Safety first

An Ask the Expert feature with Bürkert

“The quality of the exhausted compressed air is so excellent that it can be led into the control cabinets in order to avoid humid, aggressive or dust-containing ambient air entering the cabinet”
-Werner Bennek of Bürkert Fluid Control Systems

Until some years ago combining electrical and pneumatic devices in zone 1/21 environment control cabinetswas hazardous due to the wet and oily compressed air, which caused corrosion and short circuits. Today’s compressed air systems usually work with air qualities with a pressure dew point below -20°C (residual moisture of 0,88 g/m³) and an oil concentration of less than 1 mg/m³. Especially in the pharmaceutical as well as in the food and beverage industry one can expect compressed air qualities even better by several orders of magnitude. The quality of the exhausted compressed air is in fact so excellent that it can be lead into the control cabinets in order to avoid humid, aggressive or dust containing ambient air entering the cabinet. Thus working with dry and oil-free air reduces the problem of corrosion and short circuits. The detonation risk still remains due to the process conditions.

In explosion-hazard areas of zone one the pneumatic control of cylinders and pneumatic actuators is done generally by either explosion-proof single valves, directly mounted to the actuator, or ex-proof valve banks wired to a Remote-IO-system. Installing the pilot valves in a safe area is a further option – unless often not possible as the large distances between valves and actuators lead to unacceptable long switching times. Hybrid solutions combining electrical IO-systems with optional pneumatic outputs like our successful 8644 AirLINE system are state of the art for installations in save environments and in zone 2. Bürkert wanted to make the advantages of this technology available for applications in hazardous environments and developed a hybride solution for the installation in zone one combining modules of the SIMATIC ET 200iSP system from Siemens with their modular pneumatic automation system AirLINE Ex 8650. With its integrated pneumatic functions, process and productions sequences and being ATEX certified in a whole, it is designed for decentralised operations in an explosive environment. It can be used in explosion-hazard areas with a gas or dust atmosphere and therefore is most valuable for users in the process control worlds found in fine chemicals, pharmaceuticals, cosmetics and everywhere where solvents, alcohol or lacquers are employed. It even can be installed in factory automation, e.g. autofilling of solvents, alcohol or lacquers. In these application areas, the new system is so far the only compact electro-pneumatic automation solution allowing the integration of EExi pneumatic valves without additional wiring.

Connecting sensors and actuators to bus systems substantially reduces the wiring effort. Standardized interfaces and a highly flexible and modular design guarantee a fast and easy system-setup and allow pneumatic, electric and electronic modules with different functions to be combined with one another. The components are connected together by screwing or latching thereby establishing both the electrical and pneumatic connections. The pilot valves integrated in the pneumatic modules allow a wide range of different pneumatic actuators to be controlled in the field, e.g. process valves or pneumatic cylinders. The explosion protection is guaranteed through electronic limitation of voltage and current.

Engineers and users of ex-proof IO-systems welcome integrated pneumatics for their outstanding advantages: The close-to-the-process installation, a significantly reduced wiring and compact design as well as the simplified documentation, proven intrinsic safety and the little power consumption and therefore only little waste heat. Not to speak of the cost savings. Besides less wiring, less planning and less documentation, the new ex-proof electro-pneumatic automation system offers another important advantage – as all elements, valves etc. are harmonized and certified. All devices and elements are consistent to EN 60079 part 0/1/7/11/26 and EN 60529. This helps engineers, contractors and users to concentrate on their main business, exempted from engineering control cabinets.

Werner Bennek
With background and experience in electronics and physics, Werner joined Bürkert in 1991 as an internal technical sales assistant for Germany, later on overtaking functions in international sales support and application management. Today he is part of the Segment Hygienic Processing team and responsible for products and applications related to hazardous atmospheres.