ORIGINS AND DEVELOPMENT
From the very beginning in 1990, S.I.G.MA. has seriously pursed the aim of cooperating with the glass industry offering top quality materials thanks to the hard work of a team of people with more than 30 years of experience in the production of refractories. Thanks to continuous improvements in the performances of materials, in just a few years, S.I.G.MA. has become a leader in Italy in the refractory market for the glass industry. At the end of the 1990s, S.I.G.MA. turned its attention to the international market and rapidly expanded notwithstanding the strong competition. Today, more than 80 per cent of S.I.G.MA.’s products are sold internationally. Thanks to cooperation with important partners, S.I.G.MA. can supply a complete high quality range of products for the glass industry including:
• fireclay;
• high alumina;
• sillimanite;
• mullite;
• silica;
• zircon-mullite;
• zircon;
• magnesia;
• fused cast refractories;
• insulating refractories;
• special cements and concretes.

INVESTMENTS
In 2011, S.I.G.MA. will invest in a very high temperature kiln (1750°C) from Bickley. This new kiln, the eighth at the plant, will improve the quality level of some existing products, as well as sinter highly refractory products to improve performances and operation life.
This is only the latest investment of our company that has greatly improved production capacity and quality level in these last years despite the global crisis. Investments at the plant...

ORIGINS AND DEVELOPMENT
From the very beginning in 1990, S.I.G.MA. has seriously pursed the aim of cooperating with the glass industry offering top quality materials thanks to the hard work of a team of people with more than 30 years of experience in the production of refractories. Thanks to continuous improvements in the performances of materials, in just a few years, S.I.G.MA. has become a leader in Italy in the refractory market for the glass industry. At the end of the 1990s, S.I.G.MA. turned its attention to the international market and rapidly expanded notwithstanding the strong competition. Today, more than 80 per cent of S.I.G.MA.’s products are sold internationally. Thanks to cooperation with important partners, S.I.G.MA. can supply a complete high quality range of products for the glass industry including:
• fireclay;
• high alumina;
• sillimanite;
• mullite;
• silica;
• zircon-mullite;
• zircon;
• magnesia;
• fused cast refractories;
• insulating refractories;
• special cements and concretes.

INVESTMENTS
In 2011, S.I.G.MA. will invest in a very high temperature kiln (1750°C) from Bickley. This new kiln, the eighth at the plant, will improve the quality level of some existing products, as well as sinter highly refractory products to improve performances and operation life.
This is only the latest investment of our company that has greatly improved production capacity and quality level in these last years despite the global crisis. Investments at the plant in 2009 and 2010 include:
• raw material weighing equipment;
• 200-square-metre pre-assembly area;
• new oil pressure press (two presses in total); and
• new laser control grinding machine dedicated to furnace bottom blocks, channels and forehearth superstructures (two grinding machines in total).
S.I.G.MA.’s laboratory also has some very important new equipment, in particular an X-ray difractometer and an X-ray fluorescence spectrometer. These two machines enable to check refractories in a complete way, carrying out research to improve performances and develop new products.

PRODUCTION STRENGTHS
S.I.G.MA. is specialized in manufacturing forehearth and feeder refractories. Thanks to special alcoholic binder technology, S.I.G.MA. produces both complete forehearths (superstructures and channels) and expendables with very low glassy phase quantity, thus improving chemical–physical characteristics and service life. The use of an alcoholic binder avoids the presence of clay in the refractories, thus eliminating alkalies (Na2O, K2O) responsible for the glassy phase.
Clay, when used as a binder, actually brings alkalis and impurities, increasing the volume of the glassy phase, which is the weakest area of the refractory. The reason of the strong corrosion of a refractory with high glassy phase content is due to the alkalis that, infiltrating into the refractory during operation, react in particular with the glassy phase reducing its viscosity.
The consequence is both a chemical reaction between this fluid amorphous phase and the refractory and also an exudation of the glassy phase that carries away refractory grains weakening the blocks and giving defects to the glass. S.I.G.MA. refractories, manufactured with an alcoholic binder and not with clay, have a crystalline structure and very low glassy phase content. A low glassy phase means:
1. higher ‘refractoriness under load’ and higher ‘creep’;
2. better glass corrosion resistance;
3. better vapour corrosion resistance;
4. better thermal shock resistance.
Thus better performance for:
• forehearth superstructures (see points 1 and 3);
• channels (see point 2);
• expendables (see points 2 and 4).

SPECIAL REFRACTORIES FOR FOREHEARTHS AND FEEDERS
By combining its technical knowledge in refractory products with its engineers’ direct experience in the glass industry, S.I.G.MA. has developed two newly designed products aimed at improving glass corrosion resistance and thermal homogeneity of the glass gob.

High alumina product (Trademark A 95 V)
A 95 V high alumina is mainly used for forehearth channels. This quality product has very good properties in hot conditions such as volume stability, refractoriness, as well as good glass corrosion resistance up 1,270°C, and is considered the best choice when there is the risk of zircon defects (cat-stretches). A special forming process is necessary to obtain a 98-99 per cent Al2O3 product with very low glassy phase content. This is a vibrocast manufacturing process where no clay is used as a binder,  and, therefore, avoiding melting agents such as sodium and potassium (as well as impurities), which increase the quantity of glassy phase and weaken the refractory products.
The result is a crystalline structure with higher glass corrosion resistance.
The use of sintered high alumina channels for forehearths, instead of fused cast products, is possible only if the temperature does not exceed 1,270°C and if the refractory channels have the right crystalline structure (a Al2O3) with a low glassy phase content.
The strengths of S.I.G.MA. high quality alumina A 95 V for channels are:
• no clay as a binder;
• very pure raw materials (synthetic and fused);
• low glassy phase;
• crystalline structure;
• strong glass corrosion resistance up to 1,270°C.

Patented tube (Trademark ZM 7-32 KV)
The tube is the most stressed refractory piece in the feeder as there are three zones along the tube with three completely different working conditions:
1. the lower part is immersed in the fused glass;
2. the central part is surrounded by flames; and
3. the upper part is relatively cold.
All this means a strong thermal shock and, furthermore, the tube acts as a barrier and causes a temperature difference between the glass inside and outside the tube.
In particular, the traditional type of tube has a difference in temperature measured from 40 to 100°C according to the type of glass being produced.
S.I.G.MA. has developed a tube with a new geometry to solve the problems of thermal shock and improve gob homogeneity. The new concept tube is grooved along its length and incorporates specially configured holes made by moulds, thus avoiding stresses normally associated with drilled holes. This special shape and the decrease of mass increase the heat transmission from the outside to the inside of the tube, thus improving the glass homogeneity and lowering the number of rejected glass articles.
In short, two major benefits are achieved:
• thermal shocking of the tube is greatly reduced.
• gob thermal homogeneity is greatly improved.