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INSULATION OF PIPES
Selection of finish
Insulation without finish
Insulation should not be left without finish in service. The methods of applying unfinished material described in this guide refer only to situations where the finish is to be applied separately.
Foil faced
For internal use where a preapplied, semi-decorative vapour barrier is required. Care should be taken where impact damage is likely, e.g. at low-level installation.
Sheet metal
For external use where a separately applied, weatherproof impact resistant finish is required or for internal use where mechanical strength is needed, e.g. low-level pipework in boiler houses.
Polyisobutylene sheeting (PIB)
External use where a flexible weatherproof, sheet finish is required and likelihood of mechanical damage is minimal.
Glass cloth (or scrim) and mastic
External use to provide a reinforced, separately applied weatherproof finish.
Chemical resistant grades are also available.
Hard-setting composition
A hard, permanent, impact resistant finish for internal use, e.g. in
boilerhouses.
Self-setting cement
A hard, permanent, impact resistant finish for external use or for internal use where no means of drying out exists. Normally finished with mastic when used outside.
Canvas and paint
For internal use where a separate vapour barrier is preferred.
Note to Specifications
When preparing specifications for the insulation of piping, it is important to ensure that the insulation is suitable for the temperature and conditions, and that the covering is within the manufacturers' stated range of surface temperatures. Insulation thicknesses are not included in this guide, as they must be calculated to meet the appropriate operating conditions.
Multi-layer application
Where the required insulation thickness is greater than that in which the selected product is available or when specification limits individual layer thickness, it will be necessary to apply the insulation in more than one layer. In such cases an
additional clause should be inserted in the specification as indicated below. It is not always possible, because of the standard pipe sizes available, to obtain preformed insulation to fit precisely on a previous layer of insulation. A slightly smaller size can sometimes be compressed to fit without leaving a longitudinal gap. A small fillet, cut from the same material, should be used to fill any unavoidable gaps. Alternatively, an oversized section can be trimmed to ensure a snug fit.
When it is necessary to fit Rockwool preformed pipe sections in more than one layer, the first layer must be fitted close to the pipe with joints butted closely together and secured with binding wire or metal bands. Subsequent layers should be fitted in a similar manner ensuring that the joints in adjacent layers do not coincide.
Model Specifications
Without Finish
Pipework shall be insulated with Owens Corning South Africa Rockwool preformed pipe sections, thickness ... m m, ensuring that all joints are well butted together, secured to the pipe with metal bands (lacing wire may be preferred in certain applications, e.g. under mastic finish) at maximum 450 mm centres with one band not more than 50 mm from the end of each section. Bends to be insulated with carefully mitred segments of Rockwool preformed pipe sections fitted closely to the pipe and suitably banded into position. All fittings to be insulated with the same thickness of insulation.
With hard setting composition finish for internal use
Pipework shall be insulated with Owens Corning South Africa Rockwool preformed pipe sections, thickness ... mm, ensuring that all joints are well butted together. Bends to be insulated with carefully mitred segments of Rockwool preformed pipe sections. All fittings to be insulated to the same standard and finish as adjacent
pipework. The insulation to be held in place with 1,0 mm lacing wire and secured in place with 25 mm x 1,0 mm
galvanised wire mesh pulled tight to ensure close contact with the pipe. Over this a 12 mm layer of hard-setting
composition (or thickness as specified by the composition manufacturer) shall be applied in two coats and trowelled smooth. After complete drying out a coat of size shall be applied and two coats of heat-resistant paint.
With self-setting cement finish - for internal or external use
See application detail as Specification 1.4.2 except that self-setting cements should be applied to give a thickness of 6 mm (or thickness as specified by the manufacturer) and trowelled smooth. Where painting is required, the cement must be thoroughly dry before applying alkali-resistant primer and two coats of alkali-resistant paint.
Note: (a)
For External Use - The application of a final layer consisting of scrim embedded in mastic is required instead of the paint finish.
Note: (b)
The application of self-setting cement over Rockwool preformed pipe sections is greatly facilitated by a skim coat which forms a key for the self-setting cement.
With canvas finish - painted - for internal use
Pipework shall be insulated with Owens Corning South Africa Rockwool pre- formed pipe sections - Canvas covered, thickness ... mm, ensuring that all joints are well butted together. Bends to be insulated with carefully mitred segments of Rockwool preformed pipe
sections. All fittings to be insulated to the same standard and finish as adjacent
pipework. The longitudinal and circumferential canvas over- laps to be securely stuck down with suitable adhesive and neatly smoothed out. Two coats of heat- resistant paint to be applied.
Foil faced - for internal use
Pipework shall be insulated with Owens Corning South Africa Rockwool pre- formed pipe sections - Foil faced, thickness ... mm, ensuring that all joints are well butted together.
Longitudinal overlaps to be securely stuck down with suitable matching tape or by use of a proprietary self- adhesive system, if present. Butt joints to be covered with suitable self-adhesive tape not less than 50 mm wide. Bends to be insulated with carefully mitred segments of Rockwool preformed pipe sections and all joints covered with suitable self-adhesive tape. All fittings to be insulated to the same standards and finish as adjacent
pipework.
With polyisobutylene (PIB) finish - for external use
Pipework shall be insulated with Owens Corning South Africa Rockwool preformed pipe sections - PIB covered, thick- ness ... mm, ensuring that all joints are well butted together. Longitudinal overlaps to be securely stuck down by welding together with white spirit or other suitable solvent. Circumferential butt joints to be overlapped with PIB sheeting not less than 50 mm wide, and securely stuck with white spirit or other suitable solvent. Bends to be insulated with carefully mitred
segments of Rockwool preformed pipe sections covered with PIB sheeting. All fittings to be insulated to the same standard and finish as adjacent
pipework. All overlaps must be arranged to shed water and special care taken when sealing joints so as to prevent the ingress of moisture. Solvent manufacturer's instructions must be carefully followed:
Note (a)
Plain sections may also be used and the PIB sheeting applied on site.
Note (b)
The PIB sheeting should have a minimum thickness of 0,8 mm.
With glass cloth (or scrim) and mastic finish - for internal or external use
Insulation to be applied as detailed in Specification 1.4.1. Mastic then to be applied over the insulation in
accordance with the manufacturer's instructions. The glass cloth (or scrim) should be cut to size, bedded into the mastic, and smoothed to remove all wrinkles. A further coat of mastic should be applied when the first coat is dry.
Note:
Choice of mastic will depend on whether the application is internal or external. The glass cloth should be of sufficiently open weave to allow penetration of the mastic.
With sheet metal finish - for internal or external use
Insulation to be applied as detailed in Specification 1.4.1.
The sheet metal shall be formed to fit tightly over the outer circumference of the insulation with a longitudinal overlap of not less than 40 mm, the outer part of the overlap to be secured with self-tapping screws or rapid-fix rivets of the appropriate type at centres of not more than 150 mm or, where appropriate, secured with metal bands of suitable type and dimensions. Circumferential overlaps shall be not less than 40 mm and secured with self-tapping screws or easy-fix rivets, not less than four equally spaced. At suitable intervals provision should be made to accommodate expansion and contraction. All joints must be lapped 'weather wise' in order to shed water and, where exposed to weather, or if there is risk of liquid spillage onto the surface, all joints shall be sealed with flexible sealant. All bends and fittings to be covered with matching sheet metal tailored to fit and adequately sealed where necessary. All fittings which may require periodical attention, e.g. valves and flanges, should be fitted with pre-insulated, purpose-designed boxes, which can easily be removed and replaced.
Note:
Where sheet metal cladding is applied over vapour sealed insulation, special care must be taken to avoid puncturing the vapour seal. Screws and rivets should not be used.
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