Werner Alber: With flow control, the volume of a gas per unit of time is measured and it reacts sensitively to pressure and temperature fluctuations. Mass flow control, on the other hand, records the actual gas mass and ensures the values remain constant, regardless of ambient conditions. This is ideal for applications requiring precision such as in medical technology or semiconductor production.
In a nutshell: While with flow control the focus is on volume, mass flow control ensures that the same mass of gas always flows through the system, regardless of external influences.
Werner Alber: Imagine you always have to supply the same amount of gas in a process. If you set a classic volumetric flow control valve to 10 l/min, you will only get exactly the same amount of gas under certain conditions. If the temperature rises, the gas expands – at 10 l/min, there is then less gas mass. Conversely, higher pressure means that there are more molecules in 10 litres. A mass flow controller determines the mass of the flowing medium. As the mass of a gas – in contrast to the volume – is not influenced by pressure or temperature, this provides a highly precise and stable control process. This keeps the gas volume constant, repeatable and efficient. In contrast to flow control valves that have a simple control method, mass flow controllers regulate the mass flow rate and actively stabilise it to ensure process conditions are consistent. This makes it the ideal solution for applications that require high precision, dynamic response and process reliability.
Werner Alber: The crucial difference lies in the type of control. Mass flow controllers operate in a closed control loop. They continuously control the actual mass flow rate and precisely adjust the valve to keep the setpoint at a constant value. A flow control valve (such as a needle valve with flow meter) can often be passively or manually adjusted. If the process conditions change, a conventional valve must be readjusted manually – it does not "know" that anything has changed. Mass flow controllers, on the other hand, react to deviations in real time.
So you could say that an MFC thinks for itself, whereas a simple flow control valve is just a fixed restrictor. In practice, this means significantly mass flow controllers offer significantly higher precision and consistency, especially when the ambient conditions are not absolutely constant.
Werner Alber: A mass flow controller (MFC) can detect the gas flow using various physical methods. The most commonly used method is the thermal (calorimetric) principle, especially for gas applications. The heat loss and heat transfer methods are the ones that are typically used. Pressure differential-based processes are also becoming increasingly common, as they enable a faster reaction compared to thermal principles. Also worth mentioning is the Coriolis principle, which measures the mass flow rate directly. Which measuring principle is selected always depends on the specific requirements of the application.
Werner Alber: A mass flow controller consists of three central components: Sensors, control electronics and a proportional valve as a final control element. The sensors record the mass flow rate based on a specific measuring principle. The measured values are processed by the control electronics, which compare them with the setpoint value. Deviations are detected immediately and passed on to the regulator, which acts as a final control element to regulate the flow rate accordingly.
At Festo, we use piezo technology, since it allows us to control very dynamically, energy-efficiently and virtually wear-free. It is this precise coordination of all components that facilitates an exact, stable and reproducible flow control. The entire process is controlled by a higher-level control unit that synchronises all components and makes continuous adjustments.
Thanks to state-of-the-art technologies, Festo is taking classic proportional technology to a new level. We call this Controlled Pneumatics. Piezo and moving coil valves operate together with sensors and intelligent control algorithms in a closed loop. This makes pneumatic applications even more precise, energy-efficient and reliable, and also opens up new opportunities in automation.
Werner Alber: Piezo technology offers crucial advantages in mass flow controllers compared to conventional solenoid valves. It facilitates high-precision, energy-efficient and low-wear flow control. Piezo valves have a ceramic bending element that deforms when voltage is applied, thus opening or closing the valve. A major advantage is the extremely low energy consumption. Once the valve is in position, the piezo actuator requires almost no energy as no holding current is required. This not only reduces the power requirement, but also prevents unwanted heat development in temperature-controlled environments.
In addition, piezo valves are completely silent, as no coils or mechanical switching processes are required. This is particularly beneficial in environments where acoustic malfunctions have to be avoided. Their high control accuracy and fast response time support the sensitive, infinitely variable control of the mass flow rate. Thanks to their compact design, mass flow controllers with piezo valves are very space-saving to integrate, making them ideal for mobile or confined applications. They are also durable, as they contain hardly any moving parts and are virtually wear-free.
Werner Alber: Mass flow controllers with piezo technology are characterised by their wear-free, quiet and energy-saving operation; this makes them particularly suitable for applications where temperature stability, precision controllability and a long service life are crucial.
MFCs play a central role in semiconductor production in particular. Process gases such as corrosive, carrier or shielding gases must be regulated extremely precisely in order to produce flawless microchips. Even the smallest deviations in the gas flow could lead to defects on the wafers. Mass flow controllers regulate the precise supply of protective and shielding gases into process chambers and load ports to minimise contamination and ensure constant process conditions.
Another key area is medical technology and laboratory technology. In ventilator breathing devices or anaesthesia machines, mass flow controllers make sure that the mixing ratios of oxygen and other gases for patients are precisely controlled. In analytical laboratory devices, such as gas chromatographs or mass spectrometers, they ensure reproducible gas flows for high-precision measurements.
Werner Alber: Mass flow control is developing in the direction of digitalisation, miniaturisation and energy-efficient automation. Advances in the technology of mass flow controllers include the addition of the faster pressure differential method to thermal measurement methods, which permits dynamic control.
Another innovation boost can be observed in miniaturisation and new sensor technologies. Thanks to MEMS and CMOS technologies, sensors can operate even more precisely and consume very little energy, which makes mass flow controllers more compact and efficient. Overall, mass flow controllers are becoming more precise, more networked and more flexible. They consume less energy and can be integrated more efficiently into modern automation systems, thus making a significant contribution to digitalised pneumatics.
Werner Alber： 实现高效的质量流量控制，关键在于精度、能效和无缝集成。 企业必须及早检查各项流程所需的准确性和反应时间。 使用高能效执行器是切实有效的优化方法。
压电技术不但大幅降低电耗，还能避免产生热量，实现精确、无磨损的控制。 此外还建议企业采用智能诊断功能，加强维护的可规划性，增强流程稳定性。
接下来建议进行系统分析： 损失发生在哪里？ 哪些部件工作效率低下？ 有针对性的咨询或者使用先进的质量流量调节阀进行测试运行，可以快速获取优化潜力的相关信息。 可扩展的数字化解决方案可以长期提高效率、过程安全性和灵活性。
感谢 Werner Alber 对质量流量控制领域所作的深入剖析，令人茅塞顿开。 在他的阐述中，着重介绍了精确控制、数字化网络和压电技术如何提高各个行业的效率和过程安全性。 对于采用现代化质量流量控制技术的企业来说，不但能提高精度和能效，还能优化过程安全性，而这些，都是面向未来实现自动化的决定性因素。