Another look at door costs and safety
A recent article on “Exposing the hidden costs at door openings” ( PE , July 1999, p 66, File 5040) highlighted several points regarding the safety features of high-speed roll-up doors. Our company would like to clarify these points, and bring out some additional factors regarding door safety not addressed in the article.
The referenced article includes the following comments.
“Perhaps the most significant hidden cost tied to doors is the potential for work-related injuries. With the prevalence of hard, bottom-bar technology of conventional high-speed roll-up doors, workers are at risk of serious injury. In fact a hard-edge bottom bar, even equipped with a reversing feature, impacts with a downward force in excess of 150 lb/sq in.”
We feel these statements include imprecise data, while omitting other relevant information that would serve to give readers a more complete and accurate view regarding the many advanced safety features fundamental to modern high-speed roll-up door technology.
The high-speed roll-up door has emerged as not only the most economical choice of industry today, but has proven to be exponentially safer than previous technologies.
In fact, virtually all roll-up door advancements are safety driven. Today, roll-up doors often feature clear plastic strips in the fabric, which provide see-through visibility on both sides of the door. The fabric itself is often manufactured in choices of bright, easy-to-see colors that help prevent operator accidents. In addition, many models of advanced roll-up doors employ technology that detects any object in the door’s path, reversing it immediately to prevent impact. This technology assures the maximum safety of operators and equipment.
Not mentioned in the article is the fact that some doors do not possess a reversing capability. Soft bottom-edge doors stop only when coming into actual contact with whatever or whoever is below the door. For this reason, a high-speed door equipped with advanced reversing technology may be a better choice for safety.
Concerning the stated downward force of 150 lb/sq in., we feel this is not possible. A door would have to weigh about 9 tons to induce this much pressure. In reality, most models of roll-up doors exert less than 1 lb/sq in. of pressure.
To conclude, we concur with one of the article’s central topics: Safety is a major concern with any door technology. Leading manufacturers of these doors place great emphasis on the safety issue. Never before have industrial doors offered such a precision combination of safety, reliability, performance, and long-term cost savings.
— Matthew R. Nelson, Marketing Director, Albany Intl.
Author’s reply: We agree that high-speed roll-ups first offered a superior alternative to conventional doors when they were introduced around 15-yr ago. Since that time, many adaptations to high-speed roll-up doors have been required to respond to the safety needs of the workplace. For example, vision panels were added to improve the line of sight at high traffic openings, reversing edges were built onto metal bottom bars to prevent entrapment, and photo eyes were incorporated to help prevent closure on people and/or equipment in the opening itself.
But we take exception to the claim that 9 tons is required to create a 150-psi impact. Dynamic impacts produce peak forces significantly greater than the static weight of the object itself. In testing, a 2.5-lb. book dropped from 24 in. created a peak dynamic impact force of over 200 lb. Testing has also shown that some conventional hard-edge doors can develop peak dynamic impact forces in excess of 1000 lb. We believe that our statement of hard-edge bottom bar impacts “in excess of 150 lb. sq in.” is indeed the current reality, and actually a conservative measurement.
Still, original high-speed roll-up door technologies continue to focus on downward impacts and entrapment concerns without addressing their metal bottom bar. From a safety standpoint, downward impacts and entrapment are a real concern. However, lateral impacts, which occur more often, need to be addressed, as do secondary impacts resulting from flyaway bottom bars, doors reversing upward upon impact, and potential entanglement with coil cords, cables, etc.
While many adaptations have been made to conventional, high-speed roll-up doors, their basic design remained unchanged until the entire concept was reevaluated. This change resulted in soft-bottom edge technology, elimination of external electronics, internal curtain retention methods, and many other enhancements to help address the safety, performance, and durability concerns of the past.
A high-speed door system is just that — a system of integrated features designed to provide the user optimum performance. When looking to address openings as efficiently and safely as possible, a facility is faced with numerous, and sometimes confusing, options. It is important that the user is aware of the technological advances in the high-speed door industry that now provide a total system approach to productivity and personnel safety.
— Kevin King, National Sales Manager, Rite-Hite Doors, Inc.