Method of determining the normal evaporation rate (NER) and vacuum quality of a cryogenic liquid container

1. A method of determining the NER and vacuum quality of a cryogenic liquid container containing a known cryogenic liquid product and having a gas vent valve outlet, the method comprising the steps of:

a) providing a vent valve outlet gauge having a product specific NER scale positioned adjacent to a gas flow tube thereof, the gas flow tube having a flow indicator ball moveably entrapped therein such that the position of the flow indicator ball with respect to the product specific NER scale indicates the NER of the cryogenic liquid container being tested, the gas flow tube having an inlet connectable to a gas vent valve outlet of an open gas vent valve to a gas vent valve outlet of the cryogenic liquid container and an outlet open to the atmosphere such that the volume of gas leaving the gas vent valve outlet passes through the gas flow tube lifting the flow indicator ball to a level corresponding to the volume of gas flow such that the NER in pounds per day of liquid product lost is read directly from the adjacent product specific NER scale;

b) connecting the inlet of the gas flow tube to the gas vent valve outlet of the cryogenic liquid container to be tested;

c) product specific, vacuum quality interpretation scale that corresponds with the product specific NER scale of the vent valve outlet gauge; and

d) determining the vacuum quality of the cryogenic liquid container being tested by comparing the NER indicated by the flow indicator ball with respect to the provided product specific, vacuum quality interpretation scale to obtain a vacuum quality value.