8.5 If a loading computer or programme is in use, is it class approved?
If a class approved loading computer is not available, record in Comments, how stress and stability calculations are performed.
Notes: Ships of more than 65 metres in length are required by Class to be provided with a loading manual including permissible limits of still water bending moment and shear force; the results of the calculations of still water bending moments; shear forces and where applicable, limitations due to torsional and lateral loads and the allowable local loading for the structure (decks, double bottom, etc.)
Ships of more than 100 metres in length are required by Class to be provided with an approved loading instrument. An operational manual is always to be provided for the loading instrument
The loading instrument should be capable of calculating shear forces and bending moments in any load or ballast condition at specified readout points and should indicate the permissible values. Ships with very limited possibilities for variations in the distribution of cargo and ballast and ships with a regular or fixed trading pattern may be exempt from the requirement.
Class approvals for loading instruments are made under a Type Approvals process. Type-approval certificates are generally valid for periods of not more than five years. MSC Circular 1221 notes that the validity of the Type Approval Certificate itself has no influence on the operational validity of a product accepted and installed on-board ship and that a product manufactured during the period of validity of the relevant Type Approval Certificate need not be renewed or replaced due to the expiry of such Type Approval Certificate.
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8.6 Are there records indicating that the operational accuracy of the load computer is tested regularly?
Notes: At each Annual and Special Survey, the loading instrument is to be checked for accuracy and the approved loading guidance information confirmed as being available on board. Class approved data should be used and the tests should be carried out in the presence of the attending surveyor at the annual survey. Regular on-board testing should also take place and records attesting to this should be maintained. The test should involve physically entering the data for each tank into the computer and verifying the result. It is not acceptable to simply retrieve a stored test condition from the computer and compare this against the official conditions.
8.7 Is the stress and stability information included with the cargo plan and are any limitations understood by the cargo watch officers?
Notes: Inspectors should determine that prior to transfer of cargo, calculations have been made for stress and stability conditions for the start, interim and completion of transfer conditions. Regular monitoring of stress and stability should be taking place throughout cargo transfer to ensure that the conditions have been maintained within design limits.
8.8 Is the vessel free of inherent intact stability problems?
Notes: Vessels that have large width tanks will be subject to reductions of intact stability due to free surface. Although such vessels may meet IMO intact stability criteria when in fully loaded or ballasted conditions, they may be unstable when multiple tanks are slack during cargo or ballast transfer operations, or in intermediate states of loading. Trim and stability manuals generally deal only with arrival and departure conditions and operators are not made aware that stability problems may exist at intermediate stages during cargo transfers.
If a vessel has either large width cargo tanks, “U” section ballast tanks, or double bottom tanks without watertight centreline bulkheads, inspectors should ascertain that the vessel meets IMO intact stability criteria by requesting the chief officer to demonstrate, using the class approved loading instrument, the intact stability at the worst case condition. (i.e. All tanks slack and maximum free surface)
If no suitable loading instrument is provided and adequate instructions are not available, the question should be answered ‘No’, unless there is satisfactory proof that the vessel is free of inherent stability problems. Inspectors should ascertain whether all officers appear familiar with operational restrictions and that instructions are prominently posted describing action to take if stability concerns are suspected or experienced. Record a "N" response and appropriate Observation if weaknesses or other concerns are revealed.
If specific procedures have been adopted to address potential stability problems, these should be recorded as an Observation.
8.9 Are Damage Stability Verification Guidelines available and can the Master demonstrate that the vessel is normally loaded in accordance with the Stability Information Booklet (SIB)?
Every oil tanker delivered after 31 December 1979, as defined in regulation 1.28.2,of 150 gross tonnage and above , shall comply with the subdivision and damage stability criteria as specified in paragraph 3 of this regulation, after the assumed side or bottom damage as specified in paragraph 2 of this regulation, for any operating draft reflecting actual partial or full load conditions consistent with trim and strength of the ship as well as relative densities of the cargo.” (MARPOL Annex I Reg 28(1))
Every oil tanker of 5,000 tonnes deadweight or more shall have prompt access to computerised shore- based damage stability and residual structural strength calculation programs. (MARPOL Annex I Reg 37.4) Note: The vessel should have an approved stability information book (SIB), written in a language
understood by the officers on board, and the SIB should cover damage conditions that include:
any required and intended loading conditions (including the ones corresponding to multiple freeboards when so assigned to the vessel), i.e. symmetrical/unsymmetrical, homogeneous/alternating or ballast/partial/full
types (e.g. oil) of liquid cargo allowed including range of densities The vessel may have class approved on-board stability computer programme that includes damage conditions for all loading conditions presented in the SIB except for ballast, light ship and docking conditions . The methods of verifying the damage stability conditions may include pre-programmed damage cases for each loading condition, including capability for calculation of intermediate damage stages with variation of draft due to
varying cargo density
tank loading patterns
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to ensure that for any possible (alternate) loading condition the most onerous damages have been examined according to relevant stability criteria and these may be recorded in ‘comments'.
A sailing condition is deemed to be approved if the filling of each cargo and ballast tank lies within 1% of the weight in the approved condition and GMF lies within 2 cm of the approved condition GMF.
Record an observation if the vessel has ever been loaded to a condition not in accordance with the SIB. However, if the vessel was loaded to a condition according to any of the damage conditions as per the class approved on board stability computer programme and not in accordance with SIB; additional comments need to be inserted with details
8.10 Is the Master aware of the worst damage stability condition in the stability book?
8.11 Do the operator’s operating manuals include procedures for restoring stability in case of unstable conditions developing during cargo operations, where applicable?
Note: The procedures listed in the Operating Manual must be identical to those posted and practiced (Q8.8 above, refers). If not, record a "N" response and appropriate Observation.
8.12 Where applicable, are officers aware of the dangers of free surface effects and of the possibility of structural damage caused by sloshing in cargo tanks?
8.13 Are cargo and/or ballast tanks free of sloshing or other restrictions?
Important restrictions other than maximum permitted cargo density should be recorded in Comments.