Draft survey has the following three main advantages.
@ First, many countries of the world are connected by sea. Vessels can sail freely over the sea, so the same draft survey can be carried out anywhere in the world.
A Second, a vessel is such as a large container, and a draft survey is conducted before and after a large amount of dry bulk cargo is loaded, and the difference between the displacements can be used to quickly calculate the weight of the loaded cargo.
B Third, draft surveys utilize the principle of Archimedes' buoyancy, a law of nature. This law is a principle of nature recognized by everyone in the world. Draft surveys conducted according to this principle can achieve extremely high accuracy if the work environment is good.
On the other hand, the draft survey has the following two problems.
@ Draft mark readings are affected by the working environment such as weather and sea conditions. A vessel is like a large container floating on water, so it is directly affected by waves and swell. The weather and sea conditions are constantly changing, and there are always waves of 10 cm to 30 cm. If the sea becomes rough due to the passage of a low pressure, etc., the water surface will fluctuate more than 50 cm, making accurate reading of the draft marks extremely difficult. In other words, the water surface condition at the loading and unloading ports is constantly changing, and the work environment for draft survey at that time changes accordingly, which causes variations in the readings of the draft marks. Furthermore, draft mark readings can vary due to personal differences and parallax caused by the difference in height between the shore and the water surface.
A Currently, there are two types of hydrometers in the world for measuring seawater density: one for relative density and one for apparent density. Relative density hydrometers are mainly used in Japan, while apparent density hydrometers are used in many countries, including Australia.
In order to improve the draft survey problems mentioned above, it is recommended to introduce the following two points.
@ At the time of draft mark reading, a draft reading device (KENDRAFT) should be used
Imagine a situation in which you are reading the vessel's draft marks floating on the water under the various weather and sea conditions around the world. For example, let us say the correct draft mark reading is 6m83cm. If the sea is calm, you may be able to read 6m83cm, but if the sea is rough, the difference can often be more than 2cm, such as 6m81cm or 6m85cm. However, with KENDRAFT, you can get the same 6m83cm reading in any weather and sea conditions as the following movie.
Usually, the following three differences occur at the loading and unloading ports when measuring and reading draft marks.First: Differences in water surface conditions due to changes in weather and sea conditions
Second: Differences in personal error
Third: Differences in parallax caused by the quay condition where the vessel is berthed
Draft readings in a work environment with the above differences will inevitably result in fluctuations in reading values. If you make it a scientific and rational on-site response, you can reduce the variation in measured readings.
The use of KENDRAFT is highly effective in changing the current response with varied differences to a scientific and rational response.
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A The same type of seawater hydrometer should be used at the loading and unloading
@ ports
It would be best if seawater hydrometers were standardized worldwide, but due to the circumstances of each country, adjustments will take time. For the time being, it is necessary to establish a rule that the same type of hydrometer should be used at both loading and unloading ports in order to improve the quantity difference.
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By introducing the above two measures (a consistent survey from loading to unloading) into the current logistics, the on-site response will be scientifically standardized, and the quantity difference between the loading and unloading ports that has occurred so far will be greatly improved.
There are two methods to determine the quantity of a large amount of dry bulk cargo: draft survey and shore scale. Which method to use depends on the type of cargo and long-standing business practices. In the case of major dry bulk cargoes, iron ore and coal are subjected to draft survey, while grain is subjected to shore scale. Under such circumstances, it is said that there are many shortage claims for cargo that is settled on a shore scale. Due to the high unit price of such cargo, consignees often have shortage insurance. Generally, consignees file a claim for damages when the shortage ratio for the B/L quantity exceeds 0.5 % of the trade allowance. And the shortage loss minus the excess is covered by the shortage insurance.
As for the causes of shortage, there are various possible causes, such as insufficient loading quantity, loss due to sweating during sea transportation, discharge of bilge water during sea transportation, dust loss during loading and unloading handlings, quantity intake at the receiver of unloading port, but I believe that the difference in quantity due to the difference in shore scale is the largest. Shortage loss is caused by the quantity difference between the loading port and the unloading port. As a prerequisite, in principle, the quantity of loading port and the quantity of unloading port must be measured and compared on the same scale. However, there are many different types of shore scales used on-site, including hopper scales, belt scales, and truck scales. These scales are also made by different manufacturers, and management methods vary depending on the country and owner. Therefore, even though they are all referred to as shore scales, the shore scales at loading and unloading ports are not all the same. In other words, since they are measured and compared on different scales, it is natural that there will be a difference in quantity. On the other hand, a vessel has the same scale anywhere in the world, and based on that scale, the same draft survey can be performed at loading and unloading ports. At that time, by conducting a consistent survey from loading to unloading, it is possible to reduce the variation in on-site response caused by differences in water surface conditions, personal error, parallax and hydrometer types, and to make it a scientific and rational on-site response. As a result, we were able to significantly improve the quantity difference between the loading and unloading ports.
As mentioned above, there are some inconsistencies in the current method of determining quantities based on shore scale at the loading and unloading ports, and there are always some irrational aspects when comparing and verifying the loading and unloading quantities. In this situation, by introducing a consistent survey from loading to unloading by vessel and complementing the lacks of rationality of shore scale inspection, we believe that it is possible to create a system to prevent shortage claims.