Designing Pneumatic Systems with Adequate Safety Performance for Robot Cells

Integrating pneumatic components into robotic work cells presents both opportunities and risks. While pneumatic actuators and valves are essential for tasks like clamping, positioning, or tooling, they must be designed with safety in mind—especially when used in collaborative or hazardous robot operations. To ensure worker protection and regulatory compliance, these systems must achieve a Safety Performance Level (PL) appropriate for their risk—often PL d or PL e.

This article outlines how to design pneumatic systems that meet the safety performance criteria required in robotic applications, referencing the ANSI/RIA R15.06 and ANSI B11.19 standards.

Why Safety Performance Levels Matter

Pneumatic energy can cause serious injury through crushing, impact, or unexpected movement. In a robotic cell, this risk is compounded by automation and the potential for human-machine interaction. To mitigate these hazards, pneumatic systems must be included in the risk assessment process and designed to meet a required Performance Level (PLr) using the methodology from ISO 13849-1 (incorporated by reference in both ANSI/RIA and ANSI B11 standards).

Key Standards

• ANSI/RIA R15.06-2012 (R2022)
  Industrial Robots and Robot Systems – Safety Requirements
  This standard aligns with ISO 10218 and mandates a comprehensive risk assessment, particularly when integrating pneumatic components that could pose a hazard during automatic or manual intervention modes.

• ANSI B11.19-2019
  Performance Requirements for Risk Reduction Measures
  This standard defines the functional requirements of safety-related parts of control systems (SRP/CS), including those that isolate or exhaust pneumatic energy to reduce risk.

Together, these standards require that all energy sources—including pneumatic—be brought to a safe state during access or maintenance. This often means achieving Category 3 or 4 (PL d or e) safety performance in the energy isolation and control circuits.

Steps to Achieve Adequate Performance Level in Pneumatic Circuits

1. Conduct a Task-Based Risk Assessment

Use ANSI/RIA R15.06 and ANSI B11.0 to identify tasks (e.g., maintenance, programming, jam clearing) and their associated hazards. For high-force pneumatic actuators, risks often warrant PL d or PL e for injury prevention.

2. Use Redundant and Monitored Pneumatic Valves

Achieving PL d or e requires:

• Redundancy: Use dual-channel pneumatic safety valves that independently exhaust air to a safe state.

• Monitoring: Integrate sensors or feedback devices to detect valve faults and ensure proper operation.

Manufacturers like SMC, Ross, and Festo offer ISO 13849-1-certified redundant safety valves specifically designed for Category 3 or 4 circuits.

3. Integrate with the Robot’s Safety Control System

Pneumatic safety valves must be connected to the robot’s Safety Programmable Logic Controller (SPLC) or safety relay. This ensures coordinated de-energization during emergency stop (E-stop), safety gate opening, or light curtain interruption.

4. Apply Safe Exhaust and Pressure Hold

Design the system to:

• Exhaust residual pressure when access is required.

• Prevent unexpected movement by maintaining safe positions using pressure-retention valves or mechanical stops.

5. Validate with ISO 13849-2 Principles

After implementation, validate the system using tools like SISTEMA or PAScal to confirm the architecture meets the required PL. Testing must include fault detection and response time verification.

Documentation and Maintenance

ANSI B11.19 also requires:

• Documentation of all safety functions, including pneumatic controls.

• Preventive maintenance plans to ensure valves and sensors maintain reliability.

• Operator training on energy isolation procedures (LOTO) and safety system behavior.

Final Thoughts

Achieving a safe pneumatic system in a robot cell is not just about selecting the right components—it requires an integrated approach involving risk assessment, compliant design, system validation, and documentation. By aligning with ANSI/RIA R15.06 and ANSI B11.19, safety professionals can ensure their pneumatic subsystems meet the required Performance Level and contribute to a safe, productive robotic work environment.