02/03/2008 • Automation • IT and automation • Process automation / MSR technology

More energy, more freedom:

It is often necessary to revamp a production plant on a very tight schedule and without unduly interrupting production.
The previously installed signal conditioning devices have to be replaced while the sensors and actuators on the pipes and vessels remain unchanged.

The subsequent paragraphs will show how Remote I/O can be used to advantage in plant modernization making use of a combination of explosion protection methods such as intrinsic safety, increased safety and flame proofing.

Example
A plant revamp was scheduled to take some two to three weeks.
The plant technology was to remain unaltered while the control section was to be modernized.

Solution
The previously installed signal conditioning devices were to be replaced while the sensors and actuators on the pipes and vessels would remain unchanged.
FB Remote I/O slaves were installed in Zone 1 replacing the existing junction boxes.
Fig. 1
Once the Remote I/O was installed its performance could be tested via the new process control system. Afterwards the field wiring was transferred to the Remote I/O loop by loop.
The FB Remote I/O interface modules allowed energy circuits to be mounted side by side with intrinsically safe ones. This resulted in highly compact cabinet designs. There was sufficient space to include the new Ex-d fuses which can be replaced in Zone 1 without the need for a hot work permit. The fuses protect the Ex-e loops connected to high power Ex d solenoids. (Fig 2).

Fig. 2
The PROFIBUS gateway supports up to 80 analogue or 184 digital signals or any combination thereof.

HART Communication
Remote I/O offer additional benefits. HART field devices can be addressed from a central position making use of the HART-via-Profibus standard. Handheld communicators are no longer required.
Remote I/O receive HART data from the operator station via PROFIBUS. This digital communication is superimposed on the 20 mA current loop of all connected transmitter supplies and output isolators (Fig. 3).
Field devices can also be addressed via PROFIBUS using their device specific parameters.
Fig. 3

Summary
The article shows how Remote I/O simplifies engineering during plant revamps for hazardous areas. Plants can be modernized and commissioned very quickly retaining existing peripheral installations conserving space.
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