** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
SECTION XX XX XX -NOISE AND VIBRATION CONTROL
1 - GENERAL
1.01 WORK INCLUDED
A. Sound Noise Levels
Attenuators
Vibration Control
Machinery Bases
1.02 RELATED WORK
A. All Mechanical sections.
1.03 SYSTEM DESCRIPTION
A. General
1. Acoustic and vibration transmission control shall be applied
on all work to obtain the limits specified.
2. Work included :
a. All duct systems and associated equipment will be
attenuated to prevent both transmission noise and
breakout from the equipment at any part of the
system.
b. All rotating plant will be adequately isolated from the
main structure of the building to prevent the
transmission of vibration.
c. All pipework will be suitably installed to prevent undue
strain upon equipment it is connected to and isolation
of rotating equipment is also required to prevent the
transmission of vibration.
3. All systems and equipment shall be selected and installed to
meet the required noise criteria specified herein. Where
items are not covered then ASHRE Guide shall be taken as
the reference.
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
4. All Noise and vibration control studies and material selection
shall be submitted to the Engineer for approval.
B. Noise Control Generally
1. System Description
a. Systems shall be installed on the basis of noise
control to produce the results set out in the schedule
below.
b. The equipment provided by the Contractor shall be
designed and arranged to maintain these criteria.
c. Where sound characteristics of selected equipment
gives excessive noise then attenuation treatment shall
be applied to achieve the desired criteria.
Where silencers are scheduled on the drawings the
Contractor shall be responsible for any adjustment in
size required the meet the desired criteria, based on
equipment finally selected.
2. Noise Criteria ( N.C.) level
The maximum acceptable noise level for the various areas is
as follows:
Location Specified Level
Corridors NC 35-40
Meeting Rooms NC 35
Administrative Offices NC 35
Toilets, Utility Rooms NC 35-40
Control Room NC 35
Supermarket Area NC 35-40
Retail Area NC 35-40
Shops NC 35-40
Store NC 35-40
Main Entrance NC 35-40
Cafés NC 35
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
3. In-Duct Attenuation
a. Purpose made attenuators shall be provided in the
positions indicated on the drawings. The attenuators
shall reduce the sound level produced by the fan to an
acceptable level in the occupied spaces. The
attenuator shall have adequate strength and cohesion
to resist erosion by the air flow and shall not produce
dust. The acoustic infill shall be free from odour and
proof against rot, damp, vermin. Adhesive shall be
compatible with the sound absorbent material and
shall be non - flammable.
C. Vibration Control Generally
1. System Description
a. All equipment and plant shall be so designed that it
does not, in itself, vibrate excessively, particularly if
its natural frequency is below 20 Hz. The apparatus
shall be mounted upon resilient mountings such as
cork, rubber or springs, loaded close to the maximum
and designed to transmit the least energy to the base
without permitting excessive oscillation of machines.
b. Select equipment with minimum out-of-balance
forces, use control devices to isolate equipment,
piping and ducting as necessary.
c. All rotating parts of equipment shall be balanced to
best commercial tolerances before leaving the factory.
1.04 REFERENCES
A. The latest editions of the following standards shall apply :
1. American Society for Testing and Materials (ASTM )
a. ASTM E477 : Testing Duct Liner Materials and
prefabricated Silencers for Acoustical and Airflow
performance.
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
2. ASHRAE Handbook : Systems - Chapter 35 Sound and
Vibration Control. This shall be referred to for items not
specifically covered in this section.
1.05 SUBMITTALS
A. Product Data
1. Description literature for each of the actual proposed
equipment to be used including:
a. Capacity.
b. Insertion Losses.
c. Pressure Losses.
d. Fluid Flows.
e. Test Reports.
f. Certificates of approval.
B. Shop Drawings
1. Shop drawing for each of the actual proposed equipment
shall include the following:
a. Working or manufacturing drawings.
b. Calculations.
c. Installation details.
d. Accessories available indicating those included.
e. Pictures.
2 - PRODUCTS
2.01 ATTENUATORS
A. Construction
The Contractor shall supply and fix acoustic insulation and noise
attenuator units where necessary to reduce the air borne noise
transmission through the distribution duct system, so that the specified
noise criteria levels are satisfied.
- Attenuator Units
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
The attenuator units shall be inserted in the ducts where they pass
through the mechanical room walls, the gap between the wall and
attenuator being packed with felt to form an air tight seal. However
where this is not possible, the attenuator shall be fitted in the duct
between the fan and the mechanical room wall with the duct
between the silencer and the wall acoustically lagged to prevent
noise re-entry.
Attenuators shall consist of attenuator splitters which are assembled
in one attenuator casing. Splitter case shall be made from
galvanized sheet steel: absorption material moisture repellent and
abrasion proof up to approx. 3600 fpm. (18 m/s) air velocity density
90 kg/m3 mineral wool, control plates on surface of splitters is
made from galvanized steel sheet.
Sound attenuator casing shall be made from galvanized sheet steel,
with pre-drilled angle flanges.
Attenuators or splitters of large cross section or length can be
manufactured in modular section as required for ease of site
handling.
- Internal Acoustic Lining of Ducts
- Furnish and install duct lining wherever shown on Drawings.
- Where it is possible to achieve the required attenuation by lining
the interior of duct runs, this may be accomplished by applying one
inch thick lining to the inside of the ducts.
- Lining for rectangular ducts shall be semi-rigid fibrous glass blanket
and for round ducts shall be flexible fibrous glass blanket, both with
special surface treatment and for apparatus casings, large plenums,
and masonry air shafts shall be rigid coated fibrous glass board.
- Acoustic insulation shall be suited to the atmosphere in which it is to
operate, and shall be incombustible or self-extinguishing no flame
spread grade, vermin proof and adequately fixed to ducting or
mechanical room walls. Liner density shall be 3 lbs. per cu. ft.
- Duct liners shall be applied with both mechanical fasteners and an
adhesive. Adhesives must be both water and fire resistant.
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
Mechanical fasteners could be either of the welded pin or impact pin
types. The length of each pin shall be enough to accommodate the
specified liner thickness. Washers on top of the pins shall retain the
liner.
B. Performances
1. Internal lining of ductwork shall be applied where necessary to
achieve the required level. The lining shall be 25 mm thick and
32kg/m3 density otherwise as described for attenuators above with
minimum thermal conductivity of 0.055 W/mC.
2. Where internal duct lining is to be applied the duct sheet metal sizes
shall be increased to compensate and thus maintain the net free
airway sizes noted on the drawings as duct sizes.
3. Internal duct lining shall have a factory bonded PVC coating fixed to
the insulation with a synthetic rubber base adhesive which is flame
retardant when dry.
2.02 VIBRATION CONTROL DEVICES
A. Vibration isolation by means of Polyurethane Elastomers with
open and closed cell structure; with a high damping efficiency
lasting for a very long time (10 years or more), and dynamic loss
factor between 0.1 – 0.3 to ensure the isolation of vibration and
structure borne noise.
B. Vibration isolation efficiency shall be 90% on high level on any
suspended floor and 85% - 90% on the ground.
C. Isolating Compensators : Where equipment is located on vibration
isolation mounts or hangers, isolating compensators shall be
used, such that the vibration isolation of the equipment shall be
bridged out.
D. Spring Mounts:
1. Where specified shall generally be of the unhoused steel
compression type having a height to diameter ratio not
above 2.0 in the loaded condition and providing means for
leveling the equipment. Housed type spring mounts may be
used only if the design is submitted and approved.
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
2. The spring design shall be such that the operating deflection
does not exceed 2/3rds of the maximum available
deflection.
E. Supplier should choose the most suitable and stable type of
Elastomers by presenting calculations on type of the Elastomer
chosen, its density, possible thickness, loaded surface area, load
distribution and permissible values of deflection for allowing a
very efficient vibration damping.
F. Suggested Elastomers should be resistant against concrete, oils,
greases, diluted acids, lye, water and aqueous solutions as well as
hydrolysis and ozone and not be attacked microbiologically.
2.03 MACHINERY BASES
A. Provide concrete bases for all equipments. Dimensions and
thickness of each base depends on type of equipment and is
included in calculations to be submitted for approval.
B. Contractor should coordinate with civil Engineer in charge and
should have his permission after checking the following points
during calculations:
- To check if the original slab could sustain the total load of
the machines and the concrete bases as per the given
loads.
In the other words, the load carrying capacity of the slab
has to be fully rechecked.
- To check again if the existing slabs on which the machines
are placed are stiff enough and not overloaded. The original
slabs should not be overloaded and the necessary
precautions taken with the usual margins.
3 - EXECUTION
3.01 EQUIPMENT CONSIDERATION
A. Fans
1. Flexible collar connections between fans and ductwork shall
be correctly aligned.
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
2. Centrifugal fans and motor assemblies shall be mounted on
a rigid common inertia base, the whole mounted on spring
and rubber vibration isolation mounts.
3. For all fans having motor size 7.5 kw or larger, bases shall
be of steel and concrete weighing as much as the fan motor
assembly. Bases shall be sufficiently rigid to resist any
twisting or bending forces, and any dynamic forces, without
creating vibration of the base of any other member of the
assembly.
4. All holding down bolts shall be installed so as to avoid
bridging of isolation.
B. Pumps
1. All pumps shall be selected for the highest efficiency
consistent with the specified duty, but it is generally
desirable that the pump impeller diameter should not
exceed 0.90 of the maximum impeller diameter capacity of
the pump housing to reduce the possibility of tonal effects.
The motor and pump assembly shall be mounted on a rigid
steel and concrete inertia base of equivalent weight to the
pump-motor assembly, the whole mounted on spring
isolation mount selected for at least 90% isolation efficiency
but in any case having a minimum deflection of 25mm.
2. Pump bases shall be designed to support the weight of
elbows, valves and other fittings without creating undue
stress on the pump assembly.
3.02 PIPING
A. Provide flexible couplings and vibration isolators for the water
circulating pump connections, to prevent the transmission of
sound throughout the building.
B. Isolate pipe hangers with ELASTOMETRIC isolators to reduce
vibration transmission to the building.
C. Floor supports for piping in equipment rooms and adjacent to
isolated equipments should use Elastometric vibration isolators.
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
D. Hangers adjacent to noise sensitive areas should be Elastometric
or spring and rubber combination.
E. Where un-insulated pipelines penetrate masonry walls and floors
between equipment rooms and riser ducts, riser ducts and ceiling
spaces etc., they shall be isolated from direct contact with the
structure be sleeving with high density fiberglass, felt or other
approved material. Care shall be taken to provide a full acoustical
seal at such penetrations.
F. Power leads, earth-wires, and service pipes shall be provided with
flexible connections at convenient points close to the machine.
3.03 AHU
Put Elastometric pads or spring isolators as necessary and
recommended by unit supplier under each AHU to isolate vibration and
structure borne noise with efficiency 85 - 90%.
3.05 VIBRATION ISOLATOR SCHEDULE
Isolation
Equipment Isolator Type Efficiency
%
Supply and return
air centrifugal Fans
and exhaust Fans
RPM ≥ 1400 Inertia base plus Elastomer 90
mounts
RPM ≤ 1000 90
Inertia base plus spring mounts
AHU Elastomer or spring isolators 85 – 90
END OF SECTION XX XX XX
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** ADD PROJECT NAME HERE** SECTION XX XX XX NOISE& VIBRATION CNTRL
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