In a recent Letter of Interpretation, the Occupational Safety and Health Administration clarifies the application of the Lockout/Tagout (LOTO) standard, 29 CFR §1910.147, to die-setting activities and other machine setup operations.

Die-setting
OSHA says that die-setting activities constitute servicing activities and are covered by the LOTO standard — i.e., pursuant to the definitions for setting up and servicing and/or maintenance contained in §1910.147(b). (The letter specifically addresses die-setting activities with regards to hydraulic power presses.)

OSHA says that safety blocks (as described in the letter), as well as electric disconnect switches (also described in the letter), are energy isolating devices if they physically prevent the transmission or release of energy. See the §1910.147(b) definition of energy isolating device.

Although the safety blocks may provide some protection, OSHA says the reliance on control circuit devices (i.e., two-hand controls and/or a light curtain) alone or together may not protect employees from other types of hazards because neither safeguarding device physically prevents the transmission or release of hazardous energy. For example, the use of control circuitry alone does not prevent employee exposure to hazardous energy that may result from unexpected ram movement caused by potential mechanical energy (resultant from the ram/slide position and associated gravitational force), press component or control system malfunction, or press activation by others.

Grinding wheels, drill bits
OSHA says LOTO requirements apply to changing grinding wheels on a surface grinder and changing a drill bit on a radial arm drill press, unless the set-up activity meets one of the following LOTO standard exceptions:

  1. The minor servicing exception, contained in the §1910.147(a)(2)(ii) note, provides that: “Minor tool changes and adjustments, and other minor servicing activities, which take place during normal production operations, are not covered by this standard if they are routine, repetitive, and integral to the use of the equipment for production, provided that the work is performed using alternative measures which provide effective protection (see Subpart O of this Part).”
  2. The cord- and plug-connected equipment exception, contained in §1910.147(a)(2)(iii)(A), states that the LOTO standard does not apply to: “Work on cord and plug connected electric equipment for which exposure to the hazards of unexpected energization or start up of the equipment is controlled by the unplugging the equipment from the energy source and by the plug being under the exclusive control of the employee performing the servicing or maintenance.”

With respect to changing a grinding wheel on a surface grinder, OSHA says the wheel change takes place outside of the normal production process: i.e., the machine is turned off, grinding operations stop, a guard is removed, and the wheel retainer nut is loosened and removed. Therefore, the minor servicing exception does not apply and the energy source for the grinder would need to be locked or tagged out in accordance with this standard, OSHA says in the letter. [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/or maintenance within the scope of the minor servicing exception. OSHRC concluded that adjustments made to prepare for the normal production operations cannot, at the same time, be adjustments that are made during normal production operations. As such, these setting up activities, by definition, cannot fall within the minor servicing exception. See Westvaco Corp. 16 (BNA) OSHRC 1374 (90-134, 1993).]

In terms of radial arm drill presses (as addressed in the scenario in the letter), OSHA says that minor tool changes and adjustments, which are routine and repetitive and must be performed as an integral part of the production process, are permitted to be performed without LOTO if the work is performed using alternative measures that provide effective protection. Electric disconnect switches or control switches are considered effective protection if the switches:

  1. Are properly designed and applied in accordance with recognized and good engineering practice; and
  2. Control all the hazardous energy and are placed in an off position; and
  3. Are under the exclusive control of the employee performing the task.

In the event the surface grinder or drill press wiring consists of a flexible cord equipped with an attachment plug connected to permanent wiring (as permitted by 29 CFR 1910, Subpart S), OSHA says the employer may elect not to LOTO the equipment as long as: (1) the employer unplugs the cord- and plug-connected equipment; (2) unplugging controls all of the hazardous energy to which the employee may be exposed; and (3) the plug is in the exclusive control of the employee who is performing the tool change. See §1910.147(a)(2)(iii)(A) exception. In all other situations in which employees are performing servicing and maintenance activities and may be exposed to hazardous energy, LOTO must be performed to protect employees from hazardous energy, OSHA says in the letter.