How can I explain several terms related to safety valves?

There is a term definition in safety valve standards: 1. Nominal pressure – the pressure rating of the inlet flange of the safety valve; it also serves as the basis for calculating the test pressure for the strength of the valve body, with the unit being megapascals (MPa)； Code name: PN. 2. Nominal diameter: The nominal diameter of the inlet flange of the safety valve, expressed in millimeters (mm) ； Code name: DN. 3. Throat diameter: The diameter at the smallest cross-section of the flow channel on the inlet side of the valve seat, measured in millimeters (mm) ； Code name: D. 4. Lift: The actual elevation of the lift valve disc from its closed position, measured in millimeters (mm) ； Code name: H. 5. Discharge area: the minimum cross-sectional area of the fluid passage when the valve discharges, measured in square centimeters (cm2) ； Code name: Ad. 6. Curtain area: The area of the cylindrical or conical passage formed between the sealing surfaces when the valve disc rises above the valve seat, measured in square centimeters (cm2) ； Code name: Ac. 7. Set pressure: the inlet pressure at which the valve disc of the safety valve begins to rise under operating conditions. At this pressure, a measurable opening height begins to appear, and the medium is discharged continuously in a manner that can be detected visually or audibly; the unit is megapascal (MPa) ； Code name: Ps. 8. Seal test pressure: The inlet pressure used during the seal test, at which pressure the leakage rate through the sealing surface of the closing element is measured; the unit is megapascals (MPa) ； Code name: Pt. 9. Re-seating pressure: The inlet pressure when the valve disc comes into contact with the valve seat again after discharge, that is, when the opening height is zero; the unit is megapascals (MPa) ； Code name: Pr. 10. Discharge pressure: the inlet pressure when the valve disc reaches the specified opening height, expressed in megapascals (MPa) ； Code name: Pd. 11. Certified relieving pressure: the maximum allowable discharge pressure specified by standards, expressed in megapascals (MPa) ； Code name: Pdr. 12. Theoretical flowing capacity: the design calculation value of the flow rate for an ideal nozzle, where the cross-sectional area of the flow channel is equal to that of the safety valve’s flow channel; the unit is kilograms per hour (kg/h) ； Code name: Wt. 13. Realistic flowing capacity: the actual flow rate at the rated discharge pressure, measured in kilograms per hour (kg/h) ； Code name: W. 14. Coefficient of discharge: the ratio of actual discharge to theoretical discharge ； Code name: KD. 15. Derated coefficient of discharge: the product of the discharge coefficient and the derating factor (taken as 0.9) ； Codename is KDR. 16. Overpressure: the difference between the discharge pressure and the opening pressure, usually expressed as a percentage of the opening pressure ； Code name: △Po. 17. Blowdown pressure difference: the difference between the opening pressure and the closing pressure, usually expressed as a percentage of the opening pressure ； Code name: △Pb1. 18. Chatter: The valve disc of the safety valve moves back and forth rapidly and abnormally, coming into contact with the valve seat during this movement. 19 Flutter: The valve disc of a safety valve moves back and forth rapidly and abnormally, without making contact with the valve seat during this movement.