Opening three transit mixed plants on the outskirts of Columbia, S.C., since 2006, Capital Concrete is among the Carolinas’ newer players. In building
Opening three transit mixed plants on the outskirts of Columbia, S.C., since 2006, Capital Concrete is among the Carolinas’ newer players. In building operations from the ground up, the company has been able to apply to its ready mixed production recently developed control technologies proven in other manufacturing environments.
Weather-driven shutdown has been averted, safety improved, and maintenance reduced at each site by deploying a common industrial computer network protocol to distribute control of gates, motors and other components. We wanted to eliminate problems with lightning strikes on plant equipment, and digging up hard wire connections from the plant to the batch office, says Capital President Rusty Shealy, who ventured from North Carolina to South Carolina following the sale of his Charlotte-area business, Cabarus Concrete (to Asheville-based Southern Concrete Materials). We haven’t had any outages or been knocked off line by weather, he notes, even with South Carolina’s exposure to rapidly developing severe weather systems.
After conferring with plant and control panel suppliers, Stephens Mfg. and Systech Inc., respectively, about advanced technology options for standard transit mixed equipment, the producer runs what the industry calls smart valves. They operate on fieldbus hardware (note companion box), consisting of a base, or bus unit, linking Systech’s Integra controls to a plant’s material handling, weighing and discharge components. The smart valves function on a 24-VDC operating voltage, instead of the 120-volt AC power that has traditionally run ready mixed plants.
Concrete plant manufacturers are finding 120-volt AC components more difficult and expensive to source, explains Elite Batch Systems General Manager Ben Gordon. Ready mixed is one of the only industries still using 120-volt AC connections for motor starters, pneumatic, and indicating devices. Smart valves eliminate the need for individual control wiring and allow producers to run a plant through a network connection. The maintenance-free valves are lubricated for life, he adds, making oiling and maintenance by plant employees unnecessary.
At the Capital Concrete plants, the fieldbus is linked to the Integra Batch panels via twin fiber optic cables, eliminating traditional wire connections. The fiber optic cable connections offer concrete plant operators portability in equipment and batch offices; remote diagnostics and troubleshooting; isolated control connections from power surges; and, opportunity to tap into the intelligence of motor starters. A plant control can be programmed to detect when a motor is drawing more amps than usual, for example, signaling a need a maintenance check or repair.
FIELDBUS TECHNOLOGY AT A GLANCE
Announcing the 2008 IEC Fieldbus Standards, Geneva-based International Electrotechnical Commission described fieldbus as a digital network, or set of protocols that enables machines to communicate with each other with the guaranteed responsiveness, reliability and safety demanded by today’s industrial environments.
Traditional pneumatic power installations require one wire per information element to be transmitted between a controller and a device (point-to-point), while a fieldbus allows information to be transmitted over a common standardized network. The ability to use such a robust infrastructure in industrial environments reduces wiring lifecycle costs and facilitates deployment of more intelligent devices, IEC contends, thereby offering advanced configuration and diagnostics features. Thus, manufacturers are able to meet market demands for increased flexibility of automation applications, while economically managing the resulting complexity of the solution.
The 2008 IEC Fieldbus Standards reference the latest technologies. Since the last edition, published in 2003, the automation world has seen the emergence of new ethernet-based fieldbus, intended to complement the existing fieldbus, and the installation of programmable and networked equipment in safety-related applications. To follow this evolution, the 2008 edition includes profiles for Real-Time Ethernet fieldbus, together with other industry sector network profiles, which had not been included in the previous editions. This new edition also has added profiles specifically designed for the use of fieldbus technology to transmit safety-related data. Finally, the need for more guidance in the installation of fieldbus has been addressed by defining a basic guidance for the installation of communication networks in industrial premises (IEC 61918) and dedicated parts of the IEC Fieldbus Standards that for each fieldbus technology establish which options of the basic guidance apply and which additional guidance shall be used.
The standards provide a variety of established solutions that cover a wide range of application requirements, from process control to manufacturing automation. An industrial manufacturer or machine/process supplier may choose from these solutions the one that is best suited for the specific needs of the application and the environment in which it is to be implemented.