ISSN: 1097 - 7589

The Safety Alert, the fourth in Triodyne's series of landmark publications, highlights critical safety developments.

Volume 1 No. 1
Anti-Hair Entanglement

Ralph L. Barnett

When bathers or swimmers place their heads in the vicinity of active pool drains, their hair may become entangled in the drain cover or grating. For the period 1978 to 1996, the Consumer Product Safety Commission reports 49 entanglement incidents (including 13 deaths) where the victims' heads were held under the water in spas, hot tubs, and whirlpools. This paper outlines several drain cover concepts that may mitigate or eliminate the entanglement danger.

Volume 1 No. 2
Swing Gates: The Weak Link in the Chain Link

Ralph L. Barnett and Patrick M. Brinckerhoff

Children are not repelled by barbed wire toppings on chain link fences or gates when the horizontal strands are arrayed in a vertical plane. When childproofing is essential, barbed wire configurations with a 45 degree outward projection are typically used on fences, but not on gates. The persistent use of vertical arrays on gates is confounding since they compromise security and offer no functional advantages. Three gates were constructed for this study to demonstrate the feasibility and characteristics of 45 degree gate toppings.

Volume 1 No. 3
Retractable Overhead Guards For Industrial Vehicles Without Seatbelts

Ralph L. Barnett and Peter J. Poczynok

"Struck By Overhead Guard" - an ironic tragedy. While intended to protect operators of industrial vehicles against the crushing and impact hazards associated with rollover, tip over and falling objects, Rollover Protective Structures (ROPS) and Falling Object Protective Structures (FOPS) on industrial vehicles have themselves become major instruments of death and mutilation. During vehicle rollover, operators sometimes jump, climb or are thrown from their seats into the trajectory of the guard's horizontal canopy or its uprights, whereupon these operators are crushed between the operating surface and the overhead guard. To protect operators against this contingency, the operator seat belt has become the intervention system of choice. Unfortunately, extremely low seat belt usage calls into question whether the overhead guard offers a net safety benefit. This paper introduces a new guard concept that eliminates the overhead guard hazard during rollover while maintaining falling object protection and rendering seat belts or other supplementary rollover safeguards unnecessary. The standard uprights are replaced by a midplane structural frame and the rigid canopy takes the form of a passive retractable mechanism. Also, the blind spots normally associated with the uprights no longer exist.

Volume 1 No. 4
A New Interlock System: Movable Interlocked Barrier Guards With Motorized Openers for Testing

Ralph L. Barnett and Dr. Theodore Liber

A unique system is introduced for monitoring the viability of conventional position switch interlocks on movable barrier guards.

Volume 2 No. 1
Anti-Hair Entanglement: Cantilevered Grating Elements

Peter J. Poczynok, Adam K. Dybek, and Ralph L. Barnett

Hair entrapment is a failure mode shared by swimming pools, wading pools, spas, hot tubs, and whirlpool bathtub appliances. When hair is entrained in the discharge flow through a suction fitting or drain, its withdrawal will generally be resisted by gravity, drag, friction, buoyancy and interface. Large withdrawal forces obviously lead to a horrifying safety problem. In an attempt to manage the magnitude of these forces, the pool industry introduced their first standard relative to hair entrapment on November 3, 1987; ASME/ANSI A112.19.8M - 1987, Suction Fittings for Use in Swimming Pools, Wading Pools, Spas, Hot Tubs, and Whirlpool Bathtub Appliances. The 1987 ANSI standard does not recognize self-locking types of entanglement. Nevertheless, 30 cases were reported to the Consumer Product Safety Commission from January 1990 through May 1996 where hair entanglement occurred because of tangling rather than strong suction forces. An additional four cases of entanglement are reported by the CPSC from April, 1981 through February 1985. This paper explores the use of cantilevered grating elements in rectangular and circular drains for shedding these self-locking tangles.

Volume 2 No. 2
Interlocked Fixed Guards-Bolted Panels

Ralph L. Barnett and Theodore Liber

A fixed guard is defined as a protective barrier that is held in place with fasteners that may only be removed using tools not normally available to a machine's operators. The fixed barrier guard always appears at the top of the safeguarding hierarchy. When it is not feasible to use a fixed guard the hierarchy recommends the use of an interlocked movable guard. The combination case, the interlocked fixed guard, is simply not addressed. Fixed barrier guards are almost never interlocked because their infrequent removal leads to a quiescent interlock switch that cannot be relied upon when called into safety service. Furthermore, it is difficult and time consuming to test such interlocks at frequent intervals, such as once every shift. Reliability testing requires that the interlocks change states and this implies that the fixed barrier and its fasteners be removed and replaced for each test cycle.

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