Machine Design

Berke on Safety: Nonflammable Tape Burns for Lack of a Hazard Analysis

In response to market demand, a tape manufacturer modified its most popular electrical tape to make it fire retardant.

Edited by Jessica Shapiro

The first salesperson to demonstrate the tape pulled a length of it from the roll and applied a lit match to the bottom end. The hanging length of tape burst into flame, causing minor damage to the carpeting and burning holes in the salesperson’s suit.

The tape was immediately pulled off the market for reevaluation. Turns out the backing of the tape was flame retardant but the adhesive was not. Extensive tests had been done while the tape was wrapped around a mandrel, as the tape is commonly used, but not with the adhesive exposed to air as in the demonstration. Had a Preliminary Hazard Analysis (PHA) been done, the problem would have been identified and the company would have saved both money and embarrassment.

When a company has a successful product, they often modify it to meet additional customer requirements. This usually can be done without creating hazards, but sometimes they do surface. That is why hazard analysis should be performed any time a product is designed, redesigned, or modified. This is true for everything from sticky notes to general-aviation aircraft.

Another series of devices that could have benefited from a PHA were light screens modified to improve process efficiency. Light screens automatically shut off a machine when a beam of light is broken by an operator’s arm or leg or anything passing between the light source and the detector. Even a piece of metal being bent in a punch press or press brake may break the beam in process and shut off the machine.

This makes light screens a bad choice for some applications, so some manufacturers let operators remove some rays or sections of the light screen. However, anyone using the machine without knowing about the modification could place himself in harm’s way. I’ve seen many cases where a setup person did not know the light screen wasn’t protecting him when he was exchanging dies and lost a hand or arm.

A PHA would have highlighted the danger to the uninformed worker so that education and safety measures could be implemented. That said, it has been a few years since I’ve seen these accidents, so it appears most setup people are doing Lockout/Tagout as they are supposed to during machine changeovers.

An even more extensive modification was undertaken by a company that built man-lifts. The lifts let people work at elevated heights instead of using ladders or scaffolds. The company wanted to create a product that would reach higher than that of their competitor.

The new design did go higher, but it was too tall to fit through normal doorways, even when collapsed. The solution was to tilt the lift and support it with bars so it could roll through doorways. However, if the lift was not assembled correctly, it could fall on someone and injure them. Plus, a confusing owner’s manual meant that not everyone knew how to use it properly. A PHA would have offered corrective measures for redesign or better training methods.

The bottom line is that companies should perform in-depth safety studies concerning all activities in a product’s lifetime. This includes design, redesign, and modification. And they should not address serious new hazards solely with warnings and abbreviated instructions.

Lanny Berke is a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a question about safety? You can reach Lanny at [email protected]

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