Regarding the selection of styrene breather valves
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If the design of the styrene storage tank follows GB50341 (which specifies that the negative pressure should be greater than -250 Pa), the vacuum pressure is set at 0.25 kPa. Table 1 of SY-T 0511.1-2010 \"Attachments for Oil Storage Tanks – Part 1: Breather Valves\" specifies that the suction opening pressure is -295 Pa, which is lower than 0.25 kPa! So how should one choose the breather valve for this tank?
It’s not necessary to follow the standards; we can operate at the pressure required by the customer
GB50341 does not specify the negative pressure for breather valves. The pressure of the breathing valve is the basis for the design parameters of the storage tank. If the storage tank is existing, the positive and negative pressures at which the breather valve operates must not exceed the design pressure of the tank.
It seems that it is specified that a normal-pressure tank must not have a pressure lower than -250 Pa; a pressure below this value does not qualify as that of a normal-pressure tank. Styrene storage should be at atmospheric pressure, which is where the conflict lies
Regarding the negative pressure of 0.25 kPa, it mainly relates to the question of which section should be used in the calculations for tanks; do not let the term \"atmospheric pressure tank\" confuse you. The design negative pressure for many storage tanks is greater than -0.25 kPa; the vent valve can be selected accordingly.
However, when selecting a breather valve, it is necessary to calculate whether it meets the ventilation requirements, and design negative pressure is involved in this process. If the designed negative pressure is higher than 295 Pa, the calculations will be incorrect (see the calculation example in Section 4.3 of Appendix A of SYT 0511.1-2010 for details)