Atex cabinet features electrics and pneumatics

Burkert has combined its Airline Ex 8650 system with modules from Siemens' Simatic ET 200iSP system.

This allows electrical and pneumatic devices to be combined in the same control cabinet for use in Atex-rated 1/21 (explosive liquid and gas) zones.

The system provides users with a complete Atex-certified unit for use in zone 1/21, reducing cabinet space, wiring, documentation and validation.

Until recently, combining electrical and pneumatic devices in control cabinets in zone 1/21 environments was impossible because of the wet and oily compressed air, which caused corrosion and short circuits.

Today, however, compressed-air systems usually work with air qualities with a pressure dew point below -20C (residual moisture of 0.88g/m cubed) and an oil concentration of less than 1mg/m cubed.

Compressed air quality is far better in the pharmaceutical and food and beverage sectors.

The quality of the exhausted compressed air is so good that it can be channelled into the control cabinet to prevent humidity or dust within the ambient air from entering the cabinet.

A pressure-release facility is necessary for this arrangement.

While working with dry and oil-free air reduces the problem of corrosion and short circuits, a detonation risk remains due to the process conditions.

In zone 1/21 hazardous areas, the pneumatic control of cylinders and pneumatic actuators is generally achieved with either discrete explosion-proof valves directly mounted to the actuator, or explosion-proof valve banks wired to a remote-I/O-system.

Installing the pilot valves in a safe area is a further option, although often not possible, because the large distances between valves and actuators lead to unacceptably long switching times.

However, connecting sensors and actuators to bus systems substantially reduces the wiring effort.

The use of advanced Profibus DPV1 communications relieves the control engineer of the task of installing the many special expensive electrical junctions and terminations required by conventional field wired systems in Atex areas.

It also offers additional major benefits, including a more compact control system, an installation closer to the process, simplified documentation, minimal power consumption and significant cost savings.

In addition, the new explosion-proof electro-pneumatic automation system offers another important advantage: all elements are harmonised and certified.

This means users do not have to provide evidence of the safety of the system.

Instead, Burkert provides a certificate covering the complete control cabinet, enabling users to guarantee that all devices and elements are consistent to EN 60079 part 0/1/7/11/26 and EN 60529.

Because Burkert's Airline Ex 8650 unit is fully certified, it can be used in explosion-hazard areas with gas or dust atmospheres.

The system is particularly suited to decentralised process-control tasks concerning fine chemicals, pharmaceuticals and cosmetics; and it can be employed anywhere where solvents, alcohol or lacquers are utilised.

It can even be installed for direct factory automation, for example for the automatic filling of solvents, alcohol or lacquers.

In these application areas the new system allows integration of EExia pneumatic valves without additional wiring.

Standardised interfaces and a highly flexible and modular design guarantee a fast and easy system-setup and allow pneumatic, electric and electronic modules with diverse functions to be combined with each other.

The system allows up to 48 Burkert EExia solenoid valves to be seamlessly combined with Siemens' ET200iSP EExia/ib electronic digital and analogue I/O modules in single distributed I/O assemblies.

These offer extensive facilities for remote parameter setting and diagnostics, the ability to 'hot-swap' valves and electronic I/O modules under explosive conditions and the facility for easy system expansion at a later date.

The pilot valves integrated in the pneumatic modules allow a range of different actuators to be controlled in the field: for example process valves or pneumatic cylinders; explosion protection is guaranteed through electronic limitation of voltage and current.

In conjunction with the Simatic ET 200iSP system, all options for combined electrical and pneumatic system solutions within explosion-hazard zones 1/21, including extensive maintenance and diagnostic functions, are achievable and open.

The Simatic ET 200iSP communicates via Profibus DP Fieldbus using IS couplers, providing maximum openness and flexibility and guaranteeing high availability and investment security.

At Burkert's Menden production unit, construction of 8650-based control systems and cabinet-based system building has been audited by PTB; all control cabinets leaving the factory are approved by Kema.

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