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Basic Requirements
ASME/ANSI B20.1 requires 96” high enclosures at each floor level with the exception of the top floor or landing which in some cases it may be permissible to use 42” high handrails as a portion of the guarding.
Enclosures may be fabricated from woven wire, expanded metal, sheet metal, studded wall (wood or steel), or cement block. Wire or metal mesh must have openings small enough to reject a 2” ball. All enclosures must be able to withstand 100 pounds of force in any direction.
Types of loads and internal company safety standards may determine the type and height of enclosures to be used. For example, a VRC carrying small loose boxes would be considered safer if it were enclosed the full height between floor levels and to a height of 96” above the upper floor level service.
The location of a VRC will also determine the type and size of an enclosure. It may be advantageous to locate the VRC along side a wall or in a corner thus reducing the size of the enclosure required to safely enclose the VRC. The positioning of the enclosure in relationship to the VRC is important. The distance between the inside of the enclosure and the extremities of the VRC normally should be kept to a minimum to reduce the possibility of a person from being positioned between the enclosure and the VRC.”
SAFETY GATE TYPES
Many manufacturers offer special gates not listed. Consult the VRC manufacturer. Note: Gates do not take the place of fire doors where required.
 Single Swing Type Gate
This type of gate hinges on one side and latches on the other, may be either right or left-hand swing. The clear opening width is limited normally to approximately 60” to 72” maximum and requires clear space in front of the lift to swing open. Typical swing gate height is 84” but may be raised or lowered to accommodate load height requirements or to allow support between adjacent enclosure panels or walls. This style is similar to a door in a home.
 BI-parting, Double Swing Type Gates
This type of gate hinges on each side and latches in the center. This style of gate may be used for openings greater than 60” but usually not exceeding 120” in width.
 Single Panel, Counterbalanced Vertical Rising Gate
Also known as a Vertical Acting Gate. This type of gate closes to the floor and opens in the upward direction. This style of gate can be constructed to handle gate openings up to 16’ wide. Though they are normally between 72” and 96” high they can be made higher. The drawback being vertical rising gates need a vertical guide track which will be at least twice the height of the gate panel. This style gate may not be feasible in an installation where loading is on the same side two consecutive floors.
 BI-Parting or Double Panel, Counterbalanced, Vertical Rising Gate
This type of gate is the same as the single panel, counterbalanced vertical rising gate above in operation and use except the two (2) panels telescope from a nested position which only requires about 75% as much overall height.
 Horizontal Sliding Type Gate Assembly
This style gate operates in the same matter as a vertical rising gate except it functions in the horizontal direction and requires considerable storage room on one side when open. Another disadvantage of this type of gate is that it requires an overhead track above the gate opening.
 Roll-up Type Door Assembly
This style gate can be anything from an industrial type roll-up steel door to self storage facility type door. This style gate has an advantage in that the gate itself does not require a lot of space. Some disadvantages are that it is slow in operation, may require considerable maintenance, and it is mounted over the gate opening and may limit the load height. It may be of the manual or powered variety.
All of the above gates must be equipped with an electromechanical interlock system to meet the code requirement. The purpose is to discourage people from riding the carrier or carriage and to help provide a guarded opening at any landing. The locking component of the interlock system is designed to lock the gate or door in the closed position whenever the lift carrier or carriage is not present at that particular opening. The gate status component is intended to prevent operation of the VRC unless all gates are closed.
Gate Interlocks - General
Regardless of the gate or door type, all access gates must be equipped with an electromechanical interlock system to meet the code requirement and to provide a safe operating environment. The purpose of the interlocking system is to help prevent the occurrence of an unintentional or unguarded gate or door from opening at a landing level when the carrier or carriage is not present at that level and to help prevent people from being able to ride on the VRC carrier or carriage.
There are two (2) primary elements common to any code compliant interlocking system; a mechanical locking component and a status-sensing component. The locking component can be either electrically or mechanically actuated and is designed to mechanically lock the gate or door in the closed position whenever the lift carrier or carriage is not present at that particular landing. The gate status switch component is intended to provide an electrical signal to the control panel that will prevent the operation of the VRC unless all gates are fully closed.
Electromechanically Actuated Interlocks
Electromechanical interlocks are devices that normally integrate both the locking and status sensing components of the interlock system in a single housing. This type of interlock provides a solenoid actuation of a mechanical locking device and is typically mounted to a permanent structure just inside the gate and adjacent to the landing position of the carrier or carriage. This interlock receives a striker plate which is mounted to the fate/door panel from the top or side depending on the type of gate/door. This striker plate automatically captures when the lift leaves the landing and automatically opens or closes the electrical circuit to the motor starter with its presence or absence.
There are several advantages to this type of interlock system; 1) it is both a gate sensing and gate locking device, 2) it is difficult to tamper with or override, 3) it provides simple, durable, and reliable service in dirty or dusty environments, and 4) it requires close proximity to the lift carrier or carriage to be actuated by a cam on the lift which inherently creates less space between the gate/door and the for a person to stand while the gate is closed. A disadvantage is its bulky size which limits its use in applications calling for very tight running clearances such as shaft installations.
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