1. Purpose
This method statement covers on site installation of noise control and vibration isolator equipment associated with all rotating, centrifugal and reciprocating equipment i.e. pumps, chillers, air handling units and pipe connections etc.
2. Scope of Work
This procedure defines the stepwise method that will be used to ensure the correct installation of noise control equipment to avoid excess noise and vibration created by machinery or equipment and interconnected piping, conduit and ducts mountings.
Installation of all vibration isolation units, and associated spring hangers and bases, will be carried out strictly in accordance with the details specified on the contractor’s drawings, which in essence complies with the “Particular Technical Specifications” along with the specialist isolator manufacturers instructions and where indicated in the specifications, under the direct supervision of the vibrations isolation manufacturers representative.
This method also covers material and manufacturer’s performance specification which will be submitted for review from the client.
3. Responsible Personnel
Construction Manager
Mechanical Superintendent
Warehouse Manager
Specialist Manufacturers representative
Quality Controller
Commissioning Manager
4. Pre Installation Requirements
All materials and documentation relevant to a particular section of works will be checked by the construction team prior to the commencement of work, while ensuring that these are of the correct type as reviewed by the client.
Before commencement of any construction works, pre-inspections will be carried out on all materials prior to them leaving the storage area.
The client is timely invited to attend this and all inspections.
Prior to the commencement of any construction activities, areas and access will be inspected to confirm that they are in suitable condition for construction works to commence.
5. Installation Method of Noise & Vibration Isolator
The plant equipment steel structural or concrete inertia base will be placed in position as shown on contractor’s drawing and supported temporarily by blocks or shims.
Isolator equipment will then be installed on the base and when completed the isolators will be installed in the correct positions without raising the machine and frame assembly.
After the entire installation is complete and under full operational load, the noise isolators will be adjusted such that the load is transferred from the temporary blocks to the isolator.
When all vibration isolators are properly adjusted, the blocks or shims will become slightly free and will be removed. (The adjustment of AV mounts will be carried out based on static deflection).
The springs of vibration isolators for inertia bases will have a loaded working height equal to 1.0 to 1.5 times the outside diameter of the spring and will be compressed to approximately 50% of their unloaded height, or as indicated by manufacturer’s details and contract drawings.
Where any installed isolators or mounting systems permit equipment motion in all directions, there will be provided where necessary additional resilient restraints to flexibly limit start-up equipment lateral motion to 6mm.
Prior to start-up, all foreign matter between bases and equipment will be removed and it will be ensured that there is no isolation short circuits in the base, or isolators.
Electrical circuit connections to isolated equipment will be looped to allow free motion of isolated equipment.
6. Vibration Isolators for Plant & Equipment
Floor mounted equipment will be installed on to min 100mm concrete raised “Housekeeping” pads, covering the complete floor area requirements of the equipment plus a minimum of 150mm further on each side.
Vibration isolating devices and related inertia blocks will then be mounted on this concrete pad.
Unless otherwise specified on the Employer’s Drawings or in the Specification, machines to be isolated will be supported by a structural steel frame or concrete inertia bases.
These will be shown on the contractor’s drawings.
To allow movement of rotating equipment, pipe/electrical connections and flexible joints will be provided between pipe, electrical conduit or duct mountings.
Bases will be constructed of adequate “I” or channel steel members reinforced as required to prevent the base flexing at start-up and misalignment of drive and driven units.
The bases will be drilled to suit the drive and driven unit mounting templates and be complete with height saving brackets at the appropriate locations on their perimeter to receive the anti-vibration isolator mountings.
All perimeter members will be steel sections with a minimum depth equal to 1/10th of the largest dimension of the base beam depth but need not exceed 400mm provided that the deflection and misalignment is kept within limits reviewed without objection by the project manager.
Height saving brackets will be employed in all mounting locations to provide a base clearance of min 25mm.
Detailed design calculation of the base and its anti-vibration isolator arrangements plus contractor’s drawings for each base will be submitted to the client for review.
Concrete inertia bases will be formed within a structural steel perimeter channel frame reinforced as required to prevent flexing, as per manufacturer’s recommendations
9. Vibration Isolators / Flexible Connections for Pipe Works
Flexible connections will be fitted to all pump suction and discharge connections, water chillers, and other centrifugal or reciprocating rotating equipment.
The flexible connections will be full line size of the equipment connection and fitted as close as practical to the source of vibration.
Flexible connection will consist of a single convolution of reinforced rubber, wire reinforced cuffs at each end forming a raised face for sealing purposes.
Cuffs shall be backed by removable steel flanges drilled to suit the mating pipework.
For water the rubber type as specified , for other conveyance a suitable rubber will be selected in accordance with manufacturer’s recommendation.
For working temperatures up to 70oC the rubber convolution will be reinforced by multiple nylon cord, for temperatures above 70oC the reinforcement will be steel wire.
All rubber membranes will have an indelible identification system as part of their design to clearly identify the model and hence suitability for the application and working conditions.
The rubber membrane will have the date of manufacture molded into the cover to ensure that no units which have exceeded the recommended shelf life are used.
Tie Bars Installation
In general tied type flexible will be fitted. The tie bars will incorporate large rubber isolating washers to prevent vibration transmission through the tie bar assembly.
For small bore sized or for low pressures the manufacturer’s recommendations on whether tie bars should be fitted in these circumstances will be followed.
Unless otherwise indicated, all piping located in mechanical equipment rooms having connection to vibrating mechanical or electrical equipment, will be isolated from the building structure by means of noise and vibration isolation hangers for at least 15,000mm pipe length from the vibrating equipment.
All piping to be isolated will freely pass through walls and floors without rigid connections.
Penetration points will be sleeved or otherwise formed to allow passage of piping, and maintain 10 to 15mm clearance around the outside surfaces.
This clearance space will be tightly packed with glass fiber or rock wool and caulked airtight after installation of piping.
No rigid connections between equipment and building structure shall be made that degrade the noise and vibration isolation system.
Where machinery is to be mounted on an upper floor or flat roof structure care must be taken to ensure that the deflection of the isolators exceeds that of the structure onto which the machine is mounted, otherwise the structure will still absorb most of the vibrations and transmit it to other areas below.
Where machines are to be mounted on upper floors of long span and relatively low mass the vibration isolator manufacturer will be informed of all the details and his advice sought and taken as to the most suitable method of mounting in each case.
In order to resist corrosion all mountings and vibration isolating hangers will be treated as follows:
(a) Springs to be neoprene coated or hot-dip galvanized.
(b) Wearing hardware to be cadmium plated steel or stainless steel of an appropriate grade.
(c) All other metal parts, boxes, mounting pads etc. will be hot dip galvanized.
10. Installation of Duct Silencers
Supply and installation of duct silencers will be as shown on the Contractor’s Drawings or as specified where required to meet overall specified space sound levels.
Outer casting of rectangular duct silencers will be fabricated from not lighter than 0.8mm galvanized steel in accordance with the recommended practices in the ASHRAE Guide.
Seams shall be “lock-formed” and mastic filled.
Each silencer will be provided with flanged inlet and outlet.
The internal baffles or splitters will be not lighter than 0.5mm and made of galvanised perforated steel having a nominal open area of 30% as manufacturer’s recommendation.
All internal components will be spot welded in place with welds on centers not exceeding 100mm.
Spot welds will be treated after welding with anti-corrosive epoxy resin or other coating reviewed without objection by the client.
Manifold silencers will be installed with continuous metallic nosing crimped in place.
Nosing pieces and tails will be as per manufacturer’s design.
The filler material will be of inorganic mineral or glass fiber of a density sufficient to obtain the specified acoustic performance and will be packed under not less that 5% compression to eliminate voids due to vibration and settling.
Material will be inert, vermin and moisture proof.
Quality Inspections
Quantity and loading of isolation units will provide adequate deflection and not less that 90% isolation efficiency in slab on ground floor areas and not less than 95% isolation efficiency in upper level areas.
All vibration isolators will have either known un-deflected heights or calibration markings so that, after adjustment, when carrying their load, the deflection under load can be verified, thus determining that the load is within the proper range of the device and that the correct degree of vibration isolation is being provided according to the design.
All isolators shall operate in the linear portion of their load versus deflection curve.
Load versus deflection curves will be furnished by the manufacturers, and will be linear over a deflection range of not less than 50% above the design deflection.
The contractor will submit report to the client for review incorporating the manufacturer’s recommendations if any and contractor will issue a final clearance certification prior to start up of plant/equipment.
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