Vessel Trimmed by the Stern
3.3.2 Gauging Procedures – Full & Partially Full Tanks
When the bow of a vessel is deeper in the water than stern, the vessel is said to be "trimmed by the head“
Ullage gauges are usually taken on full or partially full ship or barge tanks; however, innages are sometimes used, especially on barges. As with shore tanks, the capacity table usually determines what type of gauges are taken. If the capacity table is an ullage (outage) table, then ullages should be taken. If the capacity table is an innage table, then innages should be taken. Three gauges are to be taken within a span of 3mm or 1/8 of an inch; and the average recorded to the nearest 1mm or 1/ 8 of an inch. If the first two readings are identical, that reading may be recorded without taking additional readings. If the product in the tank is in motion and it is not possible to obtain three-gauge readings within 3mm or 1/ 8 of an inch, take five readings as quickly as possible and average them. 3.3.2.1 Trim Corrections Gauging procedures are not altered for vessels that are out of trim; however, it will be necessary to apply a trim correction to the gauge reading. Trim corrections are found in the vessel's capacity tables and usually fall into one of two types.
Trimmed by the stern
Trimmed by the head
A correction, plus or minus, to the gauge. A volumetric correction, plus or minus, to be applied to the table volume. It is very important to pay attention to the arithmetic sign, plus or minus, of the trim correction as it varies, depending upon the trim, location of the gauge hatch and the type of gauge. 3.3.2.2 List Corrections List corrections are applied in the same manner as trim corrections. However, most trim and list corrections are not designed to be applied at the same time. If both trim and list conditions exist, attempt to have the vessel remove one or both. List is usually much easier for a vessel to remove than trim.
Wedge Formula, when the vessel is out of trim, small quantities of liquid material may not touch all four tank bulkheads. In this situation trim correction tables are not accurate and should not be applied. The wedge formula is a mathematical means of calculating the volume of material in the tank, under these conditions. A Wedge Table is a table where the wedge volume has been calculated, on a tank-by-tank basis, for varying innages and varying amounts of trim.
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