Modern Building Services

20 MODERN BUILDING SERVICES MARCH 2022 WORKING BUILDINGS T he operation of mechanical and electrical equipment and services generates varying degrees of noise and vibration which, if left untreated, have the potential to cause damage to the equipment itself as well as disturb occupants within a building. Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations. What is vibration? In simple terms, vibration is a mechanical phenomenon where oscillations occur about an equilibrium point. These vibrations can resonate through equipment, fixings and the building structure to create undesirable noise and discomfort for the building occupants. In the HVAC industry, most sound or noise is generated via equipment in operation and air and fluid movement through ducts and pipes. What are the effects of vibration? Unresolved vibration can cause problems affecting both the equipment itself, the building and its users. Recurring vibrations can cause: • Damage to the equipment • Transmitted noise • Discomfort for people • Safety issues for those near the vibrating equipment • Damage to the structure of the building • Increased maintenance requirements for the equipment • Decreased lifespan of the equipment • Malfunctioning equipment • Violation of regulatory requirements These potential issues are why vibration isolation is so important. What are the most common sources of vibration in buildings? HVAC equipment that is rigidly attached to a slab, wall, or ceiling can transmit vibration into the supporting structure and cause highly undesirable levels of structure-borne noise. This noise can travel far and can even spread throughout the building. Alongside the HVAC equipment, theM&E services such as pipework, conduits, and ductwork can also act as transmitters of structure-borne noise if they are rigidly connected to vibrating equipment. Other sources of vibration and noise can include imperfect joints and/or connections, general fatigue andwear of components and flowing air or fluids. Types of equipment that typically require some sort of vibration control include: • Air con units • Heat pumps • Ventilation ducts • Compressors • Power generators • Suspended piping systems • Rooftop HVAC equipment • Inline fans • Industrial processing machinery How to resolve vibration? Vibration isolation is the key to solving the problem. Isolating the source of vibration from the supporting structure is typically the most efficient approach to eliminate vibration. Carefully selected vibroacoustic isolators need to be placed, where possible, directly in between the mounting structure and the equipment that produces unwanted vibration. The isolators can then effectively absorb up to 99% of excess vibration produced by the equipment. What are vibroacoustic isolators? Products that are used to deal with vibration in HVAC equipment and services include anti-vibration mounts, spring hangers, rubber mounts and rubber sound absorbers. Products can be made of rubber, steel or a combination of both. When the machine is being used, the isolators absorb and dampen vibration, significantly minimising the impact of vibration, such as noise. Spring Mounts Antivibration spring mounts are primarily used for low frequency vibration damping (slow speed rotation around 600 RPM upwards). This could include applications like air handling units, cooling towers, chillers, air compressors, etc. Spring mounts can consist of individual or multiple open springs, or encased spring mounts for heavier equipment loads, or where stability is a problem. Rubber Mounts Rubber or elastomer mounts are suitable for machinery with radial vibration (rather than axial), and equipment prone to starts and stops. They are ideal for equipment with high frequency vibrations above 2500RPM. Rubber Levelling Mounts Rubber levelling mounts perform a similar role with the added benefit that they don’t need to be fixed to the supporting structure. They are suitable for outdoor ACUs, axial and radial fans, motors, pumps compressors and more. Raajan Bains , Technical Support Adviser at Walraven, gives an insight into the basics of vibration control in building services. FEATURE WORKING BUILDINGS Understanding the basics of vibration in HVAC