An extensive overhaul in 2017 of the previously published document, this is an essential standard for all metal formers to obtain and use in their safety-planning activities.
Ted Sberna Sr. authored this article exclusively for MetalForming magazine and PMA. He is the lead engineer/chief consultant for White Horse Safety Inc. He has more than 40 years of experience as an end user, integrator, OEM and consultant, and is a participating member of numerous ANSI B11 safety committees, including co-chairman of ANSI B11.1, as well vice chair of the ANSI Z244.1 committee on the Control of Hazardous Energy.
The article reviews the use of ANSI B11.20 as it pertains to automated press cells, as they are integrated manufacturing systems (IMSs), and explores the concept of shared space and layout analysis, which metal formers can use to help determine zones and define spans of control for safety-related control devices.
The B11.20 standard is somewhat of a well-kept secret within the stamping industry as it seems only a few organizations recognize its importance as it pertains to the overall risk-assessment process for new and existing equipment. The revised publication (in 2017; the first revision of this document was released in 1991) resulted from an extensive overhaul of the previously published document and is an essential standard for all metal formers to obtain and use in their safety-planning activities.
The press slide/die area presents numerous opportunities for personnel to interact with equipment, and those tasks cannot always be completed by following OSHA 1910.147/ANSI Z244.1 hazardous-energy-control lockout methods. Therefore, these tasks must utilize alternative methods of hazardous-energy control to comply with the standards. Here, multiple pieces of equipment, under different control systems, exist in the same space where tasks are being completed, thus the shared-space concept. This shared space is where ANSI B11.20 and B11 standards provide requirements and guidance on how the various SCSs and safety-related devices must be integrated to provide the proper safety-circuit performance to meet the requirements of a documented task-based risk assessment.
For example, consider an automated transfer press with a coil-feeding system providing the material into the first die station. While seemingly most of the focus is on the hazards and safety control for the actual press motion, the tasks in the shared space also expose personnel to hazardous situations regarding the motion during the coil-feed process and the transfer automation. Often, metal formers do not follow the requirements for the use of the alternative methods when interlocking the safety devices for this shared space with all three systems, as compared to just the press. It has been documented in the past two decades that for OSHA to consider the use of control circuits for alternative methods to lockout, they must provide effective protection. Effective in this context is defined “as effective as lockout” in a reliable fashion. This means that the safety-related interlocks for the control systems must be reliable in terms of their ability to fail in such a fashion as to remain in a safe state. Controls that do not meet these requirements require additional methods of isolation to the control circuit for the use of alternative methods.
Read the full article.