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ISO DIS 4126-11 2014 Edition, August 7, 2014 Safety devices for protection against excessive pressure - Part 11: Performance testing
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Availability date: 07/13/2021
Description / Abstract:
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.