JGC Job Code 0-5361-20-0000Doc. No. S-PM-G000-1244-0003
ARAMCO OVERSEAS COMPANY B.V. & SUMITOMO CHEMICAL CO., LTD.
Project Management Services for
Rabigh Phase II Petrochemical Project
REV DATE REASON FOR ISSUE PREP’D CHK’D APR’D4 05 Nov 2010 For ITB Y.Takahashi J.Sato J.Sato
Approved for Aramco Overseas Company B.V. Approved for Sumitomo Chemical Co., Ltd.
Signature / Date Name Signature / Date Name
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SPECIFICATIONFOR
ACOUSTIC INSULATION
Document Issue Purpose
: For Approval : For Information : For Design : For ITB :For Internal
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Contents
1 SCOPE ....................................................................................................................................................... 4
2 DEFINITION................................................................................................................................................ 4
3 APPLICABLE DRAWINGS, SPECIFICATIONS, AND CODES AND STANDARDS ...................................... 4
3.1 Project Specifications ........................................................................................................................... 4
4 ORDER OF PRECEDENCE OF DOCUMENTS........................................................................................... 4
5 DEVIATIONS AND CLARIFICATION........................................................................................................... 4
6 ACOUSTIC FUNCTION OF THE COMPONENTS ....................................................................................... 4
6.1 Porous Layer........................................................................................................................................ 56.2 Inner Mass Material.............................................................................................................................. 56.3 Cladding............................................................................................................................................... 56.4 Anti Vibration Seal................................................................................................................................ 5
7 CLASSIFICATION....................................................................................................................................... 5
7.1 Class A ................................................................................................................................................ 57.2 Class B ................................................................................................................................................ 67.3 Class C ................................................................................................................................................ 6
8 APPLICATION............................................................................................................................................. 6
8.1 Expected Insertion Loss ....................................................................................................................... 68.2 Applicable Class of Acoustic Insulation................................................................................................. 7
9 MATERIALS................................................................................................................................................ 7
9.1 Porous Layer........................................................................................................................................ 79.2 Inner Mass Materials ............................................................................................................................ 89.3 Cladding............................................................................................................................................... 89.4 Anti-vibration Seals .............................................................................................................................. 89.5 Vibration Isolation Pad.......................................................................................................................... 89.6 Support of the Cladding........................................................................................................................ 8
10 INSTALLATION........................................................................................................................................... 9
10.1 General ................................................................................................................................................ 910.2 Anti-vibration Seals .............................................................................................................................. 910.3 Vibration Isolation Pad.......................................................................................................................... 910.4 End Caps ............................................................................................................................................. 910.5 Acoustic Enclosure (Valve Box)............................................................................................................ 910.6 Prevention of Mechanical Damage ..................................................................................................... 10
11 COMBINED THERMAL AND ACOUSTIC INSULATION ............................................................................ 10
11.1 Hot Services....................................................................................................................................... 1011.2 Cold Services..................................................................................................................................... 10
12 DETERMINATION OF EXTENT OF INSULATION..................................................................................... 10
12.1 Prediction of Noise Level at Source (Lp0) ............................................................................................ 1112.2 Estimation of Sound Decay along the Pipe (At1).................................................................................. 1112.3 Estimation of Noise Reduction at Pipe Discontinuity (At2) .................................................................... 1112.4 Prediction of Pipe Noise (Lpr )............................................................................................................ 1212.5 Determination of Class and Extent of Acoustic Insulation.................................................................... 12
13 IMPLICATIONS FOR PIPING DESIGN...................................................................................................... 12
14 FIGURES .................................................................................................................................................. 13
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Figures
Fig. 1: General composition of acoustic insulation 14
Fig. 2: Typical arrangement of acoustic insulation showing cladding and end caps 14
Fig. 3: Construction details of anti-vibration seal for end caps 15
Fig. 4: Typical arrangement for branches and tees 15
Fig. 5: Main feature of acoustic insulation for vertical pipe support 16
Fig. 6: Typical acoustic enclosure for a valve 17
Fig. 7: Typical Acoustic insulation of flanged joints 18
Fig. 8: Typical Vented acoustic insulation of flanged joints (where required for safety reasons, e.g. hydrogen service) 18
Fig. 9: Typical arrangement for vibration-isolated supports in vertical pipes 19
Fig.10: Typical arrangement of acoustic insulation Class A 18
Fig.11: Typical arrangement of acoustic insulation Class B 20
Fig.12: Typical arrangement of acoustic insulation Class C 20
Fig.13: Combined Cold and Acoustic Insulation 21
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1 SCOPE
This specification provides requirements for the design, application and extent of acoustic insulation on pipes, valves and flanges. The aim is to reduce the noise radiated from piping. It does not cover the acoustic insulation of the equipment such as large vessels and machinery.
It does not consider compatibility with the environment in the selection of materials for the porous layer, cladding, fastening, sealing and surface protection. For these aspects reference should be made to any relevant specification for thermal insulation (see S-PM-G000-1390-0001 & 0002).
2 DEFINITION
COMPANY: Aramco Overseas Company B.V. and Sumitomo Chemical Co. Ltd.
3 APPLICABLE DRAWINGS, SPECIFICATIONS, AND CODES AND STANDARDS
3.1 Project Specifications
S-PM-G000-1390-0001 General Specification for Hot Insulation
S-PM-G000-1390-0002 General Specification for Cold Insulation
S-PM-G000-1244-0002 Specification for Equipment Noise Limitation
4 ORDER OF PRECEDENCE OF DOCUMENTS
The order of precedence shall be:
- This specification
- Project drawings and specifications
- Applicable Saudi Aramco Standards
- Applicable International Codes and Standards
5 DEVIATIONS AND CLARIFICATION
Any deviations or clarifications from this specification require COMPANY approval under the Waiving and Clarification Procedure (S-PM-G000-1131-0007).
6 ACOUSTIC FUNCTION OF THE COMPONENTS
Each component used in acoustic insulation is similar to that used in hot insulation. However, its function is quite different and the performance of insulation depends on the understanding of the functions described below.
The differences between acoustic and thermal insulations are described in section 10.1.
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6.1 Porous Layer
The porous layer serves the following purposes:
- It represents a vibration-isolating support to the cladding.
- It converts acoustic and vibrational energy into heat.
6.2 Inner Mass Material
The inner mass materials attenuate acoustic energy which goes through those.
6.3 Cladding
The cladding serves the following purposes:
- It is a barrier to the noise radiated by the pipe and shall therefore be completely sealed.
- It protects the porous layer from mechanical damage and provides a weather protection for the porous layer underneath. It shall therefore have sufficient strength and durability.
6.4 Anti Vibration Seal
The anti-vibration seals interrupt the vibration propagation at locations where metal-to-metal contact occurs
7 CLASSIFICATION
Three classes of acoustic insulation are defined and these are denoted as A, B and C.
They are defined by the acoustic requirements given in paragraph 8.1.
The dimensions of the acoustic insulation for these three defined classes shall be as indicated in Table 1.
Table 1 Classes of Acoustic Insulation
Class
Thickness of Porous
Layer*note 1[mm]
Cladding *note 2 Inner Mass Material *note 2
Minimum mass per unit area[kg/m2]
AluminizedSteel Sheet [mm]
Aluminum Sheet [mm]
Minimum mass per unit area[kg/m2]
AluminizedSteel Sheet [mm]
Aluminum Sheet [mm]
A 50 2.5 0.4 1.0 - - -B 100 7.5 1.0 2.8 - - -C 50 + 50 5.0 0.8 1.9 5.0 0.8 1.9
*note 1 : Where the above designated thickness for acoustic insulation is not adequate for thermal insulation requirements, the insulation thickness shall be increased as required (see Section 10).
*note 2 : Where a high mass per unit area is required for the cladding or inner mass material, this may be composed of two layers. An example of an acceptable construction is an outer layer of steel or aluminum (for mechanical protection) satisfying the requirements of .S-PM-G000-1390-0001 & 0002 and an inner layer of mineral loaded plastic (see Section 9.2 (3)).
7.1 Class A
The general requirements are given in Table 1.
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Typical arrangement of this class of acoustic insulation is shown in Fig.10 of this specification
For acoustic purposes flanges and valves need not be covered in Class A
7.2 Class B
The general requirements are given in Table 1.
Typical arrangement of this class of acoustic insulation is shown in Fig.11.
For acoustic purposes flanges and valves need not be covered in Class B.
Rigid type pipe support shall be insulated down to the concrete or steel base, see Fig. 5
7.3 Class C
The general requirements are given in Table 1.
Typical arrangement of this class of acoustic insulation is shown in Fig.12.
The porous layer shall be applied in two separate layers, 50 mm inner layer and 50 mm outer layer.
All flanges and valves shall be acoustically insulated within the extent of Class C insulation.
In spite of above requirement, flanges in hydrogen service or in toxic service such as phenol or hydrogen sulfide shall not be insulated.
Rigid type pipe support shall be insulated down to the concrete or steel base, see Fig. 5
Distance and support rings should be avoided if possible but, when used, they shall conform to paragraph 9.6.
8 APPLICATION
8.1 Expected Insertion Loss
Insertion loss is the difference in the sound pressure level at a given point near the pipe (not influenced by other noise sources), before and after the application of the acoustic insulation.
This specification defines three classes of acoustic insulation, denoted as A, B and C in terms of expected insertion loss as listed in Table 2.
Table 2. Expected Insertion Loss for Class of Insulation
ClassExpected reduction at the overall A-weighted sound level in dBA
Centrifugal pump Centrifugalcompressor Valve
A 5 7 11
B 7 11 15
C 11 15 20
It is, basically, not appropriate to express insertion loss as a single number such as dBA as it varies
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with frequency.
For the purpose of engineering, however, the reduction value in overall sound pressure level in dBA is useful, as given in Table 2.
The values given are derived from insertion losses in each octave band with typical frequency spectrum of the noise sources.
The values include a factor of safety to allow for possible deficiencies in installation and maintenance.
8.2 Applicable Class of Acoustic Insulation
Table 3 summarizes the applicable class of acoustic insulation for various pipe noises.
The table is based on insulated pipe noise less than 85 dBA.
Table 3 Applicable Class of Acoustic Insulation
*Note: Lp is Sound Pressure Level, in dBA, measured at one meter from bare pipe surface.
Source of pipe noise Expected pipe noise level (dBA ) Applicable class
Valve
9685 ≤< Lp A
10096 ≤< Lp B
Lp<100 C
CentrifugalCompressor
9285 ≤< Lp A
9692 ≤< Lp B
Lp<96 C
CentrifugalPump
9085 ≤< Lp A
9290 ≤< Lp B
Lp<92 C
9 MATERIALS
This section lists materials suitable for acoustic insulation and the particular properties necessary for acoustic purposes. All materials shall be suitable for the maximum operating temperatures and for the chemical nature of the environment. They shall conform to the specification for thermal insulation (S-PM-G000-1390-0001 & 0002) and to any relevant requirements for combustibility and surface spread of flame.
9.1 Porous Layer
Mineral wool shall be used for acoustic insulation. It shall meet the requirements as specified in the relevant section of S-PM-G000-1390-0001.
In addition to the requirement of S-PM-G000-1390-0001, the density of the porous layer may be
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allowed down to 48 [kg/m3] (3 [lb/ft3]).
9.2 Inner Mass Materials
The following materials are suitable for acoustic purposes:
(1) Lead *note 1,
(2) Mild steel plate,
(3) Mineral-loaded plastic *note 2
*note 1: These materials shall not be used over austenitic stainless steel or austenitic nickel steel/alloy piping and equipment.
*note 2 : The use of plastics as an alternative to traditional materials should be considered when choosing systems for a range of applications provided all technical and safety requirements are met. Further advice regarding the suitability of a particular plastics material or product and its limitations should be sought from suppliers.
The minimum mass per unit area of inner mass material shall be according to Table 1.
9.3 Cladding
The cladding shall be in conjunction with thermal insulation specifications (S-PM-G000-1390-0001 & 0002).
9.4 Anti-vibration Seals
The following materials are suitable for use in anti-vibration seals:
(1) Synthetic rubber,
(2) Natural rubber,
(3) Non-flammable felt
Materials containing asbestos shall not be used.
When these materials are not compatible with the operating temperature, the seal shall be made from compressed mineral wool. Note that, in many cases, the anti-vibration seal may also be required to act as a watertight seal and the material should be suitable for this.
9.5 Vibration Isolation Pad
The following materials are suitable for vibration isolation pad:
(1) Synthetic rubber,
(2) Natural rubber,
(3) Steel springs in the form of a folded band or knitted metal
9.6 Support of the Cladding
Where semi-rigid sections are used on horizontal pipe it will not normally be necessary to support the cladding; but where blankets are used semi-rigid sections, used at intervals, may be suitable for supporting the cladding through the porous layer. Any rigid spacer, as used in distance rings for
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thermal insulation, shall not be used on the horizontal pipe.
With vertical pipes, any supports which carry the weight of the cladding shall contain resilient elements to reduce the transmission of vibrations from the pipe (see Fig. 9). Where necessary, these resilient elements should contain mechanical stops to limit excess movement.
Resilient element shall not be loaded to such an extent that their operational range of deflections is exceeded. For this reason a resilient element shall not bear more than 1.5 m2 of outer surface of insulation systems.
10 INSTALLATION
10.1 General
The requirements of any relevant specification for thermal insulation (S-PM-G000-1390-0001 & 0002) shall apply, except where excluded or superseded by this specification.
An essential feature of acoustic insulation is that the cladding must not be in direct or indirect metal-to-metal contact with the pipe. Any such contact will allow a transmission of vibrations to the cladding which will reduce or nullify the noise reduction of the insulation; it may even enhance the noise radiation, because of the greater surface area of the cladding. It is also important that there should be no gaps in the insulation; joints in the porous layer shall therefore be staggered and the cladding shall overlap at all joints
10.2 Anti-vibration Seals
At locations where metal-to-metal contact would normally occur anti-vibration seals shall be applied, see Fig. 2 and 3. They shall have a minimum thickness of 3 mm and minimum width of 50 mm.
The edges of the cladding or end cap (10.4) shall be folded where they rest on the anti-vibration seal (9.4). If the seal is of porous insulation material, the outer edge shall be weatherproofed with a flexible mastic compound.
10.3 Vibration Isolation Pad
Where a steel structure is used to support the pipe, there shall be suitable vibration isolation between the steel structure and the pipe.
(See Fig.5 for typical application.)
10.4 End Caps
At all exposed flanges the acoustic insulation shall be terminated with an end cap, see Fig. 2, and this shall be located as close to the flange as possible but still allow bolt removal. The end cap shall be isolated from the pipe by means of an anti-vibration seal, see paragraph 10.2. For end caps at pipe ends see Fig. 3.
10.5 Acoustic Enclosure (Valve Box)
When noise radiated from a control valve has to be reduced, within the extent of Class C insulation for example, the equipment shall be surrounded by an acoustic enclosure (valve box). Other block valves and flanges within the acoustically insulated lines may also be necessary to be covered.
These enclosures may not be required in the lines insulated to classes A and B.
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Acoustic enclosures (valve box) shall be easily demountable to provide access to the flange or valve. Joints shall be sealed to prevent noise leakage. If it is required that a flange should be ventilated for safety reasons, a special construction such as 1/2 in. NPS drain tube or vent shall be considered. Drain and vent shall be piped to a safe location.
No part shall weight more than 25 kg and toggle connections are preferred.
The acoustic enclosure shall have an outer surface of metal sheet with a mass per unit area at least equal to that of the cladding of adjacent pipes. The porous layer shall be similar in material to that used on the piping and shall be retained by an inner surface layer which is at least 10 mm away from the flange or valve; for example, perforated-metal sheet with an open area of not less than 23%. In general, a thickness of 25 mm will be sufficient for the porous layer of a valve enclosure unless there is evidence of high noise radiation from the body of the valve.
Where acoustic enclosures are installed around flange joints they shall be of sufficient length to overlap the end of pipe insulation by at least 100 mm.
10.6 Prevention of Mechanical Damage
Where acoustic insulation may be liable to mechanical damage, special provision must be made to protect it. For example, where it may be stepped on, separately supported steps should be provided. If mechanical load cannot be avoided, the cladding should be reinforced by using stiffer plate.
11 COMBINED THERMAL AND ACOUSTIC INSULATION
11.1 Hot Services
When insulation is required for acoustic as well as thermal reasons, materials specified in section 9 of this specification shall be used for both purposes.
The thickness of insulation shall be determined by the more stringent of the two requirements.
11.2 Cold Services
The cold insulation shall be applied first to the pipe in accordance with S-PM-G000-1390-0002, and acoustic insulation shall be applied on top. Outer cladding on cold insulation and under acoustic insulation can be eliminated. The vapor seal shall conform to S-PM-G000-1390-0002. To prevent condensation at the interface between the two layers of cold and acoustic a second vapor seal shall be applied outside the porous layer. Fig.13 shall be referred for this complicated application. The vapor seal shall be applied with following materials.
Vapor seal for cold insulation surface: Vapor barrier mastic
Vapor seal for acoustic insulation surface: Aluminum foil laminated vapor barrier
12 DETERMINATION OF EXTENT OF INSULATION
Extent of insulation shall be determined according to the following procedures at the design stage of the project. The site noise survey will determine whether the design complies with the noise specification. If problems are identified final changes will be made at site.
The determination will be reflected on the P&ID markup. Generally, the following branch pipes and fittings need not be acoustically insulated unless specifically designated on the P&ID.
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vents and drains
Instrument lead pipes
Branches 2” or smaller
Branches whose diameter is equal or smaller than one tenth of trunks
12.1 Prediction of Noise Level at Source (Lp0)
For control valves, noise level will be predicted at one meter downstream from the valve and one meter out from the pipe surface. It will be provided by valve vendors and available in the data sheet of the control valve.
For centrifugal pumps and compressors, noise level will be predicted at inlet and outlet of the equipment and one meter out from pipe surface. When appropriate noise data are not available from the vendor they will be provided by Contractor acoustic engineer.
12.2 Estimation of Sound Decay along the Pipe (At1)
Acoustic energy will decay with sound traveling along inside the pipe.
If the pipe is more than about 20 diameters long, it may be necessary to take into account the attenuation in the gas along the length of the pipe. This attenuation ( At1) is given by the equation:
At1 =βr/ D [dB]
where,
β = attenuation coefficient. Unless otherwise specified, β is 0.06 for pipes containing gases or vapors, and 0.017 for pipes containing liquid.
r = distance along the pipe from noise source to the point where noise level to be calculated, in meter.
D = pipe diameter, in meter.
12.3 Estimation of Noise Reduction at Pipe Discontinuity (At2)
Sound propagation will be restricted or weakened at various pipe discontinuities.
These reductions are given for each discontinuity, as follows:
(a) ReducersAt2 = 0 [dB]
(b) ExpandersAt2 = 2 [dB] for gas or vapor services
At2 = 0 [dB] for liquid services
(c) BendsAt2 = 0 [dB]
(d) BranchesAt2 = 10 log10((d0
2+d12)/d1
2) [dB]Where,
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d0 and d1 are diameters of track (upstream) and branch (downstream), respectively.
(e) ValvesAt2 = 0 [dB] for full bore
At2 = 10 [dB] for glove, cage valves
(f) Restriction orificesAt2 = InfiniteExcessive noise may be generated at the orifice. Advice will be needed from Contractor’sprocess/acoustic engineer.
(g) Significant enlargement, such as vessel, filter and heat exchangerAt2 = Infinite
Noise generation at such equipment shall be considered separately.
12.4 Prediction of Pipe Noise (Lpr )
Sound pressure level at a point one meter from pipe surface and (r) meter from the noise source, along the pipe, is given by the following equation:
Lpr = Lp0 - At1 - ∑ )( 2At [dBA]
12.5 Determination of Class and Extent of Acoustic Insulation
Applying Lpr to Table 3, determine required class of acoustic insulation.
No acoustic insulation is required on the pipe whose Lpr is less than or equal to 85 dBA.
13 IMPLICATIONS FOR PIPING DESIGN
It is important to ensure at an early stage of the design that the piping arrangement allows for the bulk and weight of acoustic insulation. The Contractor's acoustic engineer is therefore recommended to determine the classes and extent of acoustic insulation and to mark on the engineering diagrams those sections of pipe which are to be acoustically insulated.
The design of pipe supports and hangers must allow sufficient space for the installation of acoustic insulation (see Table 1). It should also be such that the insulation can be fitted completely around the pipe. Where pipes are attached to steel structures special consideration should be given to the isolation of vibration between the pipe and the structure.
The method for supporting the piping shall be agreed between the parties responsible for the acoustic and mechanical design; due account must be taken of the stresses and possible movements of the piping system.
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14 FIGURES
Fig. 1: General composition of acoustic insulation
Fig. 2: Typical arrangement of acoustic insulation showing cladding and end caps
Fig. 3: Construction details of anti-vibration seal for end caps
Fig. 4: Typical arrangement for branches and tees
Fig. 5: Main feature of acoustic insulation for vertical pipe support
Fig. 6: Typical acoustic enclosure for a valve
Fig. 7: Typical Acoustic insulation of flanged joints
Fig. 8: Typical Vented acoustic insulation of flanged joints (where required for safety reasons, e.g. hydrogen service)
Fig. 9: Typical arrangement for vibration-isolated supports in vertical pipes
Fig.10: Typical arrangement of acoustic insulation Class A
Fig.11: Typical arrangement of acoustic insulation Class B
Fig.12: Typical arrangement of acoustic insulation Class C
Fig.13: Combined Cold and Acoustic Insulation
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FIG 1 General composition of acoustic insulation
FIG 2 Typical arrangement of acoustic insulation showing cladding and end caps
Cladding
Cladding may be fixed in position with:- rivets or- self-tapping screws or- stainless steel retaining bonds
Pipe
Porous layer
Cladding
Rivets or screw shall not be used when cladding is directly over a vapour barrier
Pipe
Porous layerRetaining bonding
Anti-vibration seal – see Fig.3 for detailClosed foam cell structure (resilient neoprene etc.) See also (10.2)
End cap (may consist of two overlapping halveswith overlap in the horizontal plane)
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FIG 3 Construction details of anti-vibration seal for end caps
FIG 4 Typical arrangement for branches and tees
1. Adhesive / sealing layer2. Closed cell foam resilient strip, see (10.2)3. Retaining band4. Shaped profile collar5. Pipe
End cap
Mastic seal
Pipe Selftappers ofblind rivets
Cladding
Porous layer
Sealedwith mastic
UPPER CONNECTION
LOWER CONNECTION
Self-tapping Screw
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FIG 5 Main feature of acoustic insulation for vertical pipe support
Insulation tosupport base
Vibration isolation pad
Anti-vibration seal
Mastic
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FIG 6 Typical acoustic enclosure for valves
Space for bolt withdrawal
Seal around End Cap(See Fig.3 for details)
Anti-vibration seals (See 6.4)
Acoustic insulation systemfor pipes
Metal box with inner insulation of mineral fiber (min.25mm) and perforated steel sheet
Water resistant mastic
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FIG 7 Typical Acoustic Insulation of flanged joints
FIG 8 Typical Vented acoustic insulation of flanged joints(where required for safety reasons, e.g., hydrogen service)
Overlap
SelftappingScrew
(not if vapour sealed)
Space may be filled with porous material
Mastic
Perforated sheet
Removable flange cover
Lockformed
SupportOverlap
Selftapping screw(not if vapour sealed)
Venting aperture
Cladding
Anti-vibration seal (if end cap is required)
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FIG 9 Typical arrangement for vibration-isolation supports in vertical pipes
FIG 10 Typical arrangement for acoustic insulation Class A
CladdingPipe
Vibration iisolation pad
Support on strapping band (or welded)Section AA
B
Detail B
Cladding
Porous layer(mineral wool 50 mm)
Pipe
Binding wire Overlap
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FIG 11 Typical arrangement for acoustic insulation Class B
FIG 12 Typical arrangement for acoustic insulation Class C
Cladding
Porous layer(mineral wool 100 mm)
Pipe
Binding wire Overlap
CladdingInner mass material
Inner porous layer(mineral wool 50 mm)
Outer porous layer(mineral wool 50 mm)
Sealing tape
Overlap
Binding wire
Pipe
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FIG 13 Combined Cold and Acoustic Insulation
Acoustic Insulation (**)(Class A, B or C)
Cold Insulation (*)
Vapor seal for cold ins. surface(Vapor barrier mastic) and outer cladding
Vapor seal for acoustic ins. surface(Aluminum foil laminated vapor barrier)
Cladding(the same as acoustic insulation)
(*) Complete cold insulation including outer cladding: Materials and installation shall be in accordance with S-PM-G000-1390-0002
(**) Complete acoustic insulation: Materials and installation shall be in accordance with this specification.