Case study: Control system maintains temperature in industrial ovens

Controlling 32 independent heating zones from one PLC and HMI has its challenges.

06/04/2008


Since 1979, Georgia Oven Co . has been developing custom thermal devices, ovens and furnaces for customers with plastics, textiles, medical, electronics and pharmaceutical applications. Today the company exclusively produces vacuum and atmospheric ovens for a variety of industries.

John Starnes, electrical designer for Georgia Oven, says the company is constantly exploring new technologies for customers that cannot use off the shelf designs or require heavily automated production type units.

One such application brought the company to Watlow , via Atlanta-based distributor Star Electric Inc. Georgia Oven’s customer was ordering a large multiple heating zone atmospheric oven to bake polyimide on stainless steel coils that make hard drive suspensions. The thermal system needed to control 32 zones of temperature with quartz glass panel heaters, each with its own limit and ability to communicate with a PLC and HMI.

The control scheme had to support changing failed system components easily without altering or shutting down the other operating zones.

Watlow’s Ez-zone ST achieved all of these operational objectives. Each package included the temperature controller, high limit, shutdown contactor, heat sink and solid state relay (SSR). The 32 units were bussed together into the PLC using Modbus, allowing the operator to set the temperature to all the zones by using a PLC.

By having the set-point retransmit via Modbus, Watlow could also individualize high limit problems and controller errors on the HMI from each of the Ez-zone units. The use of a multi-loop controller would not have solved the need for individuality in the event of a controller failure. The Ez-zone ST breaks out each zone, which allows the user to isolate one quickly or swap it out.

Starnes says that using Ez-zone ST on the initial two ovens has streamlined communications and reduced panel space for their customer, among many other benefits. “The units are simple to integrate, smaller and increase the ovens’ efficiency. These are meaningful benefits for our customer, who has come to expect innovation from us,” he says.

—Edited by Peter Welander, process industries editor, PWelander@cfemedia.com ,
Process & Advanced Control Monthly
Register here and scroll down to select your choice of free eNewsletters .





No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
2017 Lubrication Guide; Software tools; Microgrids and energy strategies; Use robots effectively
Prescriptive maintenance; Hannover Messe 2017 recap; Reduce welding errors
Safety standards and electrical test instruments; Product of the Year winners; Easy and safe electrical design
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Diagnostic functions for system safety; Specifying industrial enclosures; Effective decision support for a crisis
Transformers; Electrical system design; Selecting and sizing transformers; Grounded and ungrounded system design, Paralleling generator systems
Natural gas for tomorrow's fleets; Colleges and universities moving to CHP; Power and steam and frozen foods

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
The maintenance journey has been a long, slow trek for most manufacturers and has gone from preventive maintenance to predictive maintenance.
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.
Maintenance Manager; California Oils Corp.
Associate, Electrical Engineering; Wood Harbinger
Control Systems Engineer; Robert Bosch Corp.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me