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Standard Interpretations - Table of Contents
• Standard Number: 1910.212(a)(3)(ii); 1910.217; 1910.217(d)(9)(iv); 1910.147; 1910.147(a)(2)(ii); 1910.147(b); 1910.147(d); 1910.147(f)(1)

April 22, 2005

Mr. William H. Kincaid
Lockton Companies of St. Louis
Three City Place Drive
Suite 900
St. Louis, MO 63141

Dear Mr. Kincaid:

Thank you for your December 1, 2004, letter to the Occupational Safety and Health Administration's (OSHA's) Directorate of Enforcement Programs. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. You had specific questions regarding the Control of hazardous energy (lockout/tagout), §1910.147, requirements for die-setting operations in hydraulic power presses. Your paraphrased subject background (with comment), questions and our replies follow:

Your Subject Background: You stated that there does not appear to be specific OSHA guidance regarding the manner in which OSHA requires persons performing die-changes to be protected while removing and placing dies. However, you recognize that the preamble to 29 CFR 1910.147 provides:
It should be pointed out that OSHA is allowing the removal of the lockout or tagout devices and the re-energization of the machine or equipment only during the limited time necessary for the testing or positioning of the machine, equipment, or component thereof. This paragraph does not allow the employer or employee to disregard the requirement for locking out or tagging out during the other portions of the servicing or maintenance operation. This exception provides for a temporary measure to be used only to accomplish a particular task for which re-energization is essential.
You have noted that, for the unbolting of die-securing bolts, removal of die clamps, removal of die, replacement of the die, and re-installation of the fasteners, re-energization is not essential. Accordingly, you indicated that you are advising clients to keep their machines locked-out except for the limited portions of the die-setting operation that requires temporary energization. However, you question whether extra time required to isolate energy during die-changes yields greater worker safety. In fact, you contend that the repeated removal and re-installation of lockout devices may create more opportunities for error.

You requested OSHA's concurrence with the following alternative inch method for protecting the die-setters during die-changing operations. It is your position that, when a hydraulic power press is equipped with an inch mode actuated by two-hand control, the persons performing die-changes are protected as long as the machine remains in inch mode. The machine will not move unless somebody deliberately actuates the machine controls, then the machine moves slowly and only while both controls are actuated.

Securing the machine in inch mode can be accomplished easily by using a key-switch to select the operating modes.

Question 1: Does the lockout/tagout (LOTO) standard require that machines, including hydraulic presses, be de-energized and locked out except for the portion of die-setting that involves testing and positioning?

Reply: Yes, to the extent that employees are otherwise exposed to hazardous energy.1 During the rulemaking process, OSHA explicitly considered the need to re-energize and concluded in the preamble to the final rule (Federal Register, 54 (169), Friday, September 1, 1989, p. 36680) that it is permissible to re-energize only during the period of time necessary for the testing or positioning action, see §1910.147(f)(1).

OSHA also stated that employers must provide and use optimum safety coverage, such as a properly designed and applied safety device (e.g., a two-hand inch mechanism), for employees when they go from a de-energized state to an energized condition and subsequently return the system to a de-energized state with LOTO control. The use of an inch safety device, for example, provides employee protection during the press's operating cycle — pursuant to the §1910.212(a)(3)(ii) point-of-operation guarding requirements.2

The LOTO standard is intended to work in conjunction with the machine guarding standards to provide optimum employee protection. Compliance with the Subpart O requirements is essential during power press component test/position activities. Moreover, in some cases, the implementation of effective machine guarding techniques may eliminate worker exposure to hazardous energy, providing a feasible and acceptable alternative to LOTO. However, when machine guarding methods do not eliminate exposure to hazardous energy, LOTO is required to prevent die-setter employees from being seriously injured when performing die-set servicing activities.

Question 2: Assuming that all other required safety provisions such as operator training, control reliability, etc. are properly implemented, may die-setters unfasten, remove, replace, and refasten dies in a hydraulic press without locking out the machine as long as the press is in "inch" mode with properly installed and located two-hand controls? Would this alternative safeguarding method protect the die-setters during die-changing operations?

Reply: No, the use of a safety device, such as an inch mechanism, does not adequately control all hazardous energy exposures to die-setters when their body parts are in, on, or in close proximity to machines or equipment danger zone areas.3 As detailed in §1910.147(f)(1), an inch mechanism can protect the die-setter from hazards associated with press component motion during testing or positioning activities. However, an inch mechanism does not protect this or other employees from the hazardous energy exposure while performing other servicing and/or maintenance activities.4 Prior to placing hands or other body parts in a potentially hazardous machine area (e.g., to install, remove, adjust, clean, or repair dies), LOTO must be used to protect employees from hazardous motion of the slide and other related energy hazards. (See footnote #1 for minor servicing exceptions to this LOTO requirement.)

Bodily injuries or amputations have resulted from the intentional or inadvertent placement of a body part into the uncontrolled die space (the working area of the press between the bolster plate and the ram/slide) or into other machine danger zones (such as mechanical hazards associated power transmission equipment) during die-set tasks. For example, the following hazardous situations, which are not all inclusive, can result when employees set or remove dies:
  1. Uncontrolled potential mechanical energy may be present due to the ram/slide position and associated gravitational force causing the sudden release of stored energy causing hazardous motion;
  2. Press component malfunction (e.g., hydraulic system component failure or fluid leakage) may result in hazardous motion due to unexpected drift or sudden descent of the slide;
  3. Control components failure or electrical/mechanical interferences causing hazardous motion;
  4. The sudden dropping of the upper die when freed from the slide; or
  5. Unexpected press activation caused by human error (e.g., inadvertent press activation by others; accidental stepping on or having a part fall onto an unguarded foot control treadle).
Some recognized incident causal factors related to inadequate control measure application (and the applicable §1910.147(d) standard references) that pose significant risk to die-setter employees, include:
  1. Failure to shut off power to the power press [pursuant to §1910.147(d)(2)];
  2. Failure to utilize energy isolating device(s), including safety blocks insertion between the upper and lower die, and LOTO the press to prevent hazardous slide motion [pursuant to §§1910.147(d)(3) and (d)(4)(i)]; and
  3. Setting dies with the slide in the stroke up position [pursuant to §1910.147(d)(5)(i) for residual energy hazards].
Additionally, your letter provides a hydraulic power press die-set as a parallel to those die-set procedures for a part-revolution mechanical power press, and you specifically reference OSHA Instruction [STD 01-12-024 (formerly STD 1-12.24)], Clarification and Interpretation of 29 CFR 1910.217, Mechanical Power Press, as applied to the Safeguarding Requirements for Die-setter.5 Your contention that this directive permits dies to be changed in part-revolution mechanical power presses without locking out, as long as the machine is safely in the inch mode, is inaccurate. This 1979 OSHA Instruction describes die-setting methods that safely position the slide utilizing point-of-operation safeguarding techniques; however, this directive does not detail the energy control (LOTO) requirements for other hazardous aspects involved in the die-setting procedure. As explained above, there are hazardous situations (e.g., adjusting or repairing dies while in the press) that can result when employees place their body parts near or into a die space that is not adequately isolated and controlled in accordance with §§1910.147 and 1910.217(d)(9)(iv) safety block requirements.

In order to effectively and comprehensively address hazardous energy control situations, including those associated with mechanical power press die-setting operations, OSHA specifically addressed the supplemental nature of the LOTO standard, with respect to other standards containing Part 1910 LOTO provisions — e.g., use of blocks to control hazardous energy, see §1910.147(a)(3)(ii). OSHA concluded in the preamble to the final rule (Federal Register, 54 (169), Friday, September 1, 1989, pp. 36664-36665) that the Control of hazardous energy (lockout/tagout) standard is not intended to replace other existing standard provisions for LOTO. Rather, the LOTO standard supplements and supports these energy control requirements provisions by requiring that employers establish an energy control procedure and train employees in the energy control program (as detailed in §1910.147) whenever a Part 1910 standard contains a provision mandating LOTO.

With respect to your contention that the removal and re-installation of lockout devices may create more opportunities for error, OSHA has determined that, when an employer follows the procedure established in §1910.147(f)(1), testing and positioning activities can be performed without significant risk to employees. On the other hand, OSHA believes that the failure to control hazardous energy results in significant risk to employees. Although the chance for human error does exist, the success of an employer's program depends upon a commitment to the energy control program through, in part, the development and implementation of:
  1. Procedures to clearly and specifically outline the necessary energy control steps to be taken by employees;
  2. Effective training to teach employees about the applicable procedure for the servicing or maintenance task to be performed; and
  3. Periodic inspections and other management procedures designed to ensure accountability.
For additional program implementation information, see §1910.147 and the Safety and Health Management Guidelines, Issuance of Voluntary Guidelines (Federal Register, 54, January 26, 1989, pp. 3904-3916) at OSHA's web-site.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you may consult OSHA's website at If you have any further questions, please feel free to contact the OSHA Office of General Industry Enforcement at (202) 693-1850.


Richard E. Fairfax, Director
Directorate of Enforcement Programs

[Corrected 2/20/2008]

1 The minor servicing exception (MSE) to the LOTO standard applies to minor tool changes and other minor servicing activities, which, in part, take place during and are inherent to normal production operations (NPOs). See the note to §1910.147(a)(2)(ii) for all of the criteria associated with this exception. However, Setting up activities, by definition, involve work that prepares a press to perform its intended normal production operation; therefore, this exception generally would not apply to hydraulic and mechanical power press die-setting because the servicing activity is not taking place during NPOs. Furthermore, the Occupational Safety and Health Review Commission (OSHRC) rejected an employer's assertion that set-up activities associated with a printer-slotter machine constituted servicing and maintenance within the scope of the MSE. The OSHRC concluded that adjustments made while the machine was being set-up were not adjustments made during NPOs. See Westvaco Corp. 16 (BNA) OSHRC 1374 (90-1341, 1993) [back to text]

2 Due to varying types of hydraulic power presses and control circuit design characteristics, each manufacturer should be consulted for their recommended servicing and maintenance guidelines prior to developing the techniques and procedural steps to control hazardous energy. For example, the use of the inch mode on a particular manufacture's hydraulic power press may by-pass critical safety systems (e.g., safety interlocks, presence sensing devices) creating a false sense of employee security in the event the die-setter(s) incorrectly relies on the inch device for his or her protection. [back to text]

3 The application of and reliance on the inch device alone would not constitute compliance with the requirements of §1910.147 since the inch device is an electrical control circuit. The LOTO standard specifically excludes such control circuits as Energy isolating devices, see §1910.147(b). [back to text]

4 In order to provide effective employee protection and meet performance-oriented LOTO standard, a safe die-set energy control procedure needs to be based upon a reliable hazard analysis to determine and effectively control such hazardous energy exposure. for example, the installation and removal of dies presents potentially hazardous situations for die-setter employees because a trapping space exists between the top die (when the die shoes are together) and face of the slide or, in some instances, between the two dies (if the die shoes are fastened to the bolster plate and slide). However, during the securing and unfastening of dies, the slide (with the die shoes together) is usually in the lowest (180-degree) position. Die-setter injury may still result from the sudden dropping of the upper die shoe when freed from the slide (due to incomplete or inadequate shoe attachment to the slide) if an energized inch control is activated (e.g., due to human error; by dropping a part onto an unguarded foot control treadle). [back to text]

5 In order to further clarify this mechanical power press die-setter instruction, our directorate will up-date this OSHA Instruction (STD 1-12.24) and the Control of hazardous energy, STD 1-7.3-1990, directive to specifically address power press die-setting procedures and the applicable hazardous energy control (LOTO) requirements. [back to text]

Standard Interpretations - Table of Contents

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