an Entity references as follows:
Valve leakage refers to flow through a valve which is set in the 'off' state. The importance of valve leakage depends on what the valve is controlling. For example, a dripping tap is less significant than a leak from a six-inch pipe carrying high-pressure radioactive steam. In the United States, the American National Standards Institute specifies six different leakage classes, with "leakage" defined in terms of the full open valve capacity: