The Ins and Outs of
Automatic Door Operation
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A basic primer in how they work, what to look for, and how to analyze defects
vs. deferred maintenance. Expert door contractor, Michael Panish, takes
you through the basics for your case. A basic primer about Automatic Door
functions.
By Michael Panish
Expert Witness & Consultant
One of the most frequent calls I receive from attorneys is about injuries
sustained from an automatic door malfunction. The call usually begins
with a scenario much like, "My client, who is almost eighty years
old, was in a hotel lobby, and as she was walking through the doorway
to the parking lot, the sliding doors slammed shut on her, causing her
to break her hip." Or, upon entering a revolving door, the door suddenly
sped up, and actually trapped a young child between the door panel and
the fixed portion of the doorway crushing the boy's arm and shoulder."
" What can you tell me about the functions of the doors and why could
this have happened? Do you think my client was careless? Was something
wrong with the design of the door? How could this have been prevented?
And, was this a maintenance issue? Who do you think is at fault for the
defect in the operation of the door?"
In most cases the modern automatic door system, whether it be revolving,
swinging or bi-pass/sliding type is designed with safety in mind. Multiple
redundant safe guards have been incorporated into the design to assure
the safe and secure usage of these products. The manufacturers' designs
rely on multiple sources of sensory input to their products to assure
safe and dependable operation. These door units are failure tested, for
hundreds of thousands of cycles of usage, and are not generally put into
public venues until they perform satisfactorily and dependably. They must
meet the safety standards established by the American National Standards
Institute (ANSI) guidelines.
SO, HOW DO THEY WORK?
Beginning with the most basic system… SWINGING DOORS (they either
open inward or outward on fixed hinges) and BYPASS DOORS (the doors slide
past each other, whether in a single or double pair) contain the most
failure resistant safeguard, the ELECTRIC EYE BEAM. This sensor is used
to assure that any object in the pathway of the closeable section of the
door is protected against the door closing. In other words, picture a
flashlight beam shining unbroken across a room onto a reflecting mirror
or bicycle reflector. The door motor control would be sent a signal that
all is clear, and then, the door would be activated to close safely, without
hitting anything. However, if the beam is suddenly interrupted, a signal
is immediately sent to the device to halt its closing action. In addition,
automatic door systems usually incorporate an INFRARED CURTAIN SENSOR
type of device (motion sensor or presence sensor). While optically undetectable,
this type of sensor operates much like a shower head, spraying a fan of
water. The sensor is usually positioned on both sides of a doorway. An
infrared curtain beam rains down upon a position in front of the doorway
to either trigger opening, or initiate the closing operation when the
area protected by it is found to be occupied or clear of obstructions.
On older systems, you may also encounter a PRESSURE SENSITIVE RUBBER MAT
that contains sensors. When these mats are compressed, either by foot
traffic, or a cart, such as in the case of a supermarket entrance, these
devices send a signal to the motor controlling the door to initiate closing
or opening, as needed.
The sensors that are built into these door systems all function interactively
when working properly. They communicate via a microprocessor in the motor
control unit to activate various door commands. In addition, built into
these control boards are time delayed circuits that hold the doors in
either an open or closed mode until the sensors are cleared or the doorway
has been vacated. The harmonious interaction of these various sensing
devices is critical, and if in proper working order, may in fact disable
a malfunctioning doorway, assuring the protection of the passage of the
pedestrian. When these sensor devices are either deactivated, tampered
with, or malfunctioning due to lack of appropriate regular maintenance,
these devices can become potentially deadly.
The motive systems (control motors and conveyance methods) of the door
devices vary from manufacturer to manufacturer, some being more stable
and reliable than others. Some products may employ plastic gears and parts
that are less durable than others, sometimes made to be sacrificial in
design to insure the safe operation of the automatic door unit or to disable
a malfunctioning door device. In the more expensive and durable products,
the products manufactured with chain driven or steel gear design usually
rely upon a more sophisticated electronic control board to assure the
safe or disabling functions of the doorway actions.
In addition to the sensor controls, many doorways also have a manual door
operating switch. You may have seen these marked with a handicap symbol,
or more simply "PUSH." These switches work in conjunction with
the sensors to open the doorway, activating the motor control when the
sensors verify that the area is clear.
The most sophisticated and complex automatic door system is the REVOLVING
type. These types of doors are commonly found in airports, hotels and
any area attempting a noise or thermal lock. The complexity and sophistication
of these door systems require that there are an even greater number of
safety sensors and motor controls. In addition to the types of devices
mentioned previously, these revolving doors feature crush sensors located
on door leading edges, or fixed panels, proximity beams to determine the
speed of the rotation of the doorway, more beams to deactivate the door
(if for some reason an object or person is attempting to enter the doorway
at an inappropriate time), and an emergency stop device to halt the rotation
of the doorway immediately without delay. There are usually manual door
operating switches that can be used to slow the door rotation down, such
as in the case of wheel chair use, and monitoring devices to show the
condition of the door operation to the maintenance staff. These rotating
doors frequently have memory devices that record function faults for future
retrieval by service personnel.
With all of these safety devices in place on these doors, why do injuries
occur? Poor design? Poor supervision? Lack of maintenance? Cost? Many
of these factors play a part in causing injury. Poor design is usually
not the primary reason for the injury. Having been called upon to examine
thousands of doors during the past 25 years, and performing both installation
and maintenance on all sorts of door products, the vast majority of the
time a problem arises with any automatic or manual system, the owner of
the property is not following the recommended guidelines of the manufacturer
in one way or another. The most basic automatic door requires a daily
safety check. Warning labels on the doorway systems are often forgotten
or unheeded by managers who should take the inspection, care, and maintenance
of these doors more seriously.
When an installation of an automatic door is completed, there should be
a formal field demonstration of the product by the installer or manufacturer,
as well as an extensive service and MAINTENANCE MANUAL given to the owner
or management team of the building. Management should assure that training
of their staff is adequate to understand the responsibilities of properly
maintaining these door products. Manuals with detailed instructions that
identify the responsibilities of the owner / user to guarantee the safe
operation of the automatic door system are normally provided by the installation
team. These manuals indicate the expected intervals of recommended service
to the door system, daily safety checks, normal operation, special features
as well as a suggested recommendation of keeping a service contract with
the installer to do normal periodic maintenance and adjustments. New installations
are one thing, transference of occupancy or building ownership often leads
to problems with safety and service of these doors.
In some areas of maintenance, something AS SIMPLE AS WIPING AND CLEANING
THE ELECTRONIC EYE LENSES is required for safe operation. This may need
to be performed on a daily basis depending on the dirt and debris in the
area and weather conditions. Other more complex diagnostics are not possible
by the end users, and require regular attention from an installation professional.
In most cases the basic maintenance of these door systems are something
that should be addressed and attended to on a daily basis. I have been
told by several manufacturers of automatic door systems that their products
should be checked, tested and evaluated on a daily basis. These pieces
of machinery are complicated and should be treated with the same type
of care as if you were inspecting a theme park roller coaster ride. They
simply must be looked at every day by trained personnel. Training can
be obtained in the form of online information, video programs, and in
house training by accredited or certified technicians.
As an attorney, the trail of responsibility of an injury is yours to explore.
In pursuing the responsible parties, use the path from current owner to
original equipment manufacturer. Many times, it has been the fault of
the maintenance staff (directly linked to the owner of the property).
Normal course and inclusion of a product manufacturer is where many attorneys
choose to place the blame. However, I have found in many cases that the
actual blame is on the part of the owner of the property who chooses improperly
trained maintenance staff or uneducated personnel. They have chosen to
ignore the requirements of the manufacturer as far as service and maintenance,
and have opted to attempt to keep their costs down by not employing factory
trained service technicians when called for. This has occurred in government
owned facilities such as airports and court buildings, and has also been
the case in supermarkets, restaurants, and commercial businesses. The
decision to ignore the service requirements of the door manufacturer is
often purely economic and is usually not in the operating scope of responsibility
within many chain stores and commercial venues. They don't consider
the operation of these doors to be as important as how they stock their shelves.
Michael Panish is an expert witness, forensic analyst, and consultant in
the field of construction. He is licensed in the State of California as
a General Building Contractor, Electrical Contractor, Door, Lock &
Security Equipment Contractor, Cabinet & Millwork Contractor, and
Painting Contractor. Michael has over 35 years hands-on experience in
the construction industry. He has offices in California and New England
and is available for nationwide consultation, forensic analysis, and testimony.
Michael has consulted and testified in many injury cases pertaining to
door related issues as well as most aspects of construction defects, product
liability, and poor workmanship. Michael Panish can be reached at
(888) 902-4272
(Ask for Sharon)..
Published in:
The Advocate Magazine 2007 Product Liability Issue, Consumer Attorney's
Association Los Angeles
Plaintiff Magazine 2008, Consumer Attorney's Association Northern
California