GAS DETECTION

Gas Detection

Presentation

The Gas Detection system is based on a reliable Programmable Logic Controller (PLC) approved for use in safety applications. For even greater reliability, the PLC can be configured as a redundant system.

Any gas detection devices commercially available in the market can be conencted to the system. The detectors are connected directly to the PLC system input modules or communication modules.

System description

The system consists of a PLC with several digital input and output modules, and several analogue input and output modules, according to the facility needs in term of Gas Detection.

If necessary, and in order to minimise the cost of installation in term of cable length to pull, the system can be networked. The remote digital and analogue I/O can be connected to the system via a copper or fibre optic network with a ring topology. The ring topology insures redundancy.

Two different options are available to interface the gas detectors to the system. If the Gas detectors provide 4-20mA signal, they are connected directly to the controller analog input modules.
If the Gas detectors are addressable, they are connected on a redundant network, typically a Modbus network. The controller is equipped with a communication module to access the Gas detector data in this case.

The PLC runs the Gas Detection system application, custom developed by Jelec. It monitors the Gas level of each detector. The Gas concentration level limits are stored in the PLC's memory, and remain there even in case of a power failure.
When a limit is crossed, the program generates an alarm signal. This signal can be used to directly drive horns, strobes, sirens or can indicate the alarm condition to other systems.

Interfacing with other systems

Because the Gas Detection system is based on a PLC, it is capable of performing any task a regular PLC is usually assigned to do. It is therefore possible to use this PLC system, running the Gas Detection application, to execute other applications at the same time.

For example, the PLC system can be used to integrate any other monitoring system developed by Jelec like a Tank gauging system or a Ballast system.