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Measuring Cargo

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41 views25 pages

Measuring Cargo

Important

Uploaded by

romanpolyakov23047
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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MEASURING CARGO Our vessel has reached her destination and the cargo of crude oil should be discharged. The ship carries a huge volume of cargo in her seven (7) Cargo Tanks and two(2) Sloptanks The volume and the weight of the cargo will be calculated tank by tank. The volumes of each tank of the vessel is computed by the shipyard and published in the so called Ullage Table. The measurement used, the ULLAGE, is the distance between the surface of the il to the measuring point at deck. If you know the Ullage you can use the Ullage Table to find the volume of the cargo in any of the ship's tanks POINT OF MEASUREMENT ULLAGE Ol LeveL OIL LEVEL Our vessel is equipped with a sophisticated system for measuring the cargo in the tanks. Each cargo tank has a SAAB Level Transmitter witch measures the Ullage very accurately The Transmitters are positioned close to the centre of the tanks. Radar signals are sent down in the tank and reflects on the surface of the oil. The returning signals are picked up by the receiver and the distance to the surface is computed. The resulting ULLAGE is shown digitally in the Cargo Control Room. But before discharge the Ullages are also checked manually. There are Measuring Points close to the centre of the tanks. Usually we call them Ullage Plugs. There is a globe type Vapour Control Valve fitted to each of these Measuring Points. Using a special Electronic Ullage Tape - a so called MMC - you can measure the level of the cargo without opening the tanks to the atmosphere. Here you are taking the Ullage in CT4. The cap to the Vapour Control Valve at the Port Ullage Plug is taken off. The pipe of the MMC which protects the Sensitive Sond connected to the measuring tape, is inserted and fixed and screwed on to the valve. The Vapour Control Valve is opened and the Sensitive Sond can be lowered into the tank. When the sensitive Sond of the MMC reaches the surface of the oil this is indicated by a steady signal and the Ullage is read from the instrument. The measurement now red at the tape is 206 cm. In this case the vessel has no list and is on an even keel. You should use the Tables giving volumes in Cargo Tanks at every 5th om at an Even Keel You need to do an interpolation here to find the volume of 206 cm The difference between the volumes is 33.75 m’. Every cm gives a difference of 6.75 m*. As our company standard is to calculate Ullage using nearest half(1/2) centimetre you can also note that every 1/2 cm is worth 3.4 m°. 206 cm Ullage means less volume then 205 cm. Deduct the difference of 1 cm and you get 15749.0 m° CARGO INK NO. 1,2 3,4, EVEN KEEL. 00M WEIGHT M.TONS: UESSEL: NO. ORRH ULLAGE TABLES TRIM By THE STERN -2.00M = -2.50M -2.00M -1,50M -1.00M -0.50M ULLAGE] VOLUME VOLUME UOLUME VOLUME UOLUME UOLUME METRE | CUMTR CU.MTR CU.MTR CU.MTR —CU.MTR —CU.MIR 15789.50 15755.75| 15755.75 15722.00| 1572.00 15688.25 | 15688.25 15664.50 | 15664.50 15620.76 | 15620.76 15587.02| 1557.02 1553.26 | 15553.26 15519.52|15519.52 15485.76 |15485.26 15740.19 |15748.41 | 15756.62 |15764.85 |15773.05 15663.60 15671.80 15638.94 15655.3? 15680.03 15605.20 15571.45 15557.70 15647.16 15629.85 |15638.06 |15646.28 15613.41|15621.62 15604.33 1561254 15579.67 |15587.88 |15596.11 15562.35 |15570.58 /15578.79 15545.92 15954.15 1503.95 |15512.17| 15520.38 |15528.61 |15536.83 |15545.05 15478.42 |15486.64 |15494.86 |15503.07 |15511.30 15452.89 19470.20 15461.11 /15469.33 15477.55 15444.67 15436.45 OK, we are overdoing this a bit, but we like to show that If Ullages — as in our case - are taken off centre it will make a big difference if the ship has a trim or alist. That is why you should try to load the ship in such @ way that she is on even keel and with no list when Ullages are taken Let’ s see what happens if your ship instead had an aft trim of 1.0 m and on top of that a Port Heel of 0.7 meter - with the same Ullage as before, 206 cm. Consulting the Ullage Tables you find a separate Correction Table for List To find correction for 0.7 m. you have to interpolate. The correction is 0.16 m and the correct Ullage is 2.22 m. Next use the Ullage Table with the Corrections for Trim Also here you have to interpolate as you must find a value between 2.20 and 2.25 m. 2m means a correction of 13.49 m*. 2.22 m Ullage gives a volume of 15 624.57 m? Quite a difference in volume. — Be careful with trim and list! ULLAGE CORRECTION FOR LIST NO. LIST py | ay [0.5m [1.0m COMPARTMENT PORT| STB. CARGO TANK NO.1-CTR CARGO TANK NO.2,3,4,5,6 &7CTR CARGO TANK NO.8- CTR CARGO SIDE TANK NO.1 CARGO SIDE TANK NO.3 CARGO SIDE TANK NO.5 s CARGO SIDE TANK NO.7 HE P 226 1h 0.5m 113 +45 113 158. mm------- 07m or 0.158m —» 0.16m 2.06 +0.16 2.22 Ullage ULLAGE TABLES TRIM -2.50M BY -2.00M THE ~1.50M STERN -1.00M -0.50M 2.00M ULLAGE METRE} CU.MTR CU.MTR CU.MTR —CU.MTA 15740.19 |15748.41 | 15256.62 |15764.85 15 706.44 |15714.66 | 15722.87 /15731.10 | | 2.10 |15672.69 |15680.19/ 15689.12 |15697.55 2.15 |15658.94 /15647.16/ 15655.37 |15663.60 15537.70 |15545.92/15554.13 15503.95 2.40 (15470.20 2.45 [i436 45 2.22 Ullage----------<{5624.57> 2.20 = 15638.06 2.20 =15638.06 2.25 15604.33 +0.02 = -13.49 33.73 2.22 = 15624.57 6.746 x 2 = 13.492 or 13.49 CARGO TNK NO. 1,2 3, EUEN KEEL 0.0M VOLUME VOLUME VOLUME VOLUME voLpME woLUME | UOLUME WEIGHT cuspTa cu.mta_| Cu.MIR 05 /15781.27|15789.50/15789.50 | 1979.30 |15747.53 19755.75 | 1575.75 0.0M M.TONS 152qB.55 |15715.78| 15722.00/ 15722.00 156. ,80 1560.03 15680.25 |15698.25 15638.06 |15646.28| 15664.50 | 15664.50 1604.33 |15612.54) 15620.76 |15620.76 19962.35 |15570.58 |15978.79 | 15587.02 | 15587.02 15512.17|15520.38 |15528.61 |15556.83 |15545.05 | 15553.26 |15553.26 15478.42 | 15486.64 |15494.86 |15503.02 |15511.30 | 15519.52|15519.52 15444.67|15452.89 115461.11 |15469.33 |15477.55 | 15485.76 | 15485.76 The ship carries a huge volume of oil in her tanks. The volume of oil in the tanks differs with the temperature. The volume increases with higher temperature To be able to calculate the weight of the cargo it's very important to find the correct temperature of the oil A difference of just one degree temperature, either in Fahrenheit or Centigrades, is a lot of volume. In our ship it’s about 400 Bbls but the difference in areal big tanker, an ULCC, can amount to 1000 Bbls — and that's a lot of money. When you calculate cargoes you always have to find the volume either at a Standard temperature of 60°F or at 15°C to be able to find the weight of the oil If you have a volume measured at 85 «F you must reduce this volume to a Net Volume at 60

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