How Smart Are Your Safety Systems?

Safety Integrated 1 2014Siemens Safety Integrated strategy protects workers and boosts productivity with fail-safe controls, drives, motors, I/O and plantwide PROFISAFE communications.

Machine safety is serious business. According to the International Labor Organization (ILO), more than 2 million people die worldwide each year as a result of work-related causes; 321,000 of these are registered as fatal industrial accidents. The cost of such accidents is high enough to affect the gross domestic product (GDP). As such, in most world markets, regulations have been established that stipulate only safe machines are to be operational.

Safety concerns everyone. In every phase of a machine’s or system’s life, safety-related tasks and responsibilities arise:

  • For machine and system manufacturers: They are responsible for compliance to and implementation of the relevant regulations and directives.
  • For importers: As the party responsible for placing the machine in the market, they take over the responsibilities of the manufacturer.
  • For operators: With the first commissioning of the machine, the operator takes over responsibility for its safe operation.
  • For retrofitters: In the case of conversion or modification of the intended machine purpose, the operator takes over responsibility; this can also be transferred contractually.

In all these cases, on a global scale, Siemens provides complete safety solutions in terms of products, consulting, and support. From sensors to evaluation units to drives with integrated safety functions, Siemens Safety Integrated portfolio offers maximum, consistent safety to those who build machines and those who use them.

Fail Safe Controls

SIMATIC Safety Integrated comprises a scalable range of safety-related controllers in various designs based on different hardware platforms for all areas of factory automation, from modular controllers and embedded automation products down to PC-based controllers. Distributed field devices from the ET 200 range are employed as fail-safe I/O. There are versions for the control cabinet, or with a high degree of protection, for cabinet-free use, in modular and block design. Connection of the I/O is realized by means of PROFIsafe via PROFIBUS and/or PROFINET.

The fail-safe systems are either configured in the TIA Portal using STEP 7 Safety Advanced or with STEP 7 and S7 Distributed Safety. LAD and FBD languages as well as pre-configured, certified blocks are used for programming.

The three-fold safety value proposition—detection, evaluation, and reaction—is achieved through safety relays, programmable safety controllers, and/or distributed safety.

Fail Safe Drives

In industrial applications, drive inverters are frequently used to control the speed of equipment and machines. Generally, these drives are associated with potentially hazardous motion that must be safely shut downusing suitable protective equipment and devices.This was traditionally implemented using external circuits that in some cases could be extremely complex.Using the safety functions integrated in the SINAMICS drives, these external circuits can be eliminated in most cases.

Safe Torque Off (STO)

STO is the simplest safety function. After STO is activated, the energy supply to the motor is interrupted in a safety-relevant fashion. As a result, the motor coasts down unbraked. After STO has been activated, it is not permissible for the drive to generate torque that could result in hazardous motion.

In a conventionally wired STO application, after the emergency stop button has been pressed, the contactor safety combination opens two line connectors, and then the motor coasts down unbraked. There are a number of issues with this:

  • It increases wiring time and costs due to the safety relay and contactors.
  • It offers no protection against manipulation of the safety functions.
  • Intensive service is required care of the mechanical shutdown.
  • The power-on cycles of the drive inverter have to be taken into consideration as it is disconnected from the line supply.
  • There are no diagnostics on the drive inverter because the status display is no longer available after shutdown.

Compare these factors with STO using the safety digital inputs of SINAMICS:

  • Cost savings result from minimized wiring costs and space savings as the emergency stop pushbutton is directly connected to the SINAMICS digital inputs without using a safety contactor combination.
  • Using password-protected safety parameters in SINAMICS minimizes risks of safety functions being manipulated.
  • There are no wearing parts since the shutdown is electronic.
  • The SINAMICS drive remains connected to the line supply and its full diagnostics capability is retained.

Moreover, when applying STO using SINAMICS via PROFIsafe, the function can be simply expanded and the sensor signals can be used multiple times for several drives without any additional wiring required.

The principal benefits of a Safety Integrated approach here are threefold:

  • Less hardware and smaller control cabinets
  • Quicker installation and commissioning as a result of certified functions
  • Greater flexibility when expanding or making changes

The bottom line for machine builders: time and cost savings for each machine built, greater agility, and faster time-to-market.

For machine operating companies, there are a host of advantages to the Safety Integrated approach. First, it allows customized safety concepts, where the machine remains active but is safety monitored, thereby improving productivity and minimizing downtime. Second, it offers a significantly higher degree of protection against accidents by eliminating risk of manipulation. Internally implemented safety functions offer improved protection, while more practice-oriented safety concepts improve operator acceptance. Third, with the Safety Integrated approach, electromechanical components can be eliminated. This saves costs in maintenance and inventory, and saves space through smaller control cabinets.

An example of a safety function in the Safety Integrated drive is safely limited speed (SLS). The SLS function monitors to make sure that a parameterized maximum velocity is not exceeded. If the permitted velocity is exceeded, then the drive initiates a stop response. Parameters may be set for this; four limit value levels are available that can be toggled between when the machine is in operation and off. Additionally, variable limit values can be entered via PROFIsafe when the machine is in operation.

The safety functions of SINAMICS drives are commissioned using STARTER or Startdrive software. These tools offer screen-prompted commissioning, comprehensive diagnostic functions, acceptance test and documentation, and password-protect parameters from manipulation.

Fail-Safe Automation

The integration of Safety Integrated technology in standard automation concepts entails considerable and sustainable user benefits for enhanced competitiveness. Machine manufacturers benefit from reduced hardware and significantly simplified engineering, speeding realization of machines and systems, as well as easier adjustability to new requirements. System operators are provided with safe and more productive machines and systems. A single integrated system of safety technology and standard automation reduces downtimes due to improved diagnostics. It also increases system availability. Retrofits and modernizations are simplified. Due to flexible, modularly expandable concepts, machines and systems can be upgraded to state-of-the-art technology more efficiently.

Users can move from standard automation to Safety Integrated automation in three simple steps:

failsafecontrollerThis transition not only meets the imperative of improving machine and operator safety, but also provides compelling gains across four strategic areas for manufacturers and operators:

Increased efficiency

  • Minimized type differentiations
  • Minimized costs due to a single bus as well as engineering system
  • Easily reproducible machines due to intelligent software solutions

Increased standardization

  • Simplified operation due to uniform user interfaces
  • Improved reusability due to the application of
    libraries
  • Reduced variety of control cabinets on machines
  • Easier installation due to bus systems

Increased productivity

  • Faster commissioning, prewired and certified components
  • Minimized downtimes due to quick fault localization
    and comprehensive diagnostics functions
  • Quicker restarts after system modifications
  • Production without standstills due to additionally
    available safe, fault-tolerant systems
  • Space-, time-, and cost-saving assembly

Increased flexibility

  • Tailored solutions due to modular system
  • Easy expandability and integration in the Totally
    Integrated Automation architecture
  • Improved global market opportunities due to availability
    of required approvals and compliance with regulations (e.g.,
    EU directives)
  • Easier maintenance and system expandability due
    to long-term product and system availability

In the end, Integrated Safety is not only the right thing to do, it’s the smart thing to do. That should make the transition from standard to safety even easier.

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