Mechanical vibration isolator

The tool which is used to control vibrations and unwanted vibrations caused by mechanical devices such as motors, HVACs, chillers, pumps, etc., is called a mechanical vibration isolator. In industrial and mechanical environments, mechanical installations are usually supported by hanging or seated supports. However, in some constructions, such as hotels, hospitals and airports, there is an urgent need to control the vibrations of mechanical devices such as HVAC systems, chillers and pumps

Since most of these Installations use rotary motors as the source of developed vibrations, so non-restrain vibration not only spreads sound and mechanical vibrations to the surrounded environment and building structure, but also causes early wearing, exhausting, noise generation, loosening of connections, productivity reduction and increases maintenance costs

• Transposition and installation of machine, on the hardest possible foundation and at the farthest distance from potential receivers.
• Replacing a machine with a higher quality one or another type of machine that has less vibrations (of course, this method can be very expensive)
• Changing the speed of the device in order to prevent vibration in the structure
• Balancing the rotating components
• Add vibration absorber to the system
• Use active vibration control methods

Vibration reduction generally involves using vibration isolator springs and / or inertia blocks. The main purpose of using these inertia blocks is to minimize the frequency as much as possible. The relevant calculations in this field and the method of selecting vibration isolator are described further

Consider a vibrating machine that is screwed to a hard surface (fig. 1). The transmitted force to the surface is equivalent to the produced force by the machine. The transmitted force can be reduced by adding suspenders or damping components (that often are called vibration isolator, fig. 1b), or by adding inertial block (which is a large and heavy mass and generally it is concrete) which is directly connected to the machine (fig. 1c). The other method is adding an extra mass (sometimes under the name of vibrating mass) and suspend it (fig.1d)

Selecting vibration isolator

The vibration isolators are often classified with the Static deviation coefficient (Δ). It means that for calculating their deviation, when the machinery’s weight is imposed on them. This equation is for specifying their hardness and has other advantageous for simplifying calculation of the system’s normal frequency. The spiral spring vibration isolators are available up to 3 inches of deviation. If more flexibility is needed, فنرهای هوایی will be used. The system’s normal frequency (supposing a free degree) calculates with equation no. 7:

Δ : Static deviation of spring (inch)

g: the gravitational deviation of spring 386 in/sec^2

Important note is selecting vibration isolator

• The machine lay out
• Maximum possible distance to sensitive places
• Maximum foundation hardness
• Precise measuring of vibration isolators unit
• Adequate hardness / stiffness (specified by static deviation, generally more flexibility is better).
• Adequate transposition in order to prevent the spring collapsing / displacing when sudden loads occur or while the system is turn on and off
• Location of vibration isolators
• Loading on vibration must be done be done evenly and the machine must be balanced.
• Stability
• Side movements should be controlled by lateral vibration isolators. The spring diameter must be larger than the height of the spring compression. Vibration isolator springs must have an acceptable reliability level.
• Adjustment
• Spring must have free movement and must not be compressed completely, they also must not stroke.
• Eliminate short vibration cycle.
• Any mechanical connection between the machine and the foundation that removes the vibration isolator from the circuit, such as pipes, conductors, spring connections, etc., greatly reduces the performance of the vibration isolators and causes mechanical strokes.
• Safe performance destruction
• If the spring breaks or deviates, there must be mechanical supports so that the machine can be placed on them without any problems or damages.

More tips about selecting vibration isolator is described in the ASHRAE handbook.

• The intensity of the vibration

How much vibration is high? The recommended vibration for different applications is shown in fig. 8, 9 and 10.

.FANTAP Co

With the honor of being the first manufacturer of new constructional materials under the LINKRAN brand, FANTAP Co. is a well-known brand outside of Iran. As a manufacturer in the industrial and mechanical installations industry, FANTAP Co. is proud to SUPPLY national products with reasonable prices and global quality

FANTAP Co. offers a variety of installation support, including galvanized steel profiles , beam clamps , pipe clamps , air duct flange systems and mechanical vibration isolators with LINKRAN brand across .the country

 Researcher's name : Mr. Pedram Bodaghi & Mr. Behzad Mehrafrooz