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Door Protection Requirement Updates

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A rundown of the big changes in A17.1-2019/B44-19 and a system that can meet what they require

by James O’Laughlin

Passenger elevator door protection requirements are about to change with the release of ASME A17.1-2019/CSA B44-19 Safety Code for Elevators and Escalators. New requirements are introduced for reopening devices used in power-operated horizontally sliding doors. These requirements better address the safety of people and reduce damage caused by objects hitting elevator doors. To better understand why these changes have been implemented, it is useful to understand current door- protection requirements and some of the challenges passengers still face when they use elevators today.

When elevators became commercially feasible, building owners employed elevator operators to run each elevator and ensure the doors did not close on passengers or objects entering the cab. Over time, however, technology started to replace what had become known as “attended operation,” primarily due to the expense of needing personnel available to run many elevators seven days a week, some 24 hr a day.

Relative to door protection, one of the first technologies used was the mechanical safety edge, sometimes referred to as door bumpers or door buffers. These devices are attached to moving cab doors, and, when they come in contact with a person or object, are depressed, causing the change of state of an associated electrical contact that, in turn, generates a reopen signal back to the elevator control. Mechanical safety edges generally cover the full door opening but require contact with the person or object to cause this reopen signal to be generated (i.e., a person or object must be “hit” by the mechanical safety edge).

To address this “contact” requirement, several elevator manufacturers used the mechanical safety edge with one or two single-beam photoelectric sensors added to the safety circuit. CEDES was born in 1986 when our founder was asked to develop this single-beam solution for a major elevator manufacturer. These photoelectric sensors were located on the elevator cab near or on the cab door(s) and used to detect the presence of a leg or body in the opening so detection could occur prior to impact by the mechanical safety edge. In this configuration, there are still only one or two points of noncontact detection. Hence, body parts (e.g., head) could still get “hit” by the mechanical safety edge.

This progressed to using a light curtain — a device with many photoelectric sensors mounted in a single housing operating as a single system. A light curtain is still mounted on the elevator cab door(s) but replaces the mechanical safety edge. This is a completely noncontact solution, because the detection means does not require a person or object to contact the device to generate the reopening signal. The door reopen signal is automatically generated when one or more of the light beams become interrupted. Over the years, this solution has become the de facto standard for elevators in North America.

All these solutions fulfill the requirements defined in Section 2.13.5 of ANSI A17.1-2016/CSA B44-16, as well as earlier versions of the Code. The 2016 and previous versions of the code basically require that when a “reopening device” is used in power-operated horizontally sliding car-door applications, it must be effective for “substantially the full vertical opening of the door.”

This article will describe changes that will prompt some readers to ask, “Why fix something if it isn’t broken?” Unfortunately, the injury data does not back this sentiment, and marked improvements are needed to reduce the number of injuries that still occur during elevator-door closing.

Three studies were performed by the Department of Public Health at the Indiana University School of Medicine that provide detail on injuries still occurring in passenger- elevator applications. All studies utilized the U.S. Consumer Product Safety Commission National Electronic Injury Surveillance System (NEISS), a database that provides injury statistics based on emergency-room visits at 100 NEISS- designated hospitals.[1] The database does not include incidents that result in death or injuries treated only at the scene of an incident. Hence, it is likely that the total number of incidents that occurred in the referenced timeframes that follow are underreported:

  • For children 0-19 years old, NEISS data indicated that 18,750 elevator injuries (64.5%) were due to an elevator door closing on a body part (of the 29,030 total injuries estimated to have occurred between 1990 and 2004).[2]
  • For adults from 20-64 years old, NEISS data indicated that 23,659 elevator injuries (42.5%) were due to an elevator door closing on a body part (of the 55,614 total injuries estimated to have occurred between 1990 and 2002).[3]
  • For adults 65 years old and older, NEISS data indicated that 15,166 elevator injuries (33.8%) were due to an elevator door closing on a body part or walker wedged in a door (of the 44,870 total injuries estimated to have occurred between 1990 and 2006).[4]

A review of the raw NEISS data for 2009-2018 shows that the number of injuries classified for NEISS Product Category 1889 (elevators or other lifts, excluding escalators, hoists and jacks) has remained consistent or increased slightly since these studies were completed, including the number of injuries caused by “hit by door” or “walker wedged in door.”[7]

Using this data, the number of emergency-room visits attributed to an elevator door(s) closing on a body part or a walker being wedged in the elevator door(s) is nearly 4,000 annually. Also, additional hazards, such as the leading edge of the landing side of the landing door, still need to be addressed.

Since elevator safety is the focus of the code, the A17 Ad Hoc Committee on Door Protection has been working for more than 10 years to develop additional requirements that are included in the 2019 code update. These updates follow the committee’s work published in the 2008 code addendum for power closing of vertically sliding doors and gates. After those updates were published, the committee turned its focus to reopening devices for power- operated horizontally sliding car doors and gates, leading to new performance and product design requirements. By including design requirements for manufacturers, testing requirements needed by AHJs and end-users are simplified. These tests focus on ensuring basic operation is fulfilled, rather than requiring a battery of tests related to position, target color, target size, target shape, etc. for each elevator application.

The CEDES CabSafe™ system will be used to highlight several design requirements necessary to comply with the 2019 code. To ensure correct interpretation of the code language, CEDES will also have CabSafe third-party certified by an Accredited Elevator/Escalator Certification Organization (AECO).

The CabSafe system consists of:

  • The CabSafe 2D light curtain that detects objects between the elevator cab doors
  •  The CabSafe 3D time-of-flight (TOF) sensor to detect objects approaching
  • the entrance area
  • The CabSafe controller
    • The CabSafe 2D light curtain consists of a transmitter and a receiver that form a planar detection field of crisscross beams between them. The system is like a “traditional” light curtain in that it detects objects between the elevator cab doors, but there are several key differences that ensure 2019 code compliance. These include:
      • Continuous testing, including after the elevator doors have reached their fully open position and prior to the initiation of a door closure, to ensure the curtain is operating correctly and able to detect the target objects defined by the code
      • In dynamic-mounted systems (in which the light curtain travels with the door[s]), the receiver provides door position information (e.g., when the doors have reached full-open or have closed to a point where the 3D TOF sensor can be rendered inoperative).
      • In static-mounted systems (light curtains do not move with the doors), a separate signal provides position information (e.g., signal from elevator control or a magnetic switch).
    • The 3D TOF sensor monitors the entrance area for people or objects approaching the elevator cab doors. Features include:
      • The sensor is transom mounted and is available with surface- or flush-mount hardware.
      • Flush-mount brackets extend down from the transom only a few millimeters and may utilize a veneer (e.g., stainless steel or bronze) to match the transom material.
      • The detection field is rectangular in shape and makes 9,600 individual distance measurements within the detection field multiple times each second.
      • Objects moving toward the cab entrance at speeds greater than 0.15 m/s (6 in./s) generate a reopen signal. This value is chosen based on published data where “supervised walker ambulation” has been defined as walking speeds ≥ 0.340 m/s (1.14 ft/s) and < 0.57 m/s (1.87 ft/s).[5 & 6] Objects at slower speeds are considered stationary.
      • Stationary objects can be ignored (e.g., plants or people standing in front of the entrance), since the closing door(s) does not pose a hazard unless movement toward the entrance occurs.
    • Continuous testing, including after the elevator doors have reached their fully open position and prior to the initiation of a door closure, to ensure the sensor is operating correctly and able to detect the target objects defined by the code The TOF technology used in CabSafe 3D was chosen to gain several additional benefits, including:
      • The field of view is large and flexible enough to provide robust performance in new installations and modernization applications when landing doors may not be perfectly synchronized with the elevator cab doors (e.g., landing-door leads or elevator cab door).
      • The detection area exceeds the requirements defined by the code by having a well-defined rectangular detection field in front of the landing doors (i.e., much more than a single point on the moving line[s] 9 in. in front of the landing side of the landing door[s] and extending from 9 to 20 in. out from the leading edge of the landing side of the landing door[s] and transiting with the closing door[s] as defined by the code).
      • The CabSafe 3D detection area is stable and does not extend excessively into the lobby, minimizing, for example, false triggers when a person or object passes near the door but does not intend to enter (as seen in pedestrian doors that use ultrasonic or radar sensors).
      • The detection field is continuously tested, including when the doors have reached their fully open position and prior to the initiation of door close, even when no objects are present in the detection field. This is because CabSafe 3D “sees” the floor without needing a moving object in the detection field.
      • TOF technology is not subject to upcoming Federal Communications Commission limitations for ultra-wideband frequencies that are often required to have stable operation and prevent interference in other radar-based solutions.

The CabSafe controller monitors the 2D and 3D TOF sensors and provides a single output (solid state or relay-based) that represents the state of the system. Requirements defined for rendering the approaching object detection inoperative are also managed by the controller. This was designed to make the system robust and efficient. Additionally, the controller provides a means for configuring the 3D TOF sensor detection field in center-, left- and right-opening elevator-door applications.

With the upcoming code changes, the new requirements for reopening devices used in power-operated horizontally sliding doors can be easily fulfilled using devices such as the CabSafe. Since most of upcoming code changes discussed are design requirements, ensuring the device used can be implemented easily, third-party party AECO certification gives users the confidence their door-protection system is code compliant, allowing basic functions to be easily checked and making maintenance control programs simple to implement without the need for test objects or complicated test procedures.

References
[1] U.S. Consumer Product Safety Commission. “National Electronic Injury Surveillance System” (www.cpsc.gov/Research–Statistics/ NEISS-Injury-Data).
[2] Joseph O’Neil, MD, MPH; Gregory K. Steele, DrPH, MPH; Carrie Huisingh, MPH; and Gary A. Smith, MD, DrPH. “Elevator-Related Injuries to Children in the United States, 1990 Through 2004,” Clinical Pediatrics, Department of Public Health, Indiana University School of Medicine, Sage Publications, p. 619-625 (September 2007, journals.sagepub.com/doi/ abs/10.1177/0009922807300232).
[3] Deborah E. Morrison-Ibrahim. Retrospective Analysis of Elevator Related Injuries in Ages 20-64, 1990-2002, Department of Public Health, Indiana University School of Medicine, unpublished between 2010-2012, obtained from Dr. Gregory Steele on March 4, 2013, p. 1-35.
[4] Gregory K. Steele, DrPH, MPH; Joseph O’Neil, MD, MPH; Carrie Huisingh, MPH; and Gary A. Smith, MD, DrPH. “Elevator-Related Injuries to Older Adults in the United States, 1990 to 2006,” The Journal of TRAUMA® Injury, Infection, and Critical Care, Department of Public Health, Indiana University School of Medicine Lippincott, Williams & Wilkins p. 188-192 (January 2010, journals.lww.com/jtrauma/Abstract/2010/01000/Elevator_Related_ Injuries_to_Older_Adults_in_the.32.aspx).
[5] James E. Graham, Steve R. Fisher, Ivonne-Marie Bergés, Yong-Fang Kuo and Glenn V. Ostir. “Walking Speed Threshold for Classifying Walking Independence in Hospitalized Older Adults” University of Texas Medical Branch, Physical Therapy, Oxford Academic, p. 1,591-1,597 (November 1, 2010, doi.org/10.2522/ptj.20100018).
[6] Hubertus J. A. van Hedel, PhD, PT, “Gait Speed in Relation to Categories of Functional Ambulation After Spinal Cord Injury,” Neuroscience, Neurology & Psychiatry, EMSCI Study Group, Sage Publications, (December 5, 2008, doi. org/10.1177/1545968308324224).
[7] U.S. Consumer Product Safety Commission. “National Electronic Injury Surveillance System 1999-2018” on NEISS Online Database (May 2019, www.cpsc.gov/cgibin/NEISSQuery/UserCriteria.aspx).

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Elevator World | April 2020 Issue Cover