OSHA is considering whether to initiate rulemaking to revise its control of hazardous energy standard for general industry. One aim of this RFI is to seek public comment on the modernization of the control of hazardous energy standard without compromising worker safety. OSHA is requesting information from the public on its control of hazardous energy standard to help the agency determine how to best protect employees. OSHA’s control of hazardous energy (Lockout/Tagout) standard covers the servicing and maintenance of machines and equipment in which the unexpected energization or start-up of machines or equipment, or release of stored energy, could harm employees. These hazards exist not only for the employees working directly with the machines or equipment but also for the employees nearby. The Lockout/Tagout standard was developed to address these hazards by establishing minimum performance requirements for the control of hazardous energy. The Lockout/Tagout standard currently requires that all hazardous energy from power sources and energy stored in the machine itself be controlled using energy isolating devices (EIDs) when an employee is performing servicing or maintenance of a machine or equipment. OSHA’s definition of EIDs excludes push buttons, selector switches, and other control circuit type devices.
Nevertheless, OSHA recognizes that there have been safety advancements to control circuit type devices since OSHA adopted the standard in 1989. Accordingly, OSHA is revisiting the Lockout/Tagout standard to consider whether to allow the use of control circuit type devices instead of EIDs for some tasks or under certain conditions. OSHA seeks information, data, and comments that would help the agency determine under which conditions if any, control circuit type devices could safely be used. OSHA is also considering changes to the Lockout/Tagout standard that would reflect new industry best practices and technological advances for hazardous energy control in the robotics industry. OSHA invites information, data, and comments on these and any other issues or concerns that regulated employers, affected employees, and other interested parties may have regarding the existing Lockout/Tagout standard.
A. Control Circuit Type Devices and Other Alternative Methods to Lockout/Tagout
The OSHA standard currently requires employers to use an EID to control hazardous energy during the servicing and maintenance of machines and equipment. Over the years, some employers have stated that they believe that control circuit type devices that use approved components, redundant systems, and control-reliable circuitry are as safe as EIDs. OSHA recognizes that recent technological advances may have resulted in safety improvements to control circuit type devices.
In April 2016, OSHA granted a permanent variance to Nucor Steel Connecticut Incorporated (NSCI), permitting the use of a control circuit type device for the control of hazardous energy under the specific conditions presented in NSCI’s request for a variance.5 NSCI, a manufacturer of steel wire rod and coiled rebar, had proposed the implementation of a complete system that would provide an alternative means of compliance to the requirements of 1910.147(d)(4)(i) and (ii) with regard to grinding rolls on a roll mill stand. The engineered system used a “trapped key” concept and monitored safety-rated power relays in combination with administrative procedures. The trapped key system was designed to replace a locked out EID and to function similarly to a lockout device, in that only the employee in possession of the key could restart the
machine undergoing maintenance. The single key was controlled through administrative group lockout procedures that NSCI asserted matched the requirements of 29 CFR 1910.147.6 OSHA evaluated whether the device provided an equivalent level of employee personal control over machine re-energization, ability to account for exposed employees, and verification of isolation to that required by the OSHA standard.
OSHA reached three conclusions.
First, OSHA concluded that the alternate device allowed energy control measures to remain under the personal control of the exposed employee through control of the trapped key using a group lockbox.
Second, OSHA concluded that employees were able to verify de-energization.
Third, OSHA concluded that authorized employees were easily identified before equipment restart.
After reviewing the alternative safety measures proposed in NSCI’s application, and its responses to OSHA’s follow-up questions,8 OSHA granted the employer a variance permitting the use of this device exclusively for this task. 81 FR 20680. OSHA granted the variance based on the safety evaluation of the complete system, not just its individual components. Specifically, OSHA evaluated whether the alternative system could, as a whole, be considered as protective as an energy isolating device. OSHA concluded that
the proposed trapped key system was as effective as full lockout during this task in ensuring against internal and external failures that could lead to the release of hazardous energy. The agency determined that internal failures, such as welded relay contacts or errors in the safety relays, would not cause a critical failure without alerting employees. With respect to vulnerability from outside failures, such as attempts to bypass the system, OSHA determined that the system also provided equivalent protection to full lockout for these types of failures.
Although control circuit type devices may not permit easy visual confirmation of their application, in this instance, the system allowed the exposed employee to verify the effectiveness of the system through the attempted startup of the machine. In addition, the safety system was designed to revert to a safe mode in the event of a failure, the status of the safety system was monitored by multiple safety relays, and any faults would be signaled to operators. After completing an analysis of the company’s variance request and accompanying documentation, OSHA determined the proposed system was an effective alternative to full lockout for the task identified in the request.
As a result of the evaluation of this recent variance request, OSHA has determined that there may be a basis for amending the Lockout/Tagout standard to allow the use of control circuit type devices for hazardous energy control under certain conditions. Based on preliminary research and alliance partner feedback, OSHA believes the use of control circuit type devices is typically limited to the types of tasks that do not meet the minor servicing exception in the Lockout/Tagout standard but that also do not require either extensive disassembly of the machine or worker entrance into hazardous areas that may be difficult to escape quickly. An example of such a task is machine setup. OSHA is requesting information about how employers have been using these devices, including information about the types of circuitry and safety procedures being used and the limitations of their use, to determine under what other conditions control circuit type devices could safely be used.
As part of this RFI, OSHA is also evaluating criteria used by consensus standards to determine the safety effectiveness of control circuits. For example, the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) both have standards with detailed requirements for control circuit devices used for protection from machine hazards.9 The ISO and IEC standards evaluate the safety of a control system by considering its design and function. The IEC standards evaluate whether a system can achieve a certain “safety integrity level,” while the ISO 13849–1 consensus standard evaluates ‘‘performance levels’’ for each safety function. The ISO 13849–2 consensus standard also has safety categories that describe both the performance level required for that category and the characteristics of the error-checking of a system in that category. The highest safety category requires both the highest performance level of the control system and the most extensive error checking. Additionally, to determine the level of safety of a control system, both the IEC and the ISO standards consider the reliability of the system as a whole and its components, the operating environment, and the effects of failure.
OSHA promulgated the current version of 29 CFR 1910.147 on September 1, 1989. OSHA relied heavily on a 1982 consensus standard published by the American National Standards Institute (ANSI).10 The 1989 preamble stated that the ANSI standard was ‘‘[o]f great assistance to OSHA’’ and that ‘‘[t]he consensus standard was utilized by OSHA as the primary basis for the development of its proposed standard.’’54 FR 36645.
ANSI reaffirmed the 1982 consensus standard ‘‘without any changes in content’’ in 1988 and again in 1992. But by 2014, the Z244.1 committee recognized that, with the rapid advancement of technology, [a]dvanced control systems provide new opportunities for addressing energy control
- where conventional lockout is not feasible,
- where energy is required to perform a task,
- where repetitive cycling of an energy-isolating device increases risk, and
- where energy is required to maintain equipment in a safe state, etc.’
As a result, ANSI revised its standard to include ‘‘distinct requirements for controlling hazardous energy through three different approaches: lockout (the primary approach), tagout and alternative methods.’’
In 2016, the committee released a new consensus standard, ANSI/ASSPP Z244.1—2016 The Control of Hazardous Energy Lockout, Tagout and Alternative Methods. The standard’s Introduction states that it ‘‘provides for decision making flexibility regarding hazardous energy control methodology. Alternative methods, when used, are based upon risk assessment and application of the classic hazard control hierarchy (clause 8.1.2). However, lockout continues to be emphasized as the primary hazardous energy control method.’’ The ANSI standard requires that lockout or tagout ‘‘be used unless the user can demonstrate an alternative method will provide effective protection for persons. When lockout or tagout is not used, then alternative methods shall be used only after the hazards have been assessed and risks documented.’’ Thus, before using an alternative method, the employer is required to complete a practicability/justification analysis, a risk assessment, and other applicable evaluations. An accompanying chart and table in the standard go through the risk assessment process and the hazard control hierarchy.
OSHA is seeking information, comments, and data on the effectiveness of these approaches to control system safety and any limitations or potential issues regarding their use for some tasks that currently require lockout/tagout.
B. Addressing New Robotics Technology in Relation to Lockout/Tagout
Because robots may contain hazardous energy, the Lockout/Tagout standard can apply to their servicing and maintenance. OSHA has previously focused on industrial robots, defined as ‘‘programmable multifunctional mechanical devices designed to move material, parts, tools, or specialized devices through variable programmed motions to perform a variety of tasks.’’ OSHA is now studying the evolution of the use of robots in the workplace and how this affects employee protections related to the control of hazardous energy in the context of the Lockout/Tagout standard.
The traditional robot model involves a large device that welds metal pieces or moves panels or assemblies. This type of robot has a fixed base and an arm that moves freely. It is kept separate from workers during its operating stage and stays behind a locked door or within a locked compartment as it works. During periods of maintenance or adjustment, these robots’ movements are supposed to be limited or greatly slowed to reduce or eliminate the potential for worker injury.
The technological innovations of a new generation of robots, however, suggest that this may be changing. Unlike traditional robots, newer robots are more mobile and may be allowed to roam freely in a specified area, even if that area is separate from employees. Collaborative robots go a step further by working with human workers. In some cases, such robots are worn directly by the employees themselves, for example, as exoskeletons.
Due to these advances in robotics, OSHA is seeking information, comments, and data about any new risks of exposure to hazardous energy that employees may face as a result of increased interaction with robots. OSHA is seeking information, comments, and data on whether the agency should consider changes to the Lockout/Tagout standard that would address these new risks, as well as to account for any reduction in risks or other benefits to worker safety, associated with using robots.
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