How Pilz Safety Relays and Sensors Work Together for Maximum Protection

Safety is a necessity in industrial setups for the protection of personnel and equipment. Here, Pilz safety sensors and relays provide a safe and reliable combination, forming the backbone of effective machine safety systems.

Pilz provides innovative and reliable safety sensors, designed for safe and efficient industrial automation. Built to protect people, machines, and the surroundings, these safety sensors monitor equipment positions, safety gates, and, at times, entire areas.

Here, we are going to make a deep dive into how the Pilz safety relays and sensors work together to implement industrial safety.

About Pilz Sensor Technology and Safety Sensors

Pilz offers intelligent, robust safety sensors that are designed to monitor hazardous situations in industrial machinery, protecting personnel and equipment by detecting unsafe conditions. Further, these devices trigger safe shutdowns, ensuring compliance with industrial safety standards.

The key sensor types available under PILZ sensor technology include:

• Position sensors and safety interlock switches that monitor covers, gates, and mechanical guards (e.g., PSENmech, PSENmag, PSENcode) and ensure these are closed during operation
• Pilz Light Curtains that provide body, hand, and finger protection for access points
• Rope Pull Switches (PSENrope) and E-stop pushbuttons that are the foundation behind emergency stops at any point on a conveyor and similar systems
• Radar Sensors that offer non-contact area monitoring, ideal for frequent access zones (like PSENradar)

These highly safe, reliable, and tamper-proof sensors with an easy plug-and-play design, wide compatibility, and I/O link safety are key components of an efficient and safe industrial automation architecture. Further, these devices are built with a robust IP67/IP69K ratings for dust/water resistance, and variants resistant, which makes them ready to withstand extreme industrial conditions (heat, cold, vibration).

The Step-by-Step Process of How Pilz Safety Sensors, Relay, and Controller Work

When installed together in an industrial setting, each component of the Pilz relay module works together to ensure plant and worker safety.

• Detection via Sensor

The Pilz safety sensors serve as the system’s eyes by constantly monitoring the machine environment for potential hazards. Common types of Pilz sensor technology installed for this purpose include:

• Safety light curtains
• Safety interlock switches
• E-stop pushbuttons

• Signal Transmission

When the sensor detects an unsafe condition (e.g., a gate opening), it sends a signal to the connected Pilz safety relay. Unlike standard components, the Pilz safety sensors use specific wiring principles, such as dual-channel signaling, to ensure the signal’s integrity and detect potential faults within the wiring itself.

• Logic Processing by Safety Relay

The Pilz safety relay is the “brain” of the operation. It receives the input signals from the sensors and processes them using predefined safety logic. Primarily, its task is to monitor the integrity of the input signals and ensure they meet safety standards. This is usually achieved by checking that both channels of a dual-channel input are active within a specified time window.

• Safe State Actuation

If the logic determines that an unsafe condition exists, the safety relay immediately de-energizes the connected safety outputs for the machine’s control elements, such as motor contactors or power control systems. De-energizing them safely removes power and stops the machine’s hazardous motion.

• Continuous Monitoring for Plant Safety

The safety sensors are also connected to Pilz safety controllers. Here, the goal is continuous monitoring of connected safety devices against safe parameters and implementing emergency shutdowns. Through real-time input monitoring and fault detection, safety controllers enable hazard mitigation.

How Pilz Sensor Technology Offers Industrial Setups Maximum Protection

Being the leading provider of industrial safety sensors, the Pilz PNOZ safety relay and other safety technology help make industries safe in the following ways:

• Immediate E-Stop Response enabled by operators using the E-stop button (a sensor). This rapidly cuts power to the hazardous machine parts by initiating an instant and safe shutdown.
• Safety Gate Monitoring using safety gate switches that monitor the position of movable guards. This prevents machines from starting or immediately halts their operation to protect personnel when accessing a danger zone.
• Integration of optoelectronic safety light curtains (sensors) that create an invisible protective field. This cuts power to a machine if an operator’s body or hand breaks the light beam.
• Redundant Circuit Design for both the sensors (e.g., dual-channel E-stops or safety switches) and the safety relays. This ensures continued safety even if one channel or component fails.
• Built-in Self-Monitoring that continuously performs automatic self-checks on relays in each on-off cycle. This detects internal faults in the input circuit and guarantees that the device is effective when needed.
• Forced-Guided Contacts in the Pilz safety relays physically ensure that the normally open (N/O) and normally closed (N/C) contacts move together. This design prevents the N/O contacts from closing if the N/C contacts are welded open, a common failure point in standard relays.
• Fault Detection and Indication using LED indicators for clear diagnostics. This allows for quick identification and localization of where a safety circuit has been interrupted, enabling faster troubleshooting and reduced downtime.
• Manual Reset through a monitored reset procedure via the safety relay in case a safety function is triggered. This ensures that machinery cannot accidentally restart and provides an added layer of safety.
• Speed and Standstill Monitoring for key machinery using advanced sensors like encoders (PSENenco). This allows safe access to hazardous zones as well as controlled stopping.
• Compliance with international safety standards like EN ISO 13849-1 (up to Performance Level e) and IEC 62061 (up to SIL 3). This ensures a verified, reliable, and globally compliant safety solution.

Choosing Your Pilz Safety Sensor: Ideal Pilz Relay and Sensor Pairings

Pilz offers a comprehensive range of sensors and other safety devices, including the Pilz PNOZ Safety Relay. For an effective setup, the following Pilz device pairings are a great choice:

Sensor Type	Compatible Relay	Application	Safety Level	Benefits
Pushbuttons/Switches (e.g., PITestop)	PNOZ s2, PNOZ X1, myPNOZ	Monitoring emergency stops for plants and machinery	Up to PL e / SIL CL 3	Easy integration, robust construction, simple and reliable emergency response, and internationally certified.
Safety Gates/Position Switches (e.g., PSENmech, PSENcode, PSENmag)	PNOZ s4, PNOZ X3, myPNOZ	Monitoring the position of movable guards, interlocks, and safety doors.	Up to PL e / SIL CL 3	Prevents access to hazardous areas, detects faults like contact welding, and redundant design ensures high reliability.
Safety Light Curtains/Barriers (e.g., PSENopt, PSENopt II)	PNOZ c2, PNOZ s5, PNOZmulti	Area and zone monitoring for open access areas; automatically stops movement upon intervention.	Up to PL e / SIL CL 3	Rapid response time, non-contact protection, high productivity by only stopping movement when necessary, easy installation, and inspection.
Two-Hand Controls	PNOZ s6, PNOZ X3	Applications requiring an operator’s hands to be occupied during a hazardous movement to prevent injury.	Up to PL e / SIL CL 3	Ensures both hands are on controls simultaneously, conforming to EN 574 standards for safe operation.
Standstill and Speed Monitors	PSWZ X1P, PNOZ s9 (timer)	Detecting motor standstill or monitoring safe speeds in machinery (e.g., during maintenance or deceleration).	Up to PL d/e	Prevents injury from unexpected machine restarts, compact design, wide voltage range, and suitability for various motors.
Pressure-Sensitive Mats	PNOZ X, PNOZmulti	Area monitoring on the shop floor; stops movement when a person steps onto the mat.	Typically up to PL d/e	Flexible area guarding solution, simple integration with PNOZ relays.

Table: Ideal Pilz safety relay and sensor combinations as per their application.

Wrapping Up

Having a robust safety system is key for industries, and this can be achieved with ease with Pilz sensor technology. Through integrated monitoring, rapid response, and a reliable shutdown mechanism, these devices enable maximum protection for heavy machinery.

Implementing Industrial Safety Through Pilz Sensor Technology

Are you planning to upgrade the safety of your plant/industry? Check out the best safety relay, sensor, and controller combination for your industrial equipment.

Frequently Asked Questions

What Are the Meanings of “Automatic, Manual, and Monitored Start” Modes?

In Pilz Safety devices, the three modes are as follows:

• Automatic Start: The safety relay activates as soon as the input circuit is closed.
• Manual Start: A positive signal (e.g., from a physical reset button) is required to activate the relay.
• Monitored Start: A negative signal is needed to signal the relay to start, and the system checks for proper conditions before activation.

Why Are Standard Electromechanical Relays Ineffective for Safety Functions?

Standard relays can fail in a way that the contacts weld together after repeated use. If this happens during an E-STOP event, the machine might not stop, creating a hazardous situation. Pilz safety relays use redundant, self-monitoring circuitry to prevent this kind of single-point failure.

How Does the “Key-in-pocket” Solution Provide Maintenance Safeguarding?

The Key-in-pocket system is an access management solution that uses RFID keys and a safe list within the Pilz controller. This electronic system ensures a machine cannot restart while an employee is in a danger zone by requiring the physical key to be with the person, replacing traditional mechanical lockout/tagout (LOTO) methods.

What Should I Do if the “Fault” LED Lights Up on a Pnozsigma Unit?

A fault LED often indicates an issue like a disconnected terminator or wiring error. You should check and reconnect all components properly and possibly reset the voltage for the device.