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Friday, July 20, 2018

HYDROSTATIC BALANCE LOADING ON MARPOL TANKERS (SBT/PL)

IMO will decide next April when each of the single hull tankers should be phased out. Some tankers could possibly be required to be phased out at an early age, even below 15 years old.

IMO would thus consider means by which such tankers may continue to trade for a few extra years, provided they have a good structural condition. It was suggested at the last MEPC that MARPOL tankers (single hull tankers equipped with protectively located segregated ballast tanks – PL/SBT) should be requested to use hydrostatic balance loading (HBL) as a condition for further trading.

HBL in PL/SBT tankers can only apply if there is a hydrostatic loading condition in each of the cargo tanks. INTERTANKO commissioned Herbert Engineering Corp. to make an assessment on the use of HBL for PL/SBT tankers and the full report Evaluation of Outflow from MARPOL78 Tankers with Hydrostatic-Balance Loading is provided for information.

The Report concludes that:

  1. Use of HBL on ALL cargo tanks of SBT/PL tankers (assessment done for Aframax, Suezmax and VLCC) would improve the environmental performance of these tankers. They would be rated as the next best in performance after the double hull tankers.
  2. The cargo shut-out would be at least between 20 and 25%. This would be possible only if ballast water is added into SBTs in order to keep the ship' s draught at its maximum.
  3. It should be noted that, to bring the vessels to their load line draughts without trim, the ballast side tanks must be loaded to between 50% and 72% of their capacity. These filling levels fall within the critical sloshing zone for some tankers.  As many of the MARPOL (PL/SBT) tankers are built to minimum scantlings, it will be important to evaluate sloshing loads before attempting HBL on these vessels.

Since there are serious risks associated with this measure (see conclusion 3 above), INTERTANKO would not recommend the use of HBL on MARPOL (PL/SBT) tankers.

Click here to view full report Evaluation of Outflow from MARPOL78 Tankers with Hydrostatic-Balance Loading