2.4.1 Each cargo tank of a tanker that is connected
                           to a vapour collection system should be equipped with a cargo gauging
                           device which:
                        
                        
                        
                        
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                                 .1 provides a closed gauging arrangement that
                                 does not require opening the tank to the atmosphere during cargo transfer;
                              
                              
                              
                            
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                                 .2 allows the operator to determine the liquid
                                 level in the tank for the full range of liquid levels in the tank;
                              
                              
                              
                            
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                                 .3 indicates at the location where cargo transfer
                                 is controlled, the liquid level in the tank; and
                              
                              
                              
                            
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                                 .4 if portable, is installed on the tank during
                                 the entire transfer operation.