Technical Profile: Mill automation

by Emily Buckley
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By Alberto Caporali and Gerald Richardson

In flour milling, as in many other industries, automation has developed in an industry specific manner. Looking back half a century ago, mills already had electromechanical systems capable of at least guaranteeing essential interlocking via "chains" of relays. These mechanisms ensured the orderly shutdown of machines in case of alarms or other malfunctions, according to predetermined safety logic.

The logic that this switching provided soon developed into great control panels replicating the mill— often hand painted. At a glance, they offered an overview of the plant and the status of each machine via incandescent lights. The early, automatically sequenced start-up systems, using timer boards, greatly simplified the start-up of mills, eliminating challenging individual machine starts, floor by floor.

All in all, the last generation of electromechanical systems was well developed as far as plant interlocking and safety was concerned.

In reality, many modern control systems offer features that differ little from the old electromechanical ones. This includes control of alarms and interlocks, automatic start and stop sequencing and graphical representation of plant status.

How does one differentiate between a low-level automation system and a modern integrated solution that offers added value? It might help to note that some of the terminology that our industry has developed, such as "fully automatic," and "lights-out mill," do not objectively define the quality of an automation package. The milling industry must attain a certain level of automation maturity, before being able to distinguish between simple control systems and integrated automation systems.

To start, look at the well accepted definitions of integrated systems, as widely used in developed industrial sectors, comprising three distinct levels:

1. Enterprise Resource Planning, known as ERP systems,
2. Management Execution Systems (MES),
3. Shop floor control (or mill operation).

The common misconception is the ablilty to communicate the ERP data directly to shop floor control. In reality, the translation of ERP decisions into manufacturing operations is anything but immediate. Not only does one contend with the actual production capacity of a plant, but also with corrective functions, settings and adjustments — all of which form part of the miller’s intervening role in the plant. The production flexibility needed in running a mill does not marry well to the rigidity of an ERP system. To facilitate this, the central level, the MES, plays a crucial role in the development of a modern integrated system. The MES effectively converts the ERP demands into operative tasks, transferring them to the control system at the right moment and monitoring their progress and the plant’s status during the process. That is a more accurate definition of full automation. It should, furthermore, be capable of taking automated corrective measures when product specifications drift from pre-set standards, and when the process experiences minor changes in stability.

To attain true "lights out" status, on the other hand, it is pivotal that the "full automation" system generate informative messages, via SMS or IM (instant messenger), and that it be accessible remotely, either via intranet or internet. This enables remote emergency intervention during periods of unsupervised production.

All this was the basis for Ocrim’s recently introduced @Mill integrated software control system that comprises two levels: A) Control@Mill, a flexible and easy to use control system available on either Allen Bradley or Siemens platforms; and B) Management@Mill, the first MES specifically developed for the flour and feed milling industries, configured to be connected to most of the popular ERP systems on the market.

A fundamental characteristic of @Mill is its web-based technology that permits access to both production control and management features via intranet links or remote internet connections. Taking full advantage of paging and instant messaging technologies, the system is capable of informing an operator, whether in or out of the plant, in times of alarm. The internet access enables an operative, from any location, to instantly verify the status of the plant, and best decide how to intervene.

Control@Mill is built on a programming system created by Ocrim to combine exceptional features and easy use. To complement the system, Ocrim created the Smart Portable Controller (SPC) to replace the traditional local key overrides. The SPC is light and easily portable, containing a touch screen that is connected on an as-needed basis to sockets distributed on each of the process floors, along the length of the communications bus.

From a functional standpoint, Management@Mill generates production schedules that can be carried out automatically, with production changes controlled by recipes. These recipes include wheat mixes, moisture levels and automated mill adjustment. All operations are logged by lot and by production period. The history of each lot, in terms of raw material, production recipes, and laboratory analysis, are stored and available via a query system.

Management@mill also offers a maintenance scheduling system, based on the actual running time and number of cycles of machines, in addition to the number of alarms they may generate. Once programmed, a list is generated of the advisable maintenance functions to be undertaken, with all necessary technical and descriptive details provided, including documentation and drawings, internet support sites and other multimedia support tools.

 

Alberto Caporali is the manager of Ocrim’s automation systems and is based in Cremona, Italy. Gerald Richardson is president of CETEC, Inc., the U.S.-based North American representative for Ocrim SpA.

 

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