The Paris Memorandum on Port State Control will start a Concentrated Inspection Campaign to verify correct damage stability on oil tankers, chemical tankers and gas carriers. This inspection campaign will last for 3 months, starting on 1 September and ending on 30 November 2010.
The reasons for this Concentrated Inspection Campaign include that inspections showed tankers frequently sailing when not complying with damage stability[ds_preview] requirements or had no means of assessing damage stability or were sailing in a loading condition not covered by the approved stability book.
This has been brought forward by recent developments within IMO, with a significant number of member states now looking at loading software as the best way to ensure and document compliance with the complex issue of tankers damage stability.
The issue
All tank vessels on international voyages must meet the International Maritime Organization’s (IMO) requirements for damage stability. These regulations are contained in the MARPOL Convention for general purpose tankers, the IBC and BCH Codes for bulk chemical carriers and the IGC for gas carriers. Unlike dry cargo ships, the damage survivability of tank vessels is highly dependent on the liquid cargo, cargo density and ballast loading.
A United Kingdom’s Maritime and Coast Guard Agency (MCA) survey made in 2005 and an IMO data gathering exercise conducted in 2009 consistently show that »approximately one third of tank ships regularly sail in conditions of loading significantly different from those in the approved stability information and either have no means to assess damage stability compliance or are not using or are ignoring such verification measures where these are provided.«
Commentary on compliance options
This issue was initially brought to the attention of the IMO-Maritime Safety Committee (MSC) by the UK delegation at its 81st session in May 2006, and since then Denmark, Finland, Germany, Norway, Sweden, UK, and Intertanko proposed corrective action, and this issue remains under active consideration by IMO.
It is generally understood that since nearly all tank vessels use computer programs to evaluate intact stability and longitudinal strength for any loading condition, there is no longer a practical incentive to remain constrained to the standard loading conditions to comply with damage stability regulations. This is particularly true for tankers that change their loading patterns often, such as product, chemical and parcel tankers. Modern double hull tankers’ stability is generally more vulnerable to damage as assumed by applicable regulations than older single hull tankers, and that the new regulations (including bottom raking damage) are generally more onerous than past damage stability regulations. For these reasons the use of approved loading computers which perform direct damage stability calculations is a practical solution to demonstrate compliance with the damage stability regulations for non-standard loading conditions.
Loading computer programs with this feature are referred to as »IACS Type 3 Loading Instruments« as specified in IACS URL 5 which defines Type 3 as »software calculating intact stability and damage stability by direct application of pre-programmed damage cases for each loading condition«.
In practice the application of an IACS Type 3 Loading Computer to demonstrate operational compliance with the IMO damage stability requirements is often the best option for tanker operators, since it allows at one time a high degree of flexibility in loading patterns while ensuring at all times that the ship be operated at the highest level of safety.
Current regulatory and approval status
The IMO Maritime Safety Committee further considered this issue at its MSC 83rd session in 2007, and tasked the SLF sub-committee to develop »Guidelines for verification of damage stability requirements for tankers and bulk carriers«.
The SLF sub-committee agreed to develop both design- and operational guidance. Design guidance would cover the approval procedure to be used at the time of construction. Operational guidance would cover information for the ship’s crew on the need to confirm compliance with damage stability. Proposals should be submitted to the next session of SLF taking place in January of 2011 with the aim to complete the item by 2012.
IACS has since developed the REC 110 »Guideline for Scope of Damage Stability Verification on new oil tankers, chemical tankers and gas carriers«. This recommendation applies for new oil tankers, chemical tankers and gas carriers contracted for construction on or after 1st January 2010. It provides detailed instructions on the scope of stability verification to be applied.
Regulatory improvements
The development of the IMO guidance should be a big step towards a more uniform implementation of the regulations by the administrations and their recognized organizations such as class. The complexities of the damage stability regulations and partial ambiguities have led to a wide variety of interpretations regarding scope and content, even amongst IACS members.
In case of software developed for the direct calculation of damage stability (IACS URL5 Type 3), the calculation of intermediate stages loading/damage cases where stability is not critical, can lead to excessive calculation times that are critical for the operation of the vessel. It should be defined when calculation of the intermediate stages need not be carried out; where stability of intermediate stages of flooding is not critical (i.e. all of the calculated stability parameters are met for the sample loading conditions in the approved stability booklet) calculations of the stability for intermediate stages can be omitted by the loading instrument.
For calculations according to Annex 1of the MARPOL Convention, the IBC and the IGC Code, the permeabilities assumed for spaces flooded as a result of damage are 0 to 95 %. The realistic permeabilities are usually around 98 % to 99 % leading to of discrepancies when performing these calculations.
Industry standard
Herbert Software Solutions, Inc. (HSSI) developed a module for their industry-standard loading program CargoMax. The CargoMax Direct Damage Stability (DDS) module is a product specifically designed to allow tanker operators to load non-standard cargos or non-standard configurations, and ensure the conditions operationally comply with the damage stability requirements as well as the intact stability and longitudinal strength requirements.
The DDS module allows the user to investigate compliance of any given loading condition, and can be used to demonstrate compliance during any Flag State, Port State, Classification, or independent chartering inspections.
While IMO continues its discussion of the issue, HSSI points out that its CargoMax DDS option is a mature and thoroughly tested feature which fully meets the requirements of IACS URL 5, Type 3, for any type of tank vessel, and that has been operating on dozens of ships since 1996 and has been approved by ABS, LR, DNV, and BV Class.
HSSI had the first ABS Class approved IACS Type 3 system and the first LR Class type approval for a IACS Type 3 System .
Additional CargoMax features
CargoMax is built on the HECSALV calculation engine and has state of the art damage and grounding calculation capabilities incorporated. During a vessel emergency your most valuable assets are time and confidence CargoMax 2.0 provides timely and accurate results when you need it most. Starting with the actual loading condition, it allows the user to quickly collect and process the available data, define the extreme bounds of the problem, and evaluate scenarios for remedial action. As HECSALV is the same software used by the emergency response groups of classification societies such as ABS and GL as well as internationally by Coast Guards and Navies, key data such as the last recorded loading case can be directly transferred to these emergency response units and utilized for their calculations.
The CargoMax Performance Optimization Tool now adds trim and draft optimization for enhanced fuel savings. Trim and draft optimization has for many years been known as a way to optimize the fuel efficiency of a vessel. The applied method is to conduct model tests in calm water covering relevant speeds and drafts for the operational profile of each vessel class.
Hendrik Bruhns
