Changing Safety Standards Introduce New Opportunities For Increased Profit And Greater Safety

By J.B. Titus, Siemens Energy and Automation

In the late 1990s, industry-based safety standards began to change largely for two reasons:

• Large companies with global purchasing power wanted standards harmonization for economies of scale; and
• General references to IEC and ISO standards began to provide uniform guidelines for machine builders and manufacturers.

The first consensus standards to adapt to these changes was the American National Standards Institute and Robotic Industries Association ANSI/RIA 15.06, 1999 which introduced the "risk analysis" requirement for hazard identification in the robotics industry.

NFPA 79 electrical standard for industrial machinery was the second major standard to change. Its 2002 revision (done to harmonize NFPA-79 with its European counterpart, IEC-60204) states that "firmware and software-based systems listed for such use" could now be used in safety applications. The NFPA 79 change is significant because it eliminated the exclusive requirement for hardwired connections of sensors and actuators to electromechanical (safety) relays. Additionally, E-stops could now be attached to safety certified networks.

In these global consensus standards you can see a rapid response to market demands because they are industry driven rather than government driven. Changes to OSHA regulations, for example, require an act of Congress.

It is important for machine builders and end users to understand the implications of these changes, as they have a legal obligation to know how the standards impact their businesses. Equally important is the fact that recent options for safety compliance have been shown to improve profits for both OEMs and manufacturers. Note the "Cost of Ownership" graphic below, which illustrates how safety compliance can generate positive results directly to the bottom line.

Safety system selection considerations
With changing standards in mind, when surveying options for choosing a safety system to comply with safety standards, consider the following:

Does the application require zone control?
Safety relays may be used, but are not necessarily the best solution. Siemens recommends AS-Interface network or ET200 I/O to reduce engineering costs and downtime.

Will the system expand in the future?
If the application requires future expansion, then AS-Interface network is recommended. Expanding dedicated safety relays can be labor intensive due to rewiring and troubleshooting.

How much safety I/O is required and where is it located?
I/O count and location play a major role in the selection of a safety control architecture. The modular nature of expandable relay (AS-Interface network) systems allows the user to add inputs and outputs sized specifically for the application.

Is machine uptime the main goal?
If the priority of the application is uptime, Siemens recommends a Safety PLC or Safety Integrated PLC. The diagnostic features of a Safety Integrated PLC will pinpoint the location of issues throughout the application, allowing operators and maintenance personnel to quickly identify and fix the issue.

What are the engineering costs?
OEMs can reduce costs and improve margins via certified and listed products, including safety buses, safety distributed PLCs, safety drives, safety motion, and safety CNC technology. As a result, up to 30% to 40% cost savings can be realized on machine electrical packages.

Is panel space a factor?
Simplifying the safety design and adopting Siemens Safety Integrated products connected via safety certified bus technology can eliminate numerous electromechanical components from control panels. Typical control panel space reductions average between 20% and 40%.

By integrating safety application requirements into certified firmware and software, numerous electromechanical components are no longer needed, safety is enhanced, and profits are increased. This approach to safety compliance simplifies the application for the OEM and can generate more machine uptime for the end user.

For more information on Simplified Safety, click here.