Ted Sberna Ted Sberna
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ANSI B11.20: Applications for Press Slide/Die Areas

September 3, 2021


ANSI B11.20-2017, “Safety Requirements for the Integration of Machinery into a System,” as detailed by the B11 standards organization, specifies the safety requirements for the design, construction, setup, operation and maintenance (including installation, dismantling and transport) of integrated manufacturing systems.  This standard does not cover safety aspects of individual machines and equipment that may be covered by other standards specific to those machines and equipment (B11 “base” standard), transfer machines or transfer lines, or continuous-flow processes. 

The B11.20 standard is somewhat of a well-kept secret within the stamping industry as it seems that 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.

Significant Changes to the Standard

Some of the changes to the standard, as typical in any update of an ANSI standard, relate to updated terminology designed to be more in line with global standards. One example that end-users should be familiar with: “Safeguarding” now is referred to as “risk-reduction measures/engineering controls.” Also, the term “awareness devices” has been replaced by “awareness means.”  

Other changes are more significant, including the addition of new zone classifications and topics such as special modes. In addition, spans of control for safety-related control devices have more-detailed information than previous documents, including requirements for the minimum level of safety performance for a device. 

This 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.

Risk Assessment

The B11.20 subcommittee recommends that users evaluate whether existing IMSs have acceptable risk using generally recognized risk-assessment methods. A risk-assessment document outlines the steps needed to bring a piece of equipment into compliance, per the appropriate ANSI and OSHA codes.  The assessment considers all aspects of the safety system, as depicted in the accompanying diagram.

ansi-b11-20-applications-white-horseRecognize that zero risk does not exist and cannot be obtained.  However, a good-faith approach to risk assessment and risk reduction should achieve an acceptable risk level.

The risk assessment is a three-phase process, the first phase being the creation of the risk-adjustment (RA) document. The second phase is verification—review of the safety design’s ability to meet the intent of the RA. The third phase is actual validation testing of the final safety-control system (SCS) to ensure that it correctly performs the required safety functions as called out as risk-reduction measures in the RA document. 

In addition, alternative methods of hazardous-energy control should be analyzed and their risk-assessment documentation reviewed as part of the overall safety-system review.

Shared Space

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 requirements of a documented task-based risk assessment.

For example, consider an automated transfer press with a coil-feeding system providing 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 with 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.  

In this example, unfortunately the press-transfer and coil-feeding automation often only are interlocked so that that their controls have their automatic function disabled, however the hazardous-motion control elements remain fully enabled, albeit in a manual-control fashion.  This would not meet the analysis required—in a documented risk assessment—for appropriate risk-reduction methods for those tasks, nor the requirements of a control circuit providing for alternative-method hazardous-energy control.  The addition of some simple safety circuits easily can be provided, but without completing a review and planning process during the risk-assessment phase of a project, it becomes more costly as an afterthought and can cause other hidden or future costs.

Other examples of the shared-space concept include tandem-press lines with various types of press-to-press automaton, including robots; blanking-press lines with coil-feeding and stacking automation; progressive-die coil-fed press operations; and automated presses with blank-destacking/feeding equipment.  To utilize the concept of alternative methods in lieu of lockout, ANSI standards such as B11.20 must be followed, as well as the requirements for the use of alternative methods as defined in ANSI Z244.1.   

Layout Analysis Required

A layout analysis must be part of the review process for all of these various IMSs found in the pressroom, to be part of the risk-assessment and risk-reduction process.  The analysis will help clarify the span of control of the various safety devices used within the IMS and help determine the required level of safety performance.  ANSI B1.20, ANSI Z244.1 and additional B11 standards such as B11.0, B11.19 and B11.26 all provide guidance, as well as the C-level standards for the equipment such as B11.1, B11.2, B11.3 and B11.18.

To finalize the review and analysis for the control of hazardous energy and use of alternative methods in shared spaces found in IMS applications, refer to ANSI/ASSE Z244.1-2016 R2020, “The Control of Hazardous Energy – Lockout, Tagout and Alternative Methods.” This standard provides the following guidance to justify the use of alternative methods, with requirements detailed in various clauses of the document:

  • A practicability/justification analysis
  • A risk assessment
  • Other applicable evaluations as detailed in clauses in the standard.

This detailed documentation, along with the documentation created by following the guidance of ANSI B11.20, provides end users with defendable positions for the use of alternative methods for performing tasks in their stamping-related IMS applications. MF

Industry-Related Terms: Die, Lines, Revision, Transfer
View Glossary of Metalforming Terms

 

See also: White Horse Safety, Inc.

Technologies: Safety

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