With the more stringent life-safety related building codes all across the globe, it has become commonplace for historically non-seismic regions or the country to require seismic restraint of MEP (Mechanical, Electrical and Plumbing) equipment. The concept of seismic or base isolation as a means of earthquake protection seems to be more than 100 years old. However, until the 1980s, few structures were built using this principle. Today the concept has matured into a practical reality and is taking its place as a viable alternative to conventional (fixed base) seismic-resistant construction. Seismic Applications are basically the same as non-Seismic but complicated by the need to keep equipment in place. All mountings, hanger-cables or snubbers are designed to resist the seismic force in any zone or specification and Seismic Mounts are among the best. Seismic mounts should be used in locations where earthquakes or seismic disturbances are considered to be a potential hazard. Holding down the equipment can be achieved in two ways, a mechanical snubbing device can be placed in conjunction with standard spring isolators or spring isolators with built-in snubbing devices can be used. These are what can be referred to as seismic isolators. Typical supports for piping, trays, and other equipment are designed for the gravity, or vertical, loads but do not take into account the horizontal loading caused by earthquakes. The main purpose of seismic bracing is safety – to minimize the loss of life due to an earthquake.
The function of Seismic Vibration Isolators
- All seismic restraints are designed to withstand seismic forces of approximately 2G even at maximum rated load.
- All seismic vibration Isolators are suitable & safe for most critical applications (including Zone 4 areas).
- The function of Seismic Vibration Isolators is to absorb the vibration of rotating machines & restraints Seismic forces from all direction during earthquakes
Integrated seismic mounts for mechanical equipment are designed to combine spring mount vibration isolation with multi-directional flexible restraint to limit equipment movement under seismic disturbance. These are spring mounting systems able to withstand earthquakes, and are manufactured with mechanical anchoring systems which ensure integrity in static applications while offering multi-directional flexible restraint to limit movement during a seismic disturbance. Seismic Mounts are used where equipment requires the use of a spring type mounting for a high degree of isolation under normal operating conditions, over a range of interfering frequencies. The seismic spring mounts can also incorporate microcellular polyurethane which is effective in isolating vibration at mid to higher frequencies. Seismic mounts and restraints are designed to provide the strength and isolation necessary to maximize the chances of these systems remaining attached to the building structure.
Seismic vibration isolators are used for absorbing vibration & restraints seismic forces for air handling units, centrifugal fans, pumps & chillers, etc. when these units are installed near seismic zones. The anti-vibration mounts with the seismic structure are suggested to isolate indoor/outdoor chillers, HVAC roof-top equipment, cooling towers, condensers, fans, diesel engines, generators, pumps and air-handling units (AHU). The key characteristics include: –
- Rugged fabricated steel construction
- Heavy duty stable steel spring
- Acoustic isolation pad
- Single fully adjustable central vertical restraint bolt
- Anti-skid elastomeric acoustical pad is standard with all seismic restraints
- Fully weatherproofed
There is wide range of seismic spring mounts available in the market for full range of applications, as well as a rubber seismic mount and independent seismic restraints. All seismic isolators are manufactured using modern robotic welders. The standard finish on the housings and springs is powder coating and all hardware within the mounting is zinc electroplated. The housings can also be ordered as hot dipped galvanized for superior corrosion resistance. Also, available are cable restraints, which are used in conjunction with spring or rubber hangers for the seismic restraint of suspended piping and equipment. Proper sizing and placement of seismic isolators and accurate calculation of anchor bolt forces are imperative in adequately restraining equipment against seismic effects.
There are manufacturers out there offering a variety of seismic mounts. Select a company who is specialized in the same and opt for mounts that best fits the applicational requirement. Consult with the specialist to help you with the selection of the seismic mounts. The expert will consult with engineers and architects to determine the best possible seismic solutions for your projects.