Safe data transmission, long distances:
In the chemical, petro-chemical and pharmaceutical industries as well as in the oil and gas sector explosion hazards must be avoided by suitable means at all times. For this purpose measurement and control installations rely on Remote I/O more and more. These employ PROFIBUS which makes use of fibre optic links to bridge long distances at high speed.
Reliable, Economical Operation
Plants stretching over a wide area often employ redundancy in their control system because of the high economic importance to maintain production. Since high speed PROFIBUS only permits the use of copper cable for short distances fibre optic links (FOL) offer an ideal alternative.
There are three main differences with copper cables which make FOL the right choice in process control applications.
First fibre optic links ensure full galvanic isolation between the plant area and the control room.
Second the low energy levels of light cannot generate sparks or hot surfaces.
Third electro magnetic fields cannot cause interference in the fibres unlike in data transmission via copper cables.
Fig. 1
Furthermore the FOL Profibus-Repeater presented here offers some additional features. It can be used in a point to point application as well as in a redundant ring. It is capable of detecting Profibus faults and can induce a redundancy line change automatically.
At the Zone 1 plant level of the Remote I/O station conventional bus cables are used. As the RS485 link is not intrinsically safe the cable must be wired in a similar way to power cables as to satisfy increased safety requirements.
Summary
Fibre optic technologies are the key to bus systems extending into the hazardous area.
This enables improved efficiencies achieved in other branches of automation to be transferred to process automation without restriction. Fibre optic installations will continue to rise significantly especially as investments are being undertaken to extend the plant life by modernizing control systems.
Plants stretching over a wide area often employ redundancy in their control system because of the high economic importance to maintain production. Since high speed PROFIBUS only permits the use of copper cable for short distances fibre optic links (FOL) offer an ideal alternative.
There are three main differences with copper cables which make FOL the right choice in process control applications.
First fibre optic links ensure full galvanic isolation between the plant area and the control room.
Second the low energy levels of light cannot generate sparks or hot surfaces.
Third electro magnetic fields cannot cause interference in the fibres unlike in data transmission via copper cables.
Fig. 1
Furthermore the FOL Profibus-Repeater presented here offers some additional features. It can be used in a point to point application as well as in a redundant ring. It is capable of detecting Profibus faults and can induce a redundancy line change automatically.
At the Zone 1 plant level of the Remote I/O station conventional bus cables are used. As the RS485 link is not intrinsically safe the cable must be wired in a similar way to power cables as to satisfy increased safety requirements.
Summary
Fibre optic technologies are the key to bus systems extending into the hazardous area.
This enables improved efficiencies achieved in other branches of automation to be transferred to process automation without restriction. Fibre optic installations will continue to rise significantly especially as investments are being undertaken to extend the plant life by modernizing control systems.
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