Using a common wire: Safety PLCs with safety Ethernet

Specifying a safety PLC upfront in planning makes it possible to save significant time and money when designing the wiring and planning functionality of a project. Using Ethernet allows projects to do start/stop, speed references, and safety all over the same wire. One design used safety PLCs and safe I/O to include the guarding zones between presses.

08/13/2010


Distributing the I/O over Profinet using a Siemens Simatic S7-300F processer reduces wiring is reduced and operator safety enhanced significantly. Source: SiemensSafety systems today are growing bigger and more intricate. As they do, so, too, grows the importance of keeping costs down while working faster. Specifying a safety PLC upfront in planning makes it possible to save significant time and money when designing the wiring and planning functionality of a project.

A systems integrator in Franklin, TN, and a Siemens Solutions Partner, Advanced Engineering and its technicians have designed and installed many systems with more than 100 safety I/O points. Using Ethernet allows them to do start/stop, speed references, and safety all over the same wire.

In the estimation of Advanced Engineering, the day is coming when everything will have safety Ethernet. Simply plug up to a device to obtain control, diagnostics, and safety from it. In addition, zones can be set up, and the device reset. In smart devices, such as a drive, other functions are available as well.

The integrator works extensively in the automotive industry and has installed safety systems with more than 200 I/O safety points. Typically, that number of I/O points requires a great deal of wiring. However, by distributing the I/O over Profinet using a Siemens Simatic S7-300F processer, wiring is reduced and operator safety enhanced significantly.

There's less wiring and complexity when safety and control systems are integrated. Source: SiemensIn one case, an automaker was setting up zones for robots and stamping presses. The original specification to safeguard the zones called for many safety relays. However, the automaker was concerned with the cost for a relay based system. The suggestion was made for a design using safety PLCs and safe I/O up front that included the guarding zones between the presses. The design also determined which functions to shut down for each zone to make it safe for the operators to enter a zone.

In this instance, the quote for using safety relays reached $100,000. Done with a safety PLC, the cost was reduced to about $60,000. In addition, the automaker has since modified the system, which would have been nearly impossible with relays and which would require costly downtime. With the safety PLC system, the automaker simply added new zones into the safety PLC logic, similar to programming a normal PLC.

Ultimately, using a safety PLC is more productive than relays. For example, one company installed a safety relay system on a line of machines. It estimated that unplanned downtime caused a 20% drop in productivity. In fact, the company’s production charts revealed that as each machine was fitted with safety relays, productivity dropped 20% on average. On the other hand, safety PLCs are flexible, offer diagnostics, require few wires, and can accommodate distributed I/O points without the downtime.

Siemens offers a small PLC with distributed ET200S I/O; the heads of the I/O have safety capabilities. As the system grows, it can accommodate a central processor that can control these remote heads and allow zones to be established. Source: Siemens If safety is approached as an afterthought, if becomes very difficult to retrofit it into an existing machine. However, incorporating safety into the design at the beginning of the process has shown time and again to be cost effective. Whether an integrator or a plant, it is possible to start small. For example, Siemens offers a small PLC with distributed ET200S I/O; the heads of the I/O have safety capabilities. As the system grows, it can accommodate a central processor that can control these remote heads and allow zones to be set up.

www.adveng.com

www.sea.siemens.com

- Jim Neufeldt is president, Advanced Engineering, Franklin, TN; Edited by Jeanine Katzel, Control Engineering consulting editor. www.controleng.com.

Also read:

Integrated Safety and Motion;

Safety Sensors Rise to New Heights



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
Control Engineering Leaders Under 40 identifies and gives recognition to young engineers who...
Learn more about methods used to ensure that the integration between the safety system and the process control...
Adding industrial toughness and reliability to Ethernet eGuide
Technological advances like multiple-in-multiple-out (MIMO) transmitting and receiving
Virtualization advice: 4 ways splitting servers can help manufacturing; Efficient motion controls; Fill the brain drain; Learn from the HART Plant of the Year
Two sides to process safety: Combining human and technical factors in your program; Preparing HMI graphics for migrations; Mechatronics and safety; Engineers' Choice Awards
Detecting security breaches: Forensic invenstigations depend on knowing your networks inside and out; Wireless workers; Opening robotic control; Product exclusive: Robust encoders
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
News and comments from Control Engineering process industries editor, Peter Welander.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
Anthony Baker is a fictitious aggregation of experts from Callisto Integration, providing manufacturing consulting and systems integration.
Integrator Guide

Integrator Guide

Search the online Automation Integrator Guide
 

Create New Listing

Visit the System Integrators page to view past winners of Control Engineering's System Integrator of the Year Award and learn how to enter the competition. You will also find more information on system integrators and Control System Integrators Association.

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.