How to keep seismic disturbances at check by using seismic mounts?

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.

Taking the strain? Use anti-vibration pads to isolate vibrations

Vibration is undesirable in domains like engineered systems and habitable spaces, and methods have been developed to prevent the transfer of vibration to such systems. Those vibrations cause damage to the equipment and create unsafe working conditions. Anti-vibration pads protect both assets and people by isolating and attenuating noise and vibration, preventing damage to both machinery and the environment in which it works. Optimum performance service is however guaranteed only if the anti-vibration pads are both specified and installed correctly.

The operating conditions, like the temperature and surroundings of the application, will help to determine the best possible solutions. There are other factors that also must be studied to enable informed decision and using specifications of a suitable anti-vibration pad, such as:

  • Centre of gravity
  • Disturbing frequency
  • Static loading
  • Alignment
  • Deflection
  • Equipment configuration
  • Mass moment of inertia
  • Shock/Thrust loading
  • Natural frequency

The Anti-Vibration Pads reduce the noise and vibration generated by machinery or appliances like compressors, conveyors, diesel generators, washing machine, air-conditioning, refrigeration plants, fans, motors, pumps, etc. The bottom treads grip the floor, ensuring stability. Material is engineered to reduce noise and vibration. When the vibration damping pads are subjected to a vibrating load, the body member will dampen such vibrations. It is to be noted that when the vibration pad carries a load, the outer edge will deform from its position. This will cause a greater portion of the rim to contact the supporting surface on which vibration pad rests to provide a greater force resisting creep thereby permitting a pad to support the leg of a machine against lateral movement without being anchored to the supporting surface. There are various types of anti-vibration pads which should be identified after proper analysis. Different types are discussed below:

  1. Ribbed mounting padsAlternate low/high ribbed constructionEasy on-field installationEasy to cut pads to align with the size of the machine or leg, using knives or shearsto increase deflection, multiple layers of ribbed mounting pad can be used
  2. Cork sandwich padsThey are laminated pads having grained cork securely fused between two layers of alternate low-high ribbed rubber padsBolting not neededOffers highest level of vibration isolation and sound diminution
  3. Metal sandwich padsThey are constructed of a steel plate merged between ribbed anti-vibration padsAbility to handle very high load capacity

Below are the salient features of anti-vibration pads or anti-vibration mats:

  • These are designed scientifically resilient material that can isolate shocks and all the types of vibrations and reduce audible noise.
  • They give more deflection than any other materials
  • They have greater sound insulation ability and are cheaper than metal springs
  • They are highly resistant to cleaning compounds, oil, dirt, water, strength, heat aging, and fatigue.
  • These are mostly used for production equipment, machine tools, ventilation and heating equipment, pumps, generators, air handling units, under heavy concrete bases, electronics or sensitive laboratory apparatus, computers and data processor, business machines, etc.

There are various manufacturers out there offering a variety of anti-vibration pads with a varied price range. Select a company who is specialized in the producing anti-vibrators tool and opt that best fits the applicational requirement. The buyers first need to understand what their requirements are in terms of size and location of equipment placement. As inappropriate devices can make one life’s hard in terms of damaging the machinery or stopping the entire process of production. While anti-vibration equipment can be specified at any stage of a project, there are typically fewer restrictions if they are measured at the onset of the design phase. If considered in too late, costs may be exorbitant to adjust the space envelope or available locations for the pads or mounts to be installed. Even after the vigorous specification process, the performance of an anti-vibration pad can be stalled by incorrect fittings. All surfaces must be clean, dry and free from wreckages before the device can be fitted. The equipment to be mounted must be lifted carefully onto sufficient supports both to maintain correct alignment when lowered on to the mount, and also to prevent damage to the asset or to individuals during installations. Therefore, consult with the specialist who has great expertise in this field to help you with the selection of the best anti-vibration pads.