All the glass components fabricated by Unit Glass Industry are from Borosilicate glass 3.3. Glass plants, pipelines and components fabricated comply with international standards.

Property of Borosilicate 3.3

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Chemical Composition

• SiO2 - 80.6
• B2O3 - 12.5
• N2O - 4.2
• Al2O3 - 2.2
• Others – 0.5

Mechanical Properties

The lack of ductility of glass prevents the equalization of stresses at local irregularities and the breakage strength varies considerably about mean value i.e., 300 mpa. Due to that tensile strength is occurs which is 700 kg/cm2. For increasing the breaking the factor of safety is applied by increasing the wall thickness to allow the operation upto the values given in the table of working pressure.

• Density -2.23x103kg/m3
• Modulus of elasticity – E 6500/mm2
• Permissible tensile and bending stress – k/s6 N/mm2
• Permissible compressive stress – k/s100N mm-2
• Poisson’s ratio – m=0.2

Chemical Resistance

Borosilicate glass 3.3 is resistant to almost all chemical except hydrofluoric acid, phosphoric acid and strong caustic solutions. Hydrofluoric acid has maximum effect on glass and presence of this acid even at ppm can cause corrosion.

Phosphoric acid and caustic solution at cold conditions do not pose many problems. However at elevated temperatures the corrode glass. As shown below a maximum corrosion for different acids in the concentration range between 4 and 7 N. Above that the reaction speed decrease markedly because the eroded layer amounts to only a few thousandths of millimeter after some years. There is justification for referring to borosilicate glass 3.3 as an acid resistant material.

Optical Properties

Borosilicate glass has considerable absorption in the visible region of spectrum and therefore appears clear and colorless. In photo processes the transparency of ultra violet is of particular importance. It allows the transmittance of material in ultra violet region that photo chemical reaction and sulphochlorination can be performed in

Permissible Operating Temperature

The strain point temperature, at which deformation would take place, of borosilicate glass 3.3 is around 515° C. The glass retains is properties till this temperature. However the recommended operating temperature is considerably lower at 200° C and that too without any temperature shocks, in exceptional cases the glass components can be used beyond 200° C. Customers should consult UNITY GLASS INDUSTRY for special applications.

At sub - zero temperature borosilicate glass has better tensile strength.

These temperature mentioned above are only indicative and would vary with individual operating conditions, and the various components used in the system the limiting condition would have to base on this rapid changes of temperature would result in thermal shocks resulting in increased stress in the glass. Therefore, under normal operating conditions such as thermal shocks should be avoided. As a general guideline, sudden temperature changes of upto 120° C would be acceptable.

Permissible Operating Pressure

Borosilicate glass plant & pipeline is used in both internal pressure and vacuum application.

The maximum operating pressure for a complete system is governed by the lowest rated component in the system.

The maximum operating pressure is reduced with increasing temperature difference between the process and ambient.

The allowable operating pressures are dependent on the nominal bores of the components.