Overview
What are Safety Systems?
Industrial safety systems are specialized hardware and software solutions designed to protect personnel, machinery, and the environment by mitigating risks associated with hazardous industrial processes. Unlike standard automation components, safety systems feature redundant internal architectures and self-diagnostic capabilities to ensure that if a failure occurs, the system defaults to a "fail-safe" state (typically stopping all motion).
Key components in these systems include safety PLCs, safety relays, emergency stop (E-stop) devices, light curtains, laser scanners, and interlock switches. These devices comply with international standards such as ISO 13849-1 and IEC 61508, providing specific Safety Integrity Levels (SIL) or Performance Levels (PL) to match the risk profile of the equipment.
Main Manufacturers
PALM Parts Solution stocks and sources safety components from the industry's leading manufacturers to ensure compliance and reliability:
- Pilz: Recognized as the pioneer of the safety relay, Pilz provides a comprehensive range of monitoring and control devices.
- Allen-Bradley (Rockwell Automation): A leader in integrated safety, offering GuardLogix and Guardmaster product lines.
- Siemens: Focuses on "Safety Integrated" solutions, embedding safety functionality directly into their SIMATIC and SINAMICS lines.
- ABB: Provides Jokab Safety products, including specialized sensors and programmable safety controllers.
- Omron: Known for advanced safety light curtains and high-speed safety network integration.
- Schneider Electric: Offers the Preventa range, focusing on machine safety relays and modular safety controllers.
Typical Applications
Safety systems are mandatory across various sectors where human-machine interaction occurs:
- Automotive Manufacturing: Protecting robotic welding cells and assembly lines via safety PLC networks and light curtains.
- Material Handling: Managing E-stop circuits on long conveyor systems and implementing laser scanners on AMRs/AGVs.
- Packaging & Food/Beverage: Utilizing safety interlocks on access gates and washdown-rated light curtains to prevent injury during jams.
- Metalworking & Pressing: Implementing two-hand control systems and high-speed safety relays to stop heavy machinery instantly.
- Process Industries: Using SIL-rated safety systems to manage emergency shutdowns in chemical and oil/gas operations.
Popular Product Families
Standardizing on a specific product family ensures easier maintenance and spare parts stocking. Popular families available include:
- Pilz PNOZ: The industry standard for safety relays, including the PNOZ sigma and the modular PNOZmulti 2 configurable controller.
- Allen-Bradley GuardLogix & Compact GuardLogix: Safety-rated PLCs (5370, 5380, 5570, 5580) that allow safety and standard control in a single chassis.
- Siemens SIMATIC S7-1200F & S7-1500F: "F-series" (Fail-safe) CPUs designed for use with TIA Portal and PROFIsafe communication.
- Allen-Bradley Guardmaster: A broad range of safety relays, interlock switches, and high-quality E-stops.
- Omron Sysmac Safety: Featuring the NX-series safety controllers and high-resolution light curtains.
- Schneider Electric Preventa: Including the XPS range of safety relays and the modular XPSMCM safety controllers.
Replacement & Compatibility
Replacing safety components requires strict adherence to original safety specifications. When migrating or replacing parts:
- Point-to-Point Replacement: Simple safety relays (like various 24V DC dual-channel models) can often be cross-referenced between brands like Pilz and Schneider Electric, provided the contact ratings and terminal counts match.
- Safety PLCs: These are generally proprietary. Replacing an Allen-Bradley GuardLogix with a Siemens S7-1500F requires a complete rewrite of the safety logic and potentially a full re-validation of the machine's safety circuit.
- Network Compatibility: When upgrading components, ensure they support the existing safety protocol. For example, if your system uses CIP Safety, you must use compatible Allen-Bradley or third-party devices designed for that protocol.
- Legacy Migration: Many older ABB Jokab or Pilz systems are reaching end-of-life. We assist in identifying the modern equivalents that offer the same footprint but enhanced diagnostic capabilities.
Selection Guide
- Determine the Required Safety Level: Conduct a risk assessment to determine if you need SIL 2/PL d or SIL 3/PL e. This dictates the hardware architecture required.
- Input Count: Calculate the number of safety inputs (E-stops, gates, curtains). Fewer than three inputs usually favor a safety relay; more than five often justify a programmable safety controller.
- Output Types: Identify if you need instantaneous relay outputs or time-delayed outputs (for controlled deceleration).
- Communication Requirements: Determine if the safety system needs to report status to an HMI or SCADA. Systems using PROFIsafe, CIP Safety, or FSoE provide significantly more diagnostic data than traditional hard-wired relays.
- Environmental Factors: For food and beverage applications, select components with IP69K ratings. For hazardous areas, ensure components carry the necessary ATEX or Class/Div certifications.
22 products · ABB
Frequently asked questions
What is the difference between a standard PLC and a Safety PLC?
Safety PLCs integrate specialized diagnostic hardware and redundant processors to achieve SIL (Safety Integrity Level) ratings, whereas standard PLCs do not. A safety PLC can perform all the functions of a standard PLC, but it also monitors internal circuitry for faults and ensures a "fail-safe" state in the event of a hardware failure. Standard PLCs are used for process control; safety PLCs are used for life-critical protection.
What do SIL 2 and SIL 3 ratings mean for safety systems?
Safety Integrity Level (SIL) is a measure of the reliability and risk-reduction provided by a safety function. SIL 1 is the lowest level of risk reduction, while SIL 3 is the highest typically found in industrial automation. Most modern safety components from brands like Siemens and Allen-Bradley are rated for SIL 3, meaning they are suitable for high-risk applications where failure could cause serious injury or death.
Can I integrate safety systems with my existing industrial network?
Yes, most modern safety systems support Safety over Ethernet protocols. Leading examples include CIP Safety (used by Allen-Bradley/Rockwell), PROFIsafe (used by Siemens and ABB), and FSoE (Fail Safe over EtherCAT) used by Omron and others. These protocols allow safety signals to share the same physical network cable as standard control data without compromising safety integrity.
When should I use a safety relay versus a programmable safety controller?
A safety relay is a dedicated device designed to monitor a single safety function, such as an E-stop button or light curtain. A programmable safety controller (or Safety PLC) can handle multiple safety inputs and complex logic. Use a relay for simple, standalone machines with 1-3 safety functions. Use a programmable controller for complex lines requiring modularity or network communication.
How do I choose between a safety light curtain and a laser scanner?
Light curtains use infrared beams to create an invisible barrier around a hazard; if a beam is broken, the machine stops. Laser scanners sweep a horizontal area to detect presence. Choose light curtains for point-of-operation protection where workers frequently interact with the machine. Choose laser scanners for area protection or protecting the path of Autonomous Mobile Robots (AMRs).
What are redundancy and monitoring in safety circuits?
Redundancy involves using two or more independent components (like dual-channel wiring or two processors) to perform the same function. If one component fails, the other maintains the safety function. Monitoring refers to "feedback loops" where the system checks the status of external devices, such as ensuring a contactor has actually opened when commanded to stop.
What happens when a safety system detects a fault?
Safety systems are required to reach a "Safe State" upon any detected fault. For most machinery, this means a Category 0 stop (immediate removal of power) or a Category 1 stop (controlled deceleration followed by power removal). The system must prevent an automatic restart until the fault is cleared and a manual reset is performed.
Are safety components from different manufacturers compatible?
While some basic dry-contact safety relays are interchangeable, programmable systems and networked safety I/O (like PROFIsafe modules) are usually brand-specific and require the matching PLC and engineering software. For example, Allen-Bradley POINT Guard I/O is designed for Logix controllers and cannot be directly replaced by Siemens ET 200SP safety modules without changing the entire control architecture.
What are OSSD outputs in safety sensors?
OSSD (Output Signal Switching Device) refers to a pair of solid-state safety outputs used on modern sensors like light curtains. Unlike traditional dry contacts, OSSD outputs send short "test pulses" to detect short circuits to 24V or ground. This allows the safety controller to identify wiring faults instantly, providing a higher level of safety (Performance Level e).
How often should safety components be replaced for preventative maintenance?
The shelf life of safety components is generally long, but the "Mission Time" (service life) is typically 20 years. For older systems like Pilz PNOZ classic relays or older Allen-Bradley Guardmaster units, we recommend migration if the units are discontinued, as internal capacitors and relays degrade over time, potentially impacting the safety reaction time.