How should the safety valve on the corresponding flash tank be calculated in the event of a failure of the control valve?
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How should the safety valve on the corresponding flash tank be calculated in the event of a failure of the control valve? There are mainly the following issues: 1. Since there are control valves on both the inlet and outlet pipelines of the flash tank, which control valve should be used to determine when the safety valve installed on the flash tank fails? 2. The feed line to the flash tank carries a liquid phase; if it is assumed that the control valve on this feed line fails, then should the safety valve on the flash tank be calculated using the formulas applicable to gas discharge conditions, or should it be calculated using the formulas appropriate for a situation where the control valve fails and a liquid phase is present? 3. Are there any Chinese standards that specifically address the failure conditions of control valves, with relatively detailed requirements that take all possible scenarios into account? Internal regulations of companies or design institutes would also work; if anyone can provide them, I would be very grateful! ! 4. Also, how is the corresponding discharge temperature of the safety valve determined?
I don’t know much about this aspect; I’m waiting for an expert to answer
Firstly, the calculation of the discharge conditions for a safety valve takes multiple scenarios into account. You need to determine each of these discharge scenarios, calculate the diameter of the safety valve appropriate for each scenario, and then select the safety valve with the largest diameter. Regarding the flash tank, generally only the condition of liquid flowing in but not out is considered; as the liquid level inside the tank rises, the safety valve activates and first releases gas, with liquid following afterward. The diameter values you calculate must be sufficient to meet these requirements. For a device in gas-liquid equilibrium such as a flash tank, the discharge temperature is the phase equilibrium temperature corresponding to the discharge pressure.
It supports the upper level; it has nothing to do with the control valve. It is the amount of steam generated by your feed rate, released at the operating pressure.
Has this tank been considered for fire conditions? If fire gas emissions are taken into account, the calculated release area is usually much larger than that for liquid releases. If fires are not taken into account, and materials are considered to enter only without exiting, the maximum discharge flow (volume) after pressure buildup in the gas is equivalent to the flow rate of liquid entering the tank (in volume). In my opinion, the safety valve should be sized based on the liquid discharge volume in such cases.