1. What is the difference between flow control and mass flow control?
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.
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 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.
3. How does the control mode of a mass flow controller differ from a flow control valve?
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.
4. What are the different measuring principles 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 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.
5. How is a mass flow controller built and what components does it have?
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.
6. What are the advantages of piezo technology in mass flow controllers, and why does Festo use this technology?
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.
7. What role do mass flow controllers play in industry and in which sectors are they used?
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.
8. What, in your view, are the latest innovations and trends in mass flow control?
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.
9. What recommendations do you have forcompanies that want to create 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 at an early stage what precision and response times their processes require. A key optimisation approach is the use of energy-efficient final control elements.
Piezo technology significantly reduces power consumption, eliminates heat generation and enables precise, wear-free control. Companies should also use intelligent diagnostics functions to make maintenance more predictable and processes more stable.
A next recommended step would involve a system analysis. Where do losses occur? Which components are working inefficiently? Specific advice or a test run with modern mass flow controllers quickly provides information on any optimisation potential. Digital, scalable solutions increase efficiency, process reliability and flexibility in the long term.
Thanks to Werner Alber for the 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 energy use and optimised process reliability, all of which are decisive factors for future-proof automation.
