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 can consult OSHA's website at https://www.osha.gov.

October 4, 1983

Mr. Robert G. Lown
Vice President
Greenerd Press & Machine Company, Inc.
41 Crown Street
Nashua, New Hampshire 03061

Dear Mr. Lown:

This is in response to your letter of September 1, 1983, requesting clarification of OSHA's requirements regarding the use of self-tripping on hydraulic power presses.

The self-tripping mode for mechanical power presses is addressed in OSHA's standard 29 CFR 1910.217(c)(3)(iii)(b), which provides that a presence sensing point of operation device may not be used as a tripping means to initiate slide motion. However, this provision does not apply to hydraulic power presses, as indicated in 1910.217(a)(5).

OSHA currently is considering a project to allow self-tripping of mechanical power presses. A preproposal draft standard has been circulated for public comment. The comments are now being evaluated in order to determine what, if any, further rulemaking will be undertaken.

Machine guarding to protect employees exposed to the hazards of hydraulic presses is regulated by 29 CFR 1910.212. This particular standard does not specifically prohibit self-tripping; it does, however, require that guarding of the point of operation be designed and constructed so as to prevent the operator from having any part of his body in the danger zone during the operating cycle.

OSHA has no specific prohibition regarding the application of self-tripping on hydraulic power presses. However, we believe you should be aware that the pertinent voluntary industry consensus standards committee for hydraulic presses, ANSI B11.2, is presently in disagreement regarding the application of self-tripping.

I hope this clarification is useful to you. If I may be of further assistance, please contact me.


Bruce Hillenbrand
Director, Federal Compliance
and State Programs