Where there is no instrument air, what automatically operates the valve? Often an electric actuator. It turns electrical energy into rotary or linear motion to drive ball, butterfly or gate valves, and can directly accept 4-20mA or bus signals.

Electric actuators need no air supply; wiring alone makes them work, ideal for sites without compressed air, or for scattered valves with low cycling. But they have their own selection points.

1. How an Electric Actuator Outputs Force

Two common forms:

  • Quarter-turn: 90-degree rotation for ball and butterfly valves;
  • Linear (thrust)： straight motion for gate, globe or control valves.

Either way the core parameters are output torque (or thrust) and full-stroke time.

2. Torque Is Not Guesswork

The torque a valve needs at breakaway often far exceeds running torque. Size with margin:

  • Select 1.2 to 1.5 times the valve's maximum required torque;
  • Abrasive, viscous or cryogenic media raise breakaway torque;
  • Undersized units stall, overheat and may burn the motor.

Valve data sheets usually state required torque; match against it directly.

3. Speed and Frequency

  • Full-stroke time: seconds to tens of seconds open to close;
  • Cycling: a few times a day versus many times a minute greatly affects motor and gear life;
  • Frequent duty needs a high-cycle motor; ordinary heads overheat.

Too fast a close can cause water hammer; too slow may miss interlocks. Speed is set by process.

4. Power Supply

Electric units consume power; the supply must be clear:

  • Single-phase AC220V, three-phase AC380V, or DC24V;
  • Voltage tolerance and frequency;
  • Need for explosion-proof supply or isolation transformer.

Mismatch causes erratic motion or controller damage.

5. Protection and Explosion-Proof Rating

Outdoor heads must resist rain, dust and temperature swing:

  • Common rating IP67 (immersion) or higher;
  • Hazardous areas need Ex d / Ex e certified products;
  • Coastal or corrosive sites need coating and sealing.

Saying explosion-proof is not enough; provide the project's Ex mark, gas group and temperature class.

6. Control Signal and Bus

  • Basic: discrete or 4-20mA;
  • Smart: Modbus, Profibus, Foundation Fieldbus, etc.;
  • Bus types enable centralized monitoring, diagnostics and parameter download.

The head must speak the signal the control system emits, or add a converter.

7. Manual and Limits

  • Handwheel or lever: manual on power loss;
  • Limit switch: cuts motor at full open/close;
  • Torque switch: over-torque protection for valve and actuator.

These are basic safe-operation items, not optional.

8. Electric vs Pneumatic

Aspect Electric Pneumatic
Power Electricity Instrument air
Air-loss safety Needs battery/capacitor hold Spring to safe position
Large-bore thrust Limited Strong
Explosion-proof Certified needed Intrinsically safe
Maintenance Less Air system upkeep

No air, low cycling, yet remote monitoring wanted — electric is often easier.

9. Quick Selection

Confirm: valve type and required torque, full-stroke time, cycling frequency, power spec, protection/Ex rating, control signal or bus type, need for handwheel and limit protection.

Hand these to the supplier for matched motor power, gear ratio and controller model.

10. Common Myths

  • Myth: an electric head can be jogged indefinitely. Frequent jogging overheats; use at rated frequency.
  • Myth: more torque is always better. Too much can crush seals or limit gear.

Summary

Electric actuator selection starts with torque and speed, then power, protection and control signal. State duty and frequency clearly, and the electric option will reliably operate your valves where no air exists.

Wuxi Quankong Valve & Fluid Control Co., Ltd.
Industrial Valves | Valve Selection | Actuator Packages | Fluid Control Solutions
Email: quanvalve@foxmail.com

没有仪表风的地方，阀门靠什么自动开关？答案常常是电动执行机构。它把电能变成旋转或直行动力，驱动球阀、蝶阀、闸阀动作，还能直接接收 4-20mA 或总线信号。

电动执行机构不依赖气源，布线即可工作，特别适合没有压缩空气、或阀门分散、动作不频繁的场合。但它也有自己的选型要点。

一、电动执行机构怎么出力

常见有两种输出形式：

  • 角行程：输出 90 度旋转，驱动球阀、蝶阀；
  • 直行程（推力型）：输出直线运动，驱动闸阀、截止阀或调节阀。

无论哪种，核心参数都是输出力矩（或推力）和全行程时间。

二、力矩不能随便估

阀门在启闭瞬间需要的力矩，往往远大于稳定运行力矩。电动机构选型要留余量：

  • 按阀门最大所需力矩的 1.2 至 1.5 倍选；
  • 含颗粒、黏度高或低温的介质，起始力矩更大；
  • 力矩不足会堵转、过热，甚至烧电机。

厂家的阀门数据表通常会给出所需力矩，直接对照即可。

三、速度和频率

  • 全行程时间：从全开到全关需要几秒到几十秒；
  • 动作频率：一天动几次与一分钟动几次，对电机和齿轮寿命影响很大；
  • 频繁动作的场合要选专用高频电机，普通电动头容易过热。

关闭过快可能引起水锤，过慢又可能跟不上联锁，速度要由工艺确认。

四、电源条件

电动机构吃电，电源必须明确：

  • 单相 AC220V、三相 AC380V，或 DC24V；
  • 电压波动范围、频率；
  • 是否需防爆电源或隔离变压器。

电源不匹配，轻则动作异常，重则损坏控制器。

五、防护与防爆等级

安装在室外的电动头，要能扛住雨水、粉尘和温差：

  • 防护等级常用 IP67（防浸水）或更高；
  • 防爆区要用 Ex d / Ex e 等认证产品；
  • 沿海、腐蚀环境要考虑涂层和密封。

只写要防爆不够，应提供项目的防爆标志、气体组别和温度组别。

六、控制信号与总线

  • 基本型：开关量或 4-20mA；
  • 智能型：支持 Modbus、Profibus、Foundation Fieldbus 等；
  • 总线型便于集中监控、诊断和参数下发。

控制系统输出什么信号，电动头就要能听懂什么信号，否则需要额外转换模块。

七、手动与限位

  • 手轮或手柄：断电时手动操作；
  • 限位开关：到达全开/全关自动切断电机；
  • 转矩开关：超力矩保护，防止阀门和机构受损。

这些是安全运行的基本配置，不能省。

八、与气动方案怎么选

维度 电动 气动
动力源 电源 仪表风
失气安全 需电池/电容保位 弹簧复位到安全位
大口径推力 受限 强
防爆 需认证 本质安全
维护 较少 气路维护

没有气源、动作不频繁、又要远程监控时，电动往往更省心。

九、选型速查

确认：阀门类型与所需力矩、全行程时间、动作频率、电源规格、防护/防爆等级、控制信号或总线类型、是否需要手轮和限位保护。

把这些交给厂家，才能得到匹配的电机功率、减速比和控制器型号。

十、常见误区

  • 误区：电动头能一直点动。 频繁点动会过热，应按额定频率使用。
  • 误区：力矩越大越好。 过大可能顶坏阀门密封或限位机构。

总结

电动执行机构选型先定力矩和速度，再配电源、防护和控制信号。把工况和频率说清，电动方案才能在没气源的现场稳定可靠地替你开关阀门。

无锡泉控阀门流体控制有限公司
工业阀门 | 阀门选型 | 执行机构配套 | 流体控制解决方案
技术咨询：quanvalve@foxmail.com