There are countless types of valves for use across a variety of industries and applications. When it comes to flow control valves,valve types range from simple to sophisticated;一些阀门足够复杂，可以自动调整到压力和温度变化。无论它们的结构，流量控制阀都设计用于调节流体的流动或压力，并且通常对流量计或温度表产生的信号反应。
What’s the Function of a Flow Control Valve?
Flow control valves can serve a number of different functions within a hydraulic flow system depending on the specific type that is used. One of the most common uses of a flow control valve is to regulate thespeed of motors或系统内的圆柱体. This function is possible due to the capability of a flow control valve to affect the rate of energy transfer at any given point in a system by impacting the flow rate.
The ability to reduce or increase pressure in a system has a number of benefits. System operators can use a flow control valve to rapidly depressurize a serviceable hose and change fittings quickly. They are also used in many consumer applications such as showers, faucets, and lawn watering systems to easily reduce the amount of water consumed without impacting the overall system performance. Flow control valves are also known for their reliability and typically have a long operating lifetime as they are not prone to clogging due to their design.
Due to these flexible性能参数, flow control valves have found wide use in applications across materials handling, food processing, and automated factory and warehouse equipment.
1. Gate Valves
Gate valves是通用服务阀门主要用于开/关，无节流服务。具体地，闸阀用于需要直线流体的液体的应用 需要限制。当用户沿顺时针旋转杆以关闭（CTC）运动或顺时针以打开（CTC）运动时，栅极阀操作。当操作员移动杆时，栅极向上移动或向下移动，这就是为什么它是多匝阀;阀门必须转换几次，以便从开放到关闭，这是防止水锤效应的慢速操作。当需要最小压力损失和自由孔时，工程师还利用闸阀。流动路径中典型的闸阀没有阻塞，这导致压力损失最小。
Gate valves may be used for several fluids. Generally, gate valves are applicable for potable water, wastewater, and neutral liquids; in temperatures between -20 and 70 degrees Celsius; maximum 5 meter/second flow velocity; and up to 16 bar differential pressure. Gate valves also are applicable for gases with temperatures between -20 and 60 degrees Celsius; maximum 20 meter/second flow velocity; and up to 16 bar differential pressure.
图像ViaFlickrby Elsie esq
A linear motion valve,地球阀门停止、启动和调节流量。截止阀initiate closure via a plug featuring a flat or convex bottom that is lowered onto a horizontal seat situated in the center of the valve. When a user opens the valve, the plug raises to allow fluid to flow. Globe valves are used for on/off and throttling applications because the disk of the valve can be removed from the flow path completely or it can completely close the flow path. While this type of flow control valve does produce slightly higher pressure drops than straight-through valves like gate, plug, and ball valves, they are applicable in situations where the pressure drop through the valve is not a controlling factor.
实际的大小limit for globe valves is NPS 12 (DN 300) because the entire system pressure exerted on the disc transfers to the valve stem. It is possible, however, to have globe valves larger than NPS 12 (DN 300), and manufacturers and engineers have created and used globe valves up to NPS 48 (DN 1200).
3. Pinch Valves
一种经济高效的流量控制阀，pinch valvesare ideal for applications of slurries or liquids containing significant amounts of suspended solids. Pinch valves seal using one or more flexible elements like rubber tubes that become pinched to turn off the flow. These rubber sleeves are the valve’s only wetted part, and their flexibility allows pinch valves to close tightly around entrapped solids. Air or hydraulic pressure is placed directly on the elastomer sleeve to actuate pinch valves. A pinch valve’s body acts as a built-in actuator, which eliminates expensive hydraulic, pneumatic, or electric operators and results in the cost-effectiveness of this type of flow control valve.
4. Diaphragm Valves
Diaphragm valvesare characterized by a flexible disc that contacts a seat at the top of the valve body and forms a seal. The diaphragm is flexible and pressure-responsive; it transmits force to open, close, or control a valve. While diaphragm valves are related to pinch valves, they use an elastomeric diaphragm rather than an elastomeric liner in the valve body. The elastomeric diaphragm is attached to a compressor and separates the flow stream from the closure element. Diaphragm valves are ideal for handling corrosive, erosive, and dirty services.
There are many advantages to using diaphragm valves: they are extremely clean, feature a leak-proof seal, have a tight shut-off, are easy to maintain, and reduce leakage to the environment. Diaphragm valves also may be repaired without interrupting a pipeline. On the other hand, the disadvantages of using diaphragm valves include only being able to use them in moderate temperatures of -60 to 450 degrees Fahrenheit and in moderate pressures of approximately 300psi. Diaphragm valves cannot be used in multi-turn operations and do not have industry standard face-to-face dimensions. Also, the body of a diaphragm valve must be made of corrosive-resistant materials.
5. Needle Valves
Needle valves can provide positive shutoff in order to allow gauges and other measurement instruments to be installed or removed safely. That’s also why needle valves may be used in a range of industries, from petrochemicals to biofuels. It is the needle valve’s finely-threaded valve stem that gives it a significant mechanical advantage by allowing operators to seal it using only minimal force. One disadvantage of needle valves, however, is that the visual inspection alone is not enough to determine whether a needle valve is open or closed.
Other Types of Flow Control Valves
Butterfly valve.Abutterfly valveis operated by rotating a disk within the flow area and, due to this design, it does not have linear flow characteristics. This makes these valves less precise than the more common flow control valve types above. For this reason, it can often be dismissed as a flow control valve choice even though it is useful in some applications that do not require a very high degree of accuracy. They are also a very affordable valve option, which makes it worthwhile to consider them in the right applications.
Plug valve.Plug valvescome in a variety of configurations and are operated by rotating a cylindrical or cone-shaped plug within the valve body to regulate the flow through a hollow area of the plug. For flow control applications the most common design is an eccentric plug valve, which uses a half plug to create a higher seating force with minimal friction as it is opened and closed. This has the advantage of greater shut off capability which is ideal for flow control situations.
Ball valve.Ball valves由于其低成本，耐用性和优异的关闭能力，通常用于众多行业的流量系统。与蝶阀类似，它们对需要高精度和控制的流量控制应用并不有效。其中一个原因是球阀需要高度的扭矩来打开和关闭，这可以防止操作员进行微调。杆和球之间还存在一定量的“游戏”，这可以使得难以找到特定的流速。对于可以进行球阀的流量控制应用，例如将罐填充到合理程度的精度，耳轴或V端口球阀设计通常是最佳选择。
Flow control valves are used in a variety of applications, such as plumbing, mechanical, and gas dispensing applications. There are many factors to consider when choosing the appropriate flow control valve for an application, such as the characteristics of the fluid, service conditions, how frequently the valve is operated, and maintenance and environmental considerations. With a variety of valve types available, comparing the function and performance of various valves alongside your application specifications will help you identify the most suitable flow control valve for your application.