Process Pipework

Pipes: Insulation Product Selector

Heating Systems
Boiler Rooms
Plant Rooms
Cooling Towers

Small to medium bore pipes

For the best results Knauf Insulation recommend using Crown Pipe Insulation, a one-piece ‘snap-on’ preformed shot-free non-combustible glass mineral wool section of 80 kg/m³ nominal density.

The table below sets out the recommended finishes for pipes in a range of locations. For further information on the alternative finishes see the specification clauses which can be found here.

Large bore pipes

For pipes with a bore larger than 250mm, or in areas where access is reduced, Knauf Insulation recommend using Rocksilk Mattress, a non-combustible rock mineral wool faced, on one side with galvanised or stainless steel wire mesh to form a firm but flexible general purpose insulating mattress.

Typical Specification Clauses for Pipework

P1 Bright Class ‘O’ finish

Pipework to be insulated with Crown Pipe Insulation with bright Class ‘O’ finish, ......mm thick, ensuring that all joints are well butted together.

Longitudinal overlaps to be securely stuck down using the self-adhesive overlap. Butt joints to be covered with suitable self-adhesive tape not less than 50mm wide, bends to be insulated with carefully mitred segments of Crown Pipe Insulation covered with suitable self-adhesive tape. All fittings to be insulated to the same standard and finish as adjacent pipework.

Where the facing is to provide a vapour barrier, all joints must be sealed with adhesive or tape, and any damage to the facing must be repaired with tape or sealant.

P2 Polyisobutylene finish

Pipework to be insulated with unfaced Crown Pipe Insulation, ......mm thick, with PIB finish, ensuring that all joints are well butted together.

Longitudinal overlaps to be securely bonded by welding together with white spirit or other suitable solvent. Circumferential butt joints to be overlapped with PIB sheeting by typically 50- 75mm and securely bonded with white spirit or other suitable solvent.

Bends to be insulated with carefully mitred segments of Crown Pipe Insulation covered with PIB sheeting welded together.

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 in order to prevent the ingress of moisture.

P3 Sheet metal finish

Pipework to be insulated with unfaced Crown Pipe Insulation, ......mm thick with ...... finish, ensuring that all joints are well butted together and secured with metal bands at maximum centres of 450mm, with one band not more than 50mm from the end of each section. Bends should be insulated with carefully mitred segments of Crown Pipe Insulation, banded into position. All fittings to be insulated to the same standard as adjacent pipework.

Sheet metal to fit tightly over the outer circumference of the insulation with a longitudinal overlap of not less than 40mm, the outer part of the overlap to be secured with self tapping screws or rivets of the appropriate type at centres of not more than 150mm or, 100mm if a weatherproof finish is required or, where appropriate secured with metal bands of suitable type and dimensions.

Circumferential overlaps to be not less than 50mm and secured with self tapping screws or rivets, not less than four equally spaced. At suitable intervals provision should be made to accommodate expansion and contraction. All joints must be lapped “weatherwise” in order to shed liquids where exposed to the weather or if there is risk of liquid spillage onto the surface. All joints should be sealed with suitable 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.

P4 With hard setting composition finish – for internal use

Pipework to be insulated with unfaced Crown Pipe Insulation, .....mm thick, ensuring that all joints are well butted together.

Bends to be insulated with carefully mitred segments of Crown Pipe Insulation. All fittings to be insulated with the same standard and finish as adjacent pipework.

The insulation to be held in place with 1.0mm lacing wire and secured in place with 25mm x 1.0mm galvanised wire mesh pulled tight to ensure close contact with the pipe. Over this a 12mm layer of hard setting composition (or thickness as specified by the manufacturer) shall be applied in two coats and trowelled smooth.

After completely drying out a coat of size shall be applied and two coats of heat resisting paint.

P5 With self-setting cement finish – for internal or external use

See application detail as Specification P4, except that self-setting cements should be applied to give a thickness of 6mm (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.

For external use, apply a final layer of scrim embedded in mastic instead of the paint finish.

The application of self-setting cement over Crown Insulation is greatly facilitated by a skim coat which forms a key for the self-setting cement.

P6 With painted canvas finish – for internal use

Pipework to be insulated with Crown Pipe Insulation, .....mm thick, ensuring that all joints are well butted together. Bends to be insulated with carefully mitred segments of Crown Pipe Insulation.

All fittings to be insulated with the same thickness of insulation.

The insulation to be covered in canvas. The longitudinal and circumferential canvas overlaps to be securely stuck down with suitable adhesive and neatly smoothed out. Two coats of heat resisting-paint to be applied.

P7 With glass cloth (or scrim) finish – for internal or external use

Insulation to be applied as detailed in Specification P3. 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 in mastic and smoothed to remove all wrinkles. A further coat of mastic should be applied when the first is dry.

Note: Choice of mastic will depend on whether the application is internal or external. The glass cloth should be sufficiently open weave to allow penetration of the mastic.