齿轮执行机构
GEAR ACTUATORS

　　采用齿轮执行机构通常是为了使阀门操作更加容易。齿轮执行机构可能是正齿轮、锥齿轮或蜗轮，任何一种都可以应用在Velan的阀门上。
　　Gearing is generally applied to valves to make operation easier. The gearing may be of the spur, bevel or worm type–any of which may be applied to Velan valves.
　　齿轮和齿轮托可以是铸铁或铸钢，可以有铸造或机加工的齿轮齿，取决于负载和应用环境。
　　The gears and gear brackets may be either cast iron or cast steel and may have cast or cut teeth, depending on the loads and the application.
　　在考虑阀门的运作时，齿轮执行机构通常被忽视，导致运作无法令人满意，并不得不作成本高昂的改进。
　　Gearing is too often neglected when valve operation is considered, resulting in unsatisfactory operation requiring expensive changes.

电动执行机构
ELECTRIC ACTUATORS

　　电动控制可以应用在几乎所有通径的阀门上，使用中，可以应用在几乎所有地方或位置。
　　Motorized controls may be applied to valves of almost any size for operation in practically any position or location.
　　所有装置，无论是直接安装在阀门上，或安装在地轴架上，都可以在电力中断的情况下进行人工操作。这些装置既可以用交流电，或可以用直流电。
　　All units, whether installed directly on a valve or on a floor stand, can be manually operated in case of power failure. The units are available for either alternating or direct current.
　　Velan提供的电动装置具有大扭矩，线圈绕组经过浸渍，既防油又防潮。这些装置完全能够经受风吹雨打，具有防爆（备选功能）和防尘，具有蒸汽气密性。
　　Motor units supplied by Velan are the high torque type with windings impregnated to resist both oil and moisture. They are completely weather-proof, explosion-proof (optional) and dust and steam tight.
　　可提供各种通径和款式应用于不同的环境，此外还可以进行改型以适应特殊的要求。
　　Various sizes and styles are available for different applications, and systems and can be varied to fit special requirements.

缸体执行机构
CYLINDER ACTUATORS

　　最常用的缸体执行机构是气动执行机构，但是如果需要，也可提供油动或水动执行机构。在所有结构中，阀杆通常作为活塞杆，阀瓣直接固定在阀杆上。尾杆也作为标准配置，用于作为位置指示器，或用于紧急开启用。手轮和齿轮头可以安装在缸体的顶部，用于在缸体内工作介质丧失时应急用。
　　The most commonly-used cylinders are actuated by air, but oil and water types are also available if required. In all designs, the valve stem normally serves as a piston rod with disc fastened directly to them. Tail rods are also supplied as standard equipment to serve as position indicators and for emergency opening. Handwheels and gear heads can be mounted on top of cylinders for operation in an emergency which may arise due to the loss of operating medium in the cylinder.
　　Velan缸体执行机构可以为商用缸体执行机构或阀门定位器配置安装垫，以起到节流控制作用。我们也可以为特殊应用场合提供高压缸体执行机构。
　　Velan cylinders can be furnished with mounting pads for one of the commercial cylinders or valve positioners which provide throttling control. High pressure cylinders are also available for specific applications.

阀门执行机构大小选择
VALVE ACTUATOR SIZING

　　Velan选择执行机构的原则是针对所应用的环境，计算操作阀门所需要的推力和扭矩。最后的执行机构的选择总是要考虑执行机构工作能力适当的余量，但是要避免选择能力过大的执行机构。
　　The Velan philosophy for selecting an actuator is to calculate the required thrust and torque to operate the valve at the required service conditions. A reasonable margin of excess actuator capability over that required is always allowed for in the final actuator selection, but grossly oversized actuators are avoided.
　　由于系统操作环境多种多样，执行机构的选型还要考虑下列因素：
　　Because of the wide variations in system operating conditions, actuator sizing is based on the following:

链轮
CHAIN WHEELS

　　所有类型的Velan铸钢阀门都可以采用链轮。它们可以替代平面手轮或可以用来附加在现存的首轮上。
　　Chain wheels are available for all types of Velan cast steel valves. They may be substituted for a plain handwheel or may be used in addition to the existing handwheel.

地轴架
FLOOR STANDS

　　地轴架适用于许多通径的阀门，其尺寸大小取决于阀杆尺寸和阀杆的负载。
　　Floor stands are available in a number of sizes, and the size to be used depends on the stem size and stem load of the valve.