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Definition

Elevators fall into two categories - hydraulic and traction. A hydraulic elevator operates via a hydraulic piston located under the cab, while a traction elevator is pulled up via a cable and counterweight system above the cab. Hydraulic elevators are limited to around 7 stories in height.


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Left: hydraulic elevator / Right: traction elevator. Source: FEMA




Issues Addressed

Any elevator equipment located below the lowest floor (BFE) or in a basement is not covered by the National Flood Insurance Program. In order to qualify for coverage, all of the following techniques must be applied.[1]

Hydraulic Elevators
The jack assembly for a hydraulic elevator (above left) will, by necessity, be located below the lowest floor and therefore generally below the BFE. The jack is located in a casing, and while it will resist damage from small amounts of water seepage, total inundation by floodwaters will usually result in contamination of the hydraulic oil and possible damage to the cylinders and seals of the jack. Salt water, because it is corrosive, can be particularly damaging. The hydraulic pump and reservoirs of the hydraulic elevator are also susceptible to water damage, but they can easily be located up to two floors above the jack and above the BFE as shown in drawing above.

Traction Elevators

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Float and Control Mechanism to Control Cab Descent. Source: FEMA

For traction elevators (above right), the electric motor and most other equipment are normally located above the elevator shaft and would not be susceptible to flood damage. Some equipment, however, such as the counterweight roller guides, compensation cable and pulleys, and oil buffers, usually must be located at the bottom of the shaft. When such equipment cannot be located above the BFE, it must be constructed using flood-resistant materials where possible.

Elevator Equipment

Some equipment common to all elevators will be damaged by floodwaters unless protected. The most obvious example is the elevator cab. Depending upon the size of the cab and the types of interior materials used, a cab may cost between $5,000 and $50,000. Flood damage, which can range from superficial to nearly a complete loss, can easily be avoided by keeping the cab above floodwaters. However, in most elevator control systems, the cab automatically descends to the lowest floor upon loss of electrical power. Installing a system of interlocking controls with one or more float switches in the elevator shaft to always keep the elevator cab from descending into floodwaters (see right) will result in a much safer system. A float switch system or another system that provides the same level of safety is necessary for all elevators where there is a potential for the elevator cab to descend below the BFE during a flood. Electrical equipment is often located below the BFE for both types of elevator systems. Some electrical equipment, such as electrical junction boxes and circuit and control panels, can be located above the BFE as shown in above left drawing. Other elevator components, such as doors and pit switches, must be located at or below the lowest floor. Where this becomes necessary, components may sometimes be replaced with more floodwater-resistant models. Some elevator equipment manufacturers offer water-resistant components; design professionals should contact suppliers to determine the availability of these components.


Considerations
The cost of installing an elevator according to FEMA guidelines is minimal when compared to the cost of a typical elevator installation, and especially when it guarantees flood insurance.


Applications

Any building with an elevator is a candidate for these guidelines, especially high-rise offices.


Related Reports

FEMA: Elevator Installation for Buildings Located in Special Flood Hazard Areas


References


  1. ^ United States of America. FEMA/FIA. Office of Loss Reduction, Technical Standards Division. Elevator Installation for Buildings Located in Special Flood Hazard Areas in Accordance with the National Flood Insurance Program. 4-93 ed. [Washington, D.C.]: U.S. Dept. of Homeland Security, FEMA, 2010. Print.