Machine Guarding

"On Classification of Safeguard Devices, Part 1"
Triodyne Safety Brief
v. 1 #1 (April 1981)

Ralph L. Barnett and Peter Barroso, Jr.

Engineers cannot change the law, but we can provide guidelines to help the courts make more reasonable decisions. The first step is to stop looking at safety devices as a homogeneous lump. Safety devices differ in the amount of safety they provide and the amount of harm they can do. This article presents a classification system that makes it possible to evaluate the efficacy of safeguarding devices, breaking down devices into mutually exclusive and jointly exhaustive categories.


"Drill Press Guards"
Triodyne Safety Brief
v. 2 #4 (September 1984)

William S. Switalski and Ralph L. Barnett

An investigation into the safety of drilling reveals a number of shortcomings in drill press safety guards.


"Meat Grinder Safety Throat"
Triodyne Safety Brief
v. 3 #4 (September 1985)

Ralph L. Barnett, Gene D. Litwin, Gary M. Hutter

Every engineered system represents a tradeoff among at least three criteria: cost, safety, and function. For a meat grinder with a safety feed throat and stomper, common sense tells us that operator safety will increase as the throat diameter decreases and its length gets longer. It is just as apparent that the feed throat capacity will decrease accordingly. This paper quantifies the relationship among the through parameters, the capacity, and the stomper force.


"Safety Throats for Meat Grinding Equipment"
Journal of Engineering for Industry
v. 111 #3 (August 1989): 262-268.

Ralph L. Barnett, Gene D. Litwin, and Gary M. Hutter

For a meat grinder with a safety feed throat and stomper, common sense tells us that operator safety will increase as the throat diameter decreases and its length gets longer. It is just as apparent that the feed throat capacity will decrease accordingly. This paper quantifies the relationship among the through parameters, the capacity, and the stomper force.


"On Classification of Safeguard Devices, Part 2"
Triodyne Safety Brief
v. 1 #2 (September 1991)

Ralph L. Barnett and Peter Barroso, Jr.

Part 1 of this article described an intrinsic classification system focusing on characteristics of individual safeguarding devices. In Part 2 we are concerned with the relationships among such devices. This requires the introduction of a category which deals with those safety characteristics inherent in a system. These are ranked under Zero Order Systems in the article's functional hierarchy of safety devices and concepts.


"Safety Interlocks: The Dark Side"
Triodyne Safety Brief
v. 7 #3 (June 1992)

Frank Hall

Interlock applications bring their own risks, which tend to offset the intended safety. The balancing of those risks against the safety afforded must always be considered in the ultimate decision on whether or not the safety device should be used at all. This paper enables readers to judge for themselves the effectiveness of interlocks and various alternative safety measures.


"On the Problem of Guarding Three Roll-Bending Machines"
Triodyne Safety Brief
v. 9 # 3 (January 1994)

Ralph L. Barnett and Dennis B. Brickman

Using universal guards developed by Bethlehem Steel and the U.S. Naval Academy, experiments were conducted which identify new hazards introduced by the proposed guards. The results support the ANSI B11.12 standard which states that "No universal method of safeguarding the point of operation for general-purpose roll benders is known at this time."


"Application of the Safeguard Evaluation Protocol,"
Safety Engineering & Risk Analysis 1995 (SERA v.4)
. New York, American Society of Mechanical Engineers, 1995, 9-16

Ralph L. Barnett and Steven R. Schmid

A decision protocol is presented and analyzed for a number of candidate safeguards and machines. The protocol incorporates judicial, statutory, and voluntary value systems. The resulting paradigm allows incorporation of very diverse disciplines in the design stage, which is essential for concurrent engineering.


"On the Safety of Stationary Buffing Machines"
Triodyne Safety Brief v. 11 #1 (April 1995)

Ralph L. Barnett and Dennis B. Brickman

When a work piece locks onto the surface of a cloth buffing wheel, hazards associated with missiles, flailing, and entanglement are introduced. Classical barrier guards have been used; another approach is hooding the buffing wheel. A qualitative testing program indicated that the aggressiveness of the ensnarement and the compliant nature of the buffing wheel frustrate these proposed safeguards. New hazards are introduced by the safety devices themselves.


"On the Safety of a Portable Grinder Guard"
Triodyne Safety Brief v. 11 #3 (March 1996)

Dennis B. Brickman and Ralph L. Barnett

A rigid body mode of failure has been identified in two piece adjustable grinding wheel guards for portable grinders. Under the action of a fragment storm, the upper portion of the guard may tilt and allow an escape displacement to develop at the leading edge of the protective skirt. Three approaches for analyzing this behavior are described.


"Hand Motion During Trip and Fall Scenarios"
Triodyne Safety Abstract v. 2 # 4 (July 1997)

Ralph L. Barnett and Suzanne A. Glowiak

The full text of this paper was published in the American Society of Mechanical Engineers' International Mechanical Engineering Congress and Exposition in November 1997 and is available from Triodyne at no cost.


"Hand Trajectories Under Free Fall"
Triodyne Safety Brief v. 12 # 2 (January 1997)

Ralph L. Barnett and Suzanne A. Glowiak

Can the hands elevate during a free fall scenario? This question arises in the design of fall intervention devices, during accident reconstruction and in the study of safe climbing strategies. This paper calculates the maximum simple reaction time that will enable the hands to elevate during a "drop" event.


"Interlocks - The Baking Industry Experience"
Triodyne Safety Bulletin v. 5 # 2 (January 1997)

Steven R. Schmid

The experiences of the baking industry and interlocking of safeguards is summarized here.


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