When the fan, water pump, refrigeration compressor and other equipment in the ventilation and air conditioning system are running, the vibration will occur because the mass center of the rotating parts deviates from the axis center. The vibration is transmitted to the supporting structure (foundation or floor), and transmitted to other rooms in the form of elastic wave from the foundation of running equipment along the building structure, and then appears in the form of noise, which is called solid sound. Vibration and noise will affect people's health, work efficiency and product quality, and even endanger the safety of buildings. Therefore, some operating equipment in ventilation and air conditioning need to take vibration reduction measures.
The vibration reduction measure of air conditioning device is to install the elastic component between the vibration source and its foundation, that is, to install the elastic vibration avoidance component (such as spring damper, cork, rubber, etc.) between the vibration source and the supporting structure, and to adopt the flexible connection between the vibration source and the pipeline. This method is called the active vibration reduction method. The vibration reduction measures are taken for the precise equipment and instruments that are afraid of vibration, so as to prevent the external vibration Their impact on this method is called the passive damping method.
To weaken the vibration transmitted by the fan to the foundation is actually to eliminate the rigid connection between them, i.e. to install a damping device between the vibration source and its foundation. If the fan is installed on the vibration damping pedestal, the vibration damper or damping pad shall be installed between the pedestal and the floor or the foundation, so as to cause the vibration damping effect.
The commonly used damping pads and dampers for ventilation and air conditioning equipment are rubber damping pads, rubber dampers, spring dampers, etc.
1. damping pad
It has good elasticity, large damping ratio and convenient manufacture. It is an ideal vibration isolation material in common use. It can be used in one or more blocks, but the rubber is easy to be eroded by temperature, oil, sunlight, chemical solvent and aging. This kind of damping device is mainly made of oil resistant NBR which has been vulcanized.
The rubber vibration isolation pad is to cut the rubber material into the required area and thickness, directly under the equipment. Generally, it does not need embedded bolts for fixation, is easy to process and manufacture, and is easy to install, but it is easy to age and deform, reducing the vibration reduction effect.
2. rubber damper
It is a cone-shaped elastomer made of NBR and pasted on the inner and outer metal rings under the action of shear force. It has low natural frequency and sufficient damping, good damping effect, convenient installation and replacement, and low price.
Generally, when the rotating speed of the equipment is n > 1200R / min, rubber shock absorber should be used. The relevant product catalog and design manual provide the necessary parameters, and the shock absorber can be selected after the unit weight and static compression amount are known.
3. Spring damper
It is composed of single or several springs and cast iron shields of the same size, which are used for the installation and hoisting of the unit base. It has the advantages of low natural frequency, large static compression, large bearing capacity, good damping effect, stable performance and wide application, but its price is relatively expensive. In addition, a 10 mm thick rubber plate is padded under the bottom plate of the spring damper, which can also play a sound insulation role.
When the rotating speed of the equipment is n < 1200R / min, the spring damper should be used.
4. Metal spring and rubber combined shock absorber
When the rubber shear damper can not meet the requirements of vibration reduction, and the metal spring damper is insufficient, the combination of metal spring and rubber damper can be used.
In the actual project, in order to facilitate the design and installation, some equipment, such as fans, water pumps, refrigeration units, etc., will be equipped with their own supporting damping devices, which can be installed directly according to the construction drawings.