Fibrecoat GENERAL Polybond Fibrecoat is used to seal and protect ceramic fibre in kiln and furnace linings, ducting and other process units exposed to temperatures up to 1,800°C in acid or alkaline rich environments. Standard ceramic fibre is now classified as a Class 2 Carcinogen ie. not banned from use but requiring protective clothing (gloves, mask, glasses, overalls) when handling in the vicinity of the fibre. It also requires special disposal like asbestos. Fibre dust in a kiln atmosphere is both bad for operator health and can stick to the product being fired, especially where this is to be glazed eg. in the whiteware industry. In addition, ceramic fibre modules used to construct kiln and surface linings shrink during repeated firing cycles. With conventional straight-sided modules the subsequent gaps formed between the modules often lead to energy losses as well as kiln atmosphere corrosion of the steel casing and module fixings. The resulting corrosion particles frequently fall onto the glazed ware, which then requires re-firing, sometimes several times. This problem is particularly acute in the sanitary and porcelain industries. Hence these are prime applications for treating with Fibrecoat. Large gaps between old modules should be filled with a low shrinkage high temperature fibre matt and / or expanding fibre and coated over with Fibrecoat. Providing the filling is secure the Fibrecoat can help form a protection and seal thereby reduce the corrosion products falling onto the ware - for further information please see below or refer to Polyceramics Limited. In addition to fibre protection Fibrecoat is used for the following: Abrasion Resistance Fibrecoat fires to form a hard ceramic shell capable of withstanding high velocity gases in ducting flues up to 70m/sec. Current applications include primary and secondary aluminium melting and holding furnaces. Also fired heaters in chemical plant. Atmosphere Corrosion Fibrecoat is very inert (based on zircon) to both acid and alkali liquids and gases. Hence it will prolong the life of the fibre it is coating (up to 30-40% longer in some cases). Prevention of Kiln Dust in the Atmosphere Fibrecoat is applicable to all types of fibre material (See below). INDUSTRIES USING FIBRECOAT • Sanitary • Porcelain • Ceramics • Brick making • Heat treatment • Ferrous and non-ferrous melting and refining • Petrochemical • Chemical APPLICATION We strongly recommend that you read our Fibrecoat technical data sheet before proceeding with any application. We will be pleased to send copies of this sheet if requested. The sheet gives information on recommended gun nozzle size (for standard gravity-fed hopper, air texture guns used by Polyceramics Ltd installation engineers) and air-pressure. Generally speaking we recommend the largest air orifice (1 to 2mm) and mix outlet orifice (4 to 6mm). This enables the use of a slightly thicker mix to generate a fine spray and reduces the risk of spluttering (large globules of mix). The outer nozzle orifice size can be reduced for spraying narrow areas eg. along joints or edges. The recommended air-pressure is 5.6 to 7 kg/cm² (80-100 psi) DO’s and DONT’s • Don't spray new fibre surface with water before coating. This can cause de-lamination of the fibre. • Don't spray too quickly. Ensure a continuous and even coating - it is important to form a continuous (monocoque) coating to provide maximum strength and adherence. • Don't build up too much Fibrecoat in any one area. As a general guide the coating thickness is sufficient when the Fibrecoat just begins to ripple (run down the wall) of form droplets on the roof. • Do seek advice before spraying Fibrecoat onto joints sealed with mastic, old fibre joints or joints not filled by Polyceramic Ltd engineers. • Do ensure all fibre jointing and packaging is secure and in good condition i.e. not loose or powdery. Remove the packaging and repack if in doubt (see 'Joints and Packing' below). Lightly brush the fibre surface before use to remove loosely adhering fibre. After the first firing, re-brush the coated area and areas where there has been over-spray. • We strongly recommend a trial section be carried out before lining a complete roof or furnace. Minimum size of trial should be at least 2 square meters and include jointed areas and packing. The latter are the most vulnerable to shrinkage and / or mechanical movement. The successful adherence of the coating can normally be established in 2 to 3 weeks. • Do make the end-user aware of the risks of Fibrecoat disruption due to excessive movement of packing and stemming due to routine thermal cycling. • Do use cover sheets for areas of lining not requiring spraying. FIBRE MATERIALS Whilst Fibrecoat has proven successful in protecting all types of high temperature ceramic fibre insulation, it has been found that results can vary on the new 'body soluble fibre' ('bio-solubles' - based on silicate minerals). This may be the result of the greater shrinkage of these materials relative to other ceramic fibres. With such materials it is strongly recommended that a trial section of Fibrecoat coating be made (preferably in the roof) before proceeding to coat a large area. In particular sensitive applications eg. porcelain and sanitary ware manufacture, a wall trial may be advisable before proceeding to a roof trial. JOINTS AND PACKING Fibre Packing A common expansion allowance provided during installation of standard 300 x 300 mm and 600 x 300 mm convoluted modules. The packing is usually between 25 and 50 mm thick and used to compensate for the expansion and contraction which takes place during normal kiln / furnace cycling in an intermittent operation. This system is only used with convoluted modules. Stemmed Joints Retrofitted fibre filling in joints, which have opened up due to firing shrinkage in use. Fibre packing and 'stemming' are a potential weakness because they tend to become loose during firing shrinkage. Gaps and loose fibre can often be seen between modules on older linings due to this shrinkage. Where conventional modules are used, having plain straight faces between adjacent modules, this can provide a direct path for the hot corrosive kiln atmosphere to the metal casing and module fixing system. This inn turn can provide a path for corrosion (or fibre) particles to fall from the metal casing or packing onto the kiln ware (a familiar problem in the sanitary and porcelain industries). Additionally, the metal fixings securing the modules to the shell may corrode and ultimately lead to the modules separating from the roof and upper side walls. To avoid this problem Polyceramics Ltd recommends the use of very large modules. (up to 3 metres long) with stepped-joints. Such modules can reduce open joint surface area by as much as 85%. Lateral joints between modules tend not to open due to the very high fibre compression produced during module manufacture. The small number of longitude joints are stepped providing no direct route to the kiln or furnace case. Coating the Jumbo modules with Fibrecoat significantly reduces the fibre shrinkage and generally protects the modules from the kiln or furnace atmosphere. Further information can be obtained from Polyceramics Ltd. JOINTS Small gaps and joints between modules ie. <5mm are generally better left alone. Forcing fibre 'stemming' into them may open the joint and often leaves insufficient material to provide a good key. As a general guide fibre 'stemming' or other fillers should extend to at least halfway through the joint between modules. Refractory cementing the stemming to the inside of the joint may help temporarily but most cements are water- based and therefore subject to shrinkage themselves. Mastic may be a better alternative to fibre if it is organically bonded (caution - mastic should be fired before applying Fibrecoat). A Fibrecoat over the joint filler may help to protect the filler but is no guarantee of security. All packing and stemming should be checked for security before applying Fibrecoat, particularly in sensitive applications such as gloss firing - see Do's and Don'ts. Loose and powdery fibre should be removed and repacked with new fibre. Convoluted joints and packing should be treated in the following way: 1. Convoluted Fibre (folded fibre blaket) Between Modules If the convolution has the folded edge facing the inside of the furnace or kiln this may cause a discontinuity between the Fibrecoat on the joint and the coating on the module adjacent to it due to the roundness of the fibre joint. The discontinuity can lead to breaking away of the Fibrecoat during firing. The risk of this happening can be reduced by slitting the fibre fold with a knife to present an open, flat edge for coating. This may need pressing back into the joint to provide a relatively flat surface with adjacent modules which is more suitable for coating. 2. Edge-Sacked Fibre Rarely used for joints on new installations. Generally not a problem for coating with Fibrecoat, providing it is not loose or powdery. PACKING Only pack joints if absolutely necessary - forcing the fibre into joints produces bigger joints and the risk of damage to the sides of the modules leading to greater potential problems. 1. Convoluted Fibre If folded fibre is to be used to pack a joint the folded edge should be pushed first into the joint using a thin blade or plate. The cut edge of the fibre should then be trimmed so that it is level with the 'hot face' of the fibre modules on either side. Fibrecoat should then be sprayed across the fibre module and packing to produce a continuous refractory coat. In this way maximum coating adherence and strength can be achieved. 2. Edge-Stacked Fibre Install as above. DRYING AND FIRING Ideally Fibrecoat should be air-dried for a minimum of 8 hours before firing. Unfortunately production demands may severely limit this. Any retained heat in the lining will obviously aid the drying process. Firing should aim to remove both the free water and chemically combined water in the Fibrecoat mix. For best results the coating should be air-dried thoroughly then heated for 2 to 3 hours at a temperature of 400°C to 600°C before taking up to operating temperature. NOTE: Spray application generates fine particles of Fibrecoat, some of which may not be bonded together after the first firing. Vacuum cleaning the floor and a non-coated area is advisable after application. However, for application in the ceramic and porcelain industries, where glazing takes place, it is strongly recommended that the first full heating cycle following application of the coating be carried out without ware to be glazed. Following the first heating cycle a light brushing of the coated area is advised to remove further loose packing and coating. If dust and loose materials persist the light brushing should be repeated after each firing until the problem clears.

Polybond Ltd. Unit 6, William Street, Northam, Southampton, SO14 5QH Tel: 02380 988350    Fax: 02380 988355