ÖNORM EN ISO 4126-11

The purpose of this International Standard is to define the testing procedures to be applied for carrying out performance tests on closing, non-reclosing and combined safety devices for protection against excessive pressure as specified in ISO 4126 Parts 1, to 7, with particular reference to type testing The objective of this standard is to provide test procedures to determine the performance of the safety device under test in such a way that the test rig has no influence on the results. For reclosing devices specified in ISO 4126 Part 1, 4 and 5, the objective of the tests is to determine the performance of the safety device when operating with compressible non-condensing fluids and non-flashing liquids. For non-reclosing devices covered in ISO 4126 part 2, the objectives of the tests are to establish the bursting pressure, the opening characteristics and the device resistance to flow when opened under compressible or incompressible fluid conditions. In the case of testing with liquids the temperature of the liquid at the safety device inlet shall be limited in accordance to the following: in the case of water the maximum temperature at the inlet shall be 50 OC to avoid the risk of flashing; in case of other liquids, the maximum vapor pressure shall be 0,125 bar absolute. NOTE Flow capacity measurements obtained using test procedures detailed in this standard are valid only for ideal gasses and vapors (as real gas effects are not considered). An ideal gas behavior can generally be assumed as long as the real compressibility factor (Z) of the test gas at inlet and nozzle conditions is within the range of 0,95 and 1,05. As an example, air and nitrogen at ambient temperature may be considered as ideal gas up to a pressure of 150 bar. Under real gas conditions or pressures above 250 bar the measurement devices and accuracies shall be modified to the current state of technology and in the sense of this standard. NOTE It should be noted that actual performance of the safety device in service may be influenced by a variety of installation, process and environmental factors.