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The method of measuring the quantity is called "sounding" of tanks. Let's sound what's

"sounding" of ship's tanks!

Sounding of Tanks

The process of quantifying the quantity of liquid present inside a tank iscalled "sounding". We all are aware ofstoring water in head/gravity tankin our house. Frequently we ensure the level of water is maintained bychecking the level in the tank. We fill up the water to the required leveland stop filling. We can also say that we sound the tank level. In thesame way, a ships fuel oil (bunker) tank or cargo oil tank has to bechecked for its increase/decrease of its level during the operation of theship/operations carried out on the ship. We will learn how does soundingwork in context of ship tanks in this article and the use of marinesounding equipment

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Why to "sound" the tanks?

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To be clearer let us take the case of bunker tanks. As we are aware,bunker tanks are used to carry the entire volume of fuel required for thesafe sea passage. When a ship sails from a port to other, the fuel isgetting consumed everyday and subsequent transfer which has to bedone from various fuel oil bunker tanks to ships settling & service tanks

for the use of propulsion. So, it is always necessary to take soundingof the bunker tanks to know the exact quantity of the fuel available onboard. Also during bunkering operation, the quantity of fuel oil pumpedon board is to be monitored continuously so that the bunker tank doesnot overflow. If it overflows, it may cause a marine pollution, and asper marpol, spillage ofoil into sea is prohibited.

Sounding of cargo tanks:

Ships such as oil tankers, product carriers and OBOs as they carryoil/liquid as cargo in their cargo tanks, sounding of those tanks shouldbe continuously monitored during loading/discharging operations. Astankers are loaded at a very high rate, the level in the tanks raise fasterand has to monitored so that the safe quantity of liquid cargo isaccommodated inside the cargo tank and changing over of next cargotank can be done with-out cargo oil overflow as it may cause marinepollution.

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sounding & ullage...

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With reference to the above pictorial illustration, "Sounding" is the measure of distance

from the bottom of tank upto cargo level in the tank. "ullage" is the distance from the top of

the level of cargo to the maximum level or top of the cargo tank. As sounding increases,the ullage decreases. as ullage increases, the sounding decreaes. It is usual practice on ships

to take ullage when cargo/fuel oil is highly viscous. If the cargo/ bunkered oil is viscous,and if "sounding" is taken, then the bob may get sticky and may contribute false readings.

So what is a sounding pipe?

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A ships tank must have a pipe extending from bottom of the tank to alevel which is safe to sound the contents of the tank. A sounding pipeis a simple steel pipe, which is open at the bottom so that the liquid inthe tank gets filled up to the same level as in the tank. As the level inthe tank rises, the liquid level in the sounding pipe also increases, thusupon taking sounding, the quantity of liquid can be known.

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Within the sounding pipe, a steel flexible measuring tape, with a bobattached at the end is lowered till it strikes the bottom of the tank. Whenit strikes the bottom of the tank, the level of liquid in the tank, makes animpression on the sounding tape so that if we coil up the tape, theimpression of content of the tank is seen and the readings are noted.The noted reading indicates the height of the liquid in the tank.Sounding table is available onboard which is calibrated inconsideration with the shape of the tank, and trim of the ship. Thevolume of liquid in the tank is calculated from the sounding table.

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Sounding of ships ballast tanks:

Ships ballast tanks contains sea water. It is difficult to trace the

impression of water on the steel tape when sounding the ballast watertanks. A water finding paste can be used to identify the impression ofthe level of water present in the tank.Method to take sounding of the ballast water tank:

1. Apply the water finding paste onto the sounding tape in the area of estimated depth.

2. Drop the sounding tape inside the sounding pipe.

3. Ensure the bob strikes the striker plate at the bottom of the tank.4. Coil up the tape looking up for the impression.

5. The level is seen as change in color of the paste. Presence of water will turn the

paste color to pink from light orange.

ther gauging methods:

Automatic/Remote sounding/gauging equipments:Certain cargos carried onboard are toxic and hazardous. Sounding of

tanks is dangerous. Automation & Instrumentation are used to measurethe level of liquid in the tanks.Those may be

1. mechanically operated float gauges2. electrically powered servo-operated gauges

3. electrical capacitance gauges

4. bubbler gauges

5. differential pressure gauges6. pneumatic/hydraulic gauges

7. sonic gauges

8. radio-active methods

Read more:

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