DNVGL- OTG-08 GUIDANCE ON BOTTOM SURVEY
The Offshore Technical Guidance OTG-08 gives guidance on the execution of the Bottom Survey of mobile offshore units. The bottom survey of MOU’s may be carried out as in-water surveys by divers or ROV’s, supervised by a DNV GL surveyor. The March 2019 revision includes a new Section 5 suggesting to fulfill the MODU requirement for bottom survey by inspection from the inside of the hull. This may in principle be applicable to all units if the ability to fulfil the regulations are met. It will be particularly beneficial for units operating in areas of pour visibility or harsh environment where the traditional in-water survey by diver or ROV is less effective or challenging to carry out. It will also represent a significant opportunity of cost savings for owners.
DNVGL-OTG-09: REGULATORY COMPLIANCE OF OFFSHORE UNITS / Atlantic Canada Regions - Certifying Authority and Classification Services
In this publication we provide an overview of the regulatory regime for Mobile Offshore Units intended to operate in regions off the eastern coast of Canada. 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. Furthermore, the document stipulates requirements related to a Classification notation PROD(CAN) for hydrocarbon processing facilities intended to operate in areas under the jurisdiction of the Canada-Newfoundland & Labrador Offshore Petroleum Board (C-NLOPB).
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 guidance document 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 guidance document 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
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 guidance document 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
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 guidance document 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
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 guidance document 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.
DNVGL-OTG-18: GUIDANCE FOR LONG-TERM NEARSHORE MOORING (January 2019)
This document has been developed in order to address the issue of long term mooring near-shore. It is recognized that existing rules and standards do not fully address this issue, since our POSMOOR Rules are primarily based on offshore bottom mooring and shipping codes primarily consider short term mooring at shore. In order therefore to clarify our approach to the specific challenges of near/at shore mooring we have now issued this Offshore Technical Guidance, to be used as a supplement to our existing Offshore Standard DNVGL-OS-E301 Position Mooring Systems. The OTG addresses aspects specific to mooring in shallow water and mooring at jetties or quayside for a long period. The document is particularly relevant for floating LNG regasification units (FSRU), floating LNG liquefaction units (FLNG) taking gas from shore, and floating storage units, but may be used for any floating installation with an equivalent mooring arrangement.
DNVGL-OTG-19: GUIDANCE ON ASSESSMENT OF EARLY PHASE DESIGN AND NOVEL CONCEPTS AND TECHNOLOGY (August 2018)
This guidance has been developed to help designers and owners by showing a process that can be used for verification during early phase design or when developing novel concepts and technology. This process can be used during early concept phase through pre-FEED to FEED phase. By doing the right evaluations at an early phase significant savings may be achieved during subsequent design and construction phases.
DNVGL-OTG-20: USE OF CLASSIFICATION AS PART OF EU OFFSHORE SAFETY DIRECTIVE COMPLIANCE (Sept 2018)
This guidance has been developed to give owners of floating offshore unit an introduction to EU “Offshore Safety Directive”, and show how classification can be used as part of the work toward demonstrating compliance to the directive. It provides examples of how classification and verification can work together to ensure efficient processes for both scopes.