Cargo Calculations

Cargo Calculations

In the voyage estimation process, cargo calculations help one determine revenue that a vessel can earn for a voyage.

To determine the amount of cargo that a vessel can carry, one must know the following:

• The deadweight of the vessel (Deadweight All Told, DWAT) and Deadweight Cargo Capacity, DWCC) 
• The load line zone that she will be operating in
• The stowage factor of the cargo
• The amount of bunkers and fresh water required for the voyage

The deadweight of the vessel is the carrying capacity of a vessel, DWAT is the total carrying capacity of the vessel by weight, while DWCC is the earning capacity of the vessel or the cargo carrying capacity of the vessel by weight.
The amount of cargo that the vessel can carry could be based on weight for cargoes that have a small stowage factor (space occupied by one tonne of cargo in cubic meters), or by volume for cargoes that have a large stowage factors.
For freight calculations by weight, one must know the loadline zone the vessel will be trading in as the trading zone determines the amount of cargo that she can load. There are 3 main loadline zones in the world, as follows:

• The Tropical zone (where the vessel can load a maximum amount of cargo by weight).
• The Summer zone. 
• The Winter zone (where the vessel loads the least amount of cargo by weight). There is also a Winter North Atlantic zone, but this is only applicable to vessels less than 100 meters in length, plying in areas north of the arctic circle (66^oN).

A good estimator will maximize the amount of cargo a vessel can load, by taking the following factors into account:

• The fuel consumption during the voyage for freight calculations by weight (this helps one estimate how much fuel the vessel is required to have on board, with the required safety margin)
• If the vessel is to go, for e.g., from the summer zone to the winter zone, then how much extra cargo can be taken to submerge her winter marks so that when the vessel arrives in the winter zone, her winter loadline is not submerged? (One must note that the vessel will lighten by the amount of fuel consumed for a passage from the departure summer zone port to arrival at the summer/winter zone boundary)
• If cheaper fuel is available en-route, a good estimator will allow for the vessel to sail with just enough fuel with a margin of safety to arrive at the bunkering port (place where the vessel loads fuel) to stem bunkers as required
• For cargoes with high stowage factors the estimator must estimate the maximum amount of cargo that the vessel can carry by volume, as with these cargoes the vessel’s cubic capacity will be fully taken up without her being loaded down to her loadline mark, i.e. she is full in relation to space available for the carriage of cargo, but not in relation to her DWCC
• The estimator must accurately estimate the amount of fresh water, fuel, provisions and other weights on board that must be subtracted from DWAT to obtain DWCC

From revenue earned by way of freight for cargo carried, one must deduct the Expenses of the vessel to determine the vessel’s net income for the voyage

.

1. A bulk Carrier (Summer DWT 88,500, Winter DWT 87,750, Tropical DWT 89,250) daily consumption F.O. 45t and FW 14t. She is chartered for voyage from Odessa to Sakal taking fuel oil and FW at Aden (minimum quantity) and at Singapore (FW required quantity and maximum fuel oil possible). She is also rquired to load 9 containers at Singapore, each weighing 28 tons for Hong Kong.

Odessa to Port Said	4 days
Suez to Aden	6 days
Aden to Marmugoa	5 days
Marmugoa to Singapore	9 days – 3 days in Summer adn the rest Tropical
Singpore to Hong Kong	8 days – 1 days in Tropical 2 days in Seasonal Tropical in winter months and the rest in summer zone.
Hong Kong to Sakai	3 days – 1 day in Summer and rest Winter.

ROB at Odessa FO 848t FW 293 t and stores 180 t. Estimated consumption for Suez Canal Transit FO 50 t and FW 40 t. Ignore all port consumptions. Allow 2 days fuel and FW reserves at all times at sea. Find the amount of cargo to load at Marmugoa and FO FW to be taken on board at Aden and Singapore.

Ans. Cargo 87,334 Tons Aden 372/111 Singapore 495/154

ODESSA TO SAKAI

DAILY CONSUMPTION HO-45.0 FW 14.0

TWO DAYS RESERVE HO-90.0 FW 28.0

		F.O.	F.W.	CONST.	CARGO
Odessa	Dep	848	293	180
	Con	180	56
Port Said	Arr	668	237
	Con	50	40	For transit
	Dep	618	197
	Con	270	84
Aden	Arr	348	113
	Rod	372	111
	Dep	720	224
	Con	225	70
Marmugoa	Arr	495	154	180	87, 334
	Dep	495	154
	Con	405	126
Singapore	Arr	90	28
	Rod	495	154		252
	Dep	585	182	180
	Con	360	112
Hong Kong	Arr	225	70		-252
	Dep	225	70
	Con	135	42
Sakal	Arr	90	28	180
Dep. Hong Kong		225	70	180
Ond day consumption		45	14
Arr. Winter Zone		180	56	180	87,334
Cargo Loadable     87,334

2. A vessel has summer deadweight of 24,562 MT (Summer Draft 10,56 M TPC 25 MT) Her daily consumption of fuel oil is 25 MT and fresh water 11 MT. She is loading at Campana Bay, Chile for Le Havre, France. As per the company’s instructions, the vessel is to maintain 2 days of reserve of fuel oil and 4 days of reserve of fresh water at all times at sea. Prior departure Campana Bay, the vessel haad fuel oil 415 MT and fresh water 190 MT. The vessel will bunker enroute at Panama.

Calculate the maximum amount of cargo to load at Campana Bay and the fuel oil, fresh water to be taken at Panama to complete the voyage if, 

a) Campana Bay to Panama – Tropical Zone – 9 days

b) Panama to Seasonal Tropical Area – Tropical – 3 days

c) Seasonal Tropical Area to Seasonal Winter Zone – Summer – 8 days

d) Seasonal Winter Zone to Le Havre – Winter – 9 days.

Ans. 23,594 tons. Panama 360/173

CAMPANA BAY TO LE HAVRE

DAILY CONSUMPTION F.O. 25.0 FW 11.0

SUMMER	24,562 T
WINTER	24,012 T
TROPICAL	25,112 T
		F.O	F.W
CAMPANA	DEP.	415	190
9 DAYS	CON.	225	99
PANAMA	ARR.	190	91
	RCD.	360	173
20 DAYS	DEP.	550	264
	CON.	500	220
LE HAVRE	ARR.	50	44
			HO	FW
DEP. PANAMA		ROB	550	264
CONSUMPTION 11 DAYS			275	121
ROB ARRIVAL WINTER ZONE			275	143

Cargo Loadable 23,594 Tons

3. A vessel Summer deadweight 15,300 t, tropical dwt. 15,800 t, winter dwt 14,800 t is to load in Yokohama for Boston, calling at Singapore, Colombo and Aden. The ship is to load 4,500 t of cargo at Singapore and 850 t of cargo at Colombo. Oil fuel initially on board at Yokohama 372 t, daily consumption 48 t. Fresh water initially on board 120 t daily consumption 18 t. There are to be 3 days reserve of oil fuel and fresh water at all times. Oil fuel and FW to be taken at Yokohama, Singapore, Colombo and Aden as required.

Yokohama to Singapore, summer zone, 10 days

Singapore to Colombo, tropical zone, 5 days

Colombo to Aden, tropical zone, 6 days.

Aden to Port Said, tropical zone, 5 days.

Port Said to Boston, first 4 days summer, than 10 days winter.

Calculate the maximum amount of cargo to load at Yokohama, and also the oil fuel and fresh water to take at the various ports.

Ans. Cargo 8,592 tons, Yokohama 252/114, Singapore 240/90, Colombo 288/108, Aden 912/342

YOKOHAMA TO BOSTON

DAILY CONSUMPTION : HO 48.0 FW 18.0

Port		HO	FW	CARGO
Yokohama	Arrival	372	120
	Received	252	114	*
10 days	Departure	624	234
	Consumpt	480	180
Singapore	Arrival	144	54
	Received	240	90	* 4,500
5 days	Departure	384	144
	Consumpt	240	90
Colombo	Arrival	144	64
	Received	288	108	* 850
6 days	Departure	432	162
	Consumpt	288	108
Aden	Arrival	144	54
	Received	912	342	*
19 days	Departure	1,056	396
	Consumpt	912	342
Boston	Arrival	144	54

                                                            ROB @ Winter ZONE 9 days after departure ADE 

                                                            Consumption HO 432 FW 162

                                                            ROB                     HO 624 FW 234 Cargo 5,

                                                            CARGO LOADABLE 8,592 TONS

4. A ship, summer DWT 92546 t on 13,44 m draft adn TPC 46 is loading at Dalian (China) for Europort, bunkering at Singapore and Capetown, ROBs at DAlian FO/620 t (daily consumption 42 t at sea), FW/210 t (daily consumption 12 t) & stores 82 t. constant 524 Five days reserve of fuel and fresh water are to be maintained at all times at sea. (Ignore port consumption).

1500 t of cargo is to be loaded at Colombo.

Passages/Zones are estimated to be:

Dalian to Singapore (8 days)       : Summer 3 days, rest in Tropical.

Singapore to Colombo (6 days)   : Tropical

Colombo to Capetown (17 days)  : 3 days Tropical, than 10 days in Seasonal 

                        Tropical area – Summer & the rest in Seasonal

                        Tropical area – Tropical.

Capetwon to Europort (16 days)   :      2.5 days Tropical, then 3 days Summer, than 

                        4.5 days in Seasonal Winter Zone in Winter & the rest in Winter Zone

Find the maximum cargo that can be loaded at Dalian, and what additional quantity of cargo, if any, can be lifted from Capetwon if just the required amount of bunkers were to be taken at Singapore and Capetwon.

Ans. Cargo 88,315 tons, Singapore 892/222, Cape Town 672/192 

DALLAN TO EUROPORT

DAILY CONSUMTPION N.O. 42.0 FW. 12.0

SUMMER	92,646 T
WINTER	91,258 T
TROPICAL	93,834 T
		F.O	F.W	STORES	CARGO
DALLAN	DEP	620	210	606
	CON	336	96	606
SINGAPORE	ARR	284	114	606
	RCD	892	222	606
	DEP
	CON
COLOMBO	ARR
	RCD			606	1500
	DEP
	CON	966	276	606
CAPE TOWN	ARR	210	60	606
	RCD	672	192	606
	DEP	882	262	606
	CON	672	192	606
EUROPORT	ARR	210	60	606
CAPE TOWN	DEP	882	262	606	1500
5.5 DAYS	CON	231	66
WINTER ZONE	ARR	651	186	606	1500

CARGO LOADABLE 88315 TONS

6. A large OBO of SDWT 145,482 t on a draft of 15.36 m has TPC of 203. Her daily consumption at sea is FO/88 t and FW/26 t. Port consumption is FO/10 t & FW/38 t. She is chartered to load Indian iron ore from Mangalore for Tsingtao (China) calling at Singapore (for taking the required quantity of fuel oil and fresh water) & Yokohama (for taking sufficient FO/FW to reach Vancouver).

ROBs are estimated to be FO/1513 t, FW/408 t & stores etc. /856 t on departure Mangalore.

Mangalore to Singapore (loaded): 7 days – first day in Summer, then 1 day in Seasonal Tropical zone & the remaining in Tropical.

Singapore to Tsingtao (loaded): 14 days – first 3 days in Tropical Zone then 2 days each in Seasonal Tropical (summer) and Seasonal Tropical (Winter), Thereafter 4 days in Summer zone & the rest in Winter zone.

Tsingtao to Yokohama (in ballast): 4 days – Winter first, then Summer & then the Winter zone again.

Yokohama to Vancouver (in ballast): 15 days by Great Circle track (Winter zone throughout) OR 16 days by the Rumbling rack (Summer zone throughout).

Port stays/reserves: Half a day at Singapore 3 days at Tsingtao & 1 day at Yokohama.

Charters require two days reserve of FO/FW to be maintained between Mangalore/Yokohama & four days reserves of FO/FW to be onboard from Yokohama onwards.

Calculate what Maximum Cargo you can lift from Mangalore & what Quantity of fuel oil/fresh water would you order for Singapore and/or Yokohama.

Ans. Cargo 1,36,912 tons, Singapore 908/465 Yokohama 1,584/468 R.L. G.C. 1,496/442

Mangalore to Vancouver

7. A VLCC is delivered to Charterers at Hong Kong for a single voyage with FO/1853 t & FW/254 t being ROBs. She is to load a full cargo of crude oil from Dumai (Indonesia) for discharging 120,000 t at Sydney (Australia) & the rest at Auckland (New Zealand). Singapore is the bunkering port for FO. Required quantity of FW can be picked up from any port. On completion of discharge the vessel would be delivered back to Owners with the minimum reserves of FO & FW.

Her summer DWT is 3021,258 t (TPC 206, draft 20.16 m). Daily at sea she consumes FO/82 t 7 FW/nil (self-sufficient on generated water). In port she consumes FO/7 t 7 FW/18 t everyday.

Hong Kong to Dumai : 9.5 days

Dumal to Singapore : 2.5 days – Tropical

Singapore to Sydney : 12 days – 1 day in Tropical, then 3 days in seasonal 

Tropical in winter months, rest in Summer.

Sydney to Auckland : 5 days – 1 day in Summer, then 2 days in seasonal Winer in winter months, rest in Winter

Expected port stays are : 2 days in Dumai, 1 day each at Singapore & Sydney and 3 days at Auckland, Additionally she requires FO/45 t at Sydney and FO/74 t for discharge & COW at Auckland.

She must retain 850 t of ballast on board upto Singapore only, for even keel passage through Malacca Straits. 2 days FO & 200 t FW is to be maintained as reserve on board at all times at sea as well as in port.

The Charterers require you to advise them the maximum cargo tonnage that you can lift from Dumai, as well as the FO & FW requirements based on the above information.

Ans. 2,99,417, Singapore 857/18, Sydney FW/54

Hong Kong to Aukland

			Sea FO	FW	PORT FO	FW
S.DWT	301, 258	Daily Con	82	Nil	7	18
Winter DWT	293,606	2 days Res	164	200
			FO	FW	Ballast
Hong Kong	Dep		1853	254
9.5 days			779
Dumai	Arr		1074	254	850
Port Stay 2 days			14	36	850
	Dep		1060	218	850
2.5 days			205		850
Singapore	Arr		855	218	850
Port Stay 1 day			7	18
	Rod		857	Nil
	Dep		1705	200
12 days			984
Sydney	Arr		721	200
Port Stay 1 day			7	18
	Cow		45
	Received			72
	Dep		669	254
5 days			410
Aukland	Arr		259	254
Port Stay 3 days			21	54
	Cow		74
Redelivered			164	200
Dep Singapore			1705	200
1 day to Summer			82
Arr. Summer			1623	200	299,435

10. A tanker summer displacement 18,480 t, light displacement 6350 t, summer draft 9.60m TPC 26, FWA 18cms, loads at Baton Rouge for Boston. Distance to reach the open sea 240n.miles. River speed 12k, sea speed 14k, oil fuel consumption per day 12k 24t, at 14k 40t. Fresh water consumption whilst underway 12t per day. Pilot trimming water on board leaving Baton Rouge 85t.

The vessel loads in dock water RD 1.005 distance from Baton Rouge to Boston 2088 miles. On reaching the open sea the vessel steams for 2.5 days in summer zone before entering winter seasonal zone in winter.

Calculate the maximum amount of cargo to load assuming there is sufficient oil fuel on board to take the vessel to Boston and return to Baton Rouge with 2.5 days reserve at all times.

There is sufficient F.W. to reach Boston with 10t in reserve. Find also the draft on sailing from Baton Rough.

Ans. 11,104 Draft 9.636

	FO	FW	Ballast	Cargo	DWT
Dep B/R	580	86	85	11,104	11,855 240 miles @ 12K Consumption F24T/FW 12
Con	20	10	85
Arr BW	560	76	0	11,104	S.DWT                              12,130
2.5	100	30			520
Arr. Winter	460	46	0	11,104	11,610 Winter DWT      11610
	120	36	0
Arr. Boston	340	10	0	11,104
Con	220				Total Sea Passage 2088-240 =1848
Arr B/W	120				1848 Miles @ 14K = 5.5 Days
	20	WD	9.40	9.6
ROB B/R	100	DW All	0.144
			9.544
			0.0942
SAILING DRAFT			9.6382	@1.005

11. A vessel of Summer DWT 93542 t at summer draft of 14.40 TPC 42, stores and constant 380 t is loaded to her summer DWT at Le Have with 340 t of ballast on board and with FO 740 t and FW 350 t as ROB. She is to load 380 t of cargo from Gibralter and 780 t from Las Palmas. He route is estimated as follows:

Le Havre to Gibralter 2 days- Summer Zone

Gibralter to Casablance 0.5 days – Tropical Zone

Casablanca to Las Palmas 2 days – Tropical Zone

Las Palmas to Abidjan 1 day in Tropical then 2 days in Seasonal Tropical (S) then 5 days in Seasonal Tropical (W)

Abidjan to Cape Town 11 days – 1 day in Summer Zone, 6 days in Seasonal Tropical (W) and rest in Winter Zone

Cape Town to Durban 2 days – Winter Zone

She has to discharge 1500 t cargo at Casablance, 1000 t each at Abidjan and Cape Town, Required quantity of FO and FW is to be replanished at Las Palmas maintaining three days reserve of FO and FW at all times at sea. Daily consumption FO 341 and FW 18t.

Find how much additional cargo can she lift from Las Palmas if the ballast was pumped out at sea one day prior arrival Gibralter. (Ignore all port consumption)

Ans. FO 229 FW 163 Cargo 676

		SDWT	93,542	SD	14.4	TPC	42
		Daily CC 3 days Res	FO	34 102	FW	18 54
		HO	FW	Ballast	Const	Cargo	Cargo	DWT
Le Havre	Dep	740	350	340	380		91,732	93,542
	2 days	68	36
Gib.	Arr	672	314
	Rcd.					+380
	Dep	672	314
0.5 days	Con.	17	9
C’blanca	Arr.	655	305
	Disch					-1500
	Dep
2 days	Con.	68	36
L. Palmas	Arr.	587	269
	Rcd.	229	163			+780
	Dep	816	432	-340	380		91,392	93,020
8 days	Con.	272	144
Abidjan	Arr.	544	288
	Disch					-1000
	Dep	544	288				90,392
11 days	Con.	374	198
Cape Town	Arr	170
	Disch					-1000
	Dep	170	90
2 days	Con.	68	36
Durban	Arr	102	54
Dep. Las Palmas                        DWT                         93,020 Summer DWT                                                           93,542 Additional Cargo Loadable Las Palmas                             522 Plus Tropical to Summer 3 days Con.                              156 Additional Cargo Loadable Las Pal                                   678

Last 6 days are in Winter Zone by which time vessel will be well below here Winter Marks since she is to discharge 1,000 tones at Abidjan and bunkers consumed for 15 days Las Pimas to Winter Zone.