Types and Features of Valve Actuation Devices (Baird Valves)

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A valve actuator is a device used to operate a valve and is connected to the valve. The device can be driven by power sources such as manual, electric, pneumatic, hydraulic, or a combination thereof, and its movement can be controlled by the magnitude of stroke, torque, or axial thrust. The selection of a valve actuator should be based on a thorough understanding of the various types and performance characteristics of such actuators, and it depends on the type of valve, the operating requirements of the system, as well as the location of the valve within the pipeline or installation. At present, there are mainly two connection standards for valve actuation devices in China, namely GB/T 12222 \"Connection of multi-turn valve actuation devices\" and GB/T 12223 \"Connection of partially turned valve actuation devices\". These two standards correspond respectively to ISO 5210 and ISO 5211. \"Connection of multi-turn valve actuation devices\" is primarily applicable to the connection dimensions between actuation devices for gate valves, globe valves, throttle valves, and diaphragm valves and the valves themselves. \"Connection of drive devices for partially revolving valves\" mainly applies to the connection dimensions between drive devices used for ball valves, butterfly valves, and plug valves and the valves themselves. Valve actuation devices can be classified into straight-stroke and rotary-stroke types based on their mode of movement. The linear stroke actuation device, also known as the multi-turn valve actuation device, is mainly suitable for various types of gate valves, globe valves, and throttle valves ； A angular travel actuator is a type of rotary actuator that can rotate only 90°, and it is mainly used for various types of ball valves, butterfly valves, etc. Valve actuation devices can be classified according to the type of energy used into various forms, such as manual (handle and knob types, spring-lever types), electric (electromagnetic types, motor-driven types), pneumatic (diaphragm types, cylinder types, vane types, air-engine types, film and ratchet combination types), hydraulic (hydraulic-cylinder types, hydraulic-motor types), and hybrid (electro-hydraulic types, pneumo-hydraulic types). Among various types of valve actuation devices, electric actuators dominate and are mainly used in closed-loop valves. Pneumatic devices are widely used in applications with explosion-proof requirements these days, among which diaphragm-type pneumatic devices are mainly used in control valves. Hydraulic devices are widely used in natural emergency shut-off valves on long-distance pipelines and wellhead blowout valves. The handwheels of manual devices are mostly installed on low and medium pressure globe valves and gate valves ； Handles are used on valves such as high-pressure and ultra-high-pressure globe valves, ball valves, and stopcocks. A gas-liquid actuator is commonly used in gas transmission pipelines in outdoor areas where no power source is available; its power source is the gas in the pipeline. I. Manual valve actuation devices: Manually driven valves are the most commonly used in pipelines under various operating conditions. One type is driven directly by a handwheel or handle, while the other type is driven by a handwheel through gear transmission. 1) Handwheel or handle. Generally, when the opening and closing torque is relatively low, a single person or at most two people with normal physical strength can open and close the valve. Typically, the material of handwheels or handles is malleable cast iron, ductile cast iron, or carbon steel; aluminum alloys or plastics are also used. 2) Impact type handwheel. On high-pressure valves, impact-type handwheels are commonly used to increase the operating torque. In impact-type handwheels, an appropriate gap exists between the handwheel and the valve stem nut, allowing the handwheel to rotate by a certain angle on its own. At the moment of opening or closing the valve, the handwheel can be rotated rapidly, thereby generating an impact force on the valve stem nut. This impact force is **greater than that produced by ordinary handwheels, which increases the torque required for opening and closing the valve. 3) Gear transmission manual device. When a valve requires considerable force to be operated by one person, gear or worm gear transmissions are usually used to reduce the force needed for opening and closing it. Gear transmission systems include spur gear and bevel gear transmissions. The gear transmission ratio is usually 1:3, and it is commonly used in gate valves and globe valves. Gear drives include open-type single-stage gear drives and closed-type two-stage gear drives; currently, closed-type two-stage gear drives are more commonly used. Advantages and disadvantages of manual devices:
Advantages of the operating method:
– Threaded rod transmission mechanism mounted at the top: a. Simple structure; b. Low cost.
Disadvantages: a. High installation position, making operation inconvenient; b. Space is required at the top.
– Linkage mechanism mounted on the side: a. Easy to operate; b. High stresses can occur in the support during vibration; c. Prone to corrosion.
– Worm and gear transmission mechanism mounted on the support: a. Complete sealing and full lubrication; b. Increases the height of the driving device.
When using manual emergency shutdown, the time required for the handwheel to rotate a certain number of turns must be taken into account.
Single manual drive for manual adjustment – inexpensive. However, vibration (due to the handle on the wheel) often damages the valve’s internal components or causes the cast-iron support to break.

II. Valve electric drives:
Valve electric drives come in two types based on their mode of operation: multi-turn type (Z-type), as shown in Figure 1, and partial-turn type (Q-type), as shown in Figure 2. The former is used for lift rod-type valves, such as gate valves, globe valves, throttle valves, diaphragm valves, etc ； The latter is used for valves such as ball valves, plug valves, and butterfly valves that open and close within a 90° range. Advantages and Disadvantages of Valve Electric Actuators
Advantages:
a. High versatility, not affected by ambient temperature.
b. Wide range of output torque.
c. Easy to control, facilitating the automated operation of process systems.
d. Possible to achieve ultra-compact design.
e. Mechanism has self-locking capability.
f. Easy to install, maintain, and service.

Disadvantages:
a. Complex structure.
b. Low mechanical efficiency, usually only 25–60%.
c. The output speed cannot be too high or too low.
d. Prone to being affected by changes in power supply voltage and frequency.

III. Valve Pneumatic Actuators
Valve pneumatic actuators are widely used in applications where explosion protection is required. Based on their structural characteristics, they can be divided into three types: diaphragm-type pneumatic actuators, cylinder-type pneumatic actuators, and swing-type pneumatic actuators. In addition, there are also pneumatic motor-type actuators. Typical pneumatic devices and air circuit systems. Structure of single-cylinder pneumatic devices Advantages: a. Simple structure b. Easy access to air supply c. High switching speed possible d. Speed controllers can be installed to adjust the switching speed as needed e. Gas is highly compressible, allowing for elastic closure Disadvantages: a. Larger in size compared to hydraulic devices; not suitable for valves with large diameters and high pressures. b. Due to the compressibility of gases, it is difficult to achieve uniform velocity. IV. Hydraulic actuators The hydraulic actuator for valves consists of three main components: a power source, a control unit, and an actuating mechanism. The function of the power source is to convert the useful power of electric or pneumatic motors into hydraulic power for fluid transmission. The control section consists of control valves, such as pressure control valves, flow control valves, direction control valves, and an electrical control system. There are two types of actuators: one is the cylinder actuator, which enables reciprocating linear motion ； Another type is the oil motor actuator, which enables rotational motion. Advantages and disadvantages of hydraulic devices Advantages: a. Simple, compact structure with small size; b. High output force, as well as smooth and reliable transmission; c. Easy to achieve low or high speeds, with convenient speed adjustment; d. Enables remote automatic control; e. Higher efficiency due to the viscosity of hydraulic oil, along with self-lubricating and rust-resistant properties. Disadvantages: a. Changes in oil viscosity caused by temperature variations; b. Hydraulic components and pipes are prone to leakage; c. Difficulties in piping and maintenance; d. Not suitable for performing various calculations on signals. V. Integrated drive systems Valve hydraulic drive devices can be combined with electric and pneumatic systems to form electro-hydraulic or pneumatic-hydraulic integrated systems. Figure 9 shows the pneumatic-hydraulic actuated emergency shut-off valve of the pipeline shutdown control system. Advantages and disadvantages of electro-hydraulic actuation devices: Advantages: a. High output force; b. Rapid valve opening and closing. Disadvantages: a. High cost; b. Complex structure. Advantages and disadvantages of pneumatic-hydraulic actuation devices: Advantages: a. Compact structure, smooth operation, and the ability to generate high output torque; b. It is possible to select the most economical and suitable power source based on the actual usage conditions; c. The maximum output torque can be precisely adjusted using a constant-pressure relief valve; d. Easy speed control, wide adjustment range, and stepless speed regulation; e. Suitable for various types of automatic control systems; f. Accumulators can be used in conjunction with these valve actuation systems. Disadvantages: a. High cost; b. Complex structure, lower reliability