Pyrex Glass

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Dimension: 600mm×1200mm (max . 800mm×2000mm) Net sized glass of trengthening can be supplied Glass of cut size is available Physical Properties: Density ( at 25): 2.23±0.02g/cm3 Modulus of elasticity: 68KN/mm2 Co-efficient of expansion (20-300): 3.3±0.1×10 Softening point: 820±10 Strain point : 516±10 Heat conductivity at 90: 1.2W/mk Caloricity: (20-100) 0.82KJ×(kg×K) Thermal shock resistance: 180K Strengthening type: 300K Ldentical temperature difference: 100K Strengthening type: 300K Maximum working temperature: Short time (10h): 500 Long time (10h): 450 Chemical Performance: Water resistance: ISO719/DIN12111 HGB1 ISO720 HGA1 Acid resistance: ISO1776/DIN12116 1 Alkali resistance: ISO695/DIN52322 A2 CHEMICAL COMPOSITION The composition of borosilicate glass used for chemical plants has following approximate composion. SiO2 - 80.6% B2 O2 - 12.5% Na2O - 4.2% Al2O3 - 2.2% RESISTANCE TO CHEMICAL Borosilicate glass is inert to almost all materials except hydroflouric acid (HF) phosphoric acid((H3Po4) and hot strong caustic solutions. Of these Hydroflouric acid has the most serious effect, even when it is present in PPM (parts per million) in solutions. Where as phosphoric acid and caustic solutions cause no problems when cold but at elevatrd temprature corrosion occurs. in case of caustic solutions upto 30% concentration can be handled safely at ambient temperature. Under actual operating conditions, the effect of turbulence, and traces of other chemicals in the solution may increase of decrease the rate of attack. So it is not possible to give exact figures for corrosion by caustic solutions. THERMAL PROPERTIES Linear coefficient of thermal expansion The coefficient of thermal expansion of borosilicate glass over the temperature 0 - 300°C is 3.3 x 10-6/°C. This is very low when compared with other glasses and metals. That is why, borosilicate glass is often called low expansion borosilicate glass. Specific heat Specific heat between 25°C and 300°C is average to be 0.233Kcal/Kg, °C Thermal Conductivity Thermal conductivity is 1.0 Kcal/hr,m°C. Over the permissible operating temperature range. ANNEALING Annealing of glass is the process where the glass is heated and kept for a defined period of time to relive internal stresses. Careful cooling under controlled conditions is essential to ensure that no stresses are reintroduced by chilling/cooling. RESHAPEING In the given below are shown characteristic temperature at a determined viscosity, essential for glass reshap. Lower cooling temperature 1024 poise 515°C Upper cooling temperature 1013 poise 565°C Softening point 107 poise 795°C Reshapeing point 104 poise 120° C MECHANICAL PROPERTIES The lack of ductility of glass prevents the equalization of stresses at local irregularities or flaws and the breakage strength varies considerably about a mean value. This latter is found to occur at a tensile strength of about 700kg/cm2 In order to allow for the spread of breaking stress, a large factor of safely is applied when determining the wall thickness requirement to allow operation up to values given in the table of working pressure. OPTICAL PROPERTIES Borosilicate glass show no appreciable absorption in the visible region of spectrum and therefore appears clear and clour less. In photo chemical processes the transparency of ultra violet is of particular importance. It follows from the transmittance of material in uv region that photo chemical reactions such as chlorination & sulpho chlorination can be performed in it. WORKING TEMPERATURE Borosilicate glass retains its mechanical strength and will deform only at temperature which approach its strain point. The practical upper limit for operating temperature is much lower and is controlled by the temperature differentials in the glass which depends on the relative temprature defferentials in the glass which depends on the relative temprature of the contens of the equipment and the external surroundings. Provided borosilicate glass is not subject to rapid change in temperature, creating undue thermal shock, it can be operated safety at temperatures up to 250 °C. It must be realised that in complete plants, composed not only of borosilicate glass, but also includ other materials such as PTFE the recommended max. Operating temperature is 200°C. Operating temperatures may have to be modified so as to compensate for the effects of other factors such as pressure, thermal cycling, rapid heating cooling etc. The degree of thermal shock (usually defined as sudden chilling or heating) which it can withstand depends on many factors such as stresses due to operating conditions, stresses imposed in supporting the equipment, the wall thickness of the glass. It is therefore undesirable to give sudden temperature changes. But up to 120 °C can be accomodated. At sub-zero temperature, the tensile strength of borosilicate glass tends to increase and equipment can be used with safety at temperatures as low as -50 °C for XTRONG and components

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Tianjin City Yuantai Glass Industry and Trade Co,.

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