Custom machining can include center holes, multiple mounting holes, slots, notches and special edge profiles. Production can be based on a technical drawing, sample or specified outside diameter and thickness.

Quartz glass itself offers excellent high-temperature and chemical resistance. However, the safe operating temperature and pressure of a complete sight glass installation must be determined according to the disc dimensions, exposed viewing diameter, mounting design, gasket material, bolt loading, thermal cycle and process medium.

This distinction is important: clear fused quartz materials can have continuous working-temperature figures above 1,000°C, but the permissible temperature of an assembled industrial sight glass may be lower because of its gaskets, metal housing and installation conditions.

Key Features and Advantages

High Temperature Resistance Suitable for demanding high-temperature applications.

Excellent Thermal Stability Low thermal expansion helps withstand rapid temperature changes.

Clear Visibility Polished surfaces provide reliable process observation.

Chemical Resistance Resistant to most acids and corrosive media.

Custom Manufacturing Custom diameters, thicknesses, holes and edge finishes are available.

Long Service Life Durable performance under demanding operating conditions.

Technical Specifications

Parameter	Specification
Material	Fused Quartz Glass
SiO₂ Content	≥99.9%
Thermal Expansion	Approximately 0.5–0.6 × 10⁻⁶/K, grade-dependent
Working Temperature	Up to 1100°C,depending on quartz grade and application conditions.
Working Pressure	Determined by dimensions and complete assembly design
Chemical Resistance	Resistant to most acids and many chemicals
Important Exceptions	Not suitable for hydrofluoric acid; hot strong alkalis require evaluation
Surface Finish	Ground or Polished
Edge Finish	Ground, Polished or Chamfered
Custom Processing	Holes, Slots and Notches Available

Temperature and Pressure Notice

The temperature values stated above describe the general capability of the quartz glass material. The allowable operating temperature and pressure of an installed sight glass depend on its diameter, thickness, unsupported viewing area, mounting structure, gasket material, bolt loading, thermal cycle and process medium. Please provide complete operating conditions for engineering confirmation.

Available Sizes

Circular quartz sight glass can be manufactured in a wide range of standard and custom dimensions.

Diameter: 10–420 mm

Thickness: 1–30 mm

Shape: Round or custom-machined circular profile

Surface: Ground, fine-ground or polished

Edges: Ground, polished, chamfered or beveled

Machining: Center holes, mounting holes, slots and notches available

Custom Size Statement

Other diameters, thicknesses and machined designs can be manufactured according to your drawing or sample. When requesting a quotation, please specify the outside diameter, thickness, quantity, operating temperature, operating pressure, process medium and installation method.

Frequently Asked Questions (FAQ)

Q: When should I choose a quartz sight glass?

A: Quartz sight glass is a suitable choice when:

• The continuous operating temperature is up to approximately 1,100°C.
• The process involves rapid temperature changes or severe thermal shock.
• A low thermal expansion coefficient of approximately 0.5–0.6 × 10⁻⁶/K is required.
• The medium is corrosive or chemically aggressive, except hydrofluoric acid and hot concentrated alkalis.
• UV, visible or infrared transmission from approximately 200 to 2,600 nm is required.

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 280–300°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