Seismic Rack Enclosures & Cabinets
Earthquakes are not limited to the state of California, nor are they infrequent. Seismic events take place every day throughout much of the continental United States. In many cases, millions of dollars’ worth of technology depends on the quality and installation method of the seismic rack that it is stored in.
Most manufacturers of seismic racks and enclosures offer products that are marketed as offering “seismic protection”; however, there can be significant differences in the standards used to achieve those labels, and thus, major disparities in the level of protection that those products provide.
There are two standards by which enclosures are deemed seismic:
Telcordia GR-63 Seismic qualified enclosures are designed to meet or exceed the Telcordia NEBS Zone 4 testing objectives and requirements. GR-63 describes the protection level of an enclosure. It requires an enclosure to provide a level of protection such that the equipment inside shall sustain operation without replacement of components, manual rebooting, (or) human intervention during an earthquake.
Emcor offers IBC kits designed to anchor the 10 Series® and GUARDIAN™ frames, meeting life safety requirements for protecting building occupants from falling objects in the event of an earthquake as outlined in the International Building Code.
Telcordia GR-63 describes the protection level of an enclosure. It requires an enclosure to provide a level of protection such that the equipment inside shall sustain operation without replacement of components, manual rebooting, (or) human intervention during an earthquake.
Historical Base – Telecommunication Equipment Based
In the years following AT&T’s monopoly lawsuit, a flood of competitive local exchange carriers arose, bringing a slew of new and varied network equipment to the once homogenous collection of AT&T equipment housed in central offices throughout the country. As a result, standardized network equipment was established to ensure network compatibility and uptime. What came to be was the NEBS requirements, of which, section GR-63 applies specifically to protecting equipment in the event of seismic activity
Telcordia GR-63 Test Procedures
Specific test procedures are provided to determine seismic compatibility. The test is comprised of a composite waveform that is synthesized from typical earthquake (approx 8.3 on Richter scale).
To achieve GR-63 compliance, enclosure manufacturers turn to independent, third-party testing facilities. An enclosure is loaded to capacity and mounted on a shaker table. The shaker table then simulates an earthquake, shaking in every potential direction at varying levels of intensity up to the equivalent of an 8.3 earthquake. Accelerometers are attached to the enclosure to measure its vibration and sway during the test. To pass the test and achieve the seismic rating, the enclosure must not sway more than three inches in any direction and all components must remain operable during and after the test. This test is the same for every enclosure manufacturer, regardless of where that enclosure is going to be used or its intended purpose
General map that shows the 5 seismic zones according the USGS survey – The likelihood of a seismic event in a specific location.
A seismic zone map is based on a statistical compilation of the number and the magnitude of past earthquakes. These maps show an indication of where the next earthquake is most likely to occur, how frequently they occur and their magnitude. There is NO direct correlation between seismic zone ratings and Richter scale recordings, although experience shows the worst earthquakes occur in the higher rated seismic zones.
Installation and Equipment Distribution
Installation of the enclosure as well as how the equipment is loaded in the enclosure effect performance. –
This certification requires all racks to be secured in the same manner using concrete expansion anchors. When loading, keep the center of gravity low by placing heavier components toward the bottom of the enclosure. Ganged enclosures will produce a more stable installation than single racks.
The International Building Code (IBC) is a set of guidelines which describe how to properly secure objects -in this case enclosures- so that they do not tip over and cause injury to anyone during an earthquake.
Historical Base – Architectural / Building Based
Following the 1994 earthquakes in Los Angeles, during which more than 40 percent of the $80 billion in damages were non-structural, it became apparent that there was a need to create guidelines for securing objects to the floors, walls, or ceilings of buildings. In 2000, the IBC was created as a guideline to which businesses must adhere in order to receive funding from the Federal Emergency Management Agency (FEMA) in the aftermath of an earthquake
IBC Test Procedures
Formulas are provided to determine seismic compatibility; however, this can only be determined by knowing the specific building elements, features, location, floor level, etc.
The most common IBC test procedure uses a mathematical equation that compares potential seismic effects to objects mounted in a building. These calculations determine how the enclosure must be secured or installed in the building. A value called the “seismic design category” is assigned based on the building’s location. This is calculated based on the distance of the building to the anticipated location of an earthquake, the type of soil beneath the building and a variety of other variables. The building is also given an “importance factor” value, which is either 1.0 or 1.5. Essential buildings, such as hospitals are given a value of 1.5 due to the need for immediate uptime. Non-essential buildings are given a value of 1.0. The essential value of 1.5 would require that the electronics continue to function in the event of an earthquake whereas the non-essential value of 1.0 would simply require the enclosure to remain standing.
Very specific map that measure Short Period Spectral Response Acceleration (Ss) – How bad an earthquake can be at specific site.
In addition to viewing the entire continent as a series of potential seismic locations, the specification “IBC” has resulted in maps that measure potential seismic activity within given locations relative to identified fault lines. For localized seismic information the IBC has maps which define the probability of earthquakes within 100-foot sections relative to fault line locations. Installation and Equipment Distribution
Installation and Equipment Distribution
Installation of the enclosure as well as how the equipment is loaded in the enclosure effect performance.
Concrete expansion anchors are used to mount the rack to the floor. Anchor embedment depths will vary based on the floor type. When loading the rack, keep the center of gravity low. Ganged enclosures will produce a more stable installation than single racks.