Product

Typical Construction

The bright Class ‘O’ reinforced aluminium foil is suitable for applications above clean rooms, within air plenums or for aesthetic purposes. As well as providing fire protection, Rocksilk PyroDuct offers a high level of thermal and acoustic insulation.

Fire performance

Rocksilk PyroDuct is classified as noncombustible to Euroclass A1 to BS EN ISO 13501-1 and to BS 476: Part 4: 1970 (1984), Class 1 surface spread of flame to BS 476: Part 7:1997 and Class ‘O’ to the Building Regulations. Rocksilk PyroDuct is fully certified for duct types A and B (fire inside and outside with insulation, integrity and stability) to provide up to 2 hours fire protection for steel ductwork.

Required Thickness of Rocksilk PyroDuct

Tested in accordance with BS 476: Part 24: 1987.

Tested in accordance with BS 476: Part 24: 1987.

Tested in accordance with BS 476: Part 24: 1987.

Performance

Moisture resistance

Rocksilk PyroDuct is non-wicking when tested to BS 2972: 1989: Section 12. When exposed to 90% relative humidity and 20°C, Rocksilk PyroDuct absorbs less than 0.004% of moisture.

Weight

Thermal performance

Rocksilk PyroDuct will provide a basic level of thermal insulation and has a thermal conductivity of 0.037 W/mK.

Acoustic performance

Ventilation and extract ducts are usually low velocity and don’t generate high levels of noise. Rocksilk PyroDuct will provide effective control of noise, the actual performance varies with insulation thickness and surface finish.

Other Advantages

Installation

Rocksilk PyroDuct slabs are applied singly. Because they are manufactured in a range of thicknesses, there is no need for multi-layer applications. A consistent thickness of installation can therefore be achieved every time. Individual slabs are 1200mm long and 600mm wide. Their lightness of weight makes them easy to carry on site and simplifies installation. 

Horizontal ducts

Welded Pin Method

The fixing system of welded pins and square edge butt joints allows for fast and simple installation – there is no requirement for special vee cuts, drilling or sub-frames.

1. Weld 2.5mm diameter steel pins at 350mm longitudinal centres along the centre line of the vertical sides of the ductwork.
2. Where the dimension of the vertical sides exceed 1000mm, the steel pins should be in rows starting 50mm in from the edge and spaced apart at a maximum of 500mm centres.
3. Weld 2.5mm diameter steel pins at 350mm longitudinal centres along the horizontal surfaces of the ductwork in rows starting 50mm in from the longitudinal edge and spaced apart at a maximum of 500mm centres.
4. Cut Rocksilk PyroDuct to size so that the horizontal slabs are the same as the duct width, and vertical slabs are the height of the duct plus twice the PyroDuct thickness.
5. Attach the insulation by impaling over the welded pins and securing with 38mm spring steel washers.
6. Glue all board to board joints using a high temperature silicate based adhesive.
7. Trim off pin lengths to about 30mm excess and bend this excess to form a right angle with the insulation.
8. Although not essential, it is good practice to offset the joints for each surface.

Self-Drilling Pin Method

Self-drilling pins, such as IBS Self-Drilling Insulation Pins, may be used in place of welded pins in an identical manner. IBS pins are available from Abrasives & Screw Products Limited, tel: 01704 879311.

Pin-Free Method

Boards are cut, placed, and adhesive fixed to the duct in the same way as for the welded pin method. Steel pins may be used at board joints as a temporary measure to hold the boards together while the adhesive sets. The maximum size of duct for ‘pin-free’ fixing is 400 x 400mm. If steel straps - minimum 0.5mm thick at 500mm maximum centres, or steel wire, minimum 1.5mm diameter at 300mm centres - are wrapped around the insulation then the maximum size of the duct may be extended to 1000 x 1000mm. Thin gauge steel angles should be fitted at the corners of the duct so that the straps or wire do not crush the insulation. Adhesive should also be used to bond the insulation to the steel duct. The adhesive should be a general thixotropic silicate type with 50-55% fillers.

Vertical ducts

The installation detail for horizontal ducts is also relevant for vertical ductwork, though the horizontal and vertical surfaces referred to for horizontal ductwork will be the longest and shortest surfaces respectively in vertical ductwork.

Ductwork passing through compartment walls or floors

In accordance with The Building Regulations, the Loss Prevention Council’s "Code of Practice for the Construction of Buildings" and the recommendations given in BS 5588: Part 9: 1989, when ductwork passes through any element of construction which has a designated period of fire resistance, the integrity of that compartment should be maintained. In these situations, the ductwork at the penetration should be stiffened as follows.

When the flange is at the penetration, then a 30 x 30 x 4mm (minimum) steel angle should be rivetted around the duct using a single row of rivets with washers starting 50mm from the edge and at 150mm centres. Rocksilk Universal Slab RS33 should be used to pack any gap between the main insulation and the blockwork. 120 x 90mm sections of PyroDuct are glued to the wall and main PyroDuct insulation.