Magnetic compass

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Image
The magnetic compass is fitted on the upper bridge exactly center line of the ship   It is referred to as standard compass     1. D ry C ard    2. W et C ard   A compass point north because all magnets have two poles north pole, south pole.   The north pole of the one magnet attracted towards the south pole of another magnet     DRY CARD COMPASS   A light aluminum ring about 254mm in diameter is attached to a brass hub by silk cord which is threaded in and out through holes in the ring.   This tight silk cord is act like bicycle wheels.   There is no other connection or support between the ring and the hub.   Silk cord is used because it doesn’t shrink or stretch due to moisture or change in atmospheric temperature.     Card support: -     The bottom of the hub has small cap fi tt ed with a sapphire bearing surface.   This rests on a pivot tipped with iridium which is hard nonmagnetic metal....
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sounding pipe

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Sounding pipe


On board ships large numbers of tanks are present. It is very important to measure and record the amount of fluids in each tank.

For this purpose a lot of measuring instruments are present (including automatic). But manually measurements have to be taken to cross check with these values. Sounding is the term used in ships which means taking the measurements of liquid in tanks. Sounding of the tank means height of liquid level from bottom of the tank. Since tank heights are known, it is also possible to know the remaining height of the tank. This is called ullage. Ullage is the remaining height before the tank becomes full. Normally ullage is measured for cargo tanks and fuel oil tanks.



The above diagram shows a vertical pipe towards the after end of the tank. This pipe starts from the deck and goes to the bottom of the tank. End of sounding pipe(on deck) is closed using "sounding cap" to avoid flooding of the compartment during bad weather. In addition to the sounding cap an automatic closing arrangement is provided in machinery spaces. Height of level in the tank can be measured by measuring height of liquid in the sounding pipe. Tanks tables are calibrated to indicate volume with reference to the height of the liquid column in the sounding pipe and trim correction.

HOW TO MEASURE

As mentioned earlier height of level in the tank can be measured by measuring height of liquid in the sounding pipe. A tape called "sounding tape" is inserted into the tank through a sounding pipe. Once it reaches bottom, it is pulled up. A sounding tape has got markings in it. As we are dipping the tape into a liquid, the trace of liquid can be found. Measure this reading and this value is referred with tank calibration tables to find volume of liquid in the tank.


striker plate

The end of sounding tape is made using a heavy metal piece, it can result in rupture to tank as sounding is taken everyday.To avoid this issue, a small plate (Striker plate) is welded directly under the opening of the sounding pipe. The striker plate is replaced when it is worn out.

# The main purpose of the striker plate is to prevent damage to bottom shell plating.

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