Standard Interpretations - Table of Contents|
| Standard Number:||1910.212|
November 7, 1991
Mr. David J. Bierman
Dear Mr. Bierman:
Thank you for your letter of August 19, concerning power press brake operations. In your letter you pose several questions, as follows:
1. "Specifically - safeguarding by distance when using foot pedal, switch, or treadle - if the dies never require hands in die operation.
a. What is considered a safe distance? b. What is considered a large work piece?"
2. "Press Brakes using Light Curtain Presence Sensing Device that mutes at 1/4" above the material with foot switch or treadle. ANSI refers to guarding the unused portion of the dies during an operation (no hands in die operation).
a. How can this be done when doing multiple operations on one piece part? The part changes sizes as it is being processed, and the user is using an automatic backgauge.
b. The cost of dies is prohibitive to have a die and set-up for each similar part. Other than cutting dies to size of an operation of guarding after light curtain is muted. What options does the user have for compliance?"
3. "Reference press brakes for no hands in did operations using a light curtain presence sensing device as a primary guarding device.
a. Because, press brakes are much slower and the operations are not hands in die. How do you determine a safety distance for press brakes using light curtain?
b. Does this apply to all types of brakes (for example - hydraulic, mechanical, pneumatic)?"
The following guidance is provided to clarify the issues posed in your letter. The expression "hands in die" pertains exclusively to mechanical power press operations, and, in other words, does not apply to power press brakes. Mechanical power press operations are regulated by the Occupational Safety and Health Administration (OSHA) under the standards at 29 CFR 1910.217. Power press brakes are regulated under the performance standard at 29 CFR 1910.212. Copies of those standards are enclosed for your convenience.
Since your questions relate only to safeguarding employees from point of operation hazards during power press brake operations, 29 CFR 1910.212(a)(3)(ii) is the applicable OSHA standard. As you will note, this standard specifies that:
"The guarding device shall be in conformity with any appropriate standard therefor, or in the absence of applicable specific standards, shall be so designed and constructed as to prevent the operator from having any part of his body in the danger zone during the operating cycle."
OSHA looks to the American National Standards Institute, Inc. (ANSI) as the publishers of nationally recognized consensus standards for guidance relevant to the requirements of 29 CFR 1910.212(a)(3)(ii). Specifically, ANSI B11.3-1982, Safety Requirements for Construction, Care, and Use of Power Press Brakes, is a pertinent standard for your consideration. In this specific instance, adherents to the specifications and requirements of the ANSI B11.3 standard will ensure compliance with the OSHA regulation at 29 CFR 1910.212(a)(3)(ii). The ANSI standard may be obtained from:
American National Standards Institute, Inc.
Many alternative forms of safeguarding of the point of operation on press brakes are offered by the ANSI B11.3 standard. From your questions we assume that the press brakes in consideration are General and/or Special Purpose and Mechanical Power Press Brakes as defined by the ANSI B11.3. ANSI B11.3, Sections 4.2 and 4.4, specifically address these machine tools and will for the most part be responsive to your concerns.
In response to your specific questions, we offer the following information:
I.a. Safe distance is defined at page 27, Section 3.48 and discussed at pages 71 and 79, Sections 6.1.4(1) and 126.96.36.199 respectively, of ANSI B11.3. Since ANSI has not elected to provide a minimum dimension, OSHA has assigned a value of 6 inches (15.2 cm)from the closest edge of the dies or tooling to the edge of the material nearest the operator at which location the material is hand-held. (This OSHA determination was documented by official interpretations of this issue during the time period between 1979 and 1982.) Please note that all such operations are required to be conducted with a properly adjusted material-position gage. (Under all circumstances, press brake operators are exposed to point of operation hazards, therefore, safeguarding the operator is a requirement of OSHA and the ANSI.)
1.b Generally, a large work piece is defined to be one which assures that a safe holding distance is feasible.
2.a & 2b. Useful and productive applications of light curtain devices upon special purpose press brakes are rare. All too often these devices are installed on press brakes and most always result in limiting the use of the machine. (It is recommended that you consider the use of two-hand controls which provide a rapid advance motion of the slide to 1/4 inch (0.6 cm) maximum of the material with automatic transfer of slide control to the foot pedal for the final forming portion of the stroke. As the result of maintaining less than a 1/4 inch (0.6 cm opening, the part can be safely hand held without special concern for safe holding distance during the final forming process, if the adjacent unused portion of the dies are safeguarded.)
3.a The safety distance determination which is used for positioning light curtain devices is determined as a function of the stopping time of the slide in a manner identical to that specified by 29 CFR 1910.217(c)(3)(iii)(e). (This requirement is specified by ANSI B11.3, Section 188.8.131.52.2.) Stop time measuring instruments may be rented or purchased from many of the safety equipment companies doing business in this country.
3.b Yes, this applies to all types of power press brakes.
If we may be of further assistance, please contact us.
Standard Interpretations - Table of Contents|