Aluminosilicate Sight Glass

Key Features and Advantages

High mechanical strength

Suitable for demanding industrial viewing applications involving pressure and mechanical stress.

Elevated-temperature performance

Maintains reliable performance at temperatures higher than those suitable for many conventional glass materials.

Good thermal shock resistance

Helps the glass withstand rapid temperature changes during operation, cleaning or system start-up.

Clear process observation

Provides good optical transparency for monitoring liquid level, flow and internal equipment conditions.

Good chemical durability

Resists water, steam and many industrial fluids when the correct glass grade is selected.

Technical Specifications

Parameter	Typical Value
Maximum Operating Temperature	375°C / 707°F
Thermal Shock Resistance	ΔT 230°C
Coefficient of Linear Expansion	4.8 × 10⁻⁶ K⁻¹(20–300°C)
Maximum Operating Pressure	Up to 225 bar / 3,263 psi*
Surface Compressive Prestress	≥ 90 N/mm²
Bending Strength	Approx. 240 N/mm²
Density	2.62–2.67 g/cm³
Light Transmittance	Approx. 91.8%
Softening Point	Approx. 920 ± 10°C

Sizes

Aluminosilicate sight glass discs are available in a wide range of standard and custom dimensions.

Diameter: Typically 10–420 mm

Thickness: Typically 1–30 mm

Hole options: Without hole, centre hole, offset hole or multiple holes

Edge options: Ground, seamed or polished

Special processing: Stepped edges, grooves, notches and profiles available according to drawings

Applications

• Aluminosilicate sight glass discs are commonly used in:

• High-temperature process equipment

• High-pressure vessels and tanks

• Industrial boilers and steam equipment
• Chemical processing equipment
• Petrochemical pipelines and reactors
• Power generation equipment
• Sight flow indicators
• Furnace and thermal-processing equipment
• Oil and gas processing systems
• Custom industrial observation windows

Frequently Asked Questions (FAQ)

• Q: When should aluminosilicate sight glass be selected?
• A: Aluminosilicate sight glass should be considered when the operating temperature exceeds the typical 280–300°C limit of borosilicate sight glass, or when higher mechanical strength is required.Industrial aluminosilicate sight glass typically provides:
  • A maximum operating temperature of approximately 375°C
  • Pressure capability of up to 225 bar in a properly designed assembly
  • Bending strength of approximately 240 N/mm²
  • Thermal shock resistance of approximately ΔT 230°C
  • It is commonly selected for high-temperature boilers, steam systems, pressure vessels and heavy-duty process equipment.
  • Actual temperature and pressure ratings depend on the glass dimensions, mounting assembly, gasket material and operating conditions.

• Q: What is the difference between borosilicate, aluminosilicate, quartz and soda-lime sight glass?
• A: The main differences are operating temperature, pressure capability, thermal shock resistance and cost.
  • Soda-lime sight glass is an economical option for general, low-temperature observation applications. Its typical operating temperature is up to approximately 150°C, and it is primarily used in low-pressure systems.
  • Borosilicate sight glass offers good chemical resistance and thermal shock resistance. It is suitable for most industrial tanks, pipelines and process equipment, with a typical operating temperature of up to 280°C. Specially designed assemblies may withstand pressures up to 200 bar.
  • Aluminosilicate sight glass provides higher mechanical strength and is suitable for elevated-temperature and high-pressure applications. Its typical maximum operating temperature is approximately 375°C. Properly designed assemblies may operate at pressures up to 225 bar.
  • Quartz sight glass provides excellent high-temperature and thermal shock resistance, with a typical operating temperature of up to 1,000–1,100°C. It is commonly used in furnaces, reactors and thermal-processing equipment. However, quartz does not automatically provide the highest pressure resistance.

All pressure values are for reference only. Actual allowable pressure depends on the glass diameter, thickness, edge finish, mounting assembly, gasket, operating temperature and required safety factor.

• Q: What information is required for a quotation?
• A: Please provide the following information:
  • Material
  • Outside diameter
  • Thickness
  • Quantity
  • Operating temperature
  • Operating pressure
  • Process medium
  • Hole size and position, if required
  • Drawing or sample, if available