5. VOLUMES AND ULLAGES NOT INCLUDED IN THE CARGO TANKS CALIBRATION TABLES

 
Frequently, near the completion of the discharge, during "SOUNDING" operations in the SLOP TANKS, for ascertaining the R.O.B. (Remained On Board),the sounding or the Ullage taken with the bob,is not included into calibration tables. It is very impossible to calculate the corresponding volume. Many officers solve this problem calculating the volume by using the proportionality system, but this method is incorrect due to the shape of slop tanks and wing tanks. Down below you can find calibration tables for slop tanks port and stbd. To calculate the volume of liquid hydrocarbons you can see the example as follows:
   
CALIBRATION TABLES
SLOP TANKS P.& S.
 
     
ULLAGE mt.
VOLUME c.m.
  
20.50
207
  
20.60
192
  
20.70
176
  
20.80
164
 
20.90
151
 Volumi e Ullages non incòlusi nelle tavole di calibrazione
21.00
139
21.10
126
21.20
113
  
21.30
102
21.40
92
21.50
81
21.60
71
21.70
62
21.80
53
21.90
46
22.00
40
22.10
34
22.20
28
 

We assume the Ullage from measurement point of slop tank to be 23.06 metres; the breadth of the cargo tank to be 11.80 metres and the length 19.20 metres.

PRACTICAL EXAMPLE:

We assume also that the ullage of 23.06 metres become 22.79 metres considering the correction for trim and list of the vessel. From calibration tables you can see that the ullage od 22.79 metres is not available; therefore we have to calculate as follows:

DATA INPUTS

Difference of the last two ullages (22.20-22.10) 0.10 m.
Difference of last two volumes (34-28) 6 cub.m.
The last volume observed in the tables 28 cub.m.
The last ullage observed in the tables 22.20 m.
Length of the cargo tank 19.20 m.
The Height of the cargo tank from measurement point 23.06 m.
Corrected Ullage for TRIM and LIST. 22.79 m.

DATA OUT : VOLUME OF LIQUID HYDROCARBONS = 3.71 cub. metres