ABS-18-1999.pdf
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1、Copyright American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:11:09 MDTNo reproduction or networking permitted without license from IHS -,-,- o ” in smaller vessels, small differences in the consumables could have a significa
2、nt effect on the loading conditions and exchange sequence suitability. Flow through exchange In some specific casesflow through exchange may be more attractive than sequential exchange for double hull tankers. Using theflow through method eliminates the concerns of shallow forward and aft drafts, an
3、d extreme trims. While it may take somewhat longer to carry out, there is less total “attention time” than with the sequential method, especially when sets of tanks are simultaneously overflowed. 10 ABS Advisory Notes on Ballast Water Exchange Procedures Copyright American Bureau of Shipping Provide
4、d by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:11:09 MDTNo reproduction or networking permitted without license from IHS -,-,- STD-ABS 3B-ENGL 11999 m Ob53302 00252211 b59 m Double Hull Tankers Ship Type Volume capacity of ballast tanks (m3) Time to perfo
5、rm flow through exchange (hours) 40,900 DWT 12,900 32 Suezmax A Listed below are key findings arising from the ballast waterflow through exchange analysis of double hull tankers: 55.000 27 Applying theflow through method does not alter the stability, stress, and ship attitude. While it typically tak
6、es longer to carry out than sequential exchange, the process requires less “attention time” from the ships personnel. Suezmax (C) Double hull VLCCs, with cargo and ballast tanks arranged five long within the cargo block, have difficulty with sequential exchange. For these vessels, flow through is an
7、 attractive al temative. 74,400 46 Bulk Carriers VLCC Single Hull Three typical bulk carriers were investigated for sequential and flow through ballast exchange. These included a Handysize, Panamax, and Capesize. These ships are arranged with upper and lower hopper ballast tanks, and each design has
8、 one midships cargo hold fitted to carry ballast. 105.000 44 Listed below are key findings arising from the ballast water management analysis of bulk carriers. Sequences for the bulk carriers are quite complex, requiring many steps to maintain drafts and longitudinal strength within acceptable limit
9、s. Safe application of these sequences will require careful monitoring by the ships crew. Bending moments approach the 100% allowable value for each of the bulk carrier exchange sequences. These ships were not designed to have ballast tanks emptied during the course of the voyage and, therefore, car
10、eful planning is necessary to ensure that bending moments are maintained within acceptable levels. For all designs, it is difficult to exchange ballast in the cargo hold while maintaining compliance with forward draft, shear force and bending moment criteria. The cargo holds are generally not design
11、ed to withstand loads induced by resonant sloshing experienced during partial filling conditions. This precludes exchanging ballast in the holds during severe weather conditions. ABS Advisory Notes on Ballast Water Exchange Procedures 11 Copyright American Bureau of Shipping Provided by IHS under li
12、cense with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:11:09 MDTNo reproduction or networking permitted without license from IHS -,-,- STD=ABS 18-ENGL 1999 = Ob51102 0025222 595 Bulk Carriers Ship Type - Ballast condition Handysize - Light Ballast - Heavy Ballast Panamax -Normal
13、Ballast - Heavy Ballast Capesize - Light Ballast - Normal Ballast Sequential exchange Time to perform exchange sequence (hours) Additional time to ballast to original drafts (hours) 27 2 40 9 17 29 6 11 36 4 44 8 Bulk carriers are similar to tankers in that they are frequently in “ballast only” cond
14、itions. Normal and Heavy sequences were evaluated for each bulk carrier. Partial load conditions were not investigated. The total time involved in the ballast exchange process is as follows: Table 7 0 Sequences are relatively complex as draft forward, draft aft, and bending moments frequently approa
15、ch the limiting values. For the vessels investigated the sequences require between 12 and 19 independent steps, and up to 65 ballast movements. 0 It is difficult to concurrently maintain adequate propeller immersion and forward draft, 0 Capesize vessels generally have large double bottom ballast tan
16、ks extending two holds in length. It may not be possible to exchange some ballast tanks when the cargo hold is filled with ballast water, as excessive shear forces are encountered. In situations where the hold is emptied, the drafts are greatly reduced to near those in the light ballast condition. S
17、hear force values for all of the Heavy ballast condition sequences that were studied are close to allowables. 0 The Panamax vessel is fitted with overboard valves in the upper hopper ballast tanks. This allows quick gravity discharge of the ballast, significantly reducing the sequence time and provi
18、ding more flexibility in how the pumps are used. Flow through exchange The flow through method eliminates concerns of exceeding shear force and bending moment limits. Flow through exchange is an attractive alternative to the sequential exchange for the Capesize heavy ballast condition; it eliminates
19、 the light draft problem associated with sequential exchange. 12 ABS Advisory Notes on Ballast Water Exchange Procedures Copyright American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:11:09 MDTNo reproduction or networking per
20、mitted without license from IHS -,-,- STD-ABS LB-ENGL 1999 Ob5LL02 0025223 421 ship TYP Handy size Panamax Capesize The total time involved in the ballast exchange process, when performing operations in pairs of tanks, is as follows: Table 8 I Bulk Carriers I Volume capacity of I Time to perform flo
21、w ballast tanks (m? through exchange (hours) 17,200 46 32,300 50 69,700 45 Example of a sequential exchange procedure for a Handymax bulk carrier To illustrate the complexity of a sequential procedure the following is presented as an illustration of a procedure that was developed for a Handymax bulk
22、 carrier. This is a 28,000 DWT bulk carrier with 5 cargo holds and 5 P 5 - O - 5 5 1 (A - m IC 4- $ Sample Handymax bulk carrier ballast exchange sequence d 9 0 I O N S Mi Z ON dMnZON S90EON d9EON SMnEON dMnEON s a a t o N d9PON SMnPON dMnPON SaaSON O 4 4 f O O O O r 8 4 4 z r O O O O O r O 4 4 4 4
23、4 O O O O O O r a z r O 8 O z 4 o O O z O O z O O r O 4 O O r O 4 o 8 O r O O r O 4 4 4 8 4 o 4 o O O r O O O O O O r O O r O 4 4 4 O O O 4 4 4 4 O O O O O 8 r 5 O 4 o 4 4 O O O O O O O r O z o o 8 4 0 O O r O O O 4 o 4 4 O O O f O O - O 4 o 4 4 O O O O 4 8 O o z 4 4 0 O O O O O 4 O O r O 0 4 O o O
24、O 4 o 4 4 O O O O O O o 4 4 4 4 O O O O ABS Advisory Notes on Ballast Water Exchange Procedures 15 Copyright American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:11:09 MDTNo reproduction or networking permitted without license
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- ABS 18 1999
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