Modern Building Services

MODERN BUILDING SERVICES MARCH 2022 21 Spring and Rubber Hangers Spring hangers absorb vibration and vibration-related noise of low frequency suspended loads such as pipework, ductwork, fans and other HVAC equipment. They can include a rubber spring base cup to prevent contact between the housing and the spring, giving better efficiency. A Rubber Hanger uses a rubber absorber in place of the spring, and is usually applied in ventilation and AC systems. Sometimes they are also adjustable for use on sloping ceilings. Rubber Isolators Rubber isolators are for preventing metal-to-metal contact in machinery, generators and HVAC equipment, to prevent the transmission of vibration and noise. They are versatile and come in a range of sizes and styles. Rubber Absorption Blocks Rubber absorption blocks come in a range of configurations with either internal or external threads, or both. They are ideal for use with all kinds of elastic suspension or mounting of equipment, particularly if there is metal-to- metal contact. Rubber Pads Anti-vibration rubber pads are large rubber mats that can be cut to size for placing between the machinery and the building structure to help absorb noise and vibrations. They are commonly used for working machinery. How to select the right solution There are a number of general considerations to make when reviewing the vibration isolation needs of a HVAC installation. These would include: Equipment specifications Different types of HVAC equipment will require different solutions. You need to consider the size and weight of the equipment or pipework and its structural attachment points. This will give you an idea of howmany mounts you’ll need, and the size of thosemounts. Location of equipment The location and support surface of the equipment can affect which types of isolator are required. For example, is it ceiling mounted, floor mounted on a slab in a basement, or is it outdoors on a building rooftop? Vibration excitation of the equipment The rotational frequency (revolutions per minute) of the machinery contribute to the levels of vibration. The forces and couples generatedwill influence the isolators required to dampen the vibrations. Type of building Different types of building can have different requirements for vibration and acoustic isolation. For example; an entertainment venue, industrial facility or luxury apartment block may have more significant requirements or expectations than some other buildings. Environmental considerations Whether the equipment is placed indoors or outdoors can make a big difference, but under all circumstances, you need to consider environmental factors such as the degree of corrosivity and the minimum and maximum ambient temperature near the equipment. Special requirements For example, are there electrical, pipework or ducting connections that might modify the mechanical response of the mounting system? Are there any externally applied forces or moments; minimum or maximum clearance requirements between equipment and foundation; alignment requirements; or dynamic loads? Once you have a full overview of the installation requirements and external considerations, you need to select the anti-vibration mount or isolator that provides you with the most efficient solution. A mount with soft rubber would isolate vibrations more, but if the rubber is too soft for the application, it might not be able to recover from deformity caused by the stress forces of the equipment, and it will not be as effective. Therefore, you need to determine the level of vibration transmission to the structure so that you can select a product which is capable of dampening the vibrations effectively. The simplest way to determine vibration transmission to the structure is to use static deflection and vibration isolation efficiency charts for the products you are looking at. Effective noise vibration control can help prolong the life of machinery and subsequently reduce costs whilst ensuring a comfortable and safe environment for building occupants. FEATURE WORKING BUILDINGS