Cleanroom Technology

Volume flow controllers with a static measurement principle, as they are often used to regulate supply and exhaust air in cleanrooms, typically consist of several components, which usually need to be supplemented by a separate room pressure controller and a room pressure sensor. The effort required for installing such systems is therefore very high. Alternatively, regulation can be carried out via Direct Digital Control (DDC), but this involves even more costs and effort. At the same time, the complex adjustment options that can be realized with such programmable control are not necessary in every room situation.

In contrast, Sauter's compact solution requires only two devices for room pressure regulation: the ASV 115 volume flow compact controller with an integrated second control loop and the EGP 100 room pressure sensor. "Other systems already need three devices compared to the ASV 115 — a static pressure sensor, a controller, and an actuator," explains Ulrich Fedler, Key Account Pharma Solution at Sauter. "With the compact solution, all of this is integrated into one device." The system can be used for over- or underpressure, with a direct switch between both modes possible. Room temperature regulation is also possible with this two-device system; if an additional heating or cooling circuit is to be controlled, a valve is added.

Quick retrofitting through direct connection of the room pressure sensor

The trend in cleanroom technology is increasingly moving toward flexible solutions; for example, a simple volume flow regulation should be quickly convertible to room pressure regulation. By directly connecting the room pressure sensor to the VAV controller, this is always possible with Sauter's new system. The installation effort remains low, and no additional volume flow boxes are required, which significantly saves time and costs. Since no additional controllers are connected in between, cycle times are shortened, and high control accuracy is achieved.

Additionally, parameterization is very simple. It is carried out with the Case VAV software and can be performed by the plant builder or operator themselves. Custom-developed control applications with their algorithms are activated: "A selection menu with schematics allows the required application for each case to be chosen. After parameterization and download, this information is stored in the controller," explains Fedler. With Case VAV, all parameters can be changed, and all characteristic curves can be adjusted, making the operator more independent. Compared to a DDC control system, Sauter's solution also offers the advantage of decentralized operation, working independently. "In case of a DDC failure, the compact system continues to regulate as long as the ventilation is running," says Fedler.

Testing of control applications in a specially developed test chamber

The control applications were thoroughly tested in a specially constructed room pressure test chamber by the developers beforehand. "This ensures that only applications that prove themselves are implemented," explains Fedler. Since room pressure regulation can be set up in various ways, for example with constant supply and variable exhaust or vice versa, the control behavior can be tested under different leakage scenarios in the room. The biggest challenge in developing the compact solution was to implement the control applications and functional requirements in such a way that the hardware inputs and outputs could be maintained. "The compact volume flow controller ASV 115 has inputs and outputs that can be configured accordingly. By storing ready-made applications in the software, they are set according to the selection, enabling the connection of the room pressure sensor," says Fedler.

Another advantage of the compact system is the high positioning accuracy of the damper actuator. Thanks to the good gear design, it is possible to set the dampers precisely and minimize oscillations of the room pressure. This not only ensures exact regulation and stable control quality in dense cleanrooms, airlocks, and buffer rooms but also reliably maintains the pressure levels to prevent cross-contamination.