Seismic isolators for protecting industrial machines from the effects of earthquake

Seismic energy wave is the outburst of energy created during tectonic movement of earth crust and large man-made explosions which generate low-frequency acoustic energy. Seismic energy and its corresponding effects strongly impact the structural stability of a structure and possess severe threat to human life. Specific scientific techniques are adopted to provide structural safety and comfort by controlling the internal forces and displacement within the particular limits. One of the most common method for protecting structures against destructive effects of earthquakes is to damp the seismic energy by the structural elements like seismic mounts. These isolators provide adequate resistance to the undesired vibrations. This method offers certain level of protection however; there is a probability of structure being damages when exposed to critical situations. To overcome this scenario another method for protection of the structures against the seismic energy is to isolate the structure by installing seismic isolators whose function is to dissipate the energy and restrict transfer of vibrations from source to structures.

seismic isolation

seismic isolation

Seismic isolation is a technique used to reduce the effects of earthquake on structure, their components and protect them from damaging. It effectively decouples a supporting structure from mounting structure grouted on a shaking ground thus protecting a building or a structure’s integrity, stability and strength. Seismic isolators offer much better protection as it isolates the vibrating source and dissipates the energy internally, thus providing significant structural protection. The seismic isolators and energy dissipating devices are seen to be an effective solution. They are installed in the structure to damp the seismic energy or placed between the foundation and vertical structural systems to provide the desired result.

Seismic isolator dampens the undesired seismic energy under the ground of the structure, thus decreasing the effects of lateral loads on the above surface. As defined in physics that when external seismic forces are exerted on any structure mounted on floor, its stability is governed by its mass, stiffness and energy damping characteristics. Response or stability of structure can be controlled by changing stiffness of structure. Higher the damping effect of building lesser is the reaction towards undue acceleration and displacements. Today there are two types of seismic isolators available which include seismic spring isolators and seismic mounts that are installed in a structure to offer stability and desired strength.

Isolators amend the dynamic characteristics of the structural system by changing total mass and the distribution of mass within structure.  They act as energy dissipating mechanism and are classified in two major categories depending on their location and operating principles. When we focus on location wise seismic isolators they are generally categorised under the head of externally mounted seismic isolators and internally mounted seismic isolators. As the name suggests, external type seismic mounts are installed outside the structural location and cater to provide isolation externally through foundation of structure. Whereas, internal type seismic mounts act as an energy dissipating mechanism that provides internal stability through effective isolation. Natural disaster like earthquake cannot be prevented and is beyond human control but eliminating the potential damage by taking the precautions against the natural calamity is possible through equipment’s like seismic isolators.

 

Rubber mounts and rubber isolators for vibration and noise dampening in industrial machines

In Industrial engineering or in any manufacturing industry, most of the sound or noises are generated through rotating machine components that travel to the entire structure and mounting floor. The movement of machine parts result in high frequency sounds, vibration, and noise that affects the stability of structure and also results in the wear and tear of a highly accurate machine components.   Vibrational energy has its own independent effect on every machine tool components, which results in to uncertain machine break down and productivity loss. Technically, vibrational energy is a form of mechanical energy that moves through objects and disrupts the normal operation. In order to reduce the effect and transfer of vibrations, a scientific approach is adopted wherein vibration in any system is managed by either isolating it or by dampening it. Equipment’s like rubber mounts and vibration isolators are used for isolation of vibrating machines in the industry.

By installing rubber mounts or vibration isolation system, they prevent high frequency vibration from entering the system and dissipating the machine. Vibration isolation systems for mechanical components require some amount of damping. Damping dissipates mechanical energy from the system and attenuates vibrations more quickly. Without damping, the system will vibrate and ultimately lead to break down of the machine. One of the cheapest and best form of vibration isolator and dampening device is Rubber mounts.

Rubber mounts are usually made of neoprene or cork that are used in equipment mounting stage. Rubber mounts or rubber isolators are installed when mounting the machine.  This installation acts as a dampening layer between vibrating source and vibration receiver. It plays a vital role in industrial systems that face constant vibration issues. So, when induced with vibration it dissipates the energy by deflecting itself, ensuring minimum transfer of energy and regains its original position. Application and the area of source, which needs to be damped plays a decisive role in selecting the optimum size of rubber mounts. While there are rubber isolators as well that are used for small equipment to supplement air-handler internal isolation, or where there is little to no acoustical sensitivity.

Rubber Isolation mounts are majorly designed from cork and neoprene. They are available in many sizes solely dependent upon application. In situations where the cork pads lack to serve the purpose of vibration isolation, an alternative rubber isolator crafted from neoprene pad is used, which yields more deflection and better vibration isolation. Another factor to be taken in to account while selecting rubber isolators is the operating frequency at which the source transfers energy to the receiver. Frequency plays a vital role in selecting the form and structure of rubber mounts and isolators. Complex internal structure and variable density of dampening material used in developing rubber mounts and isolators, offer desired results and is suitable for various application. Rubber mounts and isolators prove to be very effective equipment’s that help control vibration and noise issues especially at a very reasonable operating cost.

 

Operations and application of seismic mounts for industrial areas prone to earthquake

As per principles of law of conservation of energy, it states that energy is neither created nor destroyed, it is only transforms from form to another or transferred from one object to another. Based on these principles, Mechanical vibrations are nothing but just a form of energy interchange between kinetic and potential energy.  Even in case of vibrations, the energy from the source or creator (mechanical elements like motors, engines, pumps etc.) gets transferred to the adjacent elements like structure and other mechanical elements of the system. Vibrations are also often caused due to external factors like the earthquake which has a direct impact on machines. So, to protect industrial machines from such high frequency vibrations the structures need be equipped with equipment’s like seismic mounts.

Seismic mounts are widely used instruments in locations that are prone to earthquakes or seismic disturbances and considered a potential hazard. Seismic mounts help isolate and dissipate   vibrations caused due earthquake to ensure protection of installed equipment. Basic features of seismic mounts are to offer rugged/ rigid support through its fabricated steel construction and heavy duty stable steel springs. They are equipped with acoustic isolation pad which dampens seismic vibrations.  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.

In normal operating situations, the seismic mountings provide vibration isolation generally equivalent to open spring mountings but, when subjected to physical displacements such as those generated by heavy seismic forces, equipment motion relative to the supporting structure is restricted. When correctly selected, seismic isolators will allow conformance to the design requirements and offers strong stability to the structure. Seismic isolators are equipped with multiple options depending on the load and structural stability required at the given time. Strong housing combined with spring and rubber provides maximum isolation from seismic vibrations and safeguards loaded mechanical equipment’s. Depending upon the application and loading arrangement single steel spring loaded seismic mounts or multiple steel springs loaded seismic mounts are used.

The construction of seismic isolators offers maximum flexibility which enables easy movement and re-location of mechanical equipment while also offering maximum support and resistance to the high frequency vibrations. The housing shall serve as blocking and, restraining bolts have a neoprene bushing between the bolt and the housing. One of the most common construction includes hot dipped galvanized steel housing, oil-resistant high frequency spring base isolation cup and resilient rubber base cup to provide acoustical isolation from vibrating steel spring components. Since housings are bolted or welded in position, there is an internal isolation pad. Housing are designed to resist all seismic forces.

When selecting a seismic mount, it is recommended that the calculated mass of equipment is increased 10-20% to avoid overloading of any mounting. For equipment using more than four mountings, ensure to distribute and locate them so that each mounting has equal loading. If this cannot be done, mounting selection must be made on the basis of matching static deflections as closely as possible. Seismic spring mountings shall permit freedom of equipment motion at normal operating conditions but restrain the equipment from excessive motion when subjected to foundation displacement in any direction.

 

 

Isolation equipment’s like rubber mounts and rubber hangers for dampening of vibration issues in the industry

Vibrations and dynamic chaos is highly undesired phenomenon in machines as well as mechanical or civil structures. These uncontrolled mechanical energies create disturbance, discomfort, and damage the entire mechanical system or the structure. It degrades the accuracy and precision level of the machines, resulting in heavy losses in terms of energy and resources. For these reasons, money, time and effort are spent to get rid of both vibrations and noise or chaos or to minimize them. In order to tackle the adverse effects generated through vibrations it becomes essential to understand the type of vibrations created in system and accordingly install vibration isolators.

ANDRE Rubber Mounts RMD Series

ANDRE Rubber Mounts RMD Series

The vibration isolation techniques are employed based on the type and severity of vibrations. Across the industry, vibrations are categorized under the category of either Active vibration or Passive vibration. As the name suggests, active vibration is the technique of isolating undesired vibrations or mechanical energies through installation of sensors and actuators that produce disruptive interference and creates counter effect on incoming vibrations. On the other hand, the methodology adopted to isolate undesired vibrations by means of buffering elements that creates layer between source of vibration and receiver, protects from undesired effects created through vibrations. The role of passive isolator is to absorb mechanical energies and deflect within the elastic limit under the action of load. It should be capable to regain its original shape and size once the load discontinues. One of the most popular and effective means of vibration isolation includes rubber mounts & rubber hangers.

Elastic properties of rubber permit maximum absorption and flexibility when subjected by undue vibrations. Flexibility in rubber polymers dissipates the energy and ensures minimum transfer of energy from source to receiver of the entire system. Rubber mounts are widely adopted in all automobile, industrial and non-industrial applications. Type and selection of rubber mount for a particular application is extremely critical hence, utmost care and all set of parameters needs to be taken in to account while selecting perfect rubber mounts for any set of application. One of the most basic factors to be taken in to account is the size of vibrating source. Size of system to be isolated defines the size of rubber mount. Smaller the vibrating source lesser the number of rubber isolators to be installed whereas, larger systems demand for multiple rubber mounts and isolators.

Secondly weight of system to be supported defines the type and section of rubber mounts to be selected. All rubber mounts are designed to support and work under the specified load range and any kind of overloading results in loss of isolation property as well as shelf life of rubber mount. Factor which governs any isolation methodology depends on the application in which it needs to be installed. If rubber mounts need to cater the requirement in corrosive environment, it needs to be designed and equipped with special materials or in case of acoustic environment which requires optimum level of noise reduction then, properties of rubber isolators need to be taken in to considerations. Rubber isolators and mounts are considered to be an effective solution to all vibrations problems faced across the industries.

 

 

How does a wire rope isolator work as an effective vibration dampening system?

Vibrations in industrial system is usually termed as the undesired mechanical energy generated due to rotating or sliding motions mechanical parts which when transmitted to the other elements of mechanical system results in inefficiency and loss. Vibrations tend to damage machine and sensitive electronics installed in the system. hence it becomes a challenge for any designer to reduce it to the maximum possible extent. Designers while designing any system often incorporate one of the most effective devices, which isolates the source of vibrations from the receiver and restricts the flow of energies by acting as a barrier. Modern day system designs widely incorporate equipment’s like the wire rope isolators, air springs, or elastomers.  However, the inherent property and construction of elastomers restrict its application to attenuate noise and vibration levels. On the other hand, wire rope isolator proves to be very effective and efficient to attenuate noise, vibration levels and shock too.

anti-vibration mount wire rope isolator

anti-vibration mount wire rope isolator

Wire rope isolators distinguish itself with the capability to tackle shock along with undesired vibrations, which affects the system to the maximum extent and assists designer in building noise free, vibration free and shock free system. One of the most widely adopted construction of wire rope isolators is made up of stranded stainless-steel cable that thread through aluminium-alloy retaining bars know as mounting brackets in industrial terminology. It is observed that for a specific application in specific environment, split bar is clamped on to the cables to offer required stability and strength for better vibrational control.

Application and compatibility of wire rope isolators have extended its use in every industry that makes it essential to be constructed for all working environments. In case of chemical industry where highly corrosive and volatile chemicals tend to showcase its effects on all metal component wire rope isolators need to be built with specific corrosive resistant material. Corrosion resistant metal construction gives the wire rope isolators a design strongly unaffected by temperature extremes, ozone, chemicals, oils, and abrasive environment. In modern day industry, it is very challenging and expensive to keep equipment perfectly balanced to get consistent results. Just by adding wire rope isolators on the required element, it protects machine structure, machine welds and brackets from fatigue regaining structural strength and improving performance life of the machine.

Wire rope isolators not only improves machine life, machine stability and machine welds but it also helps in building a system that can deliver consistent and reliable results with accuracy and precision. Wire rope isolators prove to be very effective and efficient because of its below mentioned characteristics which enable designer to build a strong and reliable system. Read the below given characteristics to better understand the features of wire rope isolators.

• Satisfies seismic building code requirements.

• Possesses high damping capacity and doesn’t require additional devices.

• Response can be reliably calculated with appropriate software.

• Offers mitigation or reduced magnification of seismic inputs.

• Modularity allows for customized of wire rope isolators

• strong and Versatile mounting system

• Has the capability of withstanding extreme temperature and resistant to any kind of chemicals, fluids, etc.