Industrial Glassware
Borosilicate Glass 3.3 is the premier engineering material for process vessels, reaction systems, and chemical piping across the pharmaceutical, biotechnology, and chemical process industries. Its widespread adoption is driven by exceptional chemical resistance, superior thermal stability, and complete optical transparency that allows continuous visual process monitoring.
Borosilicate glass is engineered for chemical, pharmaceutical, and process plant applications due to its near-universal corrosion resistance, low thermal expansion coefficient, and high thermal shock tolerance. Unlike commercial container or soda-lime glass, Borosilicate Glass contains strictly no heavy metals or toxic fluxes such as Lead oxide (PbO) or Arsenic. It complies fully with international standards DIN ISO 3585, EN 1595, and ASTM E438 Type I, Class A.
The physical durability, optical transparency, and chemical inertness of all Goel Glass process components are governed by this tightly controlled borosilicate formulation.
The composition of borosilicate glass used for chemical plants has following approximate composition.
| Component | Approximate Content |
|---|---|
| SiO₂ | 80.6% |
| B₂O₃ | 12.5% |
| Na₂O | 4.2% |
| Al₂O₃ | 2.2% |
As an inorganic non-metallic material without plastic ductility, glass breakage behavior is governed by tensile stresses acting on micro-flaws at the glass surface. While the intrinsic compressive strength of Borosilicate Glass 3.3 exceeds 1,000 N/mm² (10,000 kg/cm²), engineering design is based on a practical bending tensile limit of 35–45 N/mm² (350–450 kg/cm²). To accommodate statistical variations in breaking stress, generous safety factors are applied in accordance with DIN ISO 3585 and BS EN 1595 when calculating required wall thicknesses for all operating pressures and full vacuum service.
Borosilicate Glass 3.3 demonstrates near-universal inertness across virtually all chemical media, including organic solvents, strong mineral acids (HCl, HNO₃, H₂SO₄), halogens, and salt solutions. Specific process limitations and operational conditions apply to the following substances:
Hydrofluoric Acid (HF): Even at trace PPM concentrations, HF chemically attacks silica bonds, leading to severe etching and wall thinning. Borosilicate glass must not be exposed to HF or fluorinated etching agents.
Phosphoric Acid (H₃PO₄): Safe at ambient and moderate temperatures; at concentrations above 85% and temperatures exceeding 100°C, corrosion rates gradually accelerate.
Alkaline Solutions (Caustic): Chemical compatibility is conditional upon concentration and temperature. Caustic solutions (such as NaOH and KOH) up to approximately 30% concentration can be safely handled at ambient temperatures. Elevated temperatures (>50°C) and higher concentrations accelerate silicate surface dissolution.
The table below outlines characteristic temperature thresholds corresponding to specific dynamic viscosities, fundamental for hot glass forming, annealing, and reshaping:
| Characteristic | Viscosity | Temperature |
|---|---|---|
| Lower cooling temperature | 10¹⁴ poise | 515°C |
| Upper cooling temperature | 10¹³ poise | 565°C |
| Softening point | 10⁷ poise | 795°C |
| Reshaping point | 10⁴ poise | 1200°C |
The permissible internal operating pressure depends upon the nominal diameter (DN) of the glass components, geometry, and process operating temperature.
In assembled systems combining multiple items such as vessels, columns, filters, and heat exchangers, the overall permissible operating gauge pressure is always governed strictly by the component with the lowest pressure rating. All Goel Glass standard process components are engineered for full vacuum service down to 1 mbar absolute.
Unless explicitly stated as absolute pressure (bar a), all operating pressure ratings are expressed as gauge pressure (bar g) relative to atmospheric pressure.
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 temperature of the contents 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 safely at temperatures up to 250°C.
It must be realised that in complete plants, composed not only of borosilicate glass, but also include 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.
Annealing of glass is the process where the glass is heated and kept for a defined period of time to relieve internal stresses. Careful cooling under controlled conditions is essential to ensure that no stresses are reintroduced by chilling/cooling.
Borosilicate glass shows no appreciable absorption in the visible region of spectrum and therefore appears clear and colourless.
In photochemical processes, the transparency of ultra violet is of particular importance. It follows from the transmittance of material in UV region that photochemical reactions such as Chlorination and Sulpho Chlorination can be performed in it.
Borosilicate Glass with PTFE is of particular decisive importance for construction of glass installation. For example: in Seals, Bellows, Stirrers, Pumps, Heat Exchangers, Column Inserts etc.
PTFE is used with Glass because of its excellent mechanical & thermal properties. They have near universal fluid compatibility. Wear life when compared with others is very low. Particularly PTFE is maintenance free and have cryogenic stability with non wetting property.
Glass being a poor electrical conductor, surface conductivity is insignificant and varies with the quantity of water absorbed on glass surface. The specific conductivity is 10⁻¹⁰ ohm/cm at temperature of 200°C. The dielectric coefficient varies with current frequency.
The degree of thermal shock (sudden temperature fluctuation) that borosilicate glass can withstand depends on wall thickness, mechanical stresses imposed by supporting hardware, and operating conditions. Rapid or localized thermal gradients must be minimized, with a maximum recommended operational thermal differential (ΔT) of 120°C.
At sub-zero temperatures, the tensile strength of borosilicate glass increases slightly, allowing Goel Glass equipment and process components to operate safely at cryogenic service temperatures as low as −50°C.
The last two decades have seen further developments of particularly corrosion resistant plant construction materials. Typical examples of these are PTFE, tantalum, titanium, graphite and of course, Borosilicate Glass.
The combination of different corrosion resistant materials with the utilization of the specific advantages of each permits both safe and economic construction.
Maximum bolt-tightening torque* in Nm for couplings with backing flanges
| DN | Plastic (k) | Iron/Steel/ Silumin (S) |
|---|---|---|
| 12 | 1 | 1 |
| 15 | 1 | 1 |
| 25 | 2.5 | 2.5 |
| 40 | 2.5 | 3.5 |
| 50 | 2.5 | 3.5 |
| 80 | 2.5 | 3.5 |
| 100 | 3.5 | 4.5 |
| 150 | 3.5 | 4.5 |
| 200 | – | 4.5 |
| 225 | – | 4.5 |
| 300 | – | 4.5 |
| 400 | – | 6.5 |
| 450 | – | 6.5 |
| 600 | – | 11 |
| 700 | – | 20 |
| 800 | – | 20 |
| 1000 | – | 22 |
109 Boxcar Wy SE, Smyrna, GA 30080, United States
69 Yardley Crescent, Brampton ON. L6X5L7 Toronto Canada