Noise and Vibration
This section of the Specification covers the Supply, Delivery, Installation and Testing of Noise and Vibration Control Equipment to be used in the isolation of the various mechanical equipment as called for in this specification.
It is the intent of this Specification that noise levels due to mechanical equipment and related services will be controlled to the design objectives stated herein, in all occupied areas. The requirements specified are considered to be the minimum precautions necessary to achieve these objectives. The entire installation shall operate without objectionable noise and vibration as determined by the Engineer.
This Specification covers the supply, delivery to site, installation, commissioning and guarantee for two (2) years of the noise and vibration control equipment as described in the Specification including schedules of vibration control equipment and drawings.
The Sub-Contractor shall select and provide all mechanical equipment to the Specification, complying in particular with the requirements concerning balancing of the equipment, alignment of driving and driven units and operating speeds.
The Sub-Contractor shall install all mechanical plant and services in accordance with the methods of installation and precautions stated herein, and such additional precautions as may be necessary to ensure that the operation of the plant does not result in noise levels or vibration amplitude beyond the specified limits.
The Sub-Contractor shall examine all drawings and specifications including architectural and structural sets of working documents, before commencing any work on the project and shall immediately bring to the Engineer's attention any characteristics or properties of the building or any other factors which, in his opinion, would jeopardize or nullify the attainment of the design objectives.
The Sub-Contractor shall guarantee that the complete plant and installation, when operated within the design criteria, shall acoustically perform to the noise criteria specified in this section.
The Sub-Contractor shall be responsible for any corrective action which may be necessary either during construction or after completion of the works, to achieve all design objectives.
Design Objectives
Octave band sound pressure levels in the various areas within the building and at certain position outside the building due to the operation of the equipment included in this Sub-Contract shall not exceed the noise level ratings set out in the following schedule.
Where dispute arises over the classification of area under the following schedule, the Architect's area, as listed below shall be final:-
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The specified noise level limits apply to every position from 1m to 2m from the floor not closer than 1.5m from any air outlet, or equipment.
Environmental exterior noise limits are imposed on all equipment operations. Noise breakout of the equipment to the exterior shall be controlled.
Environmental vibration levels criteria shall be subjectively virtually imperceptible with respect to fellable vibration, for the majority of people, and shall at the same time, not allow reradiated structure-borne noise levels to exceed approx. NC 35 to minimise contribution to airborne noise in the audible region.
Minus 60 dB re 1G from 2 Hz to 10 Hz and
Minus 55 dB re 1G from 10Hz to 31.5 Hz
Anti Vibration Equipment / Techniques
The following summarises the type and nature of the noise and vibration control techniques and equipment to be used in the isolation of the various mechanical equipment as described in this specification:-
Steel Spring in Series with Neoprene Pads
Unless specified otherwise, spring type isolator shall be unhoused, free-standing laterally stable with levelling bolts rigidly bolted to inertia blocks/base frames. In general, diameter shall be comparable with compressed height at rated load, and horizontal spring stiffness shall be approximately equal to vertical stiffness.
Spring shall have a minimum additional travel to solid, equal to 50% of rated deflection, and in this condition, shall not exceed elastic limit of spring.
All spring shall be mounted with adequate clearance from brackets and shall be clearly in view or critical inspection.
The following spring types will meet this specification on unhoused springs:
Mason Type SLFH
Vibran Engineering (M) Sdn Bhd
86B, 2nd Floor, Jalan SS 15/4
47500 Petaling Jaya, Selangor
Kinetics Type S (preferably type FDS)
Mecomb Malaysia
46700 Petaling Jaya, Selangor
Other makes/type of isolators with known load/deflection curves may be used, subject to approval by the Engineers.
Where restrained mounts are specified, a housing shall be used that include vertical limit tops. A minimum clearance of 10mm shall be maintained around the restraining bolts and between the housing and spring so as not to interfere with spring action. Limit stops shall be out of contract during normal operations. Mounts used outdoors shall be hot dipped galvanized.
Typical selection: Kinetics FLS
Korfund WSCL
Mason SLR
WMC AWR
All steel springs shall be installed in series with two layers of neoprene ribbed or waffle pattern pads (min 8mm thickness) as described below.
The Springs shall be selected to support the calculated loads with the minimum spring deflections as specified without being compressed solid, or bridged out, or exceeding the Manufacturer's maximum rated loads under any operating condition.
In the selection of the springs, the Mechanical Contractor shall also take into account the weight distribution of the equipment under normal operating conditions, weight of unsupported pipes/ducts, and any large dynamic forces due to fluid movement, torque reaction and starting/stopping. The shop drawings submitted, the make and model number of the isolators selected and their individual calculated loads.
Inertia Blocks
To be installed where specified. The mechanical equipment shall be bolted directly on to the integral concrete inertia blocks. All concrete referred to in this specification should have a density of at least 2240-2400 kg/cu m. (140-150 lb/cuft).
In general, the length and width of the inertia block should be at least 50% greater than the length and width of the supported equipment, except where otherwise specified.
The weight of the inertia block, generally determined by thickness shall be as specified.
The base shall consist of a concrete slab cast into a welded steel base frame assembly. Frames shall be welded steel channels, of minimum 150mm (6") thickness or the same thickness as the Inertia Block and shall be reinforced with welded in 12mm (½") steel reinforcing rods or angles at 150mm (6") centres each way. Anchor bolts shall be fixed into position, and housed in steel bolt sleeves to allow minor bolt location adjustments or alternatively, pockets shall be cast into inertia block to permit the later insertion of anchor bolts.
A suitable base former of min. 10mm plywood or equivalent shall be included for forming the slab. Steel channel isolator brackets shall be welded directly to channel frames, and suitably located to accommodate the height of the deflected springs and inertia block clearance with plinth.
There shall be adequate clearance (min. 20mm) all round the spring to assure that there is no contact between any spring and any part of the mounted assembly for any possible alignment or position of the installed inertia block. The clearance between inertia block and floor/plinth shall be at least 75mm (3").
The Sub-Contractor shall supply and install all welded structural steel and reinforcement required for the inertia blocks and shall co-ordinate his installation with the main contractor who will supply the concrete. All installation work concerning these items are included with this Sub-Contract.
Ribbed or Waffle Pattern Neoprene Pads
To be used were specified - 8mm (5/16") - 9.5mm (3/8") thick 40 durometer pads as normally supplied by the manufacturers.
For typical applications, 40 durometer type neoprene pads should be loaded to a surface weight of approximately 35,000 kg/sq.m. (7150 lb/sq ft.).
Where two or more layers of neoprene pads are used, individual layers shall be separated by 1mm (20 g) thick steel shims.
Resilient Hangers
Resilient hangers are to be used for resilient suspension of pipes and ducts, where specified.
For specified deflections in excess of 12mm use spring in series with neoprene type, and for deflections less than 12mm use neoprene in shear type hangers:-
e.g.
Masons type PC3ON (Spring/neoprene and type WHD (neoprene).
Masons type PC3ON (Spring/neoprene and type WHD (neoprene).
Kinetics type SFH, SRH (spring/neoprene) and types FH, RH (neoprene)
VMC Series SH (Spring/neoprene and RHS (neoprene)
During installation, inspection shall be made to ensure that no hangers are compressed solid or bridged out, and that the stipulated minimum deflection are achieved.
Neoprene in Shear
Neoprene-in-shear isolators shall be of the double deflection type as supplied by the above manufacturers e.g.
Masons type ND
Kinetics type RD
VMC type RD/RDP
The isolators shall incorporate cast-in tapped steel loads plates to permit direct bolting to supported equipment. Cast-in drilled baseplates shall also be incorporated for direct mounting to plinths.
The isolators shall be selected to achieve the minimum deflection specified, without exceeding the manufacturer's published maximum permissible loadings.
Refrigeration Plant
Centrifugal and reciprocating chillers shall be mounted on steel springs in series with neoprene as described in the Schedule of Vibration Isolators. Limit stops are required to limit travel when machine is drained. A steel base frame suitable for point loading of the Chillers shall be provided as approved by the Engineers.
Pumps
All pumps shall be selected for the highest efficiency consistent with the specified duty and pump impeller diameter capability of the pump housing to reduce the possibility to tonal effects.
Pumps impellers, shafts, and drive couplings shall be statically and dynamically balanced to the best commercial standards, and vibration and amplitudes shall not exceed 0.02mm peak to peak displacement at 1500 rpm when measured on the machine structure, with the pumps/motors mounted on the inertia blocks specified.
The pump and motor assembly shall be mounted on a concrete filled inertia block and completely isolated as specified in the Schedule of Vibration Isolators. Pumps inertia blocks shall be sized to support the weight of elbows valves and other fittings without creating undue stress on the pump assembly.
Pump speeds shall not exceed 1500 rpm except with the approval of the Engineer.
Cooling Towers
The cooling towers together with all associated pipework shall be vibration isolated as described in the Schedule of Vibration Isolators.
Cooling Towers shall be of the low noise type, with maximum permissible sound pressure levels, dB re 2 x 10--1, N/m 2 of each tower at 2m from the side casing and 1.5m from the floor level in an open environment shall be :-
Hz
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dBA
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63
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125
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250
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500
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1K
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2K
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4K
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Max. LP at 2m from side casing of each tower
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75
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77
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79
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76
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75
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70
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69
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66
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The Sub-Contractor shall submit published sound rating data on all cooling towers offered for evaluation. All data shall be expressed as Sound Pressure Levels (SPL re 20 MicroPascals) in dBA and octave bands (63 Hz to 4000 Hz inclusive) at distances of 1.5m and 15, from the side casing of the tower. Measurements shall be made in an open environment and shall include levels in the direction of fan axis (or tower discharge axis) and two horizontal axis.
All data shall include :-
Name of Manufacturer, Model Number and type of fan.
Specification of proprietary noise reduction equipment included and/or available.
All data shall be obtained under the Mechanical Design Conditions specified at full fan speed.
Air Handling Units, Packaged Air Conditioning Units and Ventilation Fans
All air handling units and packaged air conditioning units shall be mounted or hung on steel spring isolators in series with neoprene pads, as described in the Schedule of Vibration Isolators.
All fans shall have complete impeller assemblies including drive components, and statically and dynamically balanced to the following maximum allowable criteria:-
Equipment Max. Allowable Residual
Unbalance in Kgm per Kg
Weight of rotor x 10-6
Ventilation and Air
Handling Units
(Centrifugal & Axial)
Under 600 rpm 8
600 - 1000 rpm 3
1000 - 2000 rpm 1.5
Over 2000 rpm (impeller speed) 1.2
The Sub-Contractor shall not select nor use air handling units that operate in excess of 2000 rpm without prior approval of the Engineer/Acoustic Consultant.
Vibration levels of blower/fan/impeller assemblies in all ventilation, air handling and packaged units measured on bearing caps of the built up unit on site shall not exceed 6 mm/s RMS in radial direction, and 4mm/s RMS in axial direction. The Sub-Contractor shall at the Sub-Contractor's own cost ensure and warrant that such vibration levels are complied with.
As part of this Contract, the Sub-Contractor shall supply the Sound Power Levels (re 10-12 watts) of all fans and AHUs offered.
All connections between Air Handling Units/fans and Ductwork shall be properly aligned and executed using flexible material (e.g. lead impregnated PVC or equivalent). If flexible material is used, it shall have a min. surface density of 5Kg/sq.m. (1 lb/sq ft.) and min STC 22.
Typical Selections:
Non Flame Proof type Flame Proof type
Kinetics KNB-10C Kinetics KNM-100B
Woods BM 1060 Woods BM 1185
All ventilation fans and air handling units shall be fitted with sound attenuators (on both the upstream and downstream sides of the units with respect of occupied areas) as provided for in the Schedule of Sound Attenuators. The performance values (dynamic insertion losses, air quantities, frictional losses) are given as a guide only and the precise requirements will depend on final fan selections, duct layouts, design criteria for various areas.
In cases where fan and AHU sound power levels exceed the values listed in the Schedule additional attenuation may be required.
The Air Conditioning Sub-Contractor shall submit, with the proposed shop drawings, his sound attenuator selections based on these factors. Where additional fan attenuation is required on fans (to meet the noise criteria), this shall be provided by the A/C Sub-Contractor at no additional cost to the Owners.
Where proprietary type sound attenuators are not specified, all ducts upstream (where shown on the drawings) and downstream of AHUs and fans shall be internally lined with fibreglass or rockwool for sound attenuation as specified in Clause 7.15.
Fan Coil Units
All fan coil units if supplied under the Contract, shall be suspended on neoprene in shear hangers of at least 6mm thick static deflection.
All piping serving fan coil units shall be isolated by rubber sleeves where suspended or attached to the structure. There shall be no solid connection between fan coil units and the structure. Discharge ducts shall be fitted with flexible connections.
As part of the Contract, the Sub-Contractor is required to supply noise level emissions of their proposed fan coil unit in terms of dB re 10-12 watts (db-LW) from 125Hz to 4000 Hz inclusive for all available fan speeds (where variable speed units are employed).
The Sub-Contractor shall supply test data from a recognised testing authority to substantiate the sound power level performance specified.
Fan Coil units emitted sound power levels in dB-LW re 10-12 watts, in general, shall not exceed the following values for the various occupied areas requiring the following maximum noise criteria:
Max Area - Noise Criteria
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Max Allowable dB-LW re 10-12 watts
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125 250 500 1000 2000 4000
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NC 40
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65 57 51 48 48 44
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NC 45
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68 60 55 53 53 49
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Piping
In general, water pipes shall be sized to maintain average flow velocities of no more than 2.2 m/s.
The first three hangers/supports from all Mechanical equipment shall be spring in series with neoprene types as specified in the Schedule of Vibration isolators.
All other supports/hangers beyond 100 diameter of pipe length shall incorporate an isolation medium of 8mm thickness such a waffle pattern neoprene, felt or high density fibreglass between pipe and hanger/support or between hanger/support and wall. This applies to all piping installed on this project, whether in horizontal runs or vertical pipe risers.
All pipe penetrations through wall, floors and ceiling shall be isolated from direct contact with the structure, with a fibreglass isolated sleeve caulked with a non-setting resilient compound on both sides of the penetration.
Ductwork
All ductwork shall be rigidly constructed and braced to prevent `panelling' due to airflow.
Where internal lining of ducts are used for noise attenuation, the acoustical lining material shall be fibreglass of not less than 48 Kg/cu.m. or rockwool of not less than 64 Kg/cu m. (3 to 4 lb/cu ft) density, and faced with 0.701mm (24 g) galvanised steel perforated sheet of min 30% open area.
The extent and thickness shall be as shown in the drawings or as follows, whichever is greater;
DUCTWORK
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EXTENT & MIN. THICKNESS OF LINING
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AHU/Packaged Units Supply Air and Return Air ductwork where silencing is otherwise not specified (either by silencers or lined ducts).
Ventilation Systems Ductwork connected to axial and centrifugal fans where sound attenuators or linings are not specified.
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Line internally all air and return air ducts from AHUs distances of 5m from discharges and intakes respectively with absorption material thickness of 50mm for the longer duct dimensions greater than 300mm and 25mm for similar dimensions less than 300mm.
Line all intake and discharge ductwork 4m from fans with absorption material thickness of 40mm for the longer duct dimensions greater than 300mm and 25mm for similar dimensions less than 300mm.
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Sound Attenuators (Dissipative Type)
Sound Attenuators shall consist of an outer casing, sound absorbing material and internal baffles, splitters and supports. Casings shall be of galvanised steel of not less than 1.311mm (18 g) thickness. Casings shall be tested to 150 kPa and shall show no leakage or distortion in this condition. Duct sealing compound shall be furnished by the supplier for sealing all silencers on site, where necessary, as determined by the Engineer.
Sound absorbing material shall be high density fibreglass or mineral wool, held in place with at least 5% compression to prevent voids due to settling. Absorption material density shall be min. 95-130 kg/cu.m. (6-8 lb/cu ft) rockwool, or min 48 Kg/cu.m (3-4 lb/cu ft) fibreglass, faced with min. 0.5512mm (26 g) perforated galvanised sheet metal of min 20% open area.
Combustion rating for the silencer acoustic infill shall not be less than the following, when tested in accordance with ASTM E 84.
Flame spread classification - 25
Smoke Development rating - 0
Fuel contribution - 20
The Supplier shall supply certified test data on dynamic insertion loss and self-noise with an airflow of at least 7.62m/s (1500 ft/min) face velocity. Ratings shall be determined in a duct-to-reverberant room test facility which provide for air flow through the test silencers during rating. Static pressure loss of silencers shall not exceed those listed in the silencer schedule as the airflow indicates. Airflow measurement shall be made in accordance with the applicable portion of the Air Diffusion Council (ADC) air flow test code. Tests shall be reported on the identical units for which the acoustic data is presented.
The minimum insertion losses requires are given in the Schedule of Sound Attenuators.
Maximum Supply Air Outlet Sound Power Levels - Guide to Selection
In order to meet sound levels specified elsewhere, supply air outlets shall generally have sound power levels not higher than those set out in the above schedule when delivering the specified air quantities. In case of outlets equipped with integral volume controls, the values stated apply to an outlet delivering the specified air quantity with a pressure drop not less than 1.3 kPa across the volume control or at the required control setting for the specified air quantity.
LOCATION
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SOUND POWER LEVELS IN - 12
dB re 10 watts
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250 500 1000 2000 4000
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General Office, and Clerical Areas
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50 45 41 39 36
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Retail, Supermarket, Shop lots, Department Stores, Corridors |
56 52 49 47 46
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For control of duct regenerative noise in critical spaces as indicated below, internal lining of ducts are to be implemented (as described in Section 13.2) upstream from the supply air diffuser for a minimum 2m length to the takeoff point of the branch duct. Note standard details SD-M-228.
The areas are General Office and Clerical areas.
The in-line duct velocity for the supply air take-off duct generally should not exceed 2.0 to 2.5 m/s (400 to 500 ft/min).
Testing On Completion
Sound level and vibration measurement shall be made by a testing authority approved by the Engineer. Should the tests show that noise or vibration is in excess of those specified, or that balancing of equipment is incorrect, or that vibration transmission through mountings, hangers, etc. is excessive, the Sub-contractor's shall correct the installation at his own cost. Further tests shall then be carried out at the Sub-Contractor's cost to show that the noise and vibration levels have been reduced to the limits specified.
Sound level readings shall be taken at times when the building is unoccupied or when activity in surrounding areas and background noise levels in areas tested, are at a minimum and relatively free from sudden changes. Readings
All apparatus used for sound and vibration measurements shall be approved by the Engineer.
Noise levels shall be measured with a Sound Level fitted with an Octave band analyser and conforming to International Organisation for Standardization IEC-179 and IEC-225. Overall sound levels shall be read on `A'Scale of the meter and octave band sound levels on an octave band analyser connected to the meter with its C Scale network in use.