Modular solutions for operating, monitoring and data transmission tasks in explosion-hazardous areas

Modular solutions for operating, monitoring and data transmission tasks in explosion-hazardous areas Making electrical devices safe for the application in explosive dust and gas environments is one thing, operating and handling them safely in explosive environments is another thing. The latter task moreover often requires the consideration of application-specific conditions or individual operators´ requirements. Modular solutions for switching, signalling, controlling and connecting allow to design machines and systems in a process-adequate, safe and profitable way for the application in explosion-hazardous areas. The basic idea of explosion protection is to protect man and environment by means of safe components, systems and equipment. The explosion-proof design of motors, controls and switchgears, electrical automation equipment, analytical systems and measuring systems or devices and components for heat technology is of the same importance as the application of explosion-proof installation and connection technology. Especially control, command and signalling devices have to be adjusted to a variety of requirements and wishes of individual users in different sectors.
		This can be achieved by a consistent modularisation – from end switches via limit value transmitters, command and indicator devices as well as control units to fieldbus systems. Modularity allows to consistently combine individual control and connection modules in view of the users´ requirements and to generate complete solution systems.
End switch: Pressure-proof encapsulation of ignition spark Explosion-proof end switches are used in applications where a safe and reliable signal indication is required. Even if for manufacturers of complex machines and systems, these end switches are components of their solutions, they are no components in terms of explosion protection but devices fulfilling an essential safety-related and functional task. The reason: Devices in the terms of ATEX RL 94/9/EG have an independent function, that is, they can be applied as stand-alone units – unlike the components that are also described in the guideline, such as block terminals, individual switching modules and luminous modules. This is why they can be integrated – with appropriate protection – into devices and systems without any further test. Even the miniature micro-switch - which is smaller than a sugar cube - is a device. This can be seen on the CE labelling attached to the outside, the number of the EC type approval certificate and the temperature class. These switches, whose electric connection is cast into the rear side, are applied in places where there is hardly any room for an explosion-proof switching element. They are especially suited for being applied in valves, thermostats, pressure switches, final controlling elements, filling level meters and switching devices. This worldwide smallest Ex d micro-switch demonstrates the explosion protection philosophy of all these Bartec devices. The pressure-proof encapsulation (Ex d) directly encapsulates the ignition spark. As the explosion protection becomes effective right at the place where the explosion hazard develops, the encapsulation requires a low volume and therefore a small installation size – which is ideal for the explosion-proof design of compact devices such as position sensors, position switches or magnetic switches.
One application example for explosion-proof micro-switches are limit value transmitters. They are applied in conjunction with pneumatic actuators on fittings for the signal recording of the status “Open/Closed”. For most of the versions, this final position feedback takes place via pressure-proof encapsulated end switches with appropriate connection and attachment parts. Limit value transmitters can be applied in explosion-hazardous environments of zones 1 and 2 in accordance with the certified explosion subcategories IIA, IIB and IIC and temperature classT5/T6 as well as in zones 21 and 22 in accordance with the certified maximal surface temperature.
Command and indicating devices: flexible as standard The principle of modular explosion protection is continued in the command and alarm devices of the ComEx series. ComEx adheres to a flexible system concept, which allows to realise standardised as well as customised on-site command and indicating devices. Three aesthetic standard housings made of shock and impact proof polyamid are available; up to three different command and alarm devices can be built into them. Up to three ComEx housings can be combined with each other – an option which also applies to the device series in an especially robust and corrosion-proof stainless steel housing. The operating and monitoring functions are available as pre-configured complete devices, e.g. with a signal lamp and two push buttons. Pursuant to the idea of modularity, these functions can also be arranged in a customised or application-specific way. For this purpose, almost 50 different actuator elements and installation modules such as push buttons, switches, selector switches, locks, indicator lamps, potentiometers or measuring devices are available in nearly any combination. The ComEx systems cover an ambient temperature range from -55° C to +55° C. They are applied for operating and monitoring machines, processes, drives, pumps, rolling gates, process engineering systems, etc. On-site control points: With a standard bus into the explosion-hazardous area If the operating and monitoring requirements on the system become more complex and if additional control functions should be realised, ComEx is the basis for explosion-proof, decentralised on-site control points.
		At these control points for the application in explosive areas, command, alarm and indicating devices and bus interface modules are integrated depending on the technical requirements – if required, under inclusion of controls and the complete wiring on series terminals. The installation elements can be mounted in different ways: Depending on the version, they are mounted either on mounting rails or into the front side.
The polyester housings – available in the variant equipped with a cover fastened with screws or the variant equipped with a door with hinges – are designed in accordance with the requirements of ignition protection type “increased safety”. Depending on the specification and quantity of the equipment, different housing types and different sizes are available. For on-site control points for the application in explosion-hazardous areas with combustible dusts, the ignition protection type “protection by housing” is applied.
The MODEX series made by Bartec on the one hand comprises these explosion-protected, decentralised on-site control points. On the other hand, MODEX is also the trademark of the bus modules applied there. Due to the combination of ignition protection types, they allow to direct standard bus systems continuously from the safe area to the explosion-hazardous area. This is why not only intrinsically safe components with low power requirement can be integrated into the fieldbus structure, but also non-intrinsically safe motors, valves or heating systems which require considerably higher performances than could be achieved with intrinsically safe circuits. Therefore MODEX bus modules offer a variety of advantages, among others less space required in the control stand, omission of I/O level, Ex separation as well as main distributors and field distributors, avoidance of complicated serial wiring or parallel wiring, as well as a higher flexibility in planning and engineering. Altogether, the variety of different MODEX modules – among others barriers, relays, contactors, fuses, measuring transducers, power supply units and isolating units – allows to realise quite flexible solutions for different tasks and requirements.
For “more Profibus“ in the explosion-hazardous area MODEX does not only take the standard bus, e.g. Profibus, into the explosion-hazardous area – different modules also allow a migration of the existing bus environment. The Profibus DP coupler and the Profibus DP repeater, which are specifically designed for the industrial requirements of the explosion-hazardous area of zone 1, allow to separate or generate new segments. Among other possibilities, the number of participants at the bus can be increased and the segments can be cascaded to increase the coverage range. In the end complex, open and flexible star-shaped and tree-shaped structures develop from the RS485 typical linear structure. Moreover, the devices allow a duplication of the signal in order to realise a redundant connection to a master. If signals in the Profibus have to be transmitted interference-free over large distances at high speeds, copper lines reach their ”electromagnetic” limits even if they are correctly shielded, wired and installed. By means of the LWL ring couplers and PP couplers RS485/Profibus, the Profibus is transposed from copper lines to optical waveguides (LWL), which offer considerable advantages with regard to interference resistance, speed and coverage - up to 2,600 m are possible. Both the ring coupler and the PP coupler are available for the application in zone1 or, respectively, for zone 2 and non-explosive areas. The electronics for signal conversion gets a pressure-proof encapsulation for zone 1 by the MODEX housing. Transmitter and receiver for the optical waveguide are activated in an intrinsically safe way for the version in zone 1. This guarantees that the transmitter does not reach inadmissibly high transmitting power values. For the optical waveguide couplers of zone 2 and in safe areas, the transmitting power is also limited in order to guarantee the compatibility with the devices of zone 1. Communication does not stop at explosive areas Whether components solution or complete solution – the requirement of communication with equipment, machines and systems for the operation and monitoring or for data transmission does not stop at the explosion-hazardous area. The manifold requirements occurring in practice can best be met – in technical as well as in economic terms - by means of a consistent modularisation.