Modern flour mills replace stone mills in Egypt

New, modern mills with centralised PLC/PC control have replaced giant millstones in a massive project that required the combined efforts of several global suppliers to ensure success.

A hundred years ago, grain was ground into flour using two large stones, called millstones. Since then, the science of milling grain into flour has changed dramatically. Improved equipment, better transportation and in particular computerisation have increased milling capacity, allowing mills to expand their production.

Four recently constructed mills in Egypt are a prime example. In an effort to cut costs and produce higher-grade flour, developers have built new, modern mills in the same buildings where giant millstones used to stand.

Old stones to PLC control

Danish company, United Milling Systems (UMS) designed and built four new mills in Egypt with Automatic Syd A/S as sub-supplier of the electrical systems. Two of the mills, located in Cairo and Ibrahim Awad, Alexandria, were actually converted from old stone mills into modern milling plants. The other two, located in Sowahey and Moharam Bey, Alexandria, were turnkey projects, rehabilitating old roller mills.

UMS installed a total of 34 of the new Satake SRMA roller mills in three of the locations. The SRMA not only incorporates the latest technology, such as fully electronic feeder units and a toothed belt differential drive, but is also simple and user friendly.

In the fourth mill, UMS installed a short milling system based on its disc mill. This solution allows the El Tppin mill (South Cairo & Giza Flour Mills & Bakery Co) to produce nearly twice as much flour per day, in a substantially reduced area, compared to a conventional roller mill.

Automatic Syd specialises in the design and manufacture of electrical switchboards, control panels and the development of customised PLC and PC software. It was their job to supply a centralised control station that would allow one miller to monitor the entire plant.

UMS and Automatic Syd faced a choice: they could install their own version of a proprietary system, running closed applications, or they could opt for an open communication platform.

Ten years ago, proprietary systems were the norm. But companies soon found that these closed systems were, in the long run, user unfriendly, making the process of integrating new processes and equipment difficult, expensive and time consuming, requiring diversified skills and tools. Today, these closed systems are slowly being replaced by open communication platforms.

The Modbus protocol is one of these open applications. It has become so popular that in many instances it is accepted as the de facto industry standard. This was the application chosen for the mills.

Allen-Bradley PLC5 processors were connected to the mill equipment. However, the A-B processors are not inherently Modbus compatible. Therefore, a Modbus interface was needed.

Modbus interface

Automatic Syd contacted Rockwell Automation-Denmark for a possible solution. It recommended ProSoft Technology's 3100-MCM module. This module acts as a Modbus interface, providing highly configurable Modbus Master and Slave capabilities to Allen-Bradley PLC and SLC applications.

"Quite simply, the ProSoft Modbus communication interface makes it possible for Allen-Bradley platforms to communicate with a multitude of industrial devices," said Doug Sharratt, lead developer for ProSoft Technology. "Because of our partnership with Rockwell Automation, our Modbus module is designed to fit in the A-B rack, allowing all data exchange to occur over the backplane."

The A-B PLC, with the ProSoft module installed in the rack, collects the data and displays it on the miller's PC using Allen-Bradley's RSView.

Centralised control cuts costs

"With the ProSoft module," said Arne Sigfredsen of Automatic Syd, "one miller can easily monitor the entire plant and, in case of emergencies, temporarily take over control until another miller has reached the specific machine to solve the problem. This is a cost-effective saving, since it takes fewer personnel and you get a lot of information such as alarms, stock levels, motor loads, etc from the plant."

"The 3100-MCM Modbus module was one of the first products manufactured by ProSoft Technology," said Alain Chevalin, ProSoft's regional sales manager for Europe and the Middle East. "But twelve years after its invention we are still finding new uses for it. Many industrial devices available today have implemented communications using the Modbus protocol. With our communication interfaces, users in a variety of industries are able to gather a great deal of data which can enhance the understanding of the process or, as in the case of these flour mills, allow the system to be controlled more efficiently."

The Alexandria Flour Mills and Bakery Company's mills located in Ibrahim Awad and Moharam Bey were the first two mills to go online, producing 150 tonnes and 225 tonnes of flour per day. A third, located in Sowahey, began operating shortly thereafter, also producing 225 tonnes of flour per day.

At the fourth mill, located in El Tppin, Cairo, the disc mill solution allows the mill to produce 450 tonnes of flour per day.