Fundamental steps in safe door operation

Key concepts High-speed doors boost productivity, while helping isolate specific plant areas. Quicker forklift travel and faster-acting doors create safety concerns. Industrial door accidents fall into four categories: entrapment, downward impact, lateral impact, and secondary impact. It happens time-after-time in plants across the country.

05/01/2001


Key concepts

High-speed doors boost productivity, while helping isolate specific plant areas.

Quicker forklift travel and faster-acting doors create safety concerns.

Industrial door accidents fall into four categories: entrapment, downward impact, lateral impact, and secondary impact.

It happens time-after-time in plants across the country. Industrial doors with damaged hardware, neglected of routine maintenance, or ill-designed for the application contribute to serious accidents. Concussions, skull fractures, broken collarbones, back and neck injuries, and even fatalities can result.

Door-related accidents like these can happen at any plant, unless steps are taken to prevent them. Attention to safety is the key to accident prevention, starting the moment the door selection process begins.

Improved efficiency

Since their advent two decades ago, high-speed doors have boosted material handling productivity, while helping isolate plant areas that need to be kept warm, cold, clean, or quiet.

Doorways once created traffic bottlenecks and leakage points for chilled or other conditioned air. Conventional overhead doors were slow acting. Impact doors forced reduced speed from forklifts and posed maintenance problems in high-traffic areas. Strip curtains and air curtains let forklifts pass freely, but provided poor environmental separation.

High-speed doors offer the best of both worlds. They open and close quickly, allowing lift trucks to pass through without slowing down. As a result, open-close cycles take just seconds, minimizing air exchange.

Types of accidents

Quicker forklift travel and faster-acting doors create safety concerns. If safety takes a back seat during selection, or is neglected after doors are installed, accidents can and will happen.

Industrial door accidents fall into four categories: entrapment, downward impact, lateral impact, and secondary impact.

Entrapment

In these types of accidents, a person is trapped under the door and held down by its weight or by the force of the drive system. Reversing edges were created solely to prevent this type of accident.

Now, UL 325 Section 30.1 prohibits automatic closing of a powered door unless it has a reversing edge or release system. The problem is that reversing edges operate only after impact has already occurred, and are highly unreliable. In addition, the location of reversing edges makes them susceptible to impact damage, which can go undetected until it is too late. Serious injuries can result when a reversing edge fails.

Downward impact

These accidents occur when a high-speed door comes down on a person standing in or passing through a doorway. Contrary to perception, these incidents are not the most common, and reversing edges do not help prevent a downward impact accident.

A reversing edge operating as designed must impact an object before reversing. It is merely a communications device for the door's operator. Functional activation devices, such as properly working photo sensors, help prevent these accidents.

Lateral impact

These types of accidents are the most common and can be serious. They happen when a worker runs into the door while it is on its way up or down. In other cases, a pedestrian who is inattentive or in a hurry walks or runs into the door. A failed photo sensor or missed activation can be a contributing factor.

Most high-speed doors are designed to "break away" on impact, but this feature is more to protect the door than the people.

Secondary impact

These types of accidents can cause severe injury.

  • A person is hit by a closing door and the reversing edge activates; the door reverses upwards and the person is hit again, causing further injury.

  • Impact causes the door to "break away" as designed, and the heavy bottom bar swings outward violently, striking a person on the other side of the door.

  • The door breaks away and the bottom bar swings outward, then snaps back, striking the driver.

  • Door components detach upon impact and fly off, potentially causing injury.

    • Selecting for safety

      Accidents like these need not happen. They can be prevented by matching doors to the work environment, and then installing and maintaining them properly

      There are seven steps to follow for safe industrial door operation.

      1. Study the application. Observe the door openings. What needs to be accomplished? How heavy is the vehicle traffic? Do your lift trucks carry large loads? Is vehicle speed near the door opening a concern? Are there blind corners on either side of the door? Do both lift trucks and pedestrians pass through? All these factors affect your choice of a door and related equipment.

      2. Choose the correct door. Make certain the door meets safety requirements and is an appropriate design for the application. Select an adequate cycle speed to help improve plant efficiency and reduce maintenance requirements.

      If necessary, choose vision panels large enough for vehicle drivers to clearly see what is on the other side of the door. If a seal is required to keep cold air in or dirt out, look for an effective, full-perimeter type.

      3. Select the correct activation system. There are several kinds of door activation devices. Motion detectors, photo-eye sensors, and induction loops activate doors automatically as vehicles approach, and enable high-speed travel. Radio controls, pull cords, and pushbuttons require employees to activate the door and tend to moderate traffic speed.

      If traffic at an opening tends to be congested, or if both vehicles and pedestrians use the doorway, it may be advisable to choose an activation system that controls the direction of vehicle traffic or forces it to slow down.

      4. Consider additional safety equipment. Install convex mirrors at blind corners. In high-traffic areas, or where vehicles and pedestrians use the same opening, consider warning devices to alert personnel when the door is about to cycle.

      5. Professional installation. Safe, efficient performance depends on proper installation. Entrust this job to an industrial door company with local representation that stands behind its work and provides a comprehensive, written warranty.

      6. Train your people. Be sure all the people who will use the door understand how it operates. Ask the manufacturer or local representative to conduct a training seminar.

      7. Inspect and maintain the equipment. A door appropriately chosen and properly installed needs minimal maintenance. Check the owner's manual to see what preventive maintenance must be done. Then ensure that someone does the work on schedule, without exception.

      Edited by Cheryl Firestone, Senior Editor, 630-320-7136, cfirestone@cahners.com

      More info

      The author is available to answer questions regarding this article. Mr. King can be reached at 414-355-3600 or by e-mail at kking@ritehite.com .



      Door designs that reduce safety problems

      Door engineers are always working on high-speed designs to better meet the needs of daily plant operations. The result is a range of safety innovations.

      Soft-bottom edge β€” The heavy, solid-metal bottom bar that causes many injuries in door accidents has been replaced by a soft, pliable bottom edge. If the door should descend on a person, the edge simply conforms around the person, minimizing the dynamic impact forces that can exceed 200 lb/sq in. on hard-edge doors. Similarly, the soft-bottom edge design and omni-directional release system help prevent injury and entrapment if a person walks or drives into the door.

      Safety stop β€” Soft-edge doors replace the trouble-prone reversing edge with an alternate sensing mechanism. Upon impact, an internal sensing system immediately stops the door's travel without the use of coil cords, batteries, or external electronics. Because the door does not reverse, there are no secondary impacts from the door recycling. While a reversing edge activates only upon contact with the bottom of the door, the safety stop system is triggered by separation from any direction. Elimination of rigid members on the face of the door and internalization of wind retention and sensing devices eliminate incidental contact upon impact and prevent secondary accidents from flying debris.

      Bi-rolling doors β€” These center-opening doors eliminate some of the safety concerns that go with overhead operating rollup types. They offer the fastest opening times and provide immediate, full-height visibility upon activation.



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