Generators and Seismic Activity

Natural disasters such as earthquakes, hurricanes, and intense thunderstorms are a real problem for many parts of the world. High amounts of seismic activity have destroyed many cities throughout history, and while in some cases the shear natural force was too great to prevent such damage, there have been many instances throughout history where proper design and construction have prevented extreme damage and loss of life. Good building and construction design is necessary to minimize structural damage and to protect the public and limit personal injury. To give a few examples of the kind of damage that can occur, in 1994, in Northridge, CA, a 6.7 magnitude earthquake caused over $25 billion in damage. While this is a fairly large earthquake, they are not as uncommon as one might think. Throughout the world, on average there are seventeen 7.0 magnitude earthquakes per year. In order to categorize earthquakes, scientists have created the moment magnitude scale, which measures the size of the earthquake based on the amount of energy that is released. A minor earthquake is typically considered at a magnitude of 4.9 or lower.

In order to prevent damage from smaller level earthquakes, building codes have been created to provide a minimum criteria of seismic activity protection. The International Building Code was first created in 2000, and has since been updated several times, with the latest version being created in 2012. Currently, all 50 states in the US have adopted the IBC codes in some form or another. However, certain jurisdictions only adhere to earlier versions of the IBC, such as the 2006 or 2009 version. When in doubt, always check to see what IBC code your state has. In general, states along fault lines and near the coast have the latest IBC code, as they are the most likely to experience high levels of seismic activity. Various maps are available online which show what areas of the United States are most prone to seismic activity.

Just as the building codes have been updated throughout the years, generator sets have added several devices to help dampen the effects of seismic activity. Excessive amounts of torsional vibration can completely destroy internal combustion engines, and generator sets. Some of the common anti-vibration devices are described below, each plays an important role in keeping a standby or emergency generator safe from seismic activity.

Spring isolators are typically used with generator sets where very low vibration is acceptable. There are 2 main types of spring isolators; a housed spring mounted isolator, and an open spring isolator. Housed spring isolators have an adjustable damping mechanism, and are ideal for generator sets that may be unbalanced or have slower startup and shutdown times. They are designed to provide restraint in a horizontal direction for a generator set, so there is less swaying of the generator from side to side. Open spring isolators can give you a lower vibration frequency in all directions, however, they cannot provide the same dampening effect on the generator as a housed spring isolator.

Elastomeric isolators are another type of dampening device that many generator manufacturers use. They are much more customizable, as they are typically made from natural rubber, neoprene, or silicone. This allows for manufacturers to mold them to fit what the specific generator need may be. Elastomeric isolators are typically placed at the base of the mount of the generator set, often below the fuel tank.

In areas where seismic activity is a concern, it is critical that an emergency generator have vibration isolators. If an earthquake, or serious natural disaster were to occur, it is much more likely that the emergency power system will need to be used. By ensuring your emergency generator has all of the necessary parts to function during a disaster, you can count on your generator to perform when it is needed most.

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