1. What is the difference between flow control and mass flow control?
Werner Alber: Flow control measures the volume of a gas per unit of time and reacts sensitively to pressure and temperature fluctuations. Mass flow control, on the other hand, records the actual gas mass and ensures constant values regardless of the ambient conditions – ideal for precise applications such as in medical technology or semiconductor production.
In short: While flow control focuses on volume, mass flow control ensures that the same mass of gas always flows through the system, regardless of the external influences.
2. What is a mass flow controller and how does it work?
Werner Alber: Imagine you always have to supply the same amount of gas in a process. If you set a classic volumetric flow controller to 10 l/min, you will only get exactly the same amount of gas under certain conditions. If the temperature rises, the gas will expand – at 10 l/min the gas mass will be lower. Conversely, higher pressure means that there will be more molecules in 10 liters. 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 allows for highly precise and stable control. It keeps the gas volume constant, repeatable and efficient. In contrast to simply controlled throttle valves, mass flow controllers control the mass flow and actively stabilize it to ensure consistent process conditions. This makes it the ideal solution for applications that require high precision, dynamics and process reliability.
3. How does the control method of a mass flow controller differ from that of a throttle valve?
Werner Alber: The key difference lies in the type of regulation. Mass flow controllers operate in a closed control loop: They continuously regulate the current mass flow and precisely adjust the valve to keep the desired setpoint constant. A throttle valve (such as a needle valve with a flow meter) is often passive or manually adjustable. If the process conditions change, a conventional valve has to be adjusted manually. It does not "know" that anything has changed. Mass flow controllers, on the other hand, react to deviations in real time.
You could say that: An MFC thinks for itself, whereas a simple flow controller is just a fixed flow control valve. In practice, this means that mass flow controllers provide significantly higher precision and consistency, especially when the ambient conditions are not absolutely constant.
4. What different measuring principles are there for mass flow controllers and how do they work?
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 usually used. Pressure differential-based processes, which enable a faster reaction compared to thermal principles, are also becoming increasingly widespread. The Coriolis principle is also worth mentioning. This measures the mass flow directly. The measuring principle that is selected always depends on the specific requirements of the application.
5. How is a mass flow controller constructed and what components does it contain?
Werner Alber: A mass flow controller consists of three central components: Sensors, control electronics and a proportional valve as the control element. The sensors record the mass flow based on a specific measuring principle. The measured values are processed by the control electronics, which then compares them with the specified setpoint. Deviations are detected immediately and passed on to the regulator, which acts as a control element to regulate the flow accordingly.
Here at Festo, we rely on piezo technology, which enables highly dynamic, energy-efficient and virtually wear-free control. Precise coordination of all the components enables exact, stable and reproducible flow control. The entire process is controlled by a higher-level control unit that synchronizes all the components and makes continuous adjustments.
6. What are the advantages of piezo technology in mass flow controllers and why does Festo rely on this technology?
Werner Alber: Piezo technology offers decisive advantages in mass flow controllers compared to conventional solenoid valves. They enable high-precision, energy-efficient and low-wear flow control. Piezo valves use a ceramic bending element that deforms when voltage is applied, causing the valve to open or close. One 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 power consumption, but also prevents unwanted heat generation in temperature-controlled environments.
Piezo valves are also completely silent, as no coils or mechanical switching operations are required. This is particularly advantageous in environments where acoustic interference must be avoided. Their high control accuracy and fast response time enable sensitive, infinitely variable control of the mass flow. Thanks to their compact design, mass flow controllers with piezo valves can be integrated in a particularly space-saving manner, which is ideal for mobile solutions or confined applications. They are also durable, as they contain hardly any moving parts and show practically no wear.
7. What role do mass flow controllers play in industrial settings and in which sectors are they used?
Werner Alber: Mass flow controllers with piezo technology are characterized by their wear-free, noiseless and low-power operation, making them particularly suitable for applications where temperature stability, fine controllability and a long service life are crucial.
MFCs play a central role in semiconductor production in particular. Process gases such as etching, carrier or protective gases must be regulated with the utmost precision 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 carrier gases into process chambers and load ports to minimize contamination and ensure constant process conditions.
Another key area is medical and laboratory technology. In ventilators or anesthesia machines, mass flow controllers control precise mixing ratios of oxygen and other gases for patients. In analytical laboratory devices, such as gas chromatographs or mass spectrometers, they ensure reproducible gas flows for high-precision measurements.
8. What innovations and trends do you currently see in mass flow control?
Werner Alber: Mass flow control is developing in the direction of digitalization, miniaturization and energy-efficient automation. An advance in the technology of mass flow controllers can be seen in the addition of the faster differential pressure method to thermal measurement methods, which enables dynamic control.
A further innovation boost can be observed in miniaturization and new sensor technologies. MEMS and CMOS technologies enable high-precision sensors with low energy consumption, making 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 – a significant contribution to digitalized pneumatics.
9. What recommendations do you have for companies that want to implement intelligent concepts for mass flow control or automation?
Werner Alber: The key to efficient mass flow control lies in precision, energy efficiency and seamless integration. Companies should check what accuracy and response times their processes require at an early stage. The use of energy-efficient actuators is a centralized approach to optimization.
Piezo technology significantly reduces power consumption, eliminates heat generation and enables precise, wear-free control. Companies should also rely on intelligent diagnostic functions to make servicing more predictable and processes more stable.
A system analysis is recommended for the next step: Where do the losses occur? What components are operating inefficiently? Targeted consulting or a test run with modern mass flow controllers quickly provides information on optimization potential. Digital, scalable solutions increase efficiency, process reliability and flexibility in the long term.
We would like to thank Werner Alber for this informative interview and his in-depth insights into the world of mass flow control. His expertise has highlighted how precise control, digital networking and piezo technology can increase efficiency and process reliability in numerous industries. Companies that rely on modern mass flow control benefit from greater precision, more efficient use of energy and optimized process reliability – all decisive factors for future-proof automation.
