Introduction
Automatic
vehicular gate operating systems provide convenience and security to
the end user. The popularity of these systems has grown greatly
over the past few years. With that growth has come increasing
awareness of the inherent dangers of an improperly designed, installed,
used or maintained system. In some applications, gate operators
must use high level of force to move the gate. In others,
pedestrians are mixed with vehicular traffic. In still others,
inadequate safety features are specified or installed for the system.
Persons
coming into contact with a moving gate are in danger of “pinching” a
portion of themselves or, even worse, becoming “entrapped” by the
gate. If a system is not properly designed, specified, installed,
used and maintained, serious injury or even death can result to someone
in the vicinity of a moving gate.
Over the
past thirty months, the standard, UL 325 – Standard for Door, Drapery,
Gate, Louver and Window Operators and Systems, has undergone
substantial revision in response to growing concerns over the safety of
automatic vehicular gate operating systems. This information is
provided in an effort to help you understand the current automated
gate-related contents of this standard and its impact on the gate and
gate operator industry. It will also advise you of some of the
possible changes pending for this standard.
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Underwriters Laboratories (UL) & Its Standards
Underwriters
Laboratories, Inc. (UL), a not-for-profit organization established in
1894, is self-described as “the leading third-party certification
organization in the United States and the largest in North
America.” UL’s primary stated mission is “to evaluate products in
the interest of public safety.” Note that while UL declares it is
the “leading” organization of this type, it is not the only one. There are several other testing laboratories and certification
organizations in the United States but UL remains the one most people
recognize and think of in this area.
UL standards are
voluntary standards that establish minimum requirements for many
products on the market today. The term “voluntary” in this
respect means that the standards are not initiated through any
government or similar regulatory agency mandate. The term
“minimum” also has specific meaning to this discussion in that the
industry and those who developed the standard believe that all
participants affected by the standard should meet the requirements and
that some in the industry may adopt more stringent provisions.
As you can see, these
standards are developed via an open, non-exclusionary process involving
UL scientists, industry members and other interested parties. In
addition, a number of UL Standards have undergone a “canvass” or ballot
process in order to obtain recognition by the American National
Standards Institute (ANSI) as an American National Standard. This
designation garners those standards a wider awareness and acceptance by
the public. The canvass process typically includes interested
individuals and organizations that may have direct or material interest
in a particular standard. UL 325 is one of the standards that has
used this process to attain ANSI designation. |
What is the UL 325 Standard?
The first
edition of UL 325 was released in 1973. That edition primarily
focused on the electric operation of garage doors and did not contain
any provisions related to gates or gate operators. After federal
laws were enacted in the early 1990’s that cited the provisions of UL
325 as applicable to garage door operation, the gate operator industry
initiated inclusion of electric gate operator provisions in UL
325. These provisions of the Standard were established, for all
intents and purposes, in September of 1998. Some government
agencies and other interested groups monitored the standard’s progress
and provided input on the final format of the provisions of the
standard that relate to gate operators as they were developed. As
of March 1, 2000, all manufacturers that desired UL listing and
labeling for their gate operator products were required to comply with
the changes that UL identified as requiring “substantial redesign and
retest” of the affected equipment. Additionally, March 1, 2000
was the operative date for compliance with the revised instructions
governing installation. It is important to remember that
continual compliance with the standard is a requirement of maintaining
a listing and labeling program.
For products
within the scope of the standard, UL 325:
- Contains the basic qualifying factors that
products must meet in order to be documented (listed) and marked
(labeled) as complying with the requirements of the UL 325 Voluntary
Listing and Labeling Program;
- Provides methods for testing products,
primarily related to safety performance;
- Covers installation of the products in
accordance with the National Electric Code, which is maintained by the
National Fire Protection Association and is in force nationwide (UL 325
is to be “harmonized” with this code) and
- Addresses safety concerning potential fire
and electrical hazards as well as the safety of the general public.
Based on this,
UL 325 is used as a basis to test products at a nationally recognized
testing laboratory. Gate operator manufacturers that choose to
participate in the listing and labeling program must submit their
products for testing. If the laboratory finds them to be in
compliance with the UL 325 standard, they are listed and receive a mark
(label) indicating that compliance.
It is very
important to remember that there are laboratories other than UL that
are capable of listing and labeling products; however, only products
tested by UL can receive a UL label. Therefore, a UL label is not a generic term and should not be used in that manner. It is also
important to understand that UL and the other laboratories do not
“approve” products. Approval implies acceptance of responsibility
for compliance with the standards when this responsibility ultimately
lies with the applying manufacturer and not with the laboratory (the
burden of proof of compliance always lies with the manufacturer).
In general, UL
325 contains of the following highlights as regards gate operators:
- A glossary that defines each type of operator,
- A separation of gate operators into “classes;”
- Entrapment protection criteria for each class of operator;
- Entrapment alarm criteria;
- Requirements for gate construction and installation and
- Instructional requirements placing increased
responsibility on the installers of gates and gate operators.
The term “entrapment,” as used in relation to gates and gate operators in UL
325, is defined as “the condition when an object is caught or held in a
position that increases the risk of injury.”
A key part of
the UL 325 Standard is the table that summarizes the entrapment device
options for the different classes of gate operators of the various
types of gate included in the standard. A copy of this table can
be obtained from UL but we will attempt to summarize its structure and
provisions in the following sections.
Gate
Definition and Types According to UL 325
To begin with,
we need to know what a “gate” is for purposes of this standard.
UL 325 defines a gate as “a moving barrier such as a swinging, sliding,
raising, lowering, rolling or like, barrier that is a stand-alone
passage barrier or is that portion of a wall or fence system that
controls entrance and/or egress by persons or vehicles and completes
the perimeter of a defined area.” Based on this, UL 325 goes on
to address these main types of gate operators/systems: Vehicular Barrier (Arm) operator or system – an operator (or system) that controls a
cantilever type device (or system), consisting of a mechanical or
barrier that moves in a vertical arc, intended fro vehicular traffic
flow at entrances or exits to areas such as parking garages, lots or
toll areas;
Vehicular Vertical Pivot Gate operator or system – a vehicular gate
operator (or system) that controls a gate that moves in a vertical
plane that is intended for use for vehicular entrances or exits to a
drive, parking lot or the like;
Vehicular Horizontal Slide Gate operator or
system – a vehicular gate
operator (or system) that controls a gate which slide in a horizontal
direction that is intended for use for vehicular entrances or exits to
a drive, parking lot or the like;
Vehicular Vertical Slide Gate operator or system – a vehicular gate
operator (or system) that controls a gate which moves in the vertical
direction and is intended for use for vehicular entrances and exits to
a drive, parking lot or similar location and
Vehicular Swing Gate operator or system – A vehicular gate operator (or system) that
controls a gate which swings in an arc in a horizontal plane that is
intended for use for vehicular entrances and exits to a drive, parking
lot or the like.
It is
important to note that, after the initial definition of a gate, all
gates and gate operator systems included in UL 325 are defined as vehicular
gates and not pedestrian gates. A key
provision of the design and installation of any gate system desiring UL
325 listing is the provision of a separate entrance gate for
pedestrian access that is located outside the area used by the
automatic gate operating system.
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UL 325 Gate Operator Classifications
As mentioned
above, UL 325 separates gate operators into “classes”.” For
purposes of the standard, there are four classes of gate operators as
follows: Class I – Residential Vehicular Gate Operator – operator to be used in a residential setting of one to four
single-family dwellings;
Class II – Commercial / General Access Vehicular Gate
Operator – operator to be used in a commercial setting where general
public access is expected such as a public parking lot or garage, a
gated community or multi-family housing (five or more dwellings) unit
or development;
Class III – Industrial / Limited Access Vehicular Gate
Operator – operator to be used in an industrial setting that is not
intended for use by the general public such as a warehouse,
factory or loading dock area and
Class IV – Restricted Access Vehicular Gate Operator
– operator to be used in a guarded industrial setting that is not
intended for use by the general public and in which
unauthorized access is prevented via supervision by security
personnel such as a prison or airport security area.
Entrapment
protection requirements vary dependant upon the class the operator
falls into based on it intended usage. UL 325 requires that all
classes have primary and secondary entrapment protection provisions and
that the primary and secondary provisions cannot be satisfied by the
same device or system. The type of primary and secondary
entrapment protection required varies from class to class. |
Entrapment
Protection Provisions by Operator Type & Class
Remember that
the type of gate operator used combined with the class of the
application will determine the type of entrapment protection device or
system required for both the primary and secondary protection
provisions. Horizontal Slide Gate Operators and Vertical Lift or
Pivot gate operators have different entrapment protection requirements
from Swing Gate Operators and Vertical Barrier Gate Operators in all of
the classes. The exact requirements are summarized below (note
that these terms do not always reflect the exact term used in the
standard but are our interpretation of these terms in some cases):
Horizontal Slide, Vertical Lift or Vertical Pivot
Gate Operators:
| Class |
Primary Entrapment Protection |
Secondary Entrapment Provision |
| I & II |
Inherent Entrapment System |
Non-Contact Sensor
Contact Sensor
Continuous Pressure Actuating Device |
| III |
Inherent Entrapment System
Non-Contact Sensor
Contact Sensor |
Inherent Entrapment System
Non-Contact Sensor
Contact Sensor
Continuous Pressure Actuating Device
Inherent Audio Alarm |
| IV |
Inherent Entrapment System
Non-Contact Sensor
Contact Sensor
Continuous Pressure Actuating Device |
Inherent Entrapment System
Non-Contact Sensor
Contact Sensor
Continuous Pressure Actuating Device
Inherent Audio Alarm |
Swing Gate or Vertical Barrier (Arm) Gate Operators:
| Class |
Primary Entrapment Protection |
Secondary Entrapment Provision |
| I & II |
Inherent
Entrapment System
Inherent Adjustable Clutch or
Pressure Relief |
Inherent Entrapment System
Non-Contact Sensor
Inherent
Adjustable Clutch or Pressure Relief
Continuous
Pressure Actuating Device |
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III
|
Inherent
Entrapment System
Non-Contact
Sensor
Inherent Adjustable Clutch or
Pressure Relief |
Inherent Entrapment System
Non-Contact Sensor
Inherent
Adjustable Clutch or Pressure Relief
Continuous
Pressure Actuating Device
Inherent Audio Alarm |
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IV
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Inherent Entrapment System
Non-Contact Sensor
Inherent
Adjustable Clutch or Pressure Relief
Continuous Pressure Actuating Device |
Inherent Entrapment System
Non-Contact Sensor
Inherent
Adjustable Clutch or Pressure Relief
Continuous
Pressure Actuating Device
Inherent Audio Alarm |
Entrapment
Protection Devices Defined:
UL 325 defines, in general terms, how each of these entrapment protection
devices or system should operate:
Inherent Entrapment System – An automatic sensor system that senses the
entrapment of a solid object and “responds” to that entrapment within
two (2) seconds. The system must be incorporated as a permanent
and integral part of an operator.
Non-Contact Sensor – Provision for connection of or supplied
with a device that senses a potential obstruction of the gate without
actual contact between the obstruction and the gate being required;
i.e., a photoelectric or photo-reflective sensor or equal.
Contact Sensor – Provision for connection of or supplied
with a device that senses an obstruction of the gate when actual
contact between the obstruction and the device or gate is detected;
i.e., an edge device or equal.
Inherent Adjustable Clutch – Incorporation of a mechanical clutch
mechanism that can be adjusted such that the clutch “slips” when there
is contact between the gate and an obstruction, thereby stopping the
gate’s travel.
Inherent Pressure Relief – Incorporation of an hydraulic relief valve
system that can be adjusted such that the hydraulic fluid pressure
“bleeds off” when there is contact between the gate and an obstruction,
thereby stopping the gates’ travel.
Continuous Pressure Activating Device – Provision for connection of or supplied
with an actuating device (such as a push button) requiring continuous
pressure to maintain the opening or closing travel of the gate.
Inherent Audio Alarm – Incorporation of an audible alarm device
of at least 100dB that sounds just prior to the gate beginning to
travel and during the gate’s travel.
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Other
Important Provisions of UL 325 Regarding Gate Operators
Some special
provisions extracted from the UL 325 impact gate operator installations
beyond the type of operator and the class of the installation. Specifically, UL 325 requires that:
- Class I and Class II operators must have an audio alarm that shall function if two (2) sequential
activations of the entrapment protection device(s) occur. This
should not be confused with the Inherent Audio Alarm entrapment
protection system defined above.
- Class I and Class II slide gate operators
cannot run the gate at a speed that exceeds of one (1) foot per
second. It is hoped that this speed strikes a balance between the
security needs (prevention of a second party entering the gated area
before the gate closes) and the safety issues of someone being struck
by the gate.
- Anytime a non-contact or contact sensing
device is used as the Primary Safety Device, the system shall monitor
for the presence and correct operation of such a device, including the
wiring to it, at least once during each open and close cycle of the
gate.
- In most conditions, an obstruction must be
sensed within a maximum of two (2) seconds and, when such an
obstruction is sensed, the gate operator shall stop the travel of the
gate and reverse it a minimum of two (2) inches. The purpose of
this provision is to prevent a person from being entrapped in a
stationary position by the gate system.
- If the gate operator senses a second
sequential obstruction, the operator should stop the gate travel and go
into a “lock down” condition that requires an “intended” input is
received. This intended input must be generated by a person
within the line of sight of the gate using a hard-wired device to reset
the operator once the obstruction has been resolved; it cannot come
from a timer or other automatic device.
- After any obstruction reversal caused by
either an inherent entrapment sensing system or contact sensing device,
any timer-to-close system is disabled until manually reset since both
of these systems sense direct contact with an obstruction.
- In the case of swing gate operators utilizing
inherent adjustable clutch or pressure relief protection, the gate
cannot exert more than forty (40) pounds of force after the initial
start-up; the reasoning here is similar to that of the speed limitation
on slide gate systems.
- Slide gates must have a protective cover from
the bottom of the gate up to a height of four feet for the entire
length of the gate exposed in the fence opening. The portion of
the adjacent fence that the gate and/or back frame covers in the open
position shall be similarly covered. The protective cover must
prevent a 2-1/4 inch diameter sphere from passing through the openings.
- Contact Sensors such as edge devices are not
permitted to satisfy either primary or secondary protection provisions
on swing gate systems at the present time. Many interested
parties disagree with this provision and are working to have it
modified at the present time.
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