The challenge of calculating the discharge volume of safety valves
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Currently, the material for the cold process flows through the tube side; the inlet of the tube side is at the liquid phase, while the outlet is at the gas phase； The shell side is heated with saturated steam, and during normal operation, the outlet temperature of the process fluid in the tube side is controlled at a certain level through the control valve at the shell side inlet. I am now considering installing a safety valve at the tube side outlet; it is believed that overpressure conditions occur when the valves at the tube side inlet and outlet close accidentally, allowing steam to continue heating the two-phase fluid inside the tubes and thus causing overpressure. Ask Haiyou whether this type of overpressure condition needs to be taken into account How is its leakage rate calculated if necessary?
It should be considered. The discharge volume is equal to the amount of vaporization at the discharge pressure of the safety valve.
Analysis should be conducted by first considering the grade of the steam; the highest temperature that can be reached on the tube side is the temperature of the steam. If the saturated vapor pressure at this temperature on the tube side is lower than the design pressure for that side, there is no need to consider a safety valve； If it exceeds this value, it is necessary to determine the saturation temperature corresponding to the discharge pressure; the heat load of the heat exchanger should then be recalculated based on this temperature difference. The emission amount for such a discharge condition can be obtained by dividing the heat load by the latent heat of the liquid at the discharge pressure.