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Y. Song et al.
When the fire occurs, the heat absorption of the natural gas filter separator increases
sharply and the operating temperature of the medium in the container increases accordingly. As the operating temperature of the medium in the container increases, the temperature difference between the environment and the inside of the container decreases,
and heat absorption decreases gradually.
When using the standard method and the dynamic simulation method, the corresponding operating temperature of the safety valve at an opening pressure of 1700 kPaG
is 103.7 °C and 98.0 °C, respectively. The two calculation results are slightly different,
mainly because the standard method is based on the ideal gas state and does not consider
the different compression factors of gas at different operating conditions. The dynamic
simulation method is more practical, more accurate and corresponds better to the actual
discharge process.
The operating temperature produced by the two calculation methods is lower than the
maximum operating temperature of 118 °C corresponding to the maximum allowable
stress of the pipe flange of 1700 kPaG. However, as the vessel wall temperature increases
due to the fire, the pipe flange will fail at the high operating temperature, and the process
medium may be discharged, thus affecting the safety of the device.
To sum up, the safety valve at this working condition cannot protect the equipment
from over-temperature. In the same way, not all pressure relief valves can provide sufficient protection for vessels with non-wetted walls or vessels containing single phase
fluid such as natural gas, If necessary, other protection measures such as water spray,
covering the container with earth, or depressurization systems should be considered.
4 Dynamic Relief Model of Depressurization
The natural gas filter separator system of the project is equipped with a water spray
system. When a fire occurs, the water spray system is started to cool the container, so
as to reduce the risk of equipment overpressure and overtemperature. The water film
covering the metal surface can absorb considerable heat radiation, but the effectiveness
and reliability of water spray depends on many factors, such as freezing weather, strong
wind, water supply reliability and the state of the container surface.
In addition, the natural gas filter separator is also equipped with a pressure reducing
system. Controlled depressurization can not only reduce the internal pressure and wall
pressure of the vessel, but also prevent more fuel from being added to the fire source
due to the leakage of combustible gas caused by rupture of the vessel.
The following two factors are to be considered in the design of the depressurization
system:
a) When fire occurs, the manual control device (such as valve, instrument, etc.) of the
vessel is not accessible to the operator, and the depressurization system needs to be
started remotely;
b) The depressurization system should be started in advance to maintain stress on the
vessel is within the allowable range and the allowable stress value should match the
wall temperature caused by the fire. The depressurization system is composed of a
depressurization pipeline; full bore on-off valve, restriction orifice, flare, etc. The key
Y. Song et al.
When the fire occurs, the heat absorption of the natural gas filter separator increases
sharply and the operating temperature of the medium in the container increases accordingly. As the operating temperature of the medium in the container increases, the temperature difference between the environment and the inside of the container decreases,
and heat absorption decreases gradually.
When using the standard method and the dynamic simulation method, the corresponding operating temperature of the safety valve at an opening pressure of 1700 kPaG
is 103.7 °C and 98.0 °C, respectively. The two calculation results are slightly different,
mainly because the standard method is based on the ideal gas state and does not consider
the different compression factors of gas at different operating conditions. The dynamic
simulation method is more practical, more accurate and corresponds better to the actual
discharge process.
The operating temperature produced by the two calculation methods is lower than the
maximum operating temperature of 118 °C corresponding to the maximum allowable
stress of the pipe flange of 1700 kPaG. However, as the vessel wall temperature increases
due to the fire, the pipe flange will fail at the high operating temperature, and the process
medium may be discharged, thus affecting the safety of the device.
To sum up, the safety valve at this working condition cannot protect the equipment
from over-temperature. In the same way, not all pressure relief valves can provide sufficient protection for vessels with non-wetted walls or vessels containing single phase
fluid such as natural gas, If necessary, other protection measures such as water spray,
covering the container with earth, or depressurization systems should be considered.
4 Dynamic Relief Model of Depressurization
The natural gas filter separator system of the project is equipped with a water spray
system. When a fire occurs, the water spray system is started to cool the container, so
as to reduce the risk of equipment overpressure and overtemperature. The water film
covering the metal surface can absorb considerable heat radiation, but the effectiveness
and reliability of water spray depends on many factors, such as freezing weather, strong
wind, water supply reliability and the state of the container surface.
In addition, the natural gas filter separator is also equipped with a pressure reducing
system. Controlled depressurization can not only reduce the internal pressure and wall
pressure of the vessel, but also prevent more fuel from being added to the fire source
due to the leakage of combustible gas caused by rupture of the vessel.
The following two factors are to be considered in the design of the depressurization
system:
a) When fire occurs, the manual control device (such as valve, instrument, etc.) of the
vessel is not accessible to the operator, and the depressurization system needs to be
started remotely;
b) The depressurization system should be started in advance to maintain stress on the
vessel is within the allowable range and the allowable stress value should match the
wall temperature caused by the fire. The depressurization system is composed of a
depressurization pipeline; full bore on-off valve, restriction orifice, flare, etc. The key