减压阀的基础功能与原理

　　Basic functions and principles of pressure reducing valves

　　核心作用将高压气体（钢瓶/管道）降至安全稳定的工作压力，防止设备损坏或爆炸。自动调节出口压力，即使入口压力波动（如钢瓶用尽时）也能保持输出稳定。

　　The core function is to reduce high-pressure gas (steel cylinders/pipelines) to a safe and stable working pressure, preventing equipment damage or explosion. Automatically adjust the outlet pressure to maintain stable output even if the inlet pressure fluctuates (such as when the steel cylinder is exhausted).

　　工作原理通过弹簧隔膜结构感应压力变化，动态调整阀门开合度（例：入口压力降低时开度增大以维持输出，入口压力上升时开度减小以维持输出）。关键组件：调节手柄、针阀、隔膜腔，协同实现“高压→低压”的精准转换。

　　The working principle is to dynamically adjust the valve opening and closing degree by sensing pressure changes through a spring diaphragm structure (for example, when the inlet pressure decreases, the opening degree increases to maintain output, and when the inlet pressure increases, the opening degree decreases to maintain output). Key components: adjusting handle, needle valve, diaphragm chamber, working together to achieve precise conversion from high pressure to low pressure.

　　02?减压阀选型硬核指南

　　02 Hard core guide for selecting pressure reducing valves

　　选型关键参数减压阀的材质和适用介质：在选择减压阀材质时，必须确认材质与气体的兼容性，包括减压阀密封材料。铜镀铬或黄铜减压阀：常用于惰性气体（氦气、氮气、氩气）、常见的工业气体（氧气、氢气）等，具有价格优势。316L不锈钢减压阀：适用于高纯气体、低温气体、酸性气体、碱性气体等。减压阀进出口压力表的选择和工作压力范围进出口压力表的量程建议选择系统最大压力的1.5倍。减压阀的工作压力建议使用减压阀工作范围全量程的 1/3 ～ 2/3。减压阀的精度控制控制精度：一般减压阀的输出控制压力的精度为±0.5% FS，R30的工作范围为10~50psi，输出压力的稳定性可达±0.125psi。若气体使用点要求稳定的气体压力，建议安装二级减压阀，保持稳定的气体压力输出。减压阀的流量选择要求参数解读：横轴 (X轴)：通常代表流量 ，单位如 L/min, m?/h, GPM 等。纵轴 (Y轴)：通常代表出口压力 ，单位如 bar, psi, kPa 等。

　　Key parameters for selecting the material and applicable medium of the pressure reducing valve: When selecting the material of the pressure reducing valve, it is necessary to confirm the compatibility between the material and the gas, including the sealing material of the pressure reducing valve. Copper chrome plated or brass pressure reducing valve: commonly used for inert gases (helium, nitrogen, argon), common industrial gases (oxygen, hydrogen), etc., with price advantages. 316L stainless steel pressure reducing valve: suitable for high-purity gases, low-temperature gases, acidic gases, alkaline gases, etc. The selection of inlet and outlet pressure gauges for pressure reducing valves and the recommended range for inlet and outlet pressure gauges are 1.5 times the maximum system pressure. It is recommended to use 1/3 to 2/3 of the full range of the working pressure of the pressure reducing valve. Precision control precision of pressure reducing valve: The precision of the output control pressure of a general pressure reducing valve is ± 0.5% FS, the working range of R30 is 10-50psi, and the stability of the output pressure can reach ± 0.125psi. If the gas usage point requires a stable gas pressure, it is recommended to install a secondary pressure reducing valve to maintain a stable gas pressure output. Parameter interpretation for flow selection requirements of pressure reducing valves: horizontal axis (X-axis): usually represents flow rate, with units such as L/min, m ?/h, GPM, etc. Vertical axis (Y-axis): usually represents outlet pressure, with units such as bar, psi, kPa, etc.

　　曲线形状：展示在特定入口压力和设定压力下，出口压力如何随流量的变化而变化。设定压力点?无流量或极小流量（如关闭点）时，通过调节弹簧预设的出口压力目标值，对应曲线中流量趋近于零的Y轴截距点。工作范围减压阀可稳定维持出口压力偏差的流量区间，超出后压力失稳或流量不足。下垂特性?流量增加导致出口压力下降的现象，表现为曲线的负斜率。斜率绝对值越大（曲线越陡），稳压性能越差；斜率趋零（曲线平缓）则稳压性优。

　　Curve shape: Show how the outlet pressure changes with flow rate under specific inlet pressure and set pressure. When setting a pressure point with no or minimal flow (such as a closing point), adjust the preset outlet pressure target value of the spring to correspond to the Y-axis intercept point in the curve where the flow approaches zero. The working range of the pressure reducing valve can stably maintain the flow range of the outlet pressure deviation, beyond which the pressure becomes unstable or the flow is insufficient. The phenomenon of an increase in flow rate leading to a decrease in outlet pressure, manifested as a negative slope of the curve. The larger the absolute value of the slope (the steeper the curve), the worse the voltage stabilization performance; If the slope approaches zero (the curve is gentle), the stability is better.

　　成因：阀口节流压降、阀芯位移对抗弹簧力、流道阻力上升；最大流量点保持出口压力不低于设计下限时的最大流量阈值，超限后压力骤降。曲线中右侧拐点或终止点流量值。入口压力影响入口压力升高时曲线整体上移。选型需参考最低入口压力对应的曲线。结构差异- 直接作用式：入口压力降低时下垂量增大（稳压性减弱）；

　　Cause: Pressure drop due to throttling at the valve port, displacement of the valve core against spring force, and increase in channel resistance; The maximum flow point maintains the outlet pressure not lower than the maximum flow threshold when the design lower limit is reached, and the pressure drops sharply after exceeding the limit. The flow value at the right inflection point or termination point in the curve. The inlet pressure affects the overall upward movement of the curve when the inlet pressure increases. The selection should refer to the curve corresponding to the lowest inlet pressure. Structural difference - direct action formula: When the inlet pressure decreases, the sag increases (the stability decreases);

　　- 先导式：入口压力变化对下垂量影响小（稳压性优）。减压阀的不同功能带过滤功能的减压阀带电子控制的减压阀带安全泄压的减压阀

　　-Pilot type: The change in inlet pressure has little effect on the sag (excellent stability). Different functions of pressure reducing valves: pressure reducing valves with filtering function, pressure reducing valves with electronic control, and pressure reducing valves with safety relief

　　03案例分析

　　03 Case Analysis

　　前提条件：入口压力为2.0Mpa，向工件内部充1.6MPa氮气，工件容积10L，压力控制精度±0.5%，要求在2s内充满。由于是氮气且压力控制精度不高，所以选择性价比高的黄铜减压阀。工作压力在减压阀的量程范围内，满足要求。通过选型手册可以找到上面的型号满足要求，下面验证一下流量是否满足要求？

　　Prerequisite: The inlet pressure is 2.0Mpa, and 1.6MPa nitrogen gas is filled into the interior of the workpiece. The workpiece volume is 10L, and the pressure control accuracy is ± 0.5%. It is required to be filled within 2 seconds. Due to the nitrogen gas and low pressure control accuracy, a cost-effective brass pressure reducing valve is chosen. The working pressure is within the range of the pressure reducing valve and meets the requirements. Through the selection manual, we can find the models above that meet the requirements. Now, let's verify if the flow rate meets the requirements?

　　平均流量 ≈ 0.6 × 起始流量；（起始流量 = 充气开始时容器压力为大气压时的瞬时流量）系数 0.6 是工程经验值，适用于大多数从常压充到 50%~80% 气源压力的场景；目标压力≤ 50% 气源压力取0.7，误差约 ±10%；目标压力≈80%气源压力取0.5，误差约 ±15%；根据流量特性曲线图，做入口压力2.0MPa与入口压力1334psi的平行线，大致可以知道当出口压力是1.5MPa时，起始流量大致为4000SCFH，所以平均流量为2400 SCFH=67946.4 L/min=1132.44 L/s。（1 SCFM=0.028311m^3/min=28.311L/min）t = 容器容积*(目标压力 - 大气压）/平均流量 。t=1.5*10*10/2 s= 75 L/s ＜ 1132.44 L/s，满足要求，可以选择此款减压阀。

　　Average traffic ≈ 0.6 x initial traffic; The coefficient of 0.6 (initial flow rate=instantaneous flow rate when the container pressure is at atmospheric pressure at the beginning of inflation) is an engineering empirical value, suitable for most scenarios where the gas source pressure is increased from atmospheric pressure to 50%~80%; The target pressure is ≤ 50%, and the gas source pressure is taken as 0.7, with an error of about ± 10%; The target pressure is approximately 80%, and the gas source pressure is taken as 0.5, with an error of about ± 15%; According to the flow characteristic curve, draw parallel lines between the inlet pressure of 2.0MPa and the inlet pressure of 1334psi. It can be roughly known that when the outlet pressure is 1.5MPa, the initial flow rate is approximately 4000SCFH, so the average flow rate is 2400 SCFH=67946.4 L/min=1132.44 L/s. (1 SCFM=0.028311m ^ 3/min=28.311L/min) t=container volume * (target pressure atmospheric pressure)/average flow rate. t=1.5*10*10/2 s= 75 L/s ＜ 1132.44 L/s， If the requirements are met, this pressure reducing valve can be selected.

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