckbox and the wave elevation. Negative air gap will occur if the wave elevation is higher than the underside of the deckbox. In case of negative air gap, possible slamming loads needs to be accounted for to the bottom plating and/or vertical bulkheads of the deckbox structure. The objective of this guideline is to define a recommended procedure for estimating air gap for column-stabilised units in compliance with DNVGL-OS-C103.

DNVGL- OTG-14 HORIZONTAL WAVE IMPACT LOADS FOR COLUMN STABILISED UNITS (final edition – April 2017)

The air gap of a column-stabilised unit is defined as the vertical distance between the underside of the deckbox and the wave elevation. Negative air gap will occur if the wave elevation is higher than the underside of the deckbox. In case of negative air gap, possible slamming loads needs to be accounted for to the bottom plating and/or vertical bulkheads of the deckbox structure. The object of this OTG is to provide a guideline for the loads to be used to document structural and floating integrity of MOUs that are subject to horizontal wave impact with the deck in the design conditions in compliance with DNVGL-OS-C103.

DNVGL-OTG-15 IN-WATER TERMINALS (April 2017)

DNV GL has several standards and publications relevant for designing and constructing in-water terminals, fixed or floating. These documents do not however provide specific guidance on non-floating and non-concrete in-water terminals. This guidelines specifically addresses non-floating and non-concrete in-water terminals, clarifies what rules and standards would be applicable for design and to what extent verification might be carried out, either through a normal classification approach or through verification services.