Seeking advice on the installation of emergency relief valves and safety valves in tanks Category A B, Category B A, Category C A, as well as in liquefied hydrocarbon storage tanks
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According to the specifications, emergency relief valves or pressure relief manholes must be installed on low-pressure flammable liquid storage tanks in tank farms to enable emergency pressure release in case of a fire. I would like to ask if these valves can be replaced by safety valves? Is it because the starting pressure is too low that a safety valve cannot be used as a substitute? Under conditions of micro-pressure nitrogen sealing, what is the set pressure at which this valve releases pressure? Is it sufficient as long as it is not higher than the design pressure of the storage tank? For toxic media such as acrylonitrile, does this valve allow for direct discharge into the environment after venting, or is closed-discharge required? If a pressure relief manhole is used, is it necessary to install pipes on that manhole for closed-discharge? Is a flow-limiting orifice plate required behind the emergency pressure relief valve? What is the legend/code for the emergency pressure relief valve or pressure relief manhole on the PID? Safety valves are installed on liquefied hydrocarbon storage tanks; is it unnecessary to install additional valves as well?
Of course, a safety valve cannot be used as a substitute; a low starting pressure is just one aspect of the issue, and the main reason is that safety valves are not suitable for instantaneous release. In an extreme condition such as a fire, the flow rate provided by a safety valve is not sufficient to meet the requirements. The set pressure of the emergency relief valve must be such that it is 10% less than the design pressure of the storage tank. As for toxic and harmful gases, there is no need to consider the issue of connecting pipes for export. First, the emergency relief valve, also known as an accident pressure relief device, operates very rarely; therefore, there is no need to consider gas accumulation. The second emergency relief valve activated; at this point, protecting the storage tank is the top priority, with no need to consider the medium itself. SH/T3007, you can take a look. If you have any questions, feel free to contact me directly. I’m Engineer Zhu; my mobile number and WeChat ID are both 13912008028