Your Reliable Partner For Custom Special Glass In China
Pressure- and heat-rated sight glass, gauge glass, and sight glass tubes for boilers, furnaces, reactors, tanks, and process vessels. We supply borosilicate, fused quartz, and glass-ceramic sight glass in round discs, gauge plates, tubes, and custom shapes according to DIN, ASME, or your own drawing.
Industrial sight glass gives operators a safe way to observe liquid level, flame condition, flow movement, color change, or process status without opening the vessel. It is used in boilers, reactors, furnaces, pipelines, pressure tanks, chemical equipment, and thermal processing systems where the glass must stay sealed under pressure, heat, and media exposure.
A sight glass is usually installed as a sealed window in a vessel, flange, pipe, or inspection port. Gauge glass is used in level indicators to show the liquid level directly. Both products need the right balance of temperature resistance, pressure rating, chemical resistance, optical clarity, and mechanical strength.
The correct glass depends on three main factors: working temperature, working pressure, and the medium inside the vessel. We supply common borosilicate sight glass for standard industrial use, fused quartz for high-temperature or UV applications, and glass-ceramic for thermal shock and furnace observation conditions.
A circular glass disc seated in a flanged viewport. It gives you a direct view into tanks, pipes, and reactors through a sealed, pressure-rated window. Made to DIN 7080 in the diameters and thicknesses your flange calls for.
The flat glass in a liquid-level gauge — transparent for a direct reading, or reflex (with prismatic grooves) for a sharper contrast between liquid and vapor. Made to DIN 7081, and cut to your gauge length and width.
Clear borosilicate tubes used in tubular level indicators, where the liquid column shows through the tube. They handle thermal shock well and come in the lengths and bores your gauge body needs.
Level glass built for steam boilers — rated for the pressure and temperature of saturated or superheated steam, and tough enough for years of thermal cycling. Supplied as gauge plates or round discs to match your boiler fittings.
A high-temperature sight glass for watching the process inside a furnace, kiln, or incinerator. Where ordinary glass would fail, we use quartz or glass-ceramic that stays clear and stable at extreme heat.
Don’t hesitate to contact us for more information about our company or industrial sight glass.
Selection Guide
Choose pressure vessel sight glass according to the medium, working pressure, temperature, and installation environment.
For flammable, toxic, or hazardous media, use small-diameter high-temperature and high-pressure sight glass with proper protective devices to prevent leakage. For low-pressure vessels, larger low-pressure sight glass is usually suitable.
We also provide custom moulded glass solutions for industrial sight glass and high-temperature applications. From drawing review and mould development to sample testing and batch supply, we help customers produce shaped glass parts that cannot be made by flat cutting alone.Tell us the vessel – the temperature, pressure, medium, flange size, and the standard you’re working to – and we’ll supply the right sight or gauge glass to match. We hold stock of common borosilicate sizes for fast delivery, and we make quartz and glass-ceramic parts to your drawing when the duty calls for it.
Glass-ceramic combines high temperature resistance with near-zero thermal expansion. It shrugs off sudden heating and cooling that would crack other glasses, so it’s used where the temperature swings are as extreme as the peak temperature itself.
| Property | Borosilicate Glass | Fused Quartz | Glass-Ceramic |
|---|---|---|---|
| Max continuous temperature | ~280°C for gauge glass use; higher grades can reach ~450°C | ~1,000°C | ~700°C or higher |
| Thermal shock resistance | Good | Excellent | Excellent |
| Thermal expansion / CTE | ~3.3 × 10⁻⁶ /K | ~0.55 × 10⁻⁶ /K | Near zero |
| Chemical resistance | Resistant to most acids, water and neutral solutions; not suitable for HF or hot alkali | Excellent chemical resistance; not suitable for HF or strong hot alkali | Good general chemical resistance |
| UV transmission | Partial UV transmission | High UV transmission, down to ~180 nm | Limited |
| Forms available | Round sight discs, gauge plates, tubes, custom parts | Round discs, tubes, rods, windows, custom shapes | Round discs, plates, windows |
| Common standards | DIN 7080, DIN 7081, ASME type sight glass | Custom to drawing | Custom to drawing |
| Diameter range | 17 mm to 250 mm+ | Custom to drawing | Custom to drawing |
| Thickness range | 6 mm to 30 mm+ | Custom to drawing | Custom to drawing |
We manufacture sight glass and gauge glass according to standard dimensions, customer drawings, or equipment samples. Common products include round sight glass discs, transparent gauge glass, reflex gauge glass, tubular sight glass, boiler sight glass, furnace observation glass, and custom moulded glass parts.
For standard industrial equipment, borosilicate glass is usually the most practical choice because it balances clarity, thermal shock resistance, chemical resistance, and cost. For high-temperature observation, fused quartz or glass-ceramic may be required. For steam, chemical, or pressure service, the glass size, thickness, gasket contact area, and installation design must be checked before production.
We can support cutting, edge grinding, polishing, drilling, shaping, moulding, and custom packing. If you already have a drawing, standard number, flange size, or old sample, send it to us and we can match the glass to your equipment.
Tell us the material, size, thickness, tolerance, quantity, application, and any holes, slots, edges, coating, printing, or polishing requirements. We can manufacture custom glass components from your drawing, CAD file, sketch, or sample.
Yunpu Industrial Zone, Nangang, Huangpu District, Guangzhou
+86-19860070065
sales@specialglass.net
+86 19860070065
+86 19860070065
