Is Your Machine Safety ‘On’ or ‘Off?’

By Troy Hoffman, business development lead for Safety Services and Nuala Mullan, business development lead for Safety Services, Rockwell Automation

With the increased demand on our industrial workforce, many facilities are expanding the “do more with less” approach when it comes to machine safety.

Engineering, Health and Safety (EHS) and similar professionals are more likely to have their responsibilities expanded beyond programs such as lockout/tagout (LOTO) and Confined Space. They now include knowledge, design and testing of functional safety devices such as light curtains, area scanners and guard gates that historically were the responsibility of the plant engineer or equipment manufacturer.

Although these alternative protective measures (APMs) can complement LOTO when removal of hazardous energy is required for interaction with the machine, there is still a great amount of confusion on the application of each. When do we use LOTO, and when do we use APMs?

The regulation allows for alternative methodologies to be used as long as they’re “as effective as lockout/tagout” for the particular task. And that’s where many companies run into problems.

Often, companies use the exception clause to allow the employee to “create their own” path to safety if LOTO is impractical. The exception was not written to allow for any increased risk to employees, so when it’s being used, there should be the same chance for injury as if LOTO was used for that particular task.

Following the five steps of the Machine Safety Lifecycle outlined below can help you mitigate risk associated with that task and document the process.

1. Risk Assessment

The risk assessment process serves as an effective tool for properly identifying and assessing the real hazards involved in operating a particular machine. It provides a method for determining equivalent levels of protection when designing safeguards and stating the Occupational Safety and Health Administration’s (OSHA’s) minor service exception. The process takes away the guesswork when estimating risk and prescribing safety system performance.

The risk assessment is an active, documented process that can be filed and maintained for the entire life of the machine, and serves as documented proof of “due diligence.” It establishes the foundation and early framework for the design and implementation of an effective machine safety program.

2. Safety Functional Requirements Specification

The purpose for developing the safety functional requirements specification (SFRS) is to review the initial risk reduction recommendations from the risk assessment and confirm the ability to implement them as recommended. The specification contains existing and proposed safety functions and will serve as a basis for both the safety system design and validation plan.

3. Design & Verification

Safety system design includes all aspects of the safety system, including guarding (fixed, perimeter, interlocked, etc.) and safety controls (emergency stops, light curtains, etc.) as defined in the SFRS.

Documentation should include safety controls bill-of-materials (BOM), drawings for safety control panel layout, wiring diagrams, hardware interface diagrams, and any safety or human-machine interface (HMI) software (application code) development.

Once the initial design is complete, the safety system should be verified and documented to demonstrate compliance to the safety circuit architecture and circuit-performance requirements specified in the risk assessment.

4. Installation & Validation

After the safety system is designed and verified, installation of the approved safety control hardware and guarding will occur; however, the project is still not complete. Validation will demonstrate the designed system is correctly installed and functioning in accordance with the SFRS. The validation plan is a step-by-step documented process testing normal and abnormal operation of the safety system.

5. Maintain & Improve

Using the machine safety life cycle’s iterative approach, users identify changes to the equipment, process, and interaction with the machine, and any new risk to the employee is mitigated appropriately.

Complimentary Paths to Safety

Effective safety programs can reduce risk to employees performing a variety of tasks. For activities requiring complete de-energization of a machine, companies benefit from having a robust LOTO program.

Risk reduction to an acceptable level may still be achieved for routine, repetitive and integral tasks when the machine remains energized by following a set of good engineering principles as outlined in the machine safety life cycle.

^{The Journal From Rockwell Automation and Our PartnerNetwork™ is published by Putman Media, Inc.}