Safety valve related terms: Nominal pressure: that the safety valve at room temperature, the maximum allowable pressure, high temperature equipment safety valve should not consider the material under high temperature stress reduction. Safety valve is designed and manufactured according to the nominal pressure standard. Opening pressure: also known as the rated pressure, refers to the safety valve when the valve starts to rise under the inlet pressure, the pressure began to have a measurable opening height, the media can be visually or auditory branch of the continuous discharge state . Discharge pressure: valve to achieve the required opening height of the inlet pressure. The upper limit of discharge pressure is subject to the requirements of relevant national standards or codes. Over Pressure: The difference between discharge pressure and cracking pressure, usually expressed as a percentage of cracking pressure. Back seat pressure: After discharge valve disc re-contact, that is, when the opening height becomes zero inlet pressure. Opening and closing pressure difference: the difference between cracking pressure and cracking pressure, usually expressed as a percentage of cracking pressure and cracking pressure, expressed as the pressure difference between the two when the cracking pressure is low. Back pressure: Pressure at the relief valve outlet. Rated discharge pressure: The standard specifies the upper limit of discharge pressure. Seal Test Pressure: The inlet pressure at which the seal test was conducted, at which the rate of leakage through the closure face of the closure was measured. Opening height: The actual stroke of the valve leaf leaving the closed position. Flow path area: The minimum cross-sectional area of ​​the flow path between the inlet of the valve and the sealing surface of the closure. It is used to calculate the theoretical displacement without any resistance effect. Runner Diameter: Diameter corresponding to the runner area. Curtain area: The cylindrical or conical shaped passage area formed between the sealing surfaces when the valve flap is above the valve seat. Emission Area: The minimum cross-sectional area of ​​the fluid passage during valve discharge. For the full revelation of safety valve, the discharge area is equal to the flow area; for the micro-safety valve, the discharge area is equal to the curtain area. Theoretical Displacement: The calculated displacement of an ideal nozzle equal to the cross-sectional area of ​​the flow passage and the flow passage area of ​​the safety valve. Displacement coefficient: the ratio of actual displacement to theoretical displacement. Nominal displacement coefficient: The product of the displacement coefficient and the reduction factor (0.9). Rated displacement: refers to the actual displacement allowed as a safety valve applicable standard that part. Equivalent calculation of displacement: Refers to the pressure, temperature, the nature of the media and other conditions and the rated displacement of the same conditions apply, the safety valve calculated displacement. Frequent jump: safety valve disc abnormal rapid back and forth movement in the valve disc contact valve seat. Flutter: safety valve disc abnormal rapid back and forth movement, the valve does not contact the valve seat in motion.