Back to basics: Acoustics HVAC installations for vibration reduction - PDF document

Back to basics: Acoustics HVAC installations for vibration reduction Presented by Clem Sturgess Causes of vibration Vibration is generally transferred into the structure from out of balance or misaligned rotating equipment www. vibrationisolation .com.au

Effect of vibration on equipment Constant vibration forces from misaligned or out of balance forces act on the system like bending a piece of wire backwards and forwards www. vibrationisolation .com.au Vibration noise Vibration can travel easily through structures and is reradiated from walls and ceilings as noise, many floors away from the source of the noise. www. vibrationisolation .com.au

Effect of vibration on humans www. vibrationisolation .com.au Pipework Support It is important to isolate pipework that is connected to sources of vibration. Generally the pipes should be supported up to 100 pipe diameters from the source of the vibration. www. vibrationisolation .com.au

Pipework Support The spacing of pipework hangers is dependant on the size of the pipework, however, the pipework should be supported at all changes of direction. www. vibrationisolation .com.au Pipework Support Pipework should still be isolated even if a flexible connection is used. Water can take a large distance to settle into even laminar flow in pipework. Also under high pressures, the flexible connection may be not that flexible www. vibrationisolation .com.au

Seismic vibration mount •How they work Under normal operation, seismic mounts act like standard open springs www. vibrationisolation .com.au Seismic vibration mount •How they work 3mm gaps between central block and rubber provide support in the event of seismic activity www. vibrationisolation .com.au

Seismic vibration mount •How they work 3mm gaps between central block and rubber provide support in the event of seismic activity Seismic loading on equipment Force transmitted through to structure www. vibrationisolation .com.au Isolation Sleeves Prevents bridging the rubber on the base of the mount www. vibrationisolation .com.au

How Vibration Isolation Works www. vibrationisolation .com.au Natural Frequency When an object is struck. It will vibrate at its natural frequency. www. vibrationisolation .com.au

Static deflection The more a spring or rubber deflects under load, without compressing to solid, the lower the natural frequency of the mount. This is called the static deflection . www. vibrationisolation .com.au Resonance If an object is given repeated pushes at its natural frequency it will go into resonance. It will move slightly more each time until it gets out of control. www. vibrationisolation .com.au

Startup Issues As a motor ramps up from stopped to operating speed, it must pass through the resonant frequency. The equipment may require some restraint www. vibrationisolation .com.au Effect of height The higher storeys are inherently less stable than lower storeys. So the higher in the building, the more isolation is required. www. vibrationisolation .com.au

Important factors in vibration isolation selection Isolation Efficiency Chart Static Deflection Guide www. vibrationisolation .com.au The 6 most common vibration problems www. vibrationisolation .com.au

1: Fixed Pipe Stands Problem: Well isolated pumps or chillers connected to pipes with fixed stands www. vibrationisolation .com.au 1: Fixed Pipe Stands Problem: Well isolated pumps or chillers connected to pipes with fixed stands Fixed pipe Fixed pipe mounting mounting Isolated Isolated Equipment Equipment www. vibrationisolation .com.au

1: Fixed Pipe Stands Solution: Install spring mounts on the pipe stand base so that they match pump spring deflection or Support the top of the pipework using isolation hangers and remove pipe stand Pipe stand SHS spring hanger www. vibrationisolation .com.au 1: Fixed Pipe Stands Solution: Install spring mounts on the pipe stand base so that they match pump spring deflection or Support the top of the pipework using isolation hangers and remove pipe stand spring hanger Pipe stand www. vibrationisolation .com.au

2: Noise transmitted from isolated pumps Problem: Noise transmitted from isolated pumps Pumps on Pumps on isolated inertia isolated inertia bases bases www. vibrationisolation .com.au 2: Noise transmitted from isolated pumps Solution: Check under inertia base for nuts, bolts or other debris or adjust springs to raise pumps Shifter Nut Bolt www. vibrationisolation .com.au

3: Pipework hard fixed into wall or ceiling Problem: Noise transmitted from pipework passing through a wall or ceiling Spring mounted pipework next Spring mounted pipework next to a hard grouted wall to a hard grouted wall connection connection www. vibrationisolation .com.au 3: Pipework hard fixed into wall or ceiling Solution: Seal around openings for pipework with flexible mastic or insulation 10-15mm clear gap around pipe, filled 25mm thick Rockwool sectional pipe sleeve 10-15mm clear gap around pipe, filled 25mm thick Rockwool sectional pipe sleeve for a depth of 12mm with non-setting insulation around pipe. Rockwool is to be for a depth of 12mm with non-setting insulation around pipe. Rockwool is to be flexible mastic similar to Bostik encapsulated to prevent loss of fibres flexible mastic similar to Bostik encapsulated to prevent loss of fibres Fireban One. Fireban One. 75mm 1.2mm thick steel or copper sleeve grouted 1.2mm thick steel or copper sleeve grouted into wall with non-shrinking grout into wall with non-shrinking grout www. vibrationisolation .com.au

4: Bridging of spring hangers Problem: Rod is touching the side of the hanger cage, causing bridging of isolation element Bridging Bridging www. vibrationisolation .com.au 4: Bridging of spring hangers Solution: Realign pipe clip or hanger cage so rod is central to the hole in the hanger cage www. vibrationisolation .com.au

5: Hard bolted pipework Problem: Condenser pipework hard bolted to floor or walls www. vibrationisolation .com.au 5: Hard bolted pipework Solution: Suspend pipework from raised frame www. vibrationisolation .com.au

5: Hard bolted pipework Solution: Install new wall bracket and suspend pipes from the bracket. www. vibrationisolation .com.au 6: Generator vibration transmission Problem: Incorrectly adjusted spring mounting Springs not taking the Springs not taking the generator load generator load www. vibrationisolation .com.au

6: Generator vibration transmission Solution: Adjust the height adjustment bolts until the generator is supported by the springs only www. vibrationisolation .com.au Thank you for your time If you have any further questions or noise problems then please contact us on: Phone: 3359 7100 0408 409 168 Email: c.sturgess@embelton.com