Appendix 1 [PDF]

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Appendix 1

Appendix 1 - Insulation General The following text deals with acoustic cladding and thermal insulation. The materials used for both applications may be split into three separate types: 1 2 3

Insulating materials. Protective coverings. Fixing materials.

All insulating materials must be stored in dry conditions under cover. During installation, weatherproof sheeting must be used during inclement weather and after each day’s application. Installation must be performed generally to standards normally accepted as first class workmanship. The finished cladding must be of good appearance and free from dents and sharp edges. Nameplates, code inspection plates and stampings on equipment must be left permanently visible and the cladding must be properly sealed around them. If the above requirement is impracticable, a second plate supplied by British Gas and permanently marked with the same information and with the work DUPLICATE must be fixed on the outside of the cladding in the most convenient, adjacent position. Acoustic cladding General The relevant British Gas standards are: BGC PC PWC1 Part 1 Part 2

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Acoustic cladding. Cladding of gas pipe and equipment. Notes for guidance.

Cladding is defined as an assembly comprising porous insulation material with a metal outer jacket. The purpose of the cladding in this application is to cut down noise, typically by 10-20 dB. Materials The insulation is usually in the form if semi-rigid sections. For small bore pipework, 25mm diameter and below, flexible wool or fibrous materials may be used. The insulation is typically 50-100mm thick and must comprise of non-toxic materials including materials which release non-toxic fumes during a fire.

ATC88-40915 Appendix 1

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The metal jacket must be aluminium alloy, or galvanized mild steel sheet where greater rigidity is required. The thickness of the jacket must be related to the durability and strength required, ease of fitting and costs but will normally be between 0.71 and 1.6mm thick. Galvanized materials, or any materials which contain zinc, must not be used on stainless steel due to the danger of causing zinc embrittlement. Insulation banding may be metallic or non-metallic. If metallic, it must be of the same material as the jacket. Mastic sealants and rubber or neoprene bedding strips used must be suitable for use at temperatures between -20-50°C with occasional increases up to 80°C. Nuts, bolts, screws and washers must be either stainless steel or zinc metal coated mild steel. Application of materials The basic sequence for the application of acoustic cladding: 1 2 3 4

Preparation. Insulation plus fixing. Repeat insulation and fixing if required. Metal cladding plus fixing.

All surfaces to be clad must be clean and dry. For pipework up to approximately 300mm, preformed section of insulation must be cut and profiled to fit, and secured at 450mm intervals with banding strip. For greater diameters, flexible flat forms of insulation, eg mattresses, must be used. The jacket should not be allowed to come into direct contact with the noise radiating structure or with its supports, but should cover the whole noise radiating area without gaps or voids. The finished insulation must be even, solid, tightly joined and well secured. Where two layers of insulation are specified, then both the longitudinal and circumferential seams must be staggered. The insulation must be completely covered by a metal jacket. All overlapped joints must be at least 25mm, bonded with mastic sealant, and must be arranged to shed water. The metal jacket must never touch the pipe or equipment. Clearance between the metal jacket and branches should be approximately 6mm and filled with mastic. Potential metallic contact at other similar locations is also important to consider. The metal jackets of all acoustic cladding must be continuously bonded together by a strip of jacketing metal and connected to the pipe; however, cladding must not act as an electrical bridge over isolation joints.

ATC88-40915 Appendix 1

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Thermal insulation General The relevant British Gas standard is: BGC PS PWC2 - Thermal insulation of above ground pipework and equipment. The insulation in this application is used for heat conservation, cold conservation, personnel protection, anti-condensation, frost protection and for the maintenance of operating temperatures. Temperatures applicable are from –200-1000°C depending on the application. Materials Insulating materials The insulating materials proposed for any application must be selected from the following types: a b c d e f g h i

Glass fibre. Foamed glass. Rock wool. Modified slay wool. Expanded perlite. Vermiculite (loose granular fill). Calcium silicate. Phenolic foam (not within buildings – toxic during combustion). Polyisocyanurate (not within buildings – toxic during combustion).

The insulating materials used must not contain substances which support pests or encourage the growth of fungi. They must not cause a known hazard to health from particles or toxic fumes, during application, whilst in use or on removal. The insulating materials used may be applied in layers depending on the total thickness required; in some cases up to approximately 400mm total thickness may be specified. Protective coverings Protective coverings include: 

 

ATC88-40915 Appendix 1

Vapour seals – vapour sealing compound, preferably trowelling grade, which has an interposed scrim cloth made of woven glass cloth. Vapour sealing tape may also be used. Vapour seals are used for cryogenic applications. Metal cladding – galvanized mild steel must be used, unless stainless steel is being insulated, in which case aluminium alloy sheet is used. Hard-setting composition/self-setting cement and glass cloth may also be used as protective coverings as an alternative to metal cladding in certain circumstances.

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Fixing materials To hold down insulating materials and protective coverings, the following may be used: 1 2 3 4 5 6 7 8 9

Wire netting – used to hold down insulation but only used with hard-setting or self-setting cement as a protective covering. Binding wire. Binding tape. Fixing bands. Self-tapping screws. Nuts, bolts and other fastenings. Adhesives. Anti-abrasion compound. Joint sealant

Application of materials The basic sequence for application for general heat conservation and protection: 1 2 3 4

Preparation. Insulation plus fixing. Repeat insulation and fixing if required. Metal cladding plus fixing, or self-setting or hard setting cement.

The basic sequence for application for general cold conservation and cryogenic service: 1 2 3 4 5

Preparation. Insulation plus fixing. Repeat insulation and fixing if required. Vapour seal. Metal cladding.

As far as possible, insulation of pipework must be performed with preformed sections of insulating materials not exceeding 1m in length. Each layer of insulation is secured with binding wire every 150mm on pipework; the wire must not be allowed to cut into the insulation. If insulating equipment, fixing bands are used every 300mm. Metal cladding must be applied so that all overlapped joints must be at least 75mm (40mm on 40mm diameter pipe and below). The overlapped joints must be arranged to shed water. The metal cladding must never touch the pipe or equipment. Fixing bands must be used every 450mm.

ATC88-40915 Appendix 1

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