marine inspection companies in dubai
A SURVEY’S EXTENT AND RELIABILITY
• know about the limitations of surveying;
• appreciate the need for dismantling lining etc.
The only way to carry out a totally comprehensive ship condition surveyor would be to dismantle the whole vessel and then subject every component to a meticulous scrutiny all over, slicing up parts for an internal cargo inspection dubai. Thisis obviously impossible, as the cost of dismantling and then reassembling the scantlings would be
enormous, and the time taken unacceptable. In practice the marine inspection has to carry out the most extensive inspection possible, within the limitations of the job.
There are two special problems which surveyors are up against:1 A lack of facilities for getting at the whole vessel, notably the outside of the hull due to lack of staging, inside small compartments, behind obstructions like tanks and up the mast[s]. It is rare for a surveyor to be able to check the whole of the topsides. The best the inspectors from marine inspection companies in dubai can do, very often, is to hang over the deck edge and work down as far as he can reach, also work up from the ground and test the accessible areas. There may be portable staging or a ladder light enough to shift along, meter by meter. But even with these aids there are often hull parts
which cannot be accessed from outside.
2 Inside the hull it is common to find that many of the spaces are fully lined. Often a little lining is removed, but it is rare for more than 10% of the total lined area to be stripped out to allow the surveyor to see the inside of the plating, the frames and so on.It is common for a surveyor to have to rely on this limited dismantling plus what can be seen below the sole and inside the chain locker and aft lacerate or steerage compartment, the areas which are seldom lined. Quite often no internal lining is taken off, perhaps because the buyer will not pay for it, or there are
no facilities for doing the work, or because removal will cause damage even when the work is skillfully carried out. To work out roughly how many defects probably exist but have not been seen, a rough calculation can be carried out. If say, Y is the number of defects which have been noted, and the area inspected is p% of the total area inside and outside, then the number of undiscovered defects likely to be in the hidden areas is of the order of X, and is given by the equation:
x= Y [100 – p] p
To get an idea of the percentage of the total area of the vessel which has been checked, a broad view of the outside has to be taken. Suppose that conditions are difficult, then it may be that only two-thirds of the external surface of the shell have been checked. It is relevant that outside the hull there are no frames or stringers, though there may be bilge keels, rubbing strakes etc. However, these are relatively small items and it is reasonable in this very approximate calculation to ignore them. Inside the hull there is a lot of structure, not just the hull shell and deck stiffeners, but also pillars, knees, bearers, tank supports and so on. Therefore the interior nominal area is taken as double the exterior. Next suppose that the combined lengths of the chain locker and aft lazarettos is 10% of the overall length. A further 5% of the interior has been stripped out so that the inside of the shell can be viewed. Suppose that the area below the sole amounts to 12% of the shell interior area between the chain locker and the aft lazarettos.
The approximate area which has been inspected is shown as follows:
The outside is taken as about one third the total inspect able area, namely 33% of the total. The interior is therefore roughly 66% of the total. Since only two thirds of the outside can be checked, this represents 2/3 x 33% = 22% of the total.
Adding together the total percentages of the interior which can be surveyed, inspection companies in dubai have 10% plus 5% plus 12% making a total of 27%. The inside represents 66% of the total, so we can inspect a total inside the yacht amounting to 27% of 66% of the total, making about 18%. Add this to the percentage of the whole seen outside, and we get 22% plus about 18%, giving roughly 40% in all, and naturally that leaves 60% of the vessel not surveyed because it is inaccessible.These calculations have to be treated with considerable caution, because they depend on so many assumptions. Their value lies in alerting everyone concerned to the considerable number of possible defects which may exist but are hidden in inaccessible areas. These calculations also confirm the need to carry out as much dismantling as possible, especially in such special circumstances as prior to a major lengthy offshore voyage.Steel Vessels Diploma in Yacht & Small Craft Vessels Diploma