Home »
How is a Quarry tile made?
Raw Material
The key requirement for manufacturing a quarry tile is a high quality material. The most suitable clay for this purpose is Etruria Marl. This clay possesses the ideal combination of minerals and fluxes with very specific levels of silica and iron which give the ability to produce a varied range of earthtone shades whilst attaining all the technical properties required to meet the highest requirements of all National and International product specifications.
Dennis Ruabon continues to use high quality Ruabon clay reserves from the adjacent Hafod Quarry site, a clay that has been used since 1878. The two seams used are known as Heatherbrown and Colomendy: both are renowned as the perfect clays for tile making.
Clay Preparation
Following extraction stockpiles of up to 30,000 tonnes are built in the stocking area. These are left to weather naturally for at least three months to aid the crushing and grinding process. The weathered clay is loaded to a purpose built, fully automated, clay preparation plant where it is firstly conveyed through a primary crusher to break the material into a manageable size.
From here it is fed into a Wet Pan where it is ground by two rotating 3 tonne rollers through a perforated bed into a rotating knife shredder. At this point water is added to attain a specific moisture content. The clay is then fed through two sets of medium speed crushing rollers and two sets of high speed crushing rollers. These are precision ground and set to produce a very specific and accurate grain size.
All parameters are continually checked and monitored as the clay is then conveyed directly to the tile manufacturing plant where it is either stored in a silo or used directly. Around 80 tonnes of clay is processed daily.
Extrusion
Prepared clay is fed through a shredder mixer where the extrusion moisture content is controlled prior to being vacuum extruded to de-air the clay and compact it into a stiff, malleable consistency. The clay is processed through a pressure head and a precision extrusion die to produce a continuous tile column.
The extrusion process also produces the natural texture on the face of the tiles which leads to good anti-slip properties. Silicon Carbide grit is applied to produce the Quarrundum high anti-slip. This is then further processed according to the tile type with various automated cutting, pressing, & rolling processes all integrated into the manufacturing system.
When producing Black and Summer Gold shades Manganese Dioxide and Titanium Oxide body additions are made to the clay at the shredder mixer prior to extrusion. All products are then automatically loaded onto special perforated drier trays which are stacked onto tiered drier cars.
Drying
Loaded dryer cars are conveyed through a continuous tunnel drier where they are dried to a specific, low moisture content over a period of twenty four hours. Drier conditions are controlled and monitored from the kiln control room and waste heat from the kiln firing process is utilized for the drying process.
Many years of experience and testing enables us to control shrinkage factors and eliminate any risk of cracking during this process. Moisture content and dimensional tolerances are meticulously checked throughout.
Setting
As drier cars exit the tunnel drier they are automatically unloaded by means of a vacuum disgripper which stacks the tiles into pre-set quantities on a conveyor system. The drier trays are returned directly to the extrusion area. This conveyor system delivers the tiles directly to the operators at the setting station. The tiles are then set by hand onto the kiln cars.
By use of refractory batts the tiles are built into a specific proven pattern which ensures stability and optimum passage of heat and draught when inside the kiln. The kiln cars are built in two distinct halves with a gap in between. This ensures direct heat from the kiln burners is prevented from direct contact with the product. A set kiln car can contain as many as 8,000 tiles and weigh up to 5 tonnes.
Firing
The purpose built Lingl Tunnel Kiln at over 100 metres long is one of the largest in the UK and operates 24 hours per day, 365 days per year. All aspects of the kiln firing are controlled via a kiln control room where PLC and Computer systems are closely managed by an experienced Kiln control team.
The kiln cars are pushed through the kiln over a period of approximately 80 hours, going through a precise and exacting firing and cooling curve to produce a vitrified tile of high strength and low water absorption. Typical firing temperatures are between 1080 – 1130°C.
Two distinct firing methods are used:- Oxidising, which produces the rich Ruabon Red and Summer Gold shades and Reduction Firing, which produces the famous Heatherbrown and Flame shades. Ruabon Black products are fired separately in an intermittent kiln which is conditioned independently to obtain the very heavy reducing atmosphere required to produce this special shade.
Inspection and testing
Kiln cars are unloaded by hand onto a conveyor system where all tiles are visually inspected at a sorting station prior to packing into distinct batches. Traceability is ensured by batch numbering in relation to day code imprinted on tiles during the extrusion process. All batches of tiles are fully inspected by technicians in our quality control laboratory.
Each batch must pass the stringent requirements of ISO 10545 prior to release to despatch. Tiles are further tested at various stages of manufacture to ensure compliance with both internal and external specifications