11.1 Introduction:
In a cement plant a number of control panels like Variable Frequency drives,
weighing system panels and other sub control systems are required to interface
with DCS for Control and monitoring. The standard way of interface is point-to-
point hard wire connection.
This method of interfacing is well proven and continues in modern plants too.
However, it has some advantages & disadvantage which is explained as below paragraph.
In view of today’s scenario where the high level of automation with more information
is required with elimination hardwire related malfunction problems, the concept
of interfacing the control panels on a communication bus (Field Bus) is becoming
popular. These protocols are available for the open network standards. Open
communication networks permit any supplier to offer communications facilities
that can be readily linked to many other devices.
New technologies are designed where equipment could be linked together with
out the need for complicated and labor intensive interconnection wiring. This had
the added benefit of reducing the size and ultimately cost of the control panels
and systems.
11.2 Hardwiring:
Multiple wires from each device, fed through control cabinets, often result in large
wire bundles running through the system. Due to the sheer volume of wires,
installation time is considerable and troubleshooting is complex. However, it has
the advantage of faster transmission of signals over any bus communication
system. Below is a list of some biggest challenges plants face when using point-
to- point wiring.
Challenges of conventional point-to-point wiring
- Wiring - Hard wiring each device to the main control cabinet can be very
costly and time consuming. - Troubleshooting - When troubleshooting a system, conventional wiring make
it difficult to determine where the point of failure has occurred. - Additional Equipment - With conventional point-to-point wiring, additional
input cards are needed for device status notification. - Complex disassembly and assembly – Incase of disassembly and reassembly
of the system can be very time consuming.
11.3 Industrial Networks:
Today, there are many different types of industrial networking or ‘fieldbus’ technologies
on the market. AS-i, Device Net, Profibus, and Ethernet are just some of the
systems gaining popularity. The benefit in cost, as well as the increased level of
11. Profibus Interface v/s Conventional Interface
DRIVES, WEIGHFEEDERS AND SUB CONTROL SYSTEMS