When ANSI B11.0 - 2023 Two-Hand Trip Devices Fall Short in EHS Consulting

Two-hand trip devices (THTDs) are essential safety mechanisms in many industrial settings, designed to ensure that operators keep their hands clear of hazardous areas during machine operation. According to ANSI B11.0 - 2023, section 3.15.13, a THTD requires simultaneous operation by both hands to initiate hazardous machine functions, and can be released once the operation begins. However, while these devices are effective for the operator's safety, they have limitations that EHS consultants need to understand and address.

Limited Scope of Protection

The primary limitation of THTDs is their scope of protection. As the standard notes, these devices only provide risk reduction for the person operating the control. This means that other workers in the vicinity of the machine remain unprotected. In my experience consulting with various manufacturing facilities, I've seen how this can lead to accidents if other employees are not aware of the machine's operation cycle.

Dependence on Operator Compliance

Another critical aspect where THTDs can fall short is their dependence on operator compliance. If an operator bypasses the safety mechanism or if there's a failure in the device itself, the intended safety measures are compromised. We've encountered situations where operators, under pressure to meet production targets, might not use the THTD correctly, leading to potential hazards.

Need for Additional Safety Measures

Given these limitations, EHS consultants must advocate for additional safety measures. This could include implementing presence-sensing devices, safety interlocks, or comprehensive training programs that emphasize the importance of following safety protocols. Based on available research, individual results may vary, but integrating multiple safety systems often leads to a more robust safety environment.

Real-World Application

In one of our projects, a client's facility relied heavily on THTDs for their press machines. We conducted a thorough risk assessment and found that while the THTDs were effective for the operators, there was a significant risk to maintenance staff who occasionally worked near these machines during operation. Our recommendation was to install additional safety barriers and implement strict access control measures during machine operation.

Conclusion

While ANSI B11.0 - 2023 clearly defines the role of two-hand trip devices, EHS consultants must recognize their limitations. By understanding these shortcomings, consultants can better tailor safety strategies that protect not just the operator but all personnel in the workplace. For further reading, the American National Standards Institute provides detailed resources on machine safety standards.