Without a doubt, aside from the main entryway to a multistory edifice, the most important door-ways are the elevator entrances and doors found in the lobby – likely the most used doorways in the buildings.
Using updated technology to deliver an excellent vertical-transportation experience, modern automatic-elevator systems must not only look good, but also provide safe movement of a platform up and down in hoist ways that can be constructed in the form of an enclosed shaft, an open atrium or simply on the exterior of a building structure or tower. Openings are provided in the hoistway walls of these multileveled structures at various points (stops/landings) along the elevator’s path in order to gain access to the elevator system’s moving platform. The part of the automatic elevator system that performs the alternating roles of hoistway accessibility and protection is the elevator entrance assembly. Aesthetics aside, the primary function of this assembly is to open during loading and unloading of a safely parked platform and close to prevent accidental entry by passengers when the platform is away from the landing. The assembly also must prevent flames from moving from floor to floor during a fire (ASME A17.1 Code Rule 2.11).
Aesthetics, however, should not be downplayed since the elevator entrance is often the “first appearance” interior doorway that can be capitalized upon to make a vital statement about the building and its target market. The lobby entrance to the elevator should pack the design equivalent of a book cover or the opening curtain of a broadway production. It should be the visual equivalent of “He-e-e-re’s Johnny!”. Here’s your elevator, the safest mechanical means of vertical transportation ever invented, an entrusted guardian of security and safety assurance for the building and its inhabitants. What an outstanding opportunity to convey an uplifting experience to all tenants and visitors who enter the elevator, whether on their way to/from work, visiting a client, medical professional or friend, or simply coming home.
Sadly, misplaced attempts at cost containment typically cause design professionals to overlook this opportunity and call for the lobby entrance to be inconspicuous as all the other doorways on the floor. Modern manufacturing techniques allow the elevator entrance to be dynamically and beautifully designed while meeting the many building, elevators’ life-safety, fire resistance, handicap and ADA accessibility guidelines codes/requirements, so why not take the maximum advantage of these techniques? (Building codes mandate only minimum and maximum sizes, proper means for access and egress, fire resistance and structural issues, and standards, i.e., elevator safety, accessibility and a ADAAG requirements.)
Types of Entrances
One of the most common designs used today is the single-speed, side sliding entrance. This design features a single door panel that operates by sliding horizontally along the path of the sill and hangar-track assemblies. Two important criteria limit the maximum-width opening that it can protect: the upper limit of the fire-door procedure to which the door system was successfully tested and the space available on the platform and/or within the shaft. For single -speed, side-sliding entrances, this space must be at least twice the opening width in order to have sufficient room for the door to travel from the fully closed to fully open position.
Field conditions, however, can call for a larger hoistway opening than one door panel can possibly protect, as can tight shaft conditions not allowing sufficient space for the full travel of a single-speed, side-slide door panel. In such situations, multiple-door panels are used in the entrance assembly. Again, the dual limitations of the fire-door procedure and platform/shaft size will come into play.
One type of multi paneled entrance assembly in use today is the two-speed, side-slide entrance, comprised of two door panels that work together, spreading across the entire hoistway opening (with each door panel covering half of the opening) when the entrance is in the closed positron. Upon opening, both doors then slide to one side and stack one behind the other, collapsing into a space half as wide as the original hoistway opening. Two-speed, side-slide entrances therefore have one-and-a-half times the opening size requirement for the door-travel width within the platform and/or shaft (the full opening width required in the closed position, plus the half-opening space required when the doors are nested in the opened position). Since the leading door panel travels the entire opening width in the same amount of time as the trailing door panel travels half the distance (to and from the opening’s midpoint), the leading and trailing door panels must travel at two different speeds and are commonly referred to, respectively, as the fast and slow door panels.
While multi-speed door equipment can be used to protect oversized hoistway openings, its most frequent application is found in undersized or “tight” shafts. In fact, quite counter intuitively, the tighter the field conditions, the more door panels should be deployed in the protection of the hoistway opening. for example, since three-speed, side-slide entrance assemblies are composed of three door panels, they can be used in shafts with widths as tight as one-and-a-third times of the opening size.
Other common configurations for passenger-elevator entrance assemblies can be found in the center-parting design group. Center-parting entrances are multi-paneled systems, by definition. Similar to multi-speed, side-slide entrances, center-parting entrances incorporate two or more door panels that work together to protect a hoistway opening. However, unlike side-slide entrances where all door panels slide in the same direction over to one side of the opening, the center-parting entrance door panels move in opposite directions to/from one another.
In single-speed, center-parting entrances, for example, two door panels work together, spreading across the entire hoistway opening when the entrance is in the closed position. Each door panel covers half of the opening, with the leading edges meeting in the middle of the hoistway opening. Both doors then move away from each other at the same speed, parting in the center, with one door moving to the left side of the opening as the other door moves to the right.
Single-speed, center-parting entrances are often encountered in high-traffic, high-rise buildings. In an effort to move as many passengers as time-efficiently as possible, these building structures seek to minimize passenger boarding and unloading times, while maximizing the available elevator platform area. The center-parting design is useful in both respects, helping to minimize load/unload times in two ways:
- First, center-parting designs employ faster door-open/door-close cycles than tide-slide designs. The door panels of center-parting equipment only travel to and from the midpoint of the hoistway opening, while the doors in side-sliding entrances must travel the entire distance from one side of the hoistway opening to the other. This saves boarding time because rapidly opening doors allow the process of loading and unloading to begin more quickly. And, once the boarding is completed, rapidly closing doors allow the elevator platform to get underway more quickly.
- A second factor is the reduction of congestion in front of the hoistway openings during boarding, best accomplished (short of adding additional elevator systems and platforms) by increasing the size of the hoistway openings themselves. As with all multi-paneled (two/three-speed, side-slide, etc.) door systems, single-speed, center-parting entrances are well suited in the protection of these oversize hoistway openings.
However, unlike the multi-paneled entrances of the side-slide design group, single-speed, center-parting door equipment has no inherent door travel advantages over single-speed, side-slide entrances of similar opening widths (each requiring door-travel space of at least two times the opening width). This is due to the fact that both of the center-parting door panels travel in the same plane and, therefore, cannot save any door-travel distance by stacking one behind the other in the open position. This design trait is useful in the maximization of platform square footage, however.
And often, it is the ability to maximize useable platform space that makes single-speed, center-parting doors the design of choice in high-traffic/high-volume applications. Since valuable platform space must be sacrificed to make room in multi-speed, side-slide entrances in order to “nest” or “stack” the fact door “behind” the slow door, each additional door panel in these applications causes a corresponding reduction in the usable platform space, because the door panels operate in the same plane and do not have to “stack” in front of each other.
Applications requiring extremely large hoistway openings also look to center-parting design equipment for design solutions. Multiple-speed, center-parting door equipment such as two-speed center parting (with four door panels; two moving to the right and two moving to the left) and three-speed center parting (with six door panels; three moving to the right and three to the left) provide design solutions for even the largest hoistway opening requirements.
Not all installations can be covered by the sliding elevator-entrance design (either side-slide or center-parting). Swing-door entrance assemblies are used in installations not requiring automatic operation of the hoistway-door equipment (residence lifts) or older, retrofit sites with extremely tight shafts (sufficiently tight that a collapsable car gate must be used, since there isn’t enough door-travel room for even the smallest door-paneled multi-speed entrance). These entrances employ doors that swing open wand closed on hinges/pivots that affix the “back” or “trailing” edge of the door to one side of the entrance frame.
Fire Resistance, Protection and Operation
Since most elevator-door equipment is installed in fire-rated wall systems, it must additionally assume the role of acting as a fore door. In North America, fire-door systems in general – and elevator fire-door systems in particular – receive their fire rating/classification by undergoing an intensive engineering review process that culminates in a destructive-burn test in accordance with the test criteria found in the NFPA-80, ASTM-152 and UL-10C standards (Rule 2.11.14, Testing).
These standards require that the elevator doorway must be capable of resist ion fire temperatures of 1,800ºF for a period of one and a half hours in order to ensure that the door system will prevent fire from spreading from one floor to another through the elevator shaft. At the conclusion of the burn, the doors are immediately subjected to a “hose stream test,” with the rapid change in temperature simulating the effects of an explosion.
In order to be awarded a Class B one-and-a-half hour-rated fire-door certification, the door panels of the entrance assembly must remain operable within the limits of the test criteria at the conclusion of the testing. Only elevator doors and emergency stairway doors (which assure the occupants of the building safe means of egress) are required to bear the Class B rating, the second-most-rigid fire-door rating.
The independent, third-party testing laboratories that perform the engineering analysis and burn tests will also, through a series of perpetual, random inspections of the door-manufacturing facilities (Rule 2.11.16, Factory Inspections) issue labels/markings certifying that the products will perform as required under ASME A17.1, elevator and escalator safety code (Rule 2.11.15, Marking).
The ASME A17.1 elevator safety code also addresses how the elevator is to perform in a fire emergency. The emergency-operations rules (Rule 2.27.3, Firefighters’ Emergency Operation – Automatic Elevators) specify exactly how an elevator must perform during a fire. Upon being signaled by an alarm or smoke detector, all elevators must immediately cease upward motion, reverse direction (downward) to a designated evacuation floor and remove themselves from service by closing their entrance doors. During this type of firefighters’ service operation, elevators can only be reactivated at the evacuation floor by firefighting personnel using a special key top commandeer the elevator for their exclusive use. Frequently, due to its required fireproof construction, the lobby of the building is the designated evacuation floor – another in the list of situations where lobby-elevator entrances play critical roles in the design of multistory buildings.
Structural Integrity and Safe Operation
In addition to performing the architectural and fire-protection roles outlined above, elevator entrance doors must also address several structural and safety issues. The elevator safety code ASME A17.1 sets forth stringent structural-integrity requirements for the elevator entrance in order to ensure performance under extreme impact and static-force conditions. Many of the rules even go as far as specifying what materials and devices are to be used in conjunction with the entrance assembly in order to achieve the code’s high safety standards (Rule 220.127.116.11, Panels).
There even are code requirements to ensure safe operation of the entrance assembly under normal operating conditions. From simple issues of clearances to exposures as diverse as pinching hazards (Rule 18.104.22.168, Frames), the ASMEA17.1 document has over 30 pages of rules devoted to ensuring that the elevator entrance always performs in a safe and reliable manner over a broad spectrum of operating environments/conditions.
Hoistway Entrance Door Panels: Recent Developments
During the past decade, the world of entrances and doors has become more nuanced. Elevator products – not unlike many other products today – are often called “world class”, yet we in North America have not yet accepted the world class elevator-type entrance!
The U.S. and Canada have “harmonized” their elevator safety codes into one comprehensive document, the ASME A17.1/CSA B44 Safety Code. Presently, Mexico, Central America and South America have yet to address the issue as anticipated under the extended North America Free Trade Agreement. However, task groups at the International Organization for Standardization (ISO) are presently discussing “harmonization” of the various European safety codes with the North American code.
The basic differences between North American and European standards are twofold:
- Door construction – North American doors are composed of two metal door skins vertically reinforced and insulated with mineral-rock wool or fiberglass mats. (Air-cell asbestos has now been prohibited). European doors consist of a single face skin, reinforced vertically or horizontally without insulation.
- Test standards – North American doors are tested to a test standard, which is similar to several American Standard agencies – American Society for Testing and Materials (ASTM), National Fire Protection Association (NFPA) and Underwriters Laboratories (UL) – whereas European doors are tested to their EN 81 standard.
The basic and primary differences are:
- North American – The door face is exposed to 1,800ºF within the first 30 minutes and held at that temperature for a total of 90 minutes (hence a one-and-a-half hour identification), then immediately subjected to a high-pressure, cold water hose stream test.
- European – The door face is exposed to 600ºC (1,112ºF) for a period of 60 minutes, 90 minutes or more, but is not subjected to a high-pressure, cold water hose stream test.
The North American double-skinned door is more durable, heavy, costly and soundproofed. The A17.1/B44 code language details the forces these doors must also withstand, not only regarding direct static forces on the face of the door, but also withstanding a lifting force simultaneously with the static-face load. This language has been added in the last decade as a result of alleged falling-down-the-shaft fatalities.
Numerous issues are in play as work progresses toward arriving at a “harmonized” approach:
- The recent concern in North America of this exposure is not addressed in the European codes, nor do Europeans believe the hose stream test necessary.
- The hose stream portion of the test illustrates the need to address the effects of an explosion that takes place when fire temperature reach levels to/above 1,800ºF, thereby exposing the elevator hoistway and floors above and below the fire floor, including the elevator car, platform and the people therein.
- The sale and marketing of elevator entrances also differ between North America and Europe.
- Europeans market these entrances in a standard construction and very limited sizes, types and finishes, whereas in North America, entrance frames (bucks) wrap a wall of varying thickness and finishes. In the same shaft, door panels may have several different finishes or claddings (in compliance with fire-test standards).
- North American architects or design professionals will not tolerate the restrictions European manufacturers would impose upon them with their standard “only” configurations.
- Europeans tell architects what is available; in North America, architects are at the liberty to request whatever suits their design requirements
There are numerous items that are specific to the U.S., Canada and various local jurisdictions:
- Emergency access keyholes in doors (including key-locked types).
- Access switches at top and bottom landings (Some jurisdictions require them in the sight guard rather than in the jamb).
- Bottom-of-door safety retainers (Z-brackets) between shoe guides that meet static loads.
- Upthrust retainers are an added feature on the bottom of the nylon portion of a shoe-guide assembly, which limits the manual separation at the bottom of center-opening or two-speed, center-opening doors (A17.1 Rule 22.214.171.124.8).
- Anti-pinch, flush mounted pull handles.
- Glass in the doors (other than fire-rated doors), including full-glass-panel doors in mass transit and parking lot venues (although fire-resistance ratings of one-and-a-half hours are compromised in these situations; crime is of primary concern).
- Single-skin European doors would be most difficult to accommodate these exposures.
- Smoke or draft seals around doors minimizing the proliferation of smoke or heat and/or loss to shaft-draft stacking, also to reduce high speed elevator noise. Draft seals are becoming increasingly more popular due to recent energy-saving concerns.
- In New York City, secondary swing security doors are appearing on the corridor side of sliding hoistway doors in conflict with “locked out of service” and entrapment code rules. This is called “0” clearance entrance, and NYC Rule RS-18 states that space between doors is not to exceed 6 inches.
Additional architectural design issues include
- Creation of “illusions” of raised or recessed panel designs without violating the ⅛-inch criteria of the code rule 126.96.36.199.5.
- Transom panels (flush or projected) in compliance with fire-resistant door-testing procedures and the use of oversized certificates.
A great deal of talent, knowledge, experience and planning enter into the safety, design, styling and manufacture of elevator entrances and doors. This escapes most people’s notice and appreciation, and that’s as it should be. Building owners and the riding public should unknowingly enjoy the benefits of elevator products as they deal with the priorities of their daily lives. But the next time you’re in an elevator lobby awaiting the next available cab, take a moment to appreciate the extraordinary global effort continuously underway to provide an aesthetically pleasing, safe and enjoyable elevator experience.