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 Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
The true cost of lubrication: Three keys to consider when evaluating oils; Plant Engineering Lubrication Guide; 11 ways to protect bearing assets; Is lubrication part of your KPIs?
Contract maintenance: 5 ways to keep things humming while keeping an eye on costs; Pneumatic systems; Energy monitoring; The sixth 'S' is safety
Transport your data: Supply chain information critical to operational excellence; High-voltage faults; Portable cooling; Safety automation isn't automatic
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant 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.

Maintaining low data center PUE; Using eco mode in UPS systems; Commissioning electrical and power systems; Exploring dc power distribution alternatives
Synchronizing industrial Ethernet networks; Selecting protocol conversion gateways; Integrating HMIs with PLCs and PACs
Why manufacturers need to see energy in a different light: Current approaches to energy management yield quick savings, but leave plant managers searching for ways of improving on those early gains.

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

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.