Maximum working pressure (gauge pressure)
Maximum working pressure (gauge pressure)
The highest of the following three pressures that may occur at the top of the tank in the operating position:
(a) the highest effective pressure allowed in the tank during filling (maximum filling pressure allowed);
(b) the highest effective pressure allowed in the tank during discharge (maximum discharge pressure allowed); and
(c) the effective gauge pressure to which the tank is subjected by its contents (including such extraneous gases as it may contain) at the maximum working temperature.
Unless the special requirements prescribed in Chapter 4.3 provide otherwise, the numerical value of this working pressure (gauge pressure) shall not be lower than the vapour pressure (absolute pressure) of the filling substance at 50 °C.
For tanks equipped with safety valves (with or without bursting disc) other than tanks for the carriage of compressed, liquefied or dissolved gases of Class 2., the maximum working pressure (gauge pressure) shall however be equal to the prescribed opening pressure of such safety valves (see also "Calculation pressure", "Discharge pressure", "Filling pressure" and "Test pressure").
NOTE 1: Maximum working pressure is not applicable to gravity-discharge tanks according to 6.8.2.1.14
(a).
NOTE 2: For portable tanks, see Chapter 6.7.
NOTE 3: For closed cryogenic receptacles, see Note to 6.2.1.3.6.5.