Licensed Professional Engineers
| Forensic Clues #16
A newsletter dedicated to keeping attorneys informed of the technical side of product liability cases.
Issue 16: Vol. 1 December/January 2006
By John L. Ryan and L.D. Ryan
In 1994 over 20,000 injuries occurred as a result of electronically operated overhead doors. The Consumer Product Safety Commission (CPSC) has traced the cause of death of 68 children to overhead door accidents. Other sources attribute at least 85 child deaths to overhead doors in the time period between 1974 and 1995. These numbers show the extent of the problem with overhead doors. Despite standards and legislation, people are still being injured and killed by overhead doors.
History of the Overhead Door
Overhead doors are a by-product of the industrial revolution and the onset of automotive technology. Garages were first developed in 1912, evolving from carriage houses, where people stored their carriage, usually along with the horses. New car owners didn’t want to be bothered by the smell of livestock, so garages began being built for only cars.
Shortly thereafter, attached garages began to be integral parts of homes. The size of the automobiles that they were storing called for a new type of door. Sliding doors were first used to save space, but these required garages to be twice the width of the doors. The direct predecessor of the overhead door as we now know it was a horizontally sliding door that was composed of panels hinged together, allowing the door to be folded around a corner, saving precious space. C.G. Johnson took this idea one step further in 1921, creating the first overhead door and starting an overhead door company that still dominates the industry. Mr. Johnson added an electric door opener to his invention five years later to make lifting of the door easier, simultaneously creating the hazard that still kills people today.
Types of Overhead DoorsCommercial Doors
Overhead doors are used widespread in commercial applications. Commercial overhead doors can be many sizes, from under 16’ to over 30’ in width, in a variety of heights. This diversity of the commercial overhead door market requires a broader range of safeguarding solutions than is required in residential applications. OSHA (Occupational Safety and Health Administration) regulations also come into play in most commercial door applications – anywhere employees work. Commercial overhead doors are made to last, and doors manufactured decades ago may not be up to current industry standards. Safety Engineering Resources sees many accidents involving older overhead doors that have not been updated and have no safety devices.
Residential overhead doors are found on garage doors. Overhead folding panel garage doors are the preferred solution in peoples’ homes. OSHA requirements do not apply for residential overhead doors. Residential doors are arguably more potentially hazardous than commercial overhead doors for one reason – children. Children are more likely to be injured and killed by overhead doors than adults are. Children’s inexperience prevents them from recognizing hazards as an adult could, and their bodies are more easily injured. Residences will often have children around, while commercial and industrial applications are unlikely to be exposed to children. Residential overhead doors are usually lightweight, inexpensive, with a limited lifespan, making the likelihood of a malfunction high.
Hazards of overhead doors
Inherent Pinch Point Hazards
Overhead doors have some hazards which are inherent, that is, these hazards are created by the function of the product and cannot be eliminated through design. The pinch point created by an overhead door and the ground or any obstacle is the most obvious and severe hazard. This hazard cannot easily be completely designed out of the product. The severity of the pinch point hazard can be minimized with various design elements such as the weight of the door, but an overhead door that has eliminated the crushing hazard has yet to be produced.
No safety device
Older overhead doors that were not originally equipped with safety devices, or were not later retrofitted with these devices, are extremely dangerous. Overhead doors without safety devices should not be used, these doors should be replaced or brought up to current industry standards.
Older overhead doors may lack proper safety devices
The lack of a safety device is proof of a failure to guard on the part of the manufacturer. Even though these overhead doors didn’t violate any standards when they were manufactured, this doesn’t mean that the doors are safe. Designers should have recognized the severity of the crushing hazard and developed a safety system when the product was originally produced.
Faulty Safety Devices
Overhead door safety devices can fail, resulting in an unguarded, hazardous situation. The hazard of becoming crushed on these doors is magnified since the people using the door probably are aware of the safety devices of the door. If these safety systems fail, most product users will not recognize the failure and expect the overhead door to reverse upon impact with an object. This can lead to complacency about the crushing hazard.
Some overhead doors are raised and lowered using cables. These cables can be hazardous for several reasons. If cable guides are not used, the cable can become caught on an object or entangle a person. Cables can fall off pulleys or spools, which could send the door crashing downward.
Laws and standards
After the CPSC performed an intensive study of overhead door accidents, the CPSC passed a law in 1993 that required all garage doors to have pressure-sensing sensors and optical sensors. The photoelectric sensors are mounted about six inches off of the ground and the pressure sensors are used on the bottom edge. The engagement of either of these safety devices results in the reversing of the overhead door. The first doors to use this technology were fraught with failures, but later models have become reliable.
OSHA requires electrical equipment used in employee workplaces to be certified by a Nationally Recognized Testing Laboratory (NRTL). This means that overhead doors used in any sort of business must pass all applicable safety standards. One of these safety standards is the Underwriter’s Laboratories Standard 325 (UL 325), Fourth Edition. This standard represents a huge improvement over current industry standards. While ANSI has yet to adopt the UL standard, some argue that overhead door manufacturers still are responsible for adopting the standard and adding the necessary safety features. This standard divides overhead doors into four categories based on the use and function of the door. Each of these categories has different safeguarding requirements.
Please call (479) 549-4860 to preorder Safety Engineering Resources’ upcoming Product Litigation Manual – Overhead Doors, scheduled for publication in March, for a thorough review of the requirements of the UL standard and other topics covered in this Clues.
Code of Federal Regulations (29CFR1910.212.(a)(3)(ii)) states that “(ii) The point of operation of machines whose operation exposes an employee to injury shall be guarded…”
The Code of Federal Regulations standard 29 CFR 1211 covers required safety devices for residential garage door openers. This standard calls for entrapment systems as well as secondary and backup safety devices.
The ASME B15.1 standard, “Safety Standard for Mechanical Power Transmission Apparatus” covers safeguards required for overhead door operator systems. This standard calls for emergency stopping and reversing devices, as well as other safeguarding procedures.
Safeguarding Overhead Doors
Inherent Entrapment System
Inherent Entrapment Systems are automatic sensor systems that sense the entrapment of an object and take corrective action within two seconds. Deaths have occurred in systems where people became entrapped in the opening cycles of doors by getting between the upper door edge and an obstruction, which lacked inherent systems that could detect the entrapment and reverse the lift mechanism.
Non-Contact Sensors are sensors that can detect the presence of an obstacle without physical contact. Examples of non-contact sensors are photoelectric sensors and proximity sensors.
Contact Sensors are sensors that detect the presence of an obstruction with physical contact between the obstacle and the sensor. Examples of contact sensors are edge bumper sensors that absorb shock directly and also signal the initiation of the obstruction response.
Inherent Adjustable Clutch
Inherent adjustable clutches are a type of backup safeguard where the clutch of the lift operator can be adjusted so that the clutch will slip upon contact with an obstruction, which would disengage the power being transmitted to the door mechanism. This would cause the door to stop moving.
Inherent Pressure Relief
Inherent Pressure Relief systems release the hydraulic pressure of a lift operator when an obstruction is encountered. The releasing of the hydraulic pressure would cause the door to come to a stop.
Continuous Pressure Activating Device
A continuous pressure activating device is basically a switch that requires constant pressure to continue the opening or closing cycle of a door. This safeguard ensures that the person opening or closing the door will not become entrapped, and that the person opening or closing the door will be able to monitor the door’s operation while it is closing or opening.
Inherent Audio Alarm
Inherent audio alarms are simply audible alarms that sound just before a door or gate begins to move. This helps alert people in the vicinity to the hazard of the door.