Ship Docking Survey...
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Hull Survey welcome to
＜ Docking Survey ＞
1.Introduction 2.Docking Survey 3.Survey Item 4.Type of Dry Dock 5.Safety in Dock
This document describes the general background of a "Docking Survey," which has an important role in a classification survey, and is meant to be used as a reference for surveyors before they carry out field inspections. This document was prepared by Ichiro Ishikawa, former Chief Surveyor, and is based on the prerequisites described below.
1-1. Underwater inspection
6.Procedure of Bottom Inspection 7.Course in Dock
10.Rudder 11.Propeller 12.Anchr
An underwater inspection that replaces a docking or slipway inspection which is carried out by a company approved by the Classification Society. The bottom shell, rudder and propeller should be inspected indirectly by observing the television images transmitted by an underwater camera used by a diver. Detection of abnormalities should fundamentally conform to the contents of this document; therefore, details of underwater inspection are not specially described here.
1-2.Method of repairing damage
Various types of damage, such as damage due to stranding and contact with the bottom shell, may be detected during a docking survey. Such damage is usually repaired by the shipowner under insurance, but in this document details of repairing methods will not be described. These tems will be introduced in the separate home page describing "Damage and Repair" in futuer.
1-3. Propeller The propeller and propeller shaft are inspected at the same time as a bottom inspection. However, shafts need not necessarily be inspected during a Docking Survey because "Propeller Shaft and Stern Tube Shaft Surveys" are independent from the Docking Survey under the responsibility of machinery surveyor but brief explanation is entered in this document.
1-4. Anchor and Chain Cable An inspection of the anchors and anchor chains is not a requirement of a Docking Survey; these items fall under the purview of a Special Survey. However, as it is customary to inspect these items during a Docking Survey, they are covered in this document.
1-5. Damages in Bottom Except for defects that occur because of stranding and contact with objects or the sea bed, defects in the bottom shell, such as deformation and corrosion almost never occur unexpectedly; they occur gradually over a long period. Because the most repairs to the bottom shell involve repairs to double bottom tanks, considering that the tank should be emptied and cleaned before starting repairs and hydrostatic tests carried out after repairs, the period for repairs should be estimated aproximately. Therefore, the data below should be collected before performing a bottom survey.
1-6. Study the history of the ship 6/25/2015 12:39 PM
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Before carrying out an inspection, have a look the survey report file submitted together with the survey request application, and check the recommendations and the precautionary items if any .And read old survey reports as far back as possible, at least until the previous bottom inspection. Dents in the bottom shell may be under- or over-estimated, or overlooked depending on the position to be inspected, increase or decrease in the intensity of light rays, and arrangement of blocks. Dents that have not appeared in reports in the last few years, may have been reported already in the past. There have been instances
1-7. Working Schedule The schedule for docking , undocking and sailing dates are determined by the shipowner's sailing schedule and the shipyard's docking schedule; therefore, these informations should be obtained for reference. If the docking period is as short as two or three days, both shipowner and shipyard are unlikely to carry out the big repairs to the bottom or side shell unless the shell is heavily damaged. The docking period gives you an approximate idea of the extent of the bottom shell works that is likely to be carried out. Information such as the time the ship will be docked/undocked , how many hours does it take the dock will be dry, and capacity of discharge pumps of the dock should be obtained for reference.
1-8. Marine casualties After the previous docking, instances where the ship hits the quay, or the bottom shell came in contact with the sea bed or floating objects, should be correctly entered in the log book. It is recommended to ask the superintendent or the Master about the instances of marine casualties before starting inspection . If there are any report of bottom contact, the bottom inspection should be carried out with special care; sometimes , In this case the major repairs to the bottom shell may be necessary. Another method of collecting data is to be request shipyard supervisor to show the specifications for repairs carried out to the ship, if possible.
Photo 1-1 ULCC in Dry Dock One of the world largest ship, Piere Guillaumat in LISNAVE Margueira Yard in 1978 Dimensions Lpp 401.10 x B 63.01 x 35.92 m, DW 555,031t Built at the San Nazaire Ship Yard in France BV Class It takes more than 3 hours to carry out the bottom Survey.
2. Docking Survey A docking survey is also called a bottom survey. According to the "Protocol of 1988 relating to the International Convention for the Safety of Life at Sea, 1974", a bottom inspection is defined by a lengthy expression: thst is, "Inspections of the outside of the ship's bottom". Area of the hull under the water-line are always immersed in water ; therefore, the condition of damage in the event of the stranding or bottom contact can not be observed. The objective of periodical docking is to inspect the area of hull beneath the water- line. Offshore structures in conrtast to a ship, do not sail throughout the world and suffer neither from stranding nor contacting with other object. Conversely, docking an offshore structure is very difficult; therefore, underwater inspection by an underwater camara inspection instead of docking is justifiable. There is no word corresponding to docking survey in the SOLAS Convention. But the Classification Sosieties request the periodical docking survey to the shipownes. According to their requirements ships must be in dry dock twice in 5years as shown in the following figure.
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Before 1964 the docking survey was requested every year, because at the Annual survey, docking was requested. Some shipowners put their ships twice in the year. But now the docking is only 2times in 5years. The reason of this relaxation was the improvement of paint. At that time the effectiveness of paints continued only one year or less. If the ship was not docked for more than one year, the paint would peel off and alrae and shellfishes would stick to the hull under the water line, resulting in a drop of the ship's speed . For the shipowners at that time decreased speed was bigger problem than the expence of docking. ＜ Back ｜ Home ｜ Next ＞
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