In modern industrial automation projects, the value of safety control systems is not only reflected in product performance but also in on-site installation and commissioning. As a leader in safety automation, Pilz’s safety relays and system solutions are widely used in industry, yet field projects often show “installation compliant but commissioning non-compliant.”

To help engineers avoid common issues, this article outlines the key steps from installation to commissioning of Pilz safety systems from an engineering implementation and acceptance perspective, forming a practical guide that can be directly applied.

1. Before Installation: Environmental Assessment Is the First Task

Installation is not just wiring or placing devices in a cabinet. Engineers must first evaluate whether the control cabinet environment meets product manual requirements:

• Temperature: Extreme temperatures affect relay life and reliability.

• Humidity: Moisture can cause corrosion and insulation deterioration.

• Vibration: Long-term vibration can loosen wiring or damage components.

• EMC (Electromagnetic Interference): It may cause false trips or diagnostic failures.

Especially avoid installing safety relays above variable frequency drives or other high-heat devices; adequate cooling space must be reserved. Pilz’s installation guides and wiring diagrams clearly mark these critical points, and engineers must follow them precisely.

2. Wiring Phase: Redundancy and Isolation Determine Reliability

Wiring is the “skeleton” of a safety system; any minor mistake may lead to failure. Key points include:

1) Power Supply and Grounding

• Power must be stable and clean to avoid affecting relay operation.

• Protective grounding (PE) must be reliable to ensure equipment and personnel safety.

2) Dual-Channel Emergency Stop Redundancy

Emergency stop buttons must use two independent normally closed contacts, wired to two channels. Recommended wiring:

• Separate routing for the two signal lines

• Or use a dual-core shielded cable

• Avoid a single fault affecting both channels

If SCD is enabled, wiring must strictly follow the diagram, as any parallel connection will disable diagnostics.

3) Output and Feedback Loop

Safety contacts cut power, while feedback loops (such as Y1-Y2) verify whether the contactor has actually opened. The feedback loop must be connected in series with the contactor’s normally closed auxiliary contact to form closed-loop monitoring.

4) Reset Circuit Must Be Correct

The reset button must be connected to the designated terminals; do not short the reset circuit. Shorting disables manual reset and breaks the safety confirmation mechanism.

3. Commissioning Phase: Functional Verification and Destructive Testing Are Both Required

After wiring is complete, commissioning is the key step to verify whether the safety system is truly effective. The following process is recommended:

1) Pre-Power-On Checks

• Visually inspect wiring for looseness or potential short circuits

• Use a multimeter to test continuity and eliminate wiring errors

2) Basic Functional Testing

When conditions are met (such as emergency stop reset and safety gate closed), pressing reset should energize the relay and power the load.

3) Destructive Testing (Core Acceptance Content)

• Emergency stop trigger test: Press the emergency stop; the load must cut off immediately.

• SCD short-circuit test: Simulate a short between S11 and S21. The relay with SCD should refuse to reset or alarm.

• Feedback disconnection test: Simulate feedback line disconnection; the system should enter a fault state.

4) Parameter Settings and Records

For programmable or configurable devices, set parameters such as reset mode and delay according to requirements, and archive the settings.